American Nature

AMERICAN NATURE

AN A-Z NATURAL HISTORY GUIDE

AMERICAN ANIMALS, PLANTS, MINERALS, HABITATS, LANDFORMS, PHENOMENA, STRUCTURES, CYCLES, TERMS AND CONCEPTS

Aardvark

Orycteropus afer

A strange name for a strange animal. Also called Ant bear and Anteater, the Aardvark is a badger-sized burrowing mammal of the grasslands of southern Africa, having a stocky, hairy body, large ears, a long tubular snout, and powerful digging claws. Not found in North America.

Abalone

Haliotidae

Fairly common along the Pacific coast, these large marine snails creep across rocks, propelled by a large muscular foot, and feed on algae and microscopic animals. Popular with collectors for their pearly, iridescent shells, abalones are also prized by gourmets for their tasty meat. The shell is perforated with a line of small holes along one edge, permitting the expulsion of wastes and the water that is used for breathing. During their first week of life, the tiny free-swimming larvae attach to rocks and other hard objects, and there they mature into adults up to 12 inches long. Although all species are edible, many people consider the red abalone a particular delicacy.

Abdomen

A large body cavity between the thorax (chest) and the pelvic cavity. A strong wall of muscle called the diaphragm, separates the abdomen from the thorax. But no structure separates the abdomen from the pelvic cavity.

Abdomen

Invertebrate term. Hind section of an insect's body; usually appears segmented. The abdomen is the part of the body behind the thorax of insects, crustaceans and certain other kinds of animals without backbones.

Abdominal

Does not refer to the legendary Abominable Snowman. See Abdomen.

Abominable Snowman

Also called Yeti. The Snowman is an obviously mythical creature said to live on Mount Everest and other mountains of the Himalaya range of Asia. Reports of such a creature have also come from remote parts of China and the Soviet Union. According to legend, the Abominable Snowman is a hairy beast with a large, apelike body and a face that resembles that of a human being. It supposedly has long arms that reach to its knees, and it is reported to walk erect on its thick legs. Legend says that the Snowman sometimes attacks villagers. There is no direct evidence that the Yeti exists, even though individuals have photographed “Snowman” tracks in the snows near Everest. In North America, similar reports describe a creature usually known as Bigfoot. See Bigfoot.

Acacia

Found in tropical and subtropical regions all around the world, acacias are widespread members of the legume, or pea, family. Only 15 species are native to the United States, but many others have been cultivated successfully, particularly in California and Florida. Growing as either shrubs or small trees, acacias are a source of dyes, tannins, and a gum used in medicines, foods, and manufacturing. Their wood is used for everything from furniture to fence posts. The sweet acacia, a thorny shrub or small tree, is indigenous to Texas and cultivated elsewhere. It favors dry, sandy soils and produces bright yellow heads of tiny flowers in February and March. The fragrant blossoms are used in sachets and as a perfume ingredient. Another species, the catclaw acacia, grows in dense thickets in the deserts of the Southwest. Named for the armament of hooked spines on its branches, the catclaw is decorated with elongated spikes of creamy yellow flowers in early spring and intermittently throughout the summer. The Pima and Papago Indians made a meal, pinole, from its seeds and gathered the honey produced from its nectar.

Accidental

Not regularly occurring in an area; few records existing of sightings.

Accipiter

Short, rounded wings and long tails distinguish the accipiters from all other hawks. Agile woodland birds that alternately flap their wings and then glide, they are sometimes called bird hawks because of their predominant prey, although they feed on insects and small mammals as well. The three species found across most of North America are the foot-long sharp-shinned hawk; the medium-size Cooper's hawk; and the northern goshawk, larger than a crow and formidable enough to kill ducks and rabbits.

Acid rain

Acid rain is a generic term used for precipitation that contains an abnormally high concentration of sulfuric and nitric acid. These acids form in the atmosphere when industrial gas Admissions combine with water, and have negative impacts on the environment and human health. A by-product of automobile exhaust and the combustion of coal and oil in factories and power plants, acid rain has become a serious problem in many areas. It has made many lakes uninhabitable to fish, even in areas far from the sources of pollution. It has killed or damaged trees and crops. And it has corroded masonry buildings and other man-made structures. Acid rain is produced when nitrogen oxide and sulfur dioxide are released into the atmosphere. There they combine with water vapor to form nitric acid and sulfuric acid, resulting in rainfall that is far more acidic than normal precipitation. Emission control devices designed to remove pollutants from smokestacks are available. But they must be more widely used if the problem is to be controlled.

Action and Learning

Action relates to an action or activity, in this case one carried out to provide a particular environmental service to a community. Learning is the increased capacity of citizens to become more ecologically literate and competent.

Advisories Warnings Watches (Weather)

Agencies issue weather advisories, warnings and watches to inform people about current or developing weather. An "advisory" is a bulletin that informs people that actual or expected weather conditions may cause general inconvenience or concern, but do not pose a serious threat. A "watch" alerts people that conditions are favorable for the development of severe weather, while a "warning" tells them that severe or hazardous weather is occurring or highly probable.

Aestivation

An Animal Behavior term, this is dormancy to escape heat during the summer. It is equivalent to Hibernation in the winter. Mainly found in species living in areas such as deserts where drought and very high temperatures make the environment hostile. By becoming torpid in an enclosed and humid burrow, such Animals can conserve both energy and water. Dormancy observed in an animal during summer.

Agate

Valued for their swirling bands of color, agates have long been used in mosaics, jewelry, and other ornaments. The vivid colors for which they are prized, however, are not always the gift of nature; even the ancients knew that these porous stones could be dyed in order to intensify their natural hues. Agates are deposited slowly, layer by layer, in cavities in older rocks. Composed of almost pure silica, they are a type of quartz. Their colorful patterns are caused by minute quantities of iron and other mineral impurities that highlight the concentric bands. In the United States, gemstone-quality agates have been found in Oregon, Washington, and Idaho and around Lake Superior.

Agave

Sometimes known as century plants because they take so long to bloom (not a century, by any means, but often many decades), several species of agaves flourish from Virginia to California. Tolerant of hot, dry growing conditions, they are especially common in the parched deserts of the Southwest. Most agaves consist of a dense rosette of thick, spiny-edged, spearlike leaves up to several feet long. The flowering stalk that eventually emerges from among the leaves may grow to be 20 feet tall and is topped by clusters of tubelike flowers. The blooms are pollinated by long-tongued bats that sometimes hover in the air, hummingbird style, as they lap up the nectar. Some kinds of agave die after flowering, while others bloom year after year. In Mexico the sap and pulp of certain species are used to make the alcoholic drinks pulque, mescal, and tequila. Agaves also are cultivated for their fibers, called sisal and henequen, which are used to make thread and rope. In many areas they are also planted as ornamentals-a tribute to their dramatic beauty.

Aggression

An Animal Behavior term, this is a controversial term and is best used as a loose Categorization of attack and threat behavior but sometimes it is taken to include a much broader group of activities. A Cat attacking a Cause (predatory aggression), a Bird singing (a behavior that tends to repel rivals) and a Human speaking assertively, have all sometimes been described as aggressive. As the causes of these actions probably have little in common with fighting within a species, such broad usage is probably best avoided.

Agonistic behavior

An Animal Behavior term, this is considered to be any behavioral pattern associated with fighting and retreat, such as attack, escape, threat, defense and appeasement.

Ailanthus

Ailanthus altissima

Featured in the novel A Tree Grows in Brooklyn, the ailanthus is a common sight in cities all across the country. Since it easily endures poor soils and air pollution, it thrives where few other trees can grow. A native of the Orient imported to America in the 19th century, the ailanthus is also known as the tree of heaven, a reference to its speedy growth (as much as 10 feet a year) to heights of 60 feet or more. Its featherlike compound leaves are up to three feet long, giving the tree a luxuriant, somewhat tropical look. But its branches are easily broken and its male flowers give off a rank odor, discouraging its use as a street tree. Condemned by many as a rampant weed, the ailanthus nevertheless manages to sprout, unbidden, wherever the wind carries its papery, single-winged seeds.

Air

The air or atmosphere that surrounds the earth is one of the main components of our environment. The air we breathe is part of the mixture of gases-the atmosphere-that envelops the earth and sustains life. It consists of 78% nitrogen, 21 % oxygen, and minute traces of a variety of other gases, including about .03% carbon dioxide. Water vapor also is present in varying amounts, depending on temperature and location. And as any city dweller can attest, air is adrift with a host of microscopic particles, ranging from soot and dust to salt and plant spores. Scientists believe the atmosphere began to form billions of years ago as gases escaped from the earth's interior, mainly through volcanoes. This early atmosphere lacked oxygen, until green plants developed in the ocean and released that vital gas through photosynthesis.

Air pollution

Long recognized as a threat to human health and to the environment, air pollution is a worldwide problem. The contaminants that foul the air range from dust and soot to noxious fumes such as sulfur oxides and carbon monoxide. Among the major sources are emissions from motor vehicles, factories, and power plants. An especially pernicious form of pollution the dense, dark haze known as smog-results when smoke and other gases mix with water vapor in the air. If atmospheric conditions prevent its dispersal, the results can be disastrous. In Donora, Pennsylvania, in October 1948, for example, a slow-moving ridge of warm air hung over the town for days on end, trapping the pollutants from its many industrial smokestacks. By the time the air cleared, 20 people were dead and thousands more suffered serious illness. In recent decades significant strides have been made in cleaning up our nation's dirty air. With stricter emission standards, the installation of pollution-control devices, and other measures, we all will breathe more easily. But much remains to be done before the problem is solved completely.

Air quality

Scientists collect and analyze samples of air in different regions on a regular basis to determine pollutant levels. This information is not only used by decision-makers to pinpoint the sources of air pollution and determine strategies for reducing it, but also to produce daily air-quality forecasts that warn citizens when smog levels are high.

Albatross

The largest and perhaps the most highly adapted of all seabirds, albatrosses glide effortlessly over the waves on stiffly held, very long and narrow wings. Taking advantage of winds and small updrafts, they can remain aloft for hours on end with scarcely a beat of their wings. Indeed, these nomads of the open sea come ashore only to breed, usually on remote islands. Albatrosses live mainly in southern oceans, but a few species visit North American waters. Most often seen is the black-footed albatross, which nests in the central Pacific and appears off the west coast in summer and fall. Dusky brown, with a white face, it has a wingspan of nearly 7V2 feet. The Laysan albatross, with a wingspan slightly shorter than that of its relative, is white with a blackish back, tail, and wings and also is seen in summer off the Pacific coast. It nests in the Hawaiian Islands. In typical albatross fashion, both species feed on fish, squid, and other marine animals, and some willingly accept scraps thrown from passing ships.

Alder

Growing both as shrubs and small trees, alders are found mainly in northern temperate regions. Tolerant of moist conditions, these members of the birch family often grow in dense thickets in swamps and along streams. Although they are of little value to wildlife, the nitrogen-fixing bacteria that live in nodules on their roots play an important role in enriching the soil. Because of their growth habits and their ability to add nitrogen to the soil, alders are useful in preventing erosion and helping reestablish plant growth in fire-scorched areas. The largest North American species, the red alder, reaches heights of more than 100 feet. Reseeding quickly after fires and logging operations, it is the most important hardwood in the Pacific Northwest, where it is used for making both furniture and paper.

Alderfly

Living as adults in the vegetation near ponds and streams, alderflies are named for the trees in which they often congregate. An inch or less in length, these black or dark brown insects have long, threadlike antennae and two pairs of large smoky wings. The adults-sluggish fliers that apparently do not eat-live for only a few days and die soon after mating. The aquatic larvae, on the other hand, live for a year or more underwater, where they crawl along stones and feed actively on other small insects. They come ashore to pupate, burying themselves in the mud, and emerge the following spring for their brief life as mature alderflies.

Algae

These simplest of all plants-they have no true roots, stems, leaves, or flowers-are an extremely varied group. Algae range in size from microscopic single-celled organisms to the giant kelps, seaweeds that grow to lengths of 200 feet or more. They thrive on land, in fresh water, and in the sea and may be green, blue-green, red, or brown. All of them, however, contain green chlorophyll-the substance that enables plants, using sunlight for energy, to make their own food from carbon dioxide and water, a process called photosynthesis. Millions of single-celled algae form the filmy green growth sometimes seen on damp, shaded tree trunks, walls, and roofs. Other microscopic algae live in both fresh and salt water, where they may drift in huge numbers-a very important food source for other forms of life. Common freshwater algae include threadlike spirogyra, found in billowing cottony masses in the quiet water of ponds and ditches, and volvox, which consists of thousands of individuals grouped in spheres the size of pinheads. Diatoms, encased in microscopic glassy shells, are among the most abundant of the marine algae. More commonly seen are the larger types known as seaweeds. Some algae form remarkable associations with other living plants and animals. Lichens, for instance, are dual plants made up of both algae and fungi. Single-celled algae also live inside the tissue of reef-building corals and seem to playa role in the formation of the reef.
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Algae evolution

A simple organism known as blue-green algae appeared and spread across the seas. Blue-green algae are still alive today. It was very important to the future of the planet because blue-green algae used sunlight and water to make food, and in the process, created oxygen. As the blue-green algae grew in the earth's seas, they began to fill the atmosphere with oxygen.

The oxygen blue-green algae produced made it possible for other types of organisms to develop. These organisms needed oxygen to carry out their life processes of growth, feeding, responding and reproducing. Unlike the blue-green algae, these organisms could not produce their own food. They needed oxygen to perform their life processes of growth, feeding, responding, and reproducing. In return, they produced CO2, which the algae needed to perform its life processes. A precise balance between plants and animals was established.

Alien

A species that is not native to a particular region but which has been introduced by man and has become naturalized. These imported species are a mixed blessing. Some species have been good additions to American ecosytems. Some species have created severe economic and environmental problems.

Alligator

Alligator mississippiensis

Living relics of the age of dinosaurs, alligators are our largest reptiles. American alligators grow up to 15 feet long and sometimes weigh more than 500 pounds. On land, they are awkward and slow, but in water they are agile swimmers. Their huge jaws and sharp teeth are used not to chew, but to catch and hold prey. Far from fussy feeders, alligators eat almost anything that walks, flies, or swims within their reach, including fish, small mammals, and waterfowl. In spring, bellowing by the males signals the onset of the mating season. The females lay dozens of eggs in large nesting mounds, cover them with vegetation, and guard them until the offspring hatch. Their sex is determined by the incubating temperature of the eggs. If they remain below 86°F, only females develop; if their temperature rises above 93°, all hatch as males. Alligators once were hunted to near extinction, but laws now protect them. In some parts of the Southeast the mighty reptiles again are lords of the lowland swamps and rivers.

Alligator lizard

Five species of alligator lizards are found in the western states, living in habitats as diverse as the humid forests of the Pacific Northwest and the dry grasslands of Arizona. Long-tailed, short-legged, and armored with bony plates beneath the skin, these foot-long reptiles look like miniature versions of their namesake. They all share one characteristic feature-a pleatlike fold of skin along each side of the body that expands after the animals eat and when the females are heavy with eggs.

Allogrooming

An Animal Behavior term, this is mutual grooming between Animals, especially common among primates and Birds. Allogrooming may assist in the care of the body surface because it is often directed to areas the individual cannot reach. Most often it is shown to mates. social partners and dominant individuals, and certainly also has the social function of cementing relationships between individuals.

Allopatric

Bird Biology Avian Conservation term.

Occurring in different places; usually refers to geographical separation of populations. The populations may exhibit divergence in behavior, morphology, or genetic composition.

Alluvial fan

Apron-shaped deposits of sand, gravel, and rock are a familiar sight at the foot of mountain slopes in arid regions. Known as alluvial fans, they are, in effect, deltas on dry land. During the torrential downpours that are characteristic of desert areas, tremendous amounts of debris are swept down normally dry streambeds. Dumped where the river slows down at the base of the mountain slope, the sediments accumulate as alluvial fans.

Alpine biome

Cold, snowy, windy. When you hear those words they make you think of mountains. In Latin the word for 'high mountain' is 'alpes'. That is where today's word alpine comes from.

Alpine biomes are found in the mountain regions all around the world. They are usually at an altitude of about 10,000 feet or more. The Alpine biome lies just below the snow line of a mountain. As you go up a mountain, you will travel through many biomes. In the North American Rocky Mountains you begin in a desert biome. As you climb you go through a deciduous forest biome, grassland biome, steppe biome, and taiga biome before you reach the cold Alpine biome.

In the summer average temperatures range from 40 to 60 degrees. In the winter the temperatures are below freezing. The winter season can last from October to May. The summer season may last from June to September. The temperatures in the Alpine biome can also change from warm to freezing in one day.

Because the severe climate of the Alpine biome, plants and animals have developed adaptations to those conditions. There are only about 200 species of Alpine plants. At high altitudes there is very little CO2, which plants need to carry on photosynthesis. Because of the cold and wind, most plants are small perennial groundcover plants which grow and reproduce slowly. They protect themselves from the cold and wind by hugging the ground. Taller plants or trees would soon get blown over and freeze. When plants die they don't decompose very quickly because of the cold. This makes for poor soil conditions. Most Alpine plants can grow in sandy and rocky soil. Plants have also adapted to the dry conditions of the Alpine biome. Plant books and catalogs warn you about over watering Alpine plants.

Alpine animals have to deal with two types of problems: the cold and too much high UV wavelengths. This is because there is less atmosphere to filter UV rays from the sun. There are only warm blooded animals in the Alpine biome, although there are insects. Alpine animals adapt to the cold by hibernating, migrating to lower, warmer areas, or insulating their bodies with layers of fat. Animals will also tend to have shorter legs, tails, and ears, in order to reduce heat loss. Alpine animals also have larger lungs, more blood cells and hemoglobin because of the increase of pressure and lack of oxygen at higher altitudes. This is also true for people who have lived on mountains for a long time.

Alpine meadow

Perched between forests below and snowy peaks above are the high-elevation alpine meadows of the northern Rockies and other western mountains. The meadows are best known for their annual floral displays: even while the ground remains dotted with snow and ice in spring and summer, they burst into bloom with acres of glacier lilies, bear grass, alpine buttercups, and dozens of other wildflowers. Ptarmigans and rosy finches are among the birds that forage there for seeds and insects, while marmots and ground squirrels are two of the meadows' more conspicuous mammals.

Altricial

An Animal Behavior term, this is used in describing those species in which the offspring are relatively helpless at birth and are kept for a period thereafter in a nest or other hiding place. It is the opposite of Precocial. Some birds and animals are born helpless, and hence completely dependent upon their parents. They will usually remain in the den or nest until they develop to an extent that they become partially independent.

Altruism

An Animal Behavior term, this means conferring a benefit on another individual at a cost to the individual behaving altruistically. In this general sense, altruism includes sharing food and producing warning calls. In these cases, however, the altruist may benefit if the help given is to relatives (as they share a proportion of the altruist's genes) or to social partners who will reciprocate later. Most apparent altruism comes into these Categories and so, strictly, is not altruism at all.

Alpine meadow

Amanita

The ghostly white destroying angel and the greenish-yellow death cup are among the many amanita mushrooms that are poisonous. While a few kinds are edible, experts recommend that they all be avoided because of the potentially fatal consequences of a mistaken identification. Fortunately, the amanitas have a few telltale characteristics that make recognition fairly easy. Typically, the stem has a bulbous base surrounded by a fleshy cup and a collar of loose skin near its top. Some of the amanitas have brightly colored caps and make attractive accents on the forest floor. But in the case of these fungi, it is best to look and leave alone.

Amber

Glassy and golden brown, amber has been valued for its beauty since ancient times. Early Romans fashioned it into jewelry, believing that amulets of amber worn at the neck could prevent tonsillitis and goiter; the Greeks wore it as a talisman, claiming it was formed from tears shed by exotic birds. In fact, amber is the fossilized resin of now extinct coniferous trees that lived millions of years ago. Small insects and plants sometimes were trapped in the gummy resin and preserved there when it hardened into amber, providing a glimpse of life long ago. Most of the world's amber comes from the Baltic coast of Europe, but specimens have been uncovered in New Jersey and a few other eastern states.

American copper

Lycaena phlaeas

Only an inch across, this butterfly makes up for its lack of size with brilliance and bravado. Both of the American copper's fiery orange forewings are punctuated by several blackish spots, and the lower borders of the darker hind wings also are bedecked with orange and black. A common sight in the Northeast, this flying flash of color is an unlikely aggressor, chasing off other butterflies and even blitzing dogs and birds.

Ammonite

Some 200 million years ago, while dinosaurs still roamed the earth, ammonites lived in the shallow seas that covered vast areas of present-day North America. Now extinct, these mollusks had coiled, elaborately chambered shells much like those of their descendants, the nautiluses. Most species were a few inches or so in diameter, but a few were huge. One particularly large specimen unearthed from a shale bed in Wyoming was more than five feet in diameter.

Amphibian

Frogs, toads, and salamanders, the most familiar of the amphibians, belong to a well-named group: the word amphibious is derived from the Greek for "leading a double life." And that is what amphibians do. Most begin life in water, swimming and breathing like fish, and mature into four-legged, air-breathing adults. Frogs and toads undergo the most dramatic change, or metamorphosis, from egg to adult. The eggs, deposited in water, hatch into fishlike larvae called tadpoles, with gills for breathing and long tails for swimming. In time, four legs appear, the gills are replaced by lungs, and the tail shrinks to nothing, completing the transition from life in the water to life on land. As the tadpoles of salamanders mature, they too grow legs but keep their long tails. Some develop lungs, others breathe through their skins as adults, and still others retain their gills throughout life and never leave the water. All amphibians are scale less, moist skinned, and cold-blooded. In winter most hibernate underground. Then, in spring, they revive and return to the ponds and streams, where they mate and produce a new generation. Though not so commonly seen as frogs, salamanders actually are more numerous in North America than anywhere else. They are difficult to find because most are active only by night and fond of dark, damp hiding places. But a patient search under rocks or rotting logs in the spring and summer months should turn up a few of these shy and elusive creatures.

Amphiuma

Growing to a length of 30 inches or more and equipped with legs so tiny they are barely noticeable, these brown or grayish salamanders sometimes are mistaken for snakes or eels. Unlike most of their relatives, amphiumas have strong jaws and sharp teeth that enable them to bite fiercely if provoked. They hunt for snails, crayfish, frogs, and fish by night and hide themselves in muddy burrows during the day. The females lay strings of beadlike eggs near the water’s edge, then coil around them until they hatch some five months later. Amphimacer live in swamps, ponds, and drainage ditches in the Southeast, from Virginia to Florida and west to the lower Mississippi Valley.

Amplexus

An Animal Behavior term, this is the posture adopted by pairs of Frogs and Toads during the mating season, with the male riding on the back the female.

Anchovy

Traveling in enormous schools, throngs of these silvery little fish set the water shimmering. They are closely related to herrings and sardines, and like their relatives, they are of great commercial value. Vast numbers are caught annually for use as human food and fish bait, and for processing into fishmeal and fish oil. Feeding on minute plant and animal life called plankton, anchovies are also a vital link in oceanic food chains, for they serve as a major food source for larger predatory fish and seabirds. The kinds most commonly seen in American waters are the northern anchovy, found off the Pacific coast, and the bay anchovy of the Atlantic and the Gulf of Mexico. As short as an inch and a half, and rarely exceeding six inches in length, anchovies are slender silvery fish with a faint stripe along each side. Like most anchovies, both of these American species have large eyes and very large mouths, with the upper jaw protruding beyond the tip of the lower jaw.

Anemone

As well known for their seed heads as for their flowers, the anemones have also been given the name of windflowers. Some say they earned this name because their delicate flowers seem to be blown open by breezes; others claim they are so called because their fluffy seeds are easily wafted away on the wind. Members of the buttercup family, the anemones have attractive cup-shaped flowers. (The "petals" are actually showy sepals.) They include many cultivated varieties grown as ornamentals and for the florist trade. A well-loved and widespread wild species is the dainty wood anemone, which bears solitary star like white flowers. In early spring its lovely blooms can be admired in woodlands and meadows across most of North America. Another, the lavender pasqueflower of the western plains, is so named because it blooms around Easter. Indians used to employ its crushed leaves to treat rheumatism and its flowers to stop nosebleeds. It has no medical uses today but is honored instead as the state flower of South Dakota.

Angler

Found in oceans around the world, anglerfish are notable for their unique method of capturing prey. A fleshy, often wormlike flap dangles from a spine on the angler's head and hangs in front of its face. Any fish attracted by this "bait" is quickly snapped up in the angler's huge, toothstudded jaws. So voracious are their appetites that some of the larger anglers have been known to swallow prey almost as big as themselves. The anglers' method of reproducing is as unusual as their feeding habits. By the time they are ready to breed, females are as much as 20 times the size of the stunted males. In some species, the males become permanently attached to their mates and serve only to fertilize their eggs. In other species, the males attach themselves to the females only during the breeding season, and otherwise are able to live independently. The best-known angler is the goosefish, a wide-mouthed monster with a fearsome array of teeth. Though its flesh is delicate and lobsterlike, it is usually considered too gruesome to display intact in fish markets. Its meat is sold under a variety of aliases, including monkfish, angler, and lobsterfish.

Anhinga

Anhinga anhinga

Because they often swim almost completely submerged, with only their heads and long, sinuous necks protruding from the water, anhingas are sometimes known as snakebirds. Their fan shaped tails account for another, less elegant common name-the water turkey. Large, blackish birds of southeastern swamps and marshes, anhingas are well adapted for fishing: they swim and dive easily in search of prey and impale their catch on their slender, sharply pointed bills. (They are, in fact, the only birds that do so; herons and other species with similar bills seize their prey rather than spearing it.) Anhingas then bring their catch to the surface, toss it in the air, and swallow it headfirst. Like their relatives the cormorants, anhingas have loose plumage that does not repel water, and so are often seen perched with their wings spread out to dry. But the easiest way to find them in the trackless swamps they inhabit is to watch the sky: they can be seen soaring gracefully on outstretched wings as they circle high above the treetops.

Animal

Nearly 2 million species of animals have been identified around the world, and their diversity is astonishing; they range from microscopic, single-celled organisms such as amoebas and paramecia to creatures as complex as human beings. Regardless of their size, however, all animals share one common characteristic. Unlike plants, they cannot manufacture their own food; they must instead get their nourishment by eating plants or other animals. Most animals share a number of other traits as well, characteristics related in part to the fact that they must actively seek food. A nervous system and sense organs, for instance, are essential for finding plants or prey. A means of locomotion enables animals to pursue or collect food and to avoid being eaten themselves. And a digestive system extracts nutrients and energy from whatever foods they eat. This diversity of feeding habits helps account for the tremendous variety of animal life. Cats, for example, are skilled predators equipped with muscles, claws, and teeth that would be useless to a nectar-feeding butterfly.

Despite their diversity, all animals are divided into two broad groups, those that have backbones, the vertebrates, and those that do not, the invertebrates. Insects are by far the most numerous animals in either category, with more than 800,000 species known to science.

Animal Behavior-Overview

To the casual observer, animals may seem to pass the time aimlessly-a bird sings from the treetops, a butterfly alights on a flower, a rabbit races across a meadow. But scientists have found that virtually all animal behavior has a purpose. The bird whose song seems so carefree is trying to attract a mate; the butterfly fluttering from flower to flower is searching for food; and the nimble rabbit is fleeing from a predator. Most animal behavior, in short, is tied directly or indirectly to life's most compelling requirement-staying alive.

Animal Behavior

Bluffing and battling

Animals often have to defend themselves against others of their own kind while competing for food, mates, and living space. The security of a home or territory is crucial for mating and rearing young, and each animal has its own way of marking its property and warning others to stay away. The male fox sprinkles urine on stones and trees that border its territory. Other foxes are well aware of these "keep out" signs, but if one should trespass, a conflict of some sort is likely to take place. Usually, though, the encounter is limited to bluffing and threatening until the intruder gives in and is sent on his way. Defense against predators is a different matter, because the fight, if it occurs, is usually a matter of life or death. Teeth, claws, acute senses, and even poisons are used by both predator and prey. Prey species may also defend themselves by running, hiding, or playing dead, or in the case of the armadillo or porcupine, presenting a platelike armor or a formidable array of sharp quills.

Animal Behavior

Animal language

Each animal species has its own language of sound, scent, or display through which it communicates with others of its kind. A male bird may repeat his song thousands of times a day to proclaim his territory or to court a female. And when not singing, birds use call notes to scold, beg for food, summon young, and keep the flock together. Sound is used by many animals: frogs croak, wolves howl, and elk bugle during the rutting season. Among insects, male mosquitoes locate females by the whirring sound of their wings. In the ocean, whales and porpoises have a sophisticated vocabulary of grunts, chirps, whistles, and clicks that scientists have spent years trying to decipher. Some animals use scent to communicate. The feathery antennae of the male moth can detect the scent of a female more than a mile away. Mammals such as deer and badgers use scent glands, urine, or feces to mark their territories. Like humans, some animals use facial expressions and body language to express themselves. Cats and dogs use their mouths and ears to show anger, contentment, or hunger. Members of a wolf pack greet the leader with a ceremonial nuzzle, and he in turn reminds them of his dominance with a gentle nip on the neck. Prairie dogs greet each other with a kiss. And bees do a complicated dance to announce the discovery of a new food source.

Animal Behavior

Rites of courtship

If animals failed to mate, their species would vanish. So the sometimes bizarre and complicated behavior associated with courtship plays a vital role in survival. In most cases, courtship is initiated by the males, many of which go through elaborate rituals to woo their object of desire. The fiddler crab waves an oversized claw at the female, as if to say, "Here I am!" Some male spiders, midgets compared to the females and in danger of being mistaken for prey, announce themselves with intricately choreographed dances; others pluck the female's web like a bass fiddle before coming too close. Some birds, such as hummingbirds, display dazzling colors, while others, like brown thrashers, entice mates with a repertoire of melodious songs. And some of the hawks perform dramatic aerial acrobatics, with pairs locking talons as they swoop through the air.

But seductive displays of color, movement, and song are not the only courting devices. In the ocean, many creatures rely on chemical lures to attract mates. Male oysters, for instance, announce their readiness to spawn by subtly changing the flavor of the water.

Animal Behavior

Learning VS. Instinct

While most animal behavior is instinctive rather than learned, many animals are undeniably able to acquire new skills through training. In the laboratory, rats have been taught to push levers, climb ladders, and negotiate mazes when rewarded with food. And such unusually intelligent animals as chimpanzees and dolphins have demonstrated an almost human ability to learn. In the wild, many young animals learn by imitating adults. During play they copy the hunting and killing maneuvers of their parents, and so develop the strength and timing they will need later in life. Bobcat kittens, for instance, regularly play at crouching, stalking, and ambushing mock prey, as do fox cubs. Still, clear-cut examples of learning are relatively rare in the animal world. For the most part, wild creatures are acting according to instincts or reflexes that have determined the behavior of their species for tens of generations. And such predetermined behavior, however mechanical or predictable, has served them well in the most crucial tasks of life-courtship, self-defense, communication, and ultimately, survival itself.

Animal Ecology

A habitat is any place where a particular animal or plant species lives. Examples of a habitat include a lake, a desert, or forest, or even a drop of water.

All habitats on Earth are part of the biosphere. Since the Earth is always changing, habitats are continually changing as well.

Descriptions of environments using temperature and rainfall are used to group habitats together. Habitats of similar climate and vegetation are called biomes. In different parts of the world, the same biome may contain different species, but will contain similar life forms. For example, trees are the dominant forms of the rain forest, no matter where the rainforest is located.

Animals, which live within a same-species group, and occupy an area at the same time, are part of a population. All members of the same population have certain traits in common. Populations of different plants and animals interact with each other, and together, these populations form communities. Plants and animals in a particular ecological community, or biome, must be adapted to the same living conditions so they can all survive in the same biome.

Many populations can live in the same area because each species fills a specific role in the community. This role is called a niche. What an animal eats, and where it eats are also part of its niche. Giraffes can live in the same area as gazelles because they eat different plants and don't compete with each other. Dung beetles bury the feces of these animals and lay their eggs in it. The hatching grubs feed on the feces. The buried feces also fertilize plants, which in turn feeds the gazelle and giraffe. Each plant and animal has its own niche in the ecological community, and is important in some way to the survival of the other.

Living organisms are usually classified as consumers (animals), producers (plants), or decomposers (fungi), depending on how they get their food. Consumers are, either herbivores, carnivores, or omnivores. Herbivores are called primary consumers because the feed directly on producers. Carnivores feed on other consumers. Omnivores eat both plants and animals. However, animals are seldom completely carnivorous or herbivorous. Some carnivores, such as bears, foxes, and the family cat or dog, will at times eat plants. Herbivores will sometimes eat small insects or grubs as well.

Animism

Biological Philosophy term. Seeing natural objects and phenomena as "animated" by personal spirits. Natural forces like thunder and lightning, streams, trees, the ocean, are given personal existence and treated as gods or demi-gods.

Anisogamy

An Animal Behavior term, this is the situation where germ cells (gametes) differ is size, as found in all higher Animals, the female producing relatively few large eggs and the male many times that number of much smaller sperm.

Annelid

A type of segmented worm.

Annual

Referring to an organism that completes its life cycle from birth or germination to death within a year.

The life spans of flowering plants differ dramatically. The shortest-lived are the annuals, such as corn and sunflowers, which germinate, blossom, set seed, and then die in a single growing season. The biennials, such as carrots and mullein, need two years to mature; they germinate and store food in their first year, then blossom and die in their second. Longest lived are the perennials, which survive for more than two years. Some perennials-peonies, for example-appear to die at season's end, but their underground structures survive to send up new shoots the following spring. Trees and shrubs, in contrast, have permanent woody stems that grow larger with each passing year. A plant that lives for a single growing season.

Annuli

Darkened rings which indicate periods of slower horn growth; can be counted to measure Animal's age.

Anole

Anolis carolinensis

Able to turn from green to brown, green anoles often are mistaken for chameleons. (The true chameleons are old-world lizards.) Males supplement their color by fanning a bright red flap of skin on the throat. Found in swamps and woodlands of the Southeast, these eight-inch climbers have special hooked toe pads used for clinging to branches and even scurrying up walls. Welcomed around homes, anoles earn their keep by feeding on flies and mosquitoes.

Ant

Thriving in almost every dry-land habitat from deserts and beaches to forests and human homes, ants are well known for their industrious ways. Whether exploring for food, toting burdens from place to place, or excavating tunnels, they seem to be constantly busy. Like honeybees, ants are highly social insects and live in colonies that may include thousands of individuals. A colony begins when a winged, fertile female, the future queen, mates in flight with a male. The male then dies, while the female sheds her wings and, in the seclusion of a small burrow, lays her first eggs. The vast majority of her offspring are sterile females, the worker ants whose labors keep the colony going. Eventually, however, some of the eggs develop into males and young queens that mate to form new colonies. The queen does not in any sense "rule" her colony; she just keeps laying eggs, year after year, for the rest of her life, which may last as long as two decades. Ants have a variety of lifestyles. Nomadic army ants, for instance, have no fixed colonies; they march across the land in military columns, feeding as they go. Fungus-growing ants, sometimes called parasol ants, carry pieces of leaf over their heads like umbrellas; they use the leaves to feed the fungi they cultivate as food. Dairying ants "milk" aphids for a sugary secretion called honeydew, and slave-making ants steal pupae from the nests of other species, then raise the kidnapped victims as slaves. Most ants are harmless to humans, but a few are destructive. Carpenter ants can damage buildings by tunneling in the wood. And the imported fire ant builds unsightly nest mounds in pasturelands in the Southeast and attacks livestock with its powerful sting.

Antelope

See Pronghorn

Antelope ground squirrel

Scampering across the desert floor, these frisky little rodents curve their short tail over the back, exposing the white underside. The resemblance to the white rump patch of a fleeing pronghorn antelope accounts for their name. Although antelope ground squirrels are well able to withstand the blistering heat of southwestern foothills and canyons, sometimes they are forced to retreat to their burrows or smear their heads with saliva in order to cool off. Active all year round, they spend their days hunting for fruits, seeds, and insects.

Antennae

Slender, paired sensory organs on the head of an insect or crustacean. Sometimes called feelers, antennae are the paired sense receptors protruding from the heads of a variety of creatures, such as insects, centipedes, crabs, and lobsters. They are sensitive to touch, taste, smell, and in some cases light, temperature, and moisture as well. To animals that possess them, they are as important as eyes and ears are to us. An ant's antennae, for instance, are in constant motion, tapping the ground like a blind person with a cane, pointing into the wind to receive odors, sampling food before it enters the mouth, and greeting other ants with a kind of hello. Depending on species, antennae may look like anything from threads or strings of beads to knobs or gracefully branching feathers. They are usually equipped with thousands of tiny hairs, pegs, or pits that serve as receptors. Bedbugs use their antennae to sense warm objects. The antennae of male mosquitoes can detect the sound of a female's wing beats a quarter of a mile away, while those of moths can sense a mate's odor up to a mile away. Some creatures use their antennae for other purposes as well. Fleas grasp each other with their antennae while mating, certain beetle larvae capture prey with them, and spiny lobsters use them as whips against would-be captors.

Anther

A pollen-containing structure in a flower, located on the end of the male reproductive structure, the stamen.

Antithesis

An Animal Behavior term, this is a principle proposed by Darwin that Animal signals with opposite messages were also opposite in form. For instance, he contrasted a hostile Dog, with erect posture and tail and head held high, with a friendly one, crouching low with its tail between its legs.

Anthropomorphism

Biological Philosophy term. Seeing animals or the world itself as having human characteristics, particularly as having feelings and motives like those of human beings. Everything is like us. See Pathetic fallacy.

Anthropocentrism

Biological Philosophy term. Seeing the universe as centering on humankind, so that everything in the universe is for human beings. Everything is for us.

Antlered

Majestically crowning the heads of deer, moose, elk, caribou, and reindeer, antlers serve both as ornaments and as weapons-primarily among males competing with each other during the mating season. Though they are sometimes used to fight off natural enemies such as wolves, their main purpose is to assert dominance, by means of threats and clashes, over other males of the same species. Antlers first appear when the animal is one or two years old, and are shed and replaced annually. They begin growing in early summer from knobs on the skull and consist of dense connective tissue that later hardens into bone. At first they are covered by a thin, hairy skin called velvet, which allows blood to nourish the developing antlers. As the fall mating season approaches, the velvet dries out, becomes loose, and is scraped off by the animal. In late winter the antlers fall off. They begin growing again in early summer, and the cycle repeats itself. Horns-the headgear of bison, cattle, goats, and other animals-are different from antlers. Both are bony inside, but horns have a hard outer covering similar in composition to fingernails and lack the many spikes and branches that antlers have. Also, horns are not shed but remain on the animal throughout its lifetime.

Antlers

Bony structures that grow from short pedestals on the skull of certain ungulates and are shed annually. During their development the antlers are covered with a hairy skin called velvet which has a rich supply of blood vessels and nerves. Antlers grow from the tips rather than the base (like horns). As the season progresses the antlers become ossified or boney. This ossification finally cuts off the blood vessels and nerves killing the skin and making the antler itchy. This causes the Animal to rub the antlers which removes the skin and exposes the bony surface which has become shiny by the rubbing. Antlers of mature Animals tend to be large and ornate in relation to the Animal's body size. Antlers grow during the summer season and are fully developed by the fall. They are used by the males to assert dominance over other males during courtship rituals in the fall. By December many Animals start shedding their antlers. Shedding is caused by the reabsorption of some of the basal bone which weakens the joint so that the antler falls off if it is knocked.

Ant lion

A wily hunter, the ant lion traps unsuspecting prey in a self-made sandy lair. By moving around in circles in dry sandy soil and throwing sand grains to the side, the little creature, also known as the doodlebug, digs a funnel-shaped pit about two inches wide and one inch deep. Burying itself at the bottom, it lies in wait with only its long pincerlike jaws protruding. When an ant walks by, loose sand at the edge of the pit gives way and more is hurled up by the ant lion, causing the ant to lose its footing and tumble to the bottom. The ant lion then seizes its victim in its jaws, sucks out its juices, and tosses the empty carcass aside. In all, some 60 species of these curious creatures inhabit sandy areas throughout the United States, especially in drier sections of the South. Some, rather than building sand traps, ambush their prey from behind rocks. But whatever their habits, all ant lions are the larvae of delicate flying insects that resemble damselflies.

Aperture

Biology term. The opening of a snail's shell.

Aphid

Seldom more than an eighth of an inch long, aphids are soft-bodied insects that suck sap from plants. They are often known as plant lice because of the damage they do to crops, not only by drinking the sap but also by spreading diseases. Ladybird beetles and their larvae are among the many insect enemies that help keep aphid numbers in check. Some kinds, however, are protected by ants, which feed on honeydew, a sweet, sticky substance excreted by the aphids. The typical aphid's seasonal cycle begins in spring with eggs that have wintered on trees and shrubs. When the eggs hatch, only females are produced, and they in turn give birth only to females. Several generations are born over the course of the summer, with each aphid producing up to 50 daughters in her two or three weeks of life. Finally in the autumn some males are produced. They mate with females, who lay fertilized eggs that can survive the winter and so start the cycle anew the following year.

Appeasement

An Animal Behavior term, this is behavior which inhibits attack in situations where Animals cannot escape or, as during courtship, where it is advantageous for them to do so. Often opposite in form (see the term Antithesis), as well as in the message conveyed, from Threat Displays. Thus, Gulls hide their beaks when appeasing, and then show them in threat. Other appeasing postures derive from juvenile behavior and, in Monkeys, from sexual presentation posture of females. (see the term Lordosis)

Appetitive behavior

An Animal Behavior term, this is used to describe the active searching behavior shown by Animals seeking a goal and is contrasted with the Consummatory Behavior they show when they reach it. When hungry or thirsty, a Rat will explore actively until it finds food or water. Females of many species also become more active when in heat and this makes them more likely to come into contact with males.

Apple

Malus

No one who smells wild apple trees in bloom can ever forget their sweet perfume-George Washington planted some in the shrubbery at Mount Vernon just so he could savor their fragrance. Several species of these wildlings grow throughout the eastern half of the country and up the Pacific Coast from northern California to Alaska. All of our native varieties of wild apples are crab apples, which are relatives of the larger, domesticated apples grown in orchards. Our wild apples come into flower later than the orchard trees, with blossoms ranging from shell pink to pure white, depending on the species. All bear similar fruits, however: about an inch across, they are sweetly scented, hard, and usually a glossy yellow-green. Despite their appetizing aroma, they are too sour to eat out of hand (though deer, black bears, and ruffed grouse relish them). Pioneers made cider and an orange-red jelly from wild crab apples; they also used the trees as understock on which to graft the eating apples they imported from Europe. Nowadays the wild crab apples are more often planted as ornamentals.

Aquatic insects

Ponds and streams are home to an array of aquatic insects, both immature and adult. A few, such as black fly larvae, live attached to the bottom, but most move about in one way or another. Agile water striders skitter across the surface on long, slender legs. Also seen on the surface are large groups of whirligig beetles, which give the appearance of dancing in all directions at once. Back swimmers and water boatmen use their long, oarlike legs to paddle through the water, while dragonfly nymphs dart from place to place by forcing water from their bodies in a kind of jet propulsion. And caddisfly larvae drag along their own self-made mobile homes-neatly camouflaged tubelike cases made of sticks, bits of stone, or leaves. Like their counterparts on dry land, aquatic insects must be able to breathe, and they do so in a variety of ways. The nymphs of dragonflies, damselflies, and mayflies have gills that enable them to absorb oxygen dissolved in the water. The larvae of mosquitoes, in contrast, are snorkelers; they breathe through tiny tubes that reach up to the surface. Still others are like scuba divers, taking along their own oxygen supply; water boatmen, back swimmers, and many diving beetles carry bubbles of air next to their bodies whenever they descend to the depths. Feeding methods are equally diverse. Among the plant eaters are water boatmen, which scrape algae from underwater surfaces. Some of the caddisfly larvae spin silken nets that strain bits of food from the passing current. And many aquatic insects are predators. Dragonfly nymphs have hinged lower jaws that snap out to snatch passing prey, and giant water bugs use their powerful front legs to seize fish and tadpoles twice their size. Thanks to these and other adaptations, aquatic insects are able to thrive in fresh water nearly everywhere.

Aquatic plants

Growing in the water of ponds, swamps, and marshes, aquatic plants have developed a number of strategies for coping with their habitat. Different kinds, for example, are adapted for survival in water of different depths, thus taking advantage of every bit of living space. Plants such as cattails, anchored in mud near the water's edge, and arrowheads, growing in the shallowest water just offshore, are the most like land plants; their roots may be wet, but their leaves are raised out of the water and exposed directly to the sun. Water lilies and pondweeds grow in somewhat deeper water; long stems permit their leaves to float on the surface, faceup to the sun. At still greater depths are plants that grow completely underwater, such as the bladderworts and water milfoil. Finally, there are plants that have lost all connection with the bottom, such as duckweeds, water hyacinths, and even a few ferns; they float freely on the surface, dangling their roots below. The plants that live underwater typically have lacy or strap-shaped leaves-shapes that maximize the surface exposed to sunlight and which are also resilient, preventing damage from any movement of the water. Some of the emergent plants, such as many pondweeds, have bladelike leaves at or above the water's surface and lacy or strap like leaves below. The lacy leaves and stems of underwater plants allow them to absorb oxygen, carbon dioxide, and dissolved nutrients directly from the water. Thus the roots of these plants serve mainly to anchor them in place. Many aquatics have air pockets between the tissues of their stems and leaves, which helps keep them floating. In the case of the water hyacinth, air pockets in the swollen stem serve as pontoons that keep the entire plant afloat. Aquatic plants also rely on water as a medium for dispersal. Some colonize by simply drifting along the surface. Others, such as water lilies, have floating seeds. Sweet flag often spreads by means of broken bits of root that grow into new plants, and waterweed does so with bits of the plant itself.

Aquifer

Layers of porous rock, such as sandstone, retain water that seeps into them from the surface. Resting on impermeable rock layers that prevent the water from flowing any deeper into the earth, these formations, known as aquifers, are capable of holding tremendous quantities of water and serve as natural underground reservoirs. Indeed, wells drilled into aquifers are the primary water source in many areas.

Arboreal

Tree-dwelling.

Arborvitae

Thuja

Slow-growing and long-lived, arborvitaes are handsome conical evergreen trees with fanlike sprays of branchlets sheathed in scaly foliage. Some say that their name, which means tree-of life, refers to their longevity. Others claim the name was provided by the 16th-century French explorer Jacques Cartier; while wintering in Canada, he and his crew were saved from scurvy by a vitamin-rich tea brewed from the tree.

Two species of arborvitae are native to North America. The giant arborvitae, also known as western red cedar, grows in moist soils in the mountains of the Pacific Northwest. Sometimes reaching heights of 200 feet, it has coarse, lightweight wood that is nearly impervious to insects and decay. Indians used it for making canoes, and it still is unexcelled for shingles and siding. Smaller but extremely hardy, the eastern arborvitae, or northern white cedar, is found in swampy areas from Maine to North Carolina. Its wood is valued for poles, fence posts, and lumber, and an oil distilled from its twigs has been used for medicinal purposes.

Arete

The rugged beauty of the Rockies, Cascades, and other glaciated mountains is enhanced by sharp-edged ridges called aretes. They were formed by the continued erosion of adjacent cirques-steep-sided, bowllike, glacier-carved amphitheaters. Glacial erosion enlarged the abutting cirques until finally they were separated only by the narrow, knife-edged wall of rock.

Armadillo

Dasypus novemcinctus

Looking more like a scaly lizard than a furry mammal, the nine-banded armadillo trots about in search of insects, digging them out of the ground or scraping them from leaf litter with its stout claws. The creature, 2 V2 feet long when fully grown, has little to fear from most predators, for its body, head, and tail are encased in hard, bony plates. Its name, bestowed by the Spanish conquistadores, means, "little armored one." In fact, armadillos occasionally defend themselves by curling up into armor-plated balls, but more often they flee to their burrows or dig a new one on the spot. The young are born in spring, with each female always producing a litter of identical quadruplets. The babies are soft shelled at birth, but the bony plates quickly harden, and with eyes already open, the young can walk within hours. Once found only west of the Mississippi, in Texas and neighboring states, armadillos in this century have greatly expanded their range. Nowadays these comical-looking creatures can be seen all the way east to Florida.

Arrowhead

Sagitta ria

Handsome aquatic plants, arrowheads are distinguished by their three-petaled white flowers borne in whorls of three. The commonest species, broad-leaved arrowhead, has extremely long, arrowhead-shaped leaves. But other kinds have leaves that are oval or even strap like, with no resemblance to arrowheads at all. The plants' potato like tubers, once favored foods of many Indian peoples, are responsible for such alternate names as water nut and duck potato.

Arroyo

Steep-sided, flat-bottomed channels are among the characteristic landforms of arid regions, where rainfall is scant and evaporation rapid. Known in the Southwest as arroyos or dry washes, they are the beds of ephemeral streams. Water rushes briefly, often torrentially, down the channels after desert downpours, and then, usually within hours, the streams dry up again. In parts of the Southwest, rain is so infrequent that the arroyos remain dry for most of the year.

Artesian well

Naturally pressurized, artesian wells can produce spectacular jets of water, much like the oil spurting from a gusher. They occur in places where a downward-sloping water-bearing rock layer (an aquifer) is sandwiched between two impermeable rock layers. Rainfall soaks into the upper end of the aquifer, resulting in tremendous water pressure at lower levels. If a well is drilled into the aquifer, this pressure causes water to flow to the surface. Whether drilled by man or flowing naturally through fissures in the earth, artesian wells and springs are important water sources over parts of the Great Plains and in many other areas.

Ash

Fraxinus

Popular shade and timber trees, ashes of several kinds grow throughout the United States. Most are tall, sturdy trees that typically bear featherlike compound leaves in opposite pairs. The trees also produce one-seeded fruits with single, elongated, papery wings that catch the wind. The most common and valuable of the 16 North American species is white ash. Its tough, pliant wood, ideal for baseball bats and other sporting equipment, is also used for tool handles and cabinetmaking. Herbalists and American Indians believed the tree had medicinal properties: tea made from its bark was recommended for a variety of ailments, and its seeds were valued as an appetite stimulant and fever remedy. Blue ash, another species with both decorative and practical uses, is named for the dye derived from its inner bark. A fast-growing, long-lived tree, it can be found in the limestone soils of the Midwest. Much more familiar is green ash, which takes its name from the color of its twigs. The most widely distributed of all the ashes, green ash thrives in moist soils along streams. It is especially abundant in the Mississippi Valley, where its seeds are an important food for quail, turkey, and rodents. Another common species, the black ash, also favors damp places and is named for its dark, almost black, buds. Like some of the other ashes, its wood is often split into strips for weaving into baskets and chair seats.

Aspen

Every breeze makes the aspens come to life with quaking foliage, for their leaves, suspended on long, ribbon like stems, are set to trembling by even the slightest movement of the air. In spring and summer the leaves shimmer with a shiny green on top and a paler gray-green on their undersides, and in the fall they have a luminous golden glow. The aspens' bark, smooth and pale, is often marred with deep black scars- the remnants of claw marks left by passing bears. The trees also are attractive to beavers, which eat the soft inner bark and use the trunks and branches when building their dams and lodges. Foresters classify the fast-growing aspens as "pioneer" trees, since they are among the first to return to abandoned fields and areas scorched by fire. Soft-wooded and brittle, they are of little commercial value but play an important role in anchoring the soil until other trees can reestablish themselves. Only two species of aspens grow in North America. The quaking aspen is common all across the West and Northeast; its taller relative, bigtooth aspen, is found only in the Northeast.

Assemblage

Bird Biology Avian Conservation term.

A set of organisms whose pattern of organization (with respect to competition, predation, mutualism, etc.) is unknown.

Association

Bird Biology Avian Conservation term.

A group of species living in the same place at the same time.

Assortative mating

An Animal Behavior term, this is used mating in which an individual chooses a mate non-randomly in relation to its own characteristics. If positive, the mate chosen is like itself, if negative, it is unlike itself.

Aster

Taking their name from the Greek word for star, asters do indeed shine brightly, especially in the fall. Although some kinds begin to bloom as early as July or August, the brightest displays of these blue-, white-, or purple-flowered perennials come in September and October. Because the peak of bloom often occurs around the feast of St. Michael, on September 29, our ancestors used to call them Michaelmas daisies.

Asters are found around the world, with more than 100 species native to North America. Almost every state boasts 20 to 30 different kinds, though telling one species from another can be a challenge even for the specialist. Adaptability is one reason for their success: purple New York asters, for instance, can survive even in salt marshes, while others, such as the white heath aster, prefer the parched western plains. Among the most beautiful of all is the New England aster, which, despite its name, flourishes as far south as the Carolinas and westward beyond the Mississippi. Growing to heights of six feet or more, it is covered with masses of two-inch pink to brilliant purple flowers that are true stars of the autumn.

Atlas

Bird Biology Avian Conservation term.

The result of a comprehensive survey of a large geographical area that maps the occurrence (or occurrence and relative abundance) of species in subdivisions of that area. An atlas is usually based on a grid of fixed intervals of distance or degrees latitude and longitude. It is restricted to a particular season of the year, usually the breeding season.

Atmosphere

Compared to the size of the earth, the atmosphere-the layer of air surrounding our planet-is but a thin mantle. Indeed, 99 percent of the air is concentrated within just 20 miles of the earth's surface. Far from uniform, the atmosphere consists of concentric envelopes of air that differ in temperature and composition. The lowest layer, the troposphere, contains about 80 percent of the world's air. Ranging in thickness from 6 to 10 miles, it is the arena in which winds and clouds make up what we call weather. Air temperature in the troposphere decreases with altitude until it reaches a low of about -70OP. Extending up for another 20 miles above the troposphere is the stratosphere, where the temperature rises again to about 32°. Here the sun's rays react with oxygen to form the ozone layer, which serves as a barrier protecting life on earth from damage by the sun's ultraviolet radiation. Higher still is the mesosphere, also 20 miles thick, where temperatures rise and then fall again. Next, some 400 miles high, is the ionosphere, where the sun's rays bombard what little air there is, heating it to more than 1000° and producing electrically charged particles called ions. This ion layer reflects radio waves, enabling us to "bounce" signals around the world. Beyond the ionosphere and extending for thousands of miles into space is the exosphere. There the air molecules are so few and far between that they rarely collide with each other; sometimes they even escape the earth's gravity altogether and drift off into outer space.

Atmospheric science (Science and Technology)

Atmospheric science is the study of the atmosphere, hydrosphere, cryosphere and related environments.

Attention

An Animal Behavior term, this is used to describe a state in which an Animal is more responsive to one aspect of its environment that to others. Experiments have shown that Animals may attend to and learn about some features of a situation and ignore others which are less relevant to them.

Auk

Found only in northern oceans, the 22 species of auks are stocky seabirds that stand upright like penguins. All members of the family are expert divers that use their short wings both for flying and as flippers for swimming in pursuit of fish, shrimp, and other prey. Most auks dress in basic black and white, but during the nesting season a few sport white or yellow plumes on their heads, and puffins are decorated with large, colorful bills. Auks range in size from the 6-inch least auklet of the Bering Sea to the 19-inch thick-billed murre. The giant of the family was the flightless great auk of the North Atlantic; extinct since 1844, it stood 30 inches tall. Auks spend most of the year at sea and come to land only to breed on rocky coasts or offshore islands. Some nest in burrows, others on rocky ledges; the marbled murrelet of the Pacific Northwest sometimes nests in trees. With their seafaring way of life, flipperlike wings, black-and-white plumage, and erect posture, auks are the northern counterparts of the Southern Hemisphere's penguins.

Aurora borealis

Assuming a variety of forms, the sky spectaculars known as the aurora borealis may appear as an eerie grayish glow, as flashing, fanlike bands of green, or even as a dazzling array of multicolored pleats of light draped across the heavens. Also known as the northern lights, the displays are brightest and most dramatic in the far north but are sometimes visible in the lower 48 states. They occur most frequently at times of heavy sunspot activity and are caused by charged particles from the sun hurtling toward the earth's magnetic poles. High in the atmosphere, these particles collide with molecules of air, releasing energy in the form of light. The same spectacular phenomenon takes place near the South Pole, where it is referred to as the aurora australis, or southern lights.

Autumn

Autumn (also known as Fall) is one of the four temperate seasons. It is the transition from Summer into Winter. In America, autumn is the season during which most crops are harvested and trees lose their leaves. It is also the season where days rapidly get shorter and cooler, the nights rapidly get longer, and of gradually increasing precipitation in some parts of the world. Astronomically, some Western countries consider autumn to begin with the September equinox in the Northern hemisphere and the June solstice in the Southern hemisphere. Such conventions are by no means universal, however. Meteorologists count the entire months of March, April and May in the Southern hemisphere, and September, October and November in the Northern hemisphere as autumn.Although the days begin to shorten after the Summer equinox, it is usually in September (Northern Hemisphere) or March (Southern Hemisphere) when twilight becomes noticeably shorter and the change is more abrupt in comparison with the more lingering ones of summer. Autumn is often defined as the start of the school year, since they usually begin in early September or early March. Either definition, as with those of the seasons generally, is somewhat flawed because it assumes that the seasons are all of the same length, and begin and end at the same time throughout the temperate zone of each hemisphere.

Many ancient civilizations computed the years by autumns, noting Autumn's association with the transition from warm to cold weather, and its related status as the season of the primary change from Summer into Winter, i.e., a New Year. This view has dominated in many themes and popular images. In Western cultures, personifications of Autumn are usually pretty, well-fed females adorned with fruits, vegetables and grains that ripen at this time. Most ancient cultures featured autumnal celebrations of the harvest, often the most important on their calendars. Still extant echoes of these celebrations are found in the late-Autumn festivals and holidays. One holiday with its roots as a full moon harvest festival is that of "tabernacles" (huts wherein the harvest was processed and which later gained religious significance), the many North American Indian festivals tied to harvest of autumnally ripe foods gathered in the wild, the Chinese had similar celebrations, as did many others. The predominant mood of these autumnal celebrations is a gladness for the fruits of the earth mixed with a certain melancholy linked to the imminence of harsh weather. Remembrance of ancestors is also a common theme.

Avalanche

The sudden, thundering slide of snow and ice down a mountainside is among nature's most terrifying spectacles. Called an avalanche, it can be triggered by the vibrations from a loud noise or the melting of packed snow by spring rains. Many avalanches occur after heavy snowfalls, when a slick surface develops between the new precipitation and the older snow. In some cases the old snow begins to form dense crystals beneath the new, causing the mass of snow to sweep downhill as if on ball bearings. The cascade of snow sweeps along rocks, soil, trees-anything in its path. Wet avalanches, formed of dense, slushy snow, are treacherous due to their enormous weight and their tendency to freeze upon impact. But dry avalanches, consisting of airborne, powdery snow, are the most devastating-sometimes racing down mountains at over 100 miles per hour. Avalanches are a serious danger to skiers, climbers, buildings, and anything else standing in their way. In order to avert disaster, they often are triggered intentionally at opportune moments, letting the snow slide when it can do the least damage.

Avalanche lily

See Dogtooth violet.

Avens

Geum

Unlike their showy cousins the roses, the avens are rather modest wildflowers. Their blooms, usually an inch or so across, come in yellow, orange, or white. Nodding from stalks one to four feet tall, the flowers of many species mature into burrlike fruits equipped with hooks that hitch a ride by clinging to clothing or to the fur of animals. The long-plumed avens, in contrast, produce fruits with long wispy hairs; reminiscent of feather dusters, they have inspired such colorful alternative names as prairie smoke and old man's whiskers.

Though the various kinds of avens differ in the habitats they prefer and in their seasons of bloom, all share one characteristic-a thick, aromatic root. Indians and colonists boiled the root in water, then added milk and sugar to make a chocolate-flavored drink. Home-brewed ale was laced with avens root, both for the spicy zest it imparted and because it kept the beer from souring. The root was also mixed with wine to produce a cure-all tonic that, as one 19th-century herbalist put it, "restores to health the most shattered and enfeebled constitutions."

Avocet

Recurvirostra americana

Boldly patterned in black and white, American avocets are long-legged, duck-sized shorebirds with slender, strikingly upcurved bills. They are found mainly in the West; where they inhabit marshes and shallow lakes, but occasionally summer on brackish lagoons along the southern Atlantic coast. Avocets use their upcurved bills to forage in a special way that enables them to take food other shorebirds miss. Sweeping their bills back and forth just beneath the water's surface, they catch tiny crustaceans, aquatic insects, and drifting seeds, located with their acute sense of touch. During the breeding season avocets lay three or four eggs in a shallow depression in sand or on firm mud near the water's edge. They provide little in the way of a nest lining, but if the water level rises, the birds quickly build up the nest with sticks or any other debris they can find in order to keep the eggs from being flooded. Often several pairs nest in loose colonies and will come to each other's defense by mobbing any predator that comes too near. Both male and female share in tending the eggs; the male does most of the incubating during the first week, and then the female takes over. The young are downy at hatching and, with their tiny webbed feet, manage to begin diving and swimming within a matter of hours.

Awn

A bristle found in flowers of many grasses.

Axil

The angle where upper surface of a leaf meets the stem on a plant.

Azalea

Rhododendron

Found in a kaleidoscope of brilliant colors, wild azaleas, like their cultivated cousins, are prized for their showy flowers. Often among the first to bloom in spring, these beautiful shrubs add splashes of white, pink, yellow, orange, red, and even lavender to the woodland environments that they prefer. Some of the native azaleas are known as wild honeysuckle, and their funnel-shaped flowers, with long, protruding stamens, do resemble the blossoms of that familiar vine. One pink-flowered species, the Florida pinxter, even mimics the honeysuckle's perfume. Unlike their relatives, the evergreen rhododendrons, which retain their elegant foliage all year round, most azaleas shed their leaves in winter. The only species native to the Pacific Coast is the western azalea, a colorful shrub that flourishes from southern Oregon to southern California. Eastern North America, on the other hand, offers a wider variety of wild azaleas than any other region of the world, with a total of 18 different species.

Back swimmer

Swimming upside down in freshwater ponds and streams and using their long hind legs as oars, back swimmers look very much like tiny rowboats. They often are seen just below the surface and can remain underwater for hours on end because, like scuba divers, they carry along their own supply of oxygen-a bubble of air trapped among hairs on the body. Although they are only half an inch long, back swimmers are fierce predators, willing to attack small fish and tadpoles as well as insect prey. Piercing their victims with their sharp beaks, they suck out the body fluids. They also can pierce a human finger if handled carelessly, causing a painful sting.

Bacteria

Probably the most widespread of living things, bacteria are also the most abundant. A spoonful of garden soil may contain 100 billion of these Single-celled microscopic organisms. Able to survive almost everywhere on earth, some kinds live in the steaming water of hot springs, while others thrive on glacial ice.

Bacteria are responsible for a variety of diseases, such as cholera, tuberculosis, tetanus, and typhoid fever. In plants they cause many kinds of blights and wilts. They are, however, crucial to the existence of all other forms of life. Many benign bacteria inhabit the intestines of animals, helping to digest food and supplying essential vitamins. Others speed the process of decay, recycling nutrients and making them available once again to plants. Still others convert nitrogen from the air into a form that plants can use. Some are even used to prepare foods, including yogurt, certain cheeses, and sauerkraut. Without the ubiquitous bacteria, life as we know it could not exist on earth.

Badger

Taxidea taxus

Found in deserts and grasslands from Ohio to the Far West, badgers are chunky, short-legged members of the weasel family. They grow to about two feet long and can weigh as much as 25 pounds. Except for black feet and black-and white facial markings, their coarse fur is yellowish gray and once was used for making brushes.

Active mostly by night, badgers hunt all year round, although they stay underground in their burrows during the severest winter weather. Their sturdy front claws enable them to dig rapidly-so fast, in fact, that these digging dynamos can escape predators by excavating a burrow right on the spot. Their food consists mainly of small mammals such as mice and ground squirrels, but birds and insects are also taken. It has been reported that badgers may actually form special hunting partnerships with coyotes. The coyote uses its keen sense of smell to locate an underground rodent, the badger digs the animal out, and the two then share the meal.

Mating occurs in summer or early fall, and up to five young are born the following spring on a bed of dry grass in the den where the mother has spent the winter. They are weaned in about six weeks but remain with the mother for several months before setting out on their own.

Badlands

Sharp, toothlike ridges and steep, V-shaped gullies etched into barren, semiarid hills make for "bad lands to cross." And that is exactly how Indians and fur traders long ago described the rugged, nearly impassable terrain covering a vast stretch of southwestern South Dakota. Found in several other places on the Great Plains, these moonscapes were formed by flash floods that stripped away surface soil and vegetation, then gnawed away at layers of weak, easily eroded rock. Our most extensive and scenic badlands area, encompassing hundreds of square miles of spectacular, multicolored cliffs, has been preserved in Badlands National Park in South Dakota.

Bait shyness

An Animal Behavior term, this is used to describe the failure of pest Animals to eat poison put out for them. This may stem partly from neophobia and partly from the avoidance Animals show for foods that have previously made them sick.

Balance of Nature

Biological Philosophy term. The idea that nature, undisturbed by human beings, achieves an ideal balance of different species, that, until it is disturbed, it remains in balance, and that it returns to that state after the disturbance. This is connected to the notion, left over from the time of belief in The Great Chain of Being, that every creature has its place in the harmonious workings of nature and is well adapted to its niche. The mythic notion of constancy survived into a more scientific age, because ecologists were unconsciously applying to ecosystems the physicists' and mathematicians' notions of the stability of mechanical systems. See Carrying Capacity.

Bald cypress

Taxodium distichum

Unlike most conifers, this handsome relative of California's giant redwood is deciduous: in autumn the bald cypress sheds its feathery foliage and remains bald throughout the winter. Equally unusual are its knees, twisted knobs of wood that rise from the roots and stand three or four feet above the surface of swamps, where the tree grows best. Botanists speculate that these strange protuberances may supply air to the bald cypress's waterlogged roots, or perhaps they help to stabilize it on its muddy bed. A characteristic tree of southern wetlands, the bald cypress is typically festooned with silvery clumps of Spanish moss. Common from Florida to eastern Texas, it also ranges as far north as Delaware and up the Mississippi Valley to southern Indiana. The largest tree in swamps throughout its range, it sometimes reaches a height of 150 feet, with a diameter of 12 feet near the base of its swollen, buttressed trunk. Not surprisingly, the wood of this swamp dweller is extraordinarily resistant to decay. Sometimes known as the "wood eternal," bald cypress is valued for uses ranging from greenhouse construction to railroad ties.

Baneberry

Actaea

Clusters of attractive white or crimson berries crown the knee-high stalks of baneberries. But as their name suggests, the pea-sized fruits of these widespread woodland perennials are poisonous. Mice and ruffed grouse eat them with no ill effect, but they can be fatal to humans. Pretty, too, but harmless, puffs of feathery white flowers top the plants from midsummer into fall. The blossoms make the baneberries an appealing choice for woodland gardens and shady spots in rockeries. In many areas the white-fruited baneberries are called doll's eyes because their glossy, ivory colored berries, each marked with a single black spot, seem to gaze up like the eyes of an old-fashioned china doll. Since they also look as if they could be strung on a thread, the plants are known as white beads and necklaceweed as well.

Barberry

Berberis

Attractive throughout the year, the common barberry produces dangling clusters of yellow bell-shaped flowers in the spring. Throughout the summer it wears a cloak of dense green foliage that turns to red in fall. Then it drops its leaves to expose an array of bright red berries that remain on the shrub well into winter. The barberry was imported from Europe in colonial times. Because of its fierce armament of spines, farmers planted it in hedges to protect their fields, and early settlers used its yellow sap for dye and made jellies from the berries. Ironically, this plant is now recognized as an enemy of agriculture. Because it serves as an alternate host for black stem rust, a fungal disease that attacks wheat, oats, rye, and barley, it has been the target of repeated attempts at eradication. In 1726 the colony of Connecticut passed a law calling for its elimination, and now most grain-producing states prohibit its cultivation. Not all the barberries are a bane, however. The Japanese barberry, a popular ornamental, is completely immune to black stem rust.

Bark

The appearance of its bark gives each tree a distinctive signature-so much so, in fact, that experts can identify some trees by their bark alone. Unmistakable, for instance, are the mottled, flaky patterns on sycamore bark and the vertically peeling skin of the shagbark hickory. Bark acquires its telltale textures and patterns because trees, as they grow, become too big for their skins, causing the bark to give way under pressure. And each species has its own way of splitting, peeling, flaking, or shredding on the surface as new bark is added underneath. Botanists distinguish between two layers of bark-the tree's visible outer skin and a soft, thin layer of inner bark. The inner bark is made up of living cells that transport sugars from one part of the tree to another; the much thicker outer bark is composed of dead cork cells that protect the delicate inner tissue. Outer bark must be waterproof to prevent dehydration and tough enough to protect the tree against insects and disease, as well as sun, wind, rain, and ice. For some trees, especially in arid western forests, bark may also serve as fireproofing. Ponderosa pines, for instance, often go unscathed in forest fires thanks to their two-inch armor of corky bark, and the thick reddish bark of the giant sequoias is virtually impervious to flame.

Bark beetle

Sometimes called engraver beetles, these small black or brown cylindrical insects and their larvae dig intricately patterned networks of tunnels beneath the bark of hickories, pines, firs, and many other kinds of trees. The adults first excavate brood galleries, with the females laying eggs at intervals along their lengths. When the eggs hatch, the larvae dig tunnels that branch out in distinctive patterns. After transforming into adults, the beetles emerge from holes at the ends of their tunnels. Some species of bark beetles live only on dead wood, while others attack living trees. Among the most destructive are the elm bark beetles, which transmit Dutch elm disease. The insects themselves do little damage, but they carry a fungus that blocks the elms' water- and sap transporting vessels, causing the trees to die.

Barnacle

Firmly attached to piers, boats, driftwood, seaside rocks, and even whales, barnacles seem as immovable and eternal as the sea itself. Once thought to be cousins of shellfish, they actually are more closely related to lobsters and crabs. They begin life as free-swimming larvae, then glue themselves to underwater surfaces by means of a powerful self-made cement. After forming their limestone shells, barnacles remain fixed to the same spot for the rest of their lives. Only their feathery legs ever protrude from the shell; swaying in the water, they sweep food into the creature's mouth. At low tide, clusters of goose barnacles, looking much like the heads of geese on long, leathery necks, can be seen attached to log pilings. The other familiar type, acorn barnacles, resemble tiny volcanoes and usually encrust rocks. One species of acorn barnacle, found near Puget Sound in Washington, grows to the size of a layer cake and is prized as food.

Barn owl

Tyto alba

Truly creatures of the night, common bam owls spend the day sleeping in hollow trees or hidden among dense foliage. At dusk they venture out, flying silently with mothlike wing beats, to hunt for mice and voles. Aided by facial feathers arranged to channel sound into the ears, their hearing is so acute that the birds can locate and capture prey even in total darkness. As their name implies, bam owls often nest in barns or other buildings, but they also use natural cavities. A clutch consists of anywhere from 3 to 11 eggs, depending on the availability of prey. Since incubation begins as soon as the first egg is laid, each brood includes young of several sizes. If food is scarce, it is the younger nestlings that starve, leaving the older and more aggressive offspring to perpetuate the species. Although bam owls are usually secretive, during the breeding season they proclaim their presence with loud bill snapping during courtship flights. And, as if to announce their coming of age, the young hiss and squeal noisily just before leaving the nest to set out on their own.

Barometric pressure

We live at the bottom of an ocean of air extending many miles into the sky. And the weight of all that air pressing down on us, called barometric pressure, is constantly changing, becoming heavier or lighter depending on the density of the air above us at any given moment. One device that is commonly used to measure atmospheric pressure is the mercury barometer. It does so by balancing the weight of the air with the weight of a column of mercury in a calibrated vertical tube. The top end of the tube is sealed, creating a vacuum, while the bottom end is open, allowing some of the mercury to spill out into a cup exposed to the pressure of the air. When atmospheric pressure rises, the mercury is forced higher into the tube; when it falls, the mercury drops. On the average, air pressure at sea level is 14.7 pounds per square inch, the equivalent of about 30 inches of mercury. A rising or falling barometer indicates impending changes in the weather. Low pressure is associated with clouds and storms, and high pressure with fair skies. Barometric pressure also decreases at higher elevations because less air is pressing down from above.

Barracuda

Sphyraena

It would be hard to mistake a barracuda for any other fish. Torpedo-shaped, with large knifelike teeth and a protruding lower jaw, these fearsome hunters roam warm coastal seas and occasionally venture into deeper water offshore. As they skirt the shallows in search of prey, barracudas are frequently attracted by the glint of moving objects. Many fishermen, reeling in their lines, have seen the steely flash of a barracuda as it slashes at their catch. Divers and swimmers also may be startled by these insistent marauders, though attacks on humans are rare. The Pacific barracuda and the great barracuda, the commonest species, are both fast, voracious predators. Found off the Atlantic and Gulf coasts, great barracudas are the largest of the group, occasionally reaching 6 feet in length. While they are sometimes caught for food, they often carry a toxin that has been known to cause fatal poisoning. Not all barracudas, however, are poisonous; Pacific barracudas, which range from Alaska to California, are a popular food fish on the West Coast.

Barrier island

In the shallow water along some seacoasts, waves and currents deposit long narrow ridges of sand called barrier islands. Standing as buffers between the mainland and the open sea, they are backed by quiet lagoons. Padre Island in the Gulf of Mexico and Hatteras Island, North Carolina, are well-known barrier islands. Though often anchored by vegetation, barrier islands are constantly battered by winds and water; some last only a few years, others a few thousand.

Basalt

Dark and fine-grained, basalt is the most common of all volcanic rocks. It forms when lava rich in iron and magnesium oozes through fissures in the earth's crust and solidifies on the surface. The mineral content of the lava causes the rock's dark color, and rapid cooling on the earth's surface results in its fine texture. Basaltic lava may pile up in the form of volcanoes or create lateral fissure flows that flood vast areas.

Basswood Tilia

When our several species of basswoods come into bloom in early summer, they are enveloped in fragrance and abuzz with the humming of hundreds of honeybees. The trees, in fact, often are called bee trees, since their plentiful nectar produces an especially delicious honey. Also known as lindens and limes, basswoods are popular ornamental and shade trees. Because they are relatively unbothered by diseases or air pollution, they are a familiar sight along city streets in many parts of the country. The trees' fibrous inner bark was traditionally used for making rope, and the soft, white, easily worked wood is excellent for carving. Animals such as rabbits and deer eat both the buds and twigs, while birds and squirrels feed on the dangling clusters of pea-sized fruits.

Bauxite

Named for Les Baux, France, where it was first discovered, bauxite is the ore from which most aluminum is made. It comes in various forms, which may be as soft as dirt or as hard as rock, and its mottled surface is often dotted with pealike spheres. The color also varies; depending on the presence of impurities in the ore, it can range from brown or red to pink or ivory. When wet, soft bauxite gives off a strong smell of fresh earth or clay. Composed mainly of aluminum hydroxide, bauxite deposits are found near the earth's surface and are formed by the weathering of aluminum-rich rocks. The ore is mined with earth movers and dynamite, then shipped to processing plants, where it is refined and smelted into aluminum. Though a number of states contain deposits, most of the bauxite mined in this country comes from Arkansas.

Bayberry

Myrica

Shrubs or small trees that bear clusters of small grayish fruits covered with an aromatic wax, bayberries are also known as wax myrtles and candleberries. The wax can be extracted by boiling the berries in water and has long been used for making scented candles, soap, and sealing wax. The resinous, leathery leaves are sometimes brewed into a tea that herbal healers have traditionally recommended for a variety of illnesses, and the bark of some species is used in a medicine prescribed to ease swelling. The northern bayberry, a shrubby species, is found in the northeastern states, mainly in sandy seaside areas. The southern bayberry, often growing to tree size, ranges from New Jersey south and west to eastern Texas. The Pacific bayberry, yet another well-known species, has dense, shiny evergreen leaves and thrives along the coast from Washington to southern California. Like all the bayberries, its fruits are eaten by myrtle warblers and several other birds.

Bayou

Derived from a Choctaw Indian word meaning stream, bayou is a term applied to some sections of swampy wetland in the Gulf Coast region, especially in Louisiana, Mississippi, and Texas. Often occupying abandoned river channels or oxbow lakes, bayous are filled with shallow, slow-moving, or even stagnant water. Bald cypress trees rise from the sluggish waters, where river otters, amphibians, alligators, and other wildlife reside. Bayou Lafourche, southwest of New Orleans, is among the most extensive of these characteristic southern swamplands.

Bear

Ursus

Of America's three kinds of bears-black bears; brown, or grizzly, bears; and polar bears-the most familiar and most widely distributed are black bears. Our smallest species, averaging about 300 pounds, they inhabit forests and mountainous areas across much of North America. Despite their name, their color varies from cinnamon to black, with a white race found in far western Canada.

The brown, or grizzly, bears once flourished throughout the western half of the continent, but today they are confined to Alaska, western Canada, and wilderness areas south of the Canadian border in the Rocky Mountains. Up to 9 feet from snout to tail and weighing more than 1,600 pounds, Alaskan brown bears are the world's largest flesh-eating land mammals.

The great white polar bears, weighing as much as 1,000 pounds, seldom venture far south of the Arctic Ocean. Accomplished swimmers, they are well adapted for hunting seals on frigid ice floes. Like all the bears, they are very dangerous when threatened or alarmed.

Bears feed on almost anything that is edible and are as fond of berries, roots, and leaves as they are of rodents, fish, and carrion. In the fall they begin to gorge on rich foods in preparation for their long winter sleep. While bears are not true hibernators, they spend the colder months sleeping in dens dug in hillsides, under trees, or in other protected spots. The females give birth to their young in these snug winter nests. The cubs-usually twins-are tiny, blind, and helpless at birth and remain with their mothers for a year or more.

Bearberry

Arctostaphylos uva-ursi

A ground-hugging evergreen shrub with leathery, oval leaves, bearberry ranges across much of North America, forming dense carpets over barren, sandy soils. Clusters of tiny pink or white urn-shaped flowers adorn its branches in spring, and it is decorated in winter with brilliant red berries eaten by birds and bears. Though rather bland and mealy, the fruits are nourishing and were consumed by native Americans, who also mixed the dried leaves with tobacco for smoking. Recommended by herbalists for many ailments, the leaves do in fact contain an astringent that is effective in treating problems of the urinary tract.

Beardtongue

Penstemon

Named for the tuft of colored "whiskers" on the flowers' tonguelike fifth stamen, beard tongues are attractive wildflowers found in most of North America. The trumpet-shaped blossoms may be tiny or up to two inches long; they come in a rainbow of hues, enlivening grasslands and deserts with welcome splashes of color. Some, such as mat beardtongue, are low growers, but most are upright, robust plants topped with clusters of flowers. A large and complex group, the beardtongues are hard to identify precisely, challenging even the experts.

Bear grass

Xerophyllum tenax

Unmistakable and unforgettable, bear grass produces handsome, rounded clusters of creamy white, starlike flowers atop sturdy stalks up to six feet tall. Stands of them, swaying in the breeze, are a common sight in open woodlands and alpine meadows on many northwestern mountains. A closely related species, turkey beard, grows in dry, sandy areas, such as pine barrens, in some of the eastern states. Tufts of long, grasslike leaves, normally tough and unpalatable, grow from the base of the plant. In spring, while still young and tender, they are eaten by bears-hence the name bear grass. Other names include basket grass and squaw grass, alluding to the fact that Indians wove the leaves into clothing and baskets.

Beaver

Castor canadensis

The master builders among North American mammals, beavers were busy erecting their complex dams and lodges while early humans still lived in caves. Propped up by their scaly, paddle-shaped tails, these animal engineers use their chisel like teeth to cut down aspens, willows, and other trees. (The pointed stumps they leave behind are unmistakable signs of their presence.) The logs are then used to dam a stream, creating a shallow pond in which the beavers build a dome-shaped lodge of branches, rocks, and mud. One family, including a pair of adults and several offspring, lives in each lodge. By day they stay inside; at dusk they leave through an underwater exit to cut down more trees, feed on the tender bark, and store branches on the bottom of the pond to serve as a winter food supply. Growing to three to four feet in length and weighing as much as 60 pounds, beavers are our largest rodents. The hind feet are webbed for swimming underwater, where beavers may remain for as long as 15 minutes at a time. At the first sign of danger, an alarmed beaver warns its fellows by slapping the water with its tail as it dives to safety. By the late 19th century, beavers had been trapped to near extinction for their lustrous brown fur. Now protected by law, they have made a dramatic comeback in recent years and are found all across the continent. Some people even consider them a nuisance when their dams flood roads or cropland. But many more praise beavers as water conservationists that also create living space for other animals and plants.

Bedrock

The solid rock which lies buried beneath soil, sand, or gravel (but which in some areas stands exposed at the earth's surface) is known as bedrock. While the type of rock differs from place to place, bedrock is found everywhere and helps determine the contours of the landscape.

Bedstraw

Galium

Sweet-smelling plants that often grow in sprawling mats, bedstraws have a long and varied history of use. According to one legend, the Virgin Mary laid a thick cushion of bedstraw in the manger at Bethlehem. American colonists used the plant as a mattress stuffing, and herbalists have prescribed bedstraws for everything from fading freckles to eliminating kidney stones. Many kinds of bedstraws grow throughout the United States, preferring moist woods and meadows. Most have bristly stems, produce clusters of small white flowers, and bear whorls of four to eight lance-shaped leaves. Cleavers, the best-known species, is named for the prickly little hooks that line its stems and fruits, catching onto anything they touch. Its roasted seeds serve as a coffee substitute, and its vitamin-rich shoots can be cooked for a nourishing vegetable. Another widespread species, yellow bedstraw, grows up to three feet tall and produces long dense heads of bright yellow flowers. Cheese makers traditionally used its leaves and stems to curdle milk, and dyes are extracted from its roots and flowers.

Bee

Of more than 3,500 kinds of bees found in North America, only the well-known honeybees and bumblebees are social insects that live and raise their young in large, rigidly organized colonies. The vast majority are solitary species that lay their eggs in nests provisioned with pollen and nectar and then leave their young to fend for themselves. In contrast to the elaborate, multichambered wax combs of honeybees, the nests of most of the solitary bees are tunnels bored into soil, twigs, logs, and similar places. The tunnel typically is divided into a series of chambers, with a single egg laid on a pollen ball in each cell. A few parasitic species, s1.lch as cuckoo bees, deposit their eggs in the nests of others. Bumblebees, like honeybees, build multiple brood cells of wax, usually in underground chambers such as abandoned mouse nests. Among the most useful of all insects, bees playa vital role in pollinating plants. As they fly from flower to flower gathering pollen and nectar, pollen grains stick to the hairs on their bodies and then rub off on the next flowers they visit, thus fertilizing them. The bees also actively collect pollen for use as food, both for themselves and for their young. They derive added nourishment by inserting their long, tonguelike mouthparts deep inside blossoms and sucking out nectar.

Bee balm

Monarda didyma

In midsummer, the brilliant red blossoms of bee balm are often abuzz with bumblebees. Ruby throated hummingbirds also come to sip the nectar deep in its clusters of tubular flowers. Growing up to five feet tall with fragrant opposite leaves, bee balm is a member of the mint family. Oswego Indians were known to brew a tea from its refreshingly scented leaves, a practice that colonists imitated when real tea became scarce at the time of the Revolutionary War. Still known as Oswego tea in many areas, this beautiful wildflower has a preference for moist, partly shaded soil. It flourishes throughout the eastern part of the country and is widely cultivated as an ornamental.

Beech

Fagus grandifolia

Soaring to heights of 100 feet or more, with a trunk as much as 4 feet thick, the American beech is one of our most magnificent woodland trees. All too often, however, its trunk is disfigured with unsightly scars; its distinctive smooth gray bark seems to be irresistible to vandals, whose whittled initials can mar the tree's unfurrowed bole for decades. Luckily, the beech's bark is not its only attraction. The oval leaves with sawtooth margins have a beautifully silky texture when they first open in spring and, after turning yellow in the fall, often remain on the tree throughout the winter. Its nuts, encased in spiny burs, provide food for a wide variety of wildlife, including foxes, bears, deer, and many kinds of birds. Nutritious and sweet-tasting, they also are enjoyed by humans, whether eaten raw or cooked, or ground as a coffee substitute. Once common across much of eastern North America, the beech in earlier times was often doomed to immediate destruction. Realizing that its presence was a sign of deep, fertile soil, pioneers hacked down beech groves wherever they found them and converted the land to fields for growing crops.

Beechdrops

Epifagus virginiana

Growing just 5 to 16 inches tall beneath their giant host, the beech tree, beechdrops are modest parasites that seem all stems and very little else. From August to October, however, dainty white tubular blossoms striped with purple appear along the upper parts of their slender brownish stalks. Along the lower stems, budlike, self-pollinating flowers produce an abundance of seeds. Although they depend upon beech roots to survive, their host is not harmed.

Beetle

Totaling about 300,000 species, beetles form the largest group of animals in the world, outnumbering all the fish, amphibians, reptiles, birds, and mammals combined. Their extraordinary success stems in part from their great adaptability. Found in nearly every habitat except oceans, they live in the soil, burrow in wood and other plant tissue, and also inhabit freshwater ponds and streams. One species is even capable of tunneling into the lead sheathing of telephone cables. Almost all can fly, though they are rather unskilled compared to other insects. Beetles go through a complete metamorphosis: beginning life as soft-bodied larvae, usually called grubs, they pass through a pupal stage and emerge as hard-bodied adults. The larvae of some species are quite active, moving about in search of prey; others live in the soil, where they feed on roots and other plant parts.

The stiff, shieldlike front wings of adult beetles protect the abdomen and the delicate hind wings, which do the flying. Thus armored, they can burrow into the ground or force their way under logs and stones without injuring their bodies or tearing their wings. Another key to the beetles' success is their chewing mouthparts, which allow them to eat many kinds of food. Most are vegetarians, but some are predators, and still others are scavengers, feeding on everything from dung to clothing fibers. Some, such as the weevils, are very destructive, causing millions of dollars in damage each year to crops and stored foods. Others, such as the ladybird beetles, are highly beneficial, preying on aphids and other insects that are harmful to plants and man.

Behaviorism

An Animal Behavior term, this is used to refer to the school of psychology founded by J. B. Watson, which rejected introspection and stressed the importance of objective observation. Their studies were largely concerned with experiments on learning carried out in highly controlled and simplified laboratory situations.

Bell

A pendant of hair-covered skin that hangs from under the throat of an Animal, e.g., the Moose.

Bellflower

Campanula

Nodding on slender stalks, the delicately flared blossoms of most of the bellflowers look like dainty pastel church bells. Two familiar domestic varieties, which have graced garden plots since colonial days, are Canterbury bells and harebells, also known as bluebells of Scotland. While most of the bellflowers are blue or lavender, Canterbury bells come in pink and white as well. Common wild species include the southern harebell, with clusters of tiny blue bells, and the tall bellflower, with blooms that are starshaped rather than bell-like.

Benthic

Meaning to be found on the floor of lakes, ponds, oceans and other bodies of water.

Berry

Fleshy fruit containing several seeds.

Berry

See Fruit.

Beryl

The radiant emerald and the blue-green aquamarine, two highly prized gems, both are forms of beryl, a mineral found in many parts of North America. Pure beryl crystals are colorless, but most contain impurities, which result in a splendid variety of colors, ranging from red and yellow to blue and green. Not all beryl crystals are of gemstone quality, however; industrial grade beryl is mined for beryllium, an extremely strong, light, versatile metal used by the aerospace industry and in nuclear reactors. Beryl crystals, which are six-sided and very hard, are usually found in granite pegmatite. This coarse-grained rock cools so slowly within the earth that it often produces crystals of enormous size. One stupendous example, unearthed from the Black Hills of South Dakota, was a beryl crystal that weighed 100 tons.

Biennial

A plant that takes two years to complete its life cycle.

Biennial

See Annual.

Bigeye

Small reddish fish with large glassy eyes, bigeyes are found in warmer waters off both the Atlantic and Pacific coasts. Also known as catalufas, they are nocturnal hunters that feed on shrimp, crabs, and other fish. The glasseye snapper bright red with a covering of rough scales-is found from New Jersey to the Gulf of Mexico. The equally colorful popeye catalufa is a well-known Pacific species. Although bigeyes are relatively common, most members of the family are too small to be of commercial value.

Bigfoot

Bigfoot is supposedly a humanlike creature said to live in the Pacific Northwest. Bigfoot has been reported most often in the mountains of California, Oregon, and Washington, and of British Columbia in Canada. Canadians call it Sasquatch. Bigfoot stories resemble those about the Abdominal Snowman, a hairy beast said to live in the Himalaya. Hundreds of people have reported seeing the Bigfoot or its footprints. They describe the creature as standing from 7 to 10 feet tall and weighing more than 500 pounds. Like an ape, it has thick fur, long arms, powerful shoulders, and a short neck. It supposedly walks like a human being and leaves footprints that measure about 16 inches long and about 6 inches wide. Evidence of the Bigfoot’s existence has not been sufficient to convince most scientists. Many scientists believe that some of the evidence, which includes footprints and photographs, has been faked. Bigfoot is apparently similar to the Abominable Snowman, which is also called Yeti. The Snowman is also an obviously mythical creature said to live on Mount Everest and other mountains of the Himalaya range of Asia. Reports of such a creature have also come from remote parts of China and the Soviet Union. According to legend, the Abominable Snowman is a hairy beast with a large, apelike body and a face that resembles that of a human being. It supposedly has long arms that reach to its knees, and it is reported to walk erect on its thick legs. Legend says that the Snowman sometimes attacks villagers. There is no direct evidence that the Yeti exists, even though individuals have photographed “Snowman” tracks in the snows near Everest. See Abominable Snowman.

Bighorn

Ovis canadensis

The Bighorn is a species of wild mountain sheep found only in North America. Male Bighorn sheep have massive horns that curve backward from the forehead, down and then forward. The horns may measure more than 4 feet long, with a circumference of up to about 17 inches at the base. Female Bighorn have very short horns that are only slightly curved. Bighorns are also called Mountain sheep. They live in mountains from east-central British Columbia in Canada to Baja California in northwestern Mexico. Bighorns that inhabit the slopes of the Rocky Mountains and Sierra Nevada are dark grayish-brown in color. Those that live farther south in the mountains of the desert have coats of pale buff.

All Bighorns are creamy-white on the lower parts of their bodies, with patches of creamy-white on their rumps. The size of Bighorns varies, depending on their sex and the regions in which they live. The rams (males) generally are much larger than the ewes (females). In the northern mountains, Bighorn rams may stand up to 3 ½ feet high at the shoulder and may weigh up to 300 pounds. Ewes in this region typically weigh less than 160 pounds. In the desert mountains, rams rarely weigh more than 200 pounds and most ewes weigh less than 120 pounds.

Male Bighorn usually live in groups of 2 to 15 animals. Females and young live in separate groups, usually of 5 to 30 animals. During the mating season, rams often engage in long, spectacular fights. In these battles, which may last for hours, two or more rams repeatedly charge at one another and fiercely crash their horns together. Typically, the male with the largest horns wins.

Ewes bear one lamb about 175 days after mating. Male Bighorn reach maturity at about 7 to 8 years of age. Females mature at about age 4. Bighorns feed on grasses and low shrubs. Their chief enemies include Wolves, Coyotes, and Mountain lions. Bighorns also are endangered by diseases of livestock and by the spread of industrial developments, which have destroyed much of the animal’s habitat. See also Dall Sheep and Stone Sheep.

Billfish

Marlins, sailfish, spearfish-all the members of the billfish family--are prized by sport fishermen, not only for their large size but also for the spectacular battles they wage when hooked. Surging from the water, they leap and violently twist about as they struggle to break free. All are recognizable by their bills, long, swordlike extensions of their upper jaws. (In contrast to the flattened swords of swordfish, which belong to a separate family, billfish bills are rounded in cross section.) Rapid swimmers, some of the billfish have been clocked at speeds of 60 miles an hour. Knifing through schools of mackerel or herring, they stun their prey by thrashing about with their bills, then swallow their victims before they are able to regain their senses. Although they use their bills mainly to stun rather than stab, billfish have occasionally been known to pierce the sides of sharks, whales, and even wooden boats. All the billfish have long dorsal fins, but those of the silvery blue sailfish-very high in relation to the diameter of their bodies-are big and dramatic enough to suggest the great sails of clipper ships. Slender, efficient swimmers, they fold their sails against their bodies when racing through the water. Blue marlin are the heaviest billfish, sometimes weighing more than a ton. Spearfish, less common than marlin and sailfish, are smaller and have relatively short bills. Whatever their size or shape, though, billfish make coveted trophies and are often seen decorating the walls of seaside restaurants.

Biodiversity

The variety of life forms, the ecological roles they perform, and the genetic diversity they contain. The variety from molecular, population, and interspecific levels up to the heterogeneity of ecosystems and landscapes. The variety of organisms found within a specified geographic region. The variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur.

Biogeography

The study of the geographic distributions of organisms, both past and present.

Biological assessment

A document prepared for the Section 7 process to determine whether a proposed major construction activity under the authority of a Federal action agency is likely to adversely affect listed species, proposed species, or designated critical habitat.

Biological opinion

A document that is the product of formal consultation, stating the opinion of the Service on whether or not a Federal action is likely to jeopardize the continued existence of listed species or result in the destruction or adverse modification of critical habitat.

Biological reproduction

Biological reproduction is the process by which new individual organisms are produced. Reproduction is a fundamental feature of all known organisms and each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: Asexual and Sexual. In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a cell into two daughter cells is an example of asexual reproduction. Asexual reproduction is not, however, limited to this process. Sexual reproduction requires the involvement of two individuals, typically one of each gender. Normal human reproduction is a common example of sexual reproduction. In general, more-complex organisms reproduce sexually while simpler, usually unicellular, organisms reproduce asexually.

Biological species concept

The idea that species are groups of natural populations that are reproductively isolated from other such groups.

Bioluminescence

An Animal Behavior term, this is used to describe the production of light by Plants and Animals. Bioluminescence may be used in visual displays or, as in some deep-sea Fish, to help in food searching in dark surroundings.

Biomarker

The variation, induced by a substance foreign to the body, in cellular or biochemical components or processes, structures, or functions that is measurable in a biological system or sample.

Biome

An ecosystem usually identified in terms of characteristic forms of vegetation. A biome is the type of habitat in certain places, like mountain tops, deserts, and tropical forests, and is determined by the climate of the place. A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that particular environment. The climate and geography of a region determines what type of biome can exist in that region. Major biomes include deserts, forests, grasslands, tundra, and several types of aquatic environments. Each biome consists of many ecosystems whose communities have adapted to the small differences in climate and the environment inside the biome.

All living things are closely related to their environment. Any change in one part of an environment, like an increase or decrease of a species of animal or plant, causes a ripple effect of change in through other parts of the environment.

The earth includes a huge variety of living things, from complex plants and animals to very simple, one-celled organisms. But large or small, simple or complex, no organism lives alone. Each depends in some way on other living and nonliving things in its surroundings.

Biosphere

The global realm of all living things.

Biotechnology (Health)

The term used to describe a collection of technologies that use living organisms to create improved products and processes. The primary use of biotechnology from a health perspective is in the development of new medicines, or biopharmaceuticals.

Biotechnology

The term used to describe a collection of technologies that use living organisms to create improved products and processes. These technologies are being used to develop new medicines, to improve yields from fish stocks, forest growth and agricultural crops, to promote energy production from biological sources, to improve treatment of liquid effluents, and to assist in cleanup of wastes and the environment.

Birch

Betula

The bark of the birches is their best-known feature, and rightly so, for it is their most striking characteristic. The smooth, chalky white bark of paper birches is the most familiar, but the bark of other species is equally distinctive. It varies from the silvery yellow of yellow birches to the salmon-pink of young river birches and the shiny, deep mahogany of mature sweet birches. It usually has a papery texture, peeling from the trunk in thin, pliable strips. Twelve species of these handsome trees range far and wide across North America. The cold tolerant paper birch grows north to the edge of the Arctic tundra, while the river birch flourishes as far south as Louisiana. Widespread in the west is the water birch, named for its fondness for damp soils. Another species, the gray birch, thrives on soils too poor for most other hardwoods; in New England, stands of this so called "poverty birch" almost always mark the worn-out fields of abandoned farms. All birches are pioneer trees. Producing tiny, winged seeds so light that they can drift for miles on the wind, the birches are among the first trees to colonize land that has been stripped by fire or logging. In a relatively short time, thick stands of fast-growing, colorful birches hide the scars of man's misuse while protecting the soil against erosion.

Bird

Warm-blooded, feathered, egg-laying vertebrates that have a beak and wings, and are usually able to fly. Unique among all animals in having feathers, birds are the most widespread and numerous land-dwelling vertebrates. Of the roughly 9,100 species of birds in the world, about 850 have been found in North America and some 650 of these nest here regularly. The number of individual birds in North America has been estimated at 5 to 6 billion. Among the most abundant species are the redwinged blackbird, the European starling, and the common grackle, each probably numbering more than 100 million. Runners-up include the American robin, the yellow-rumped warbler, the song sparrow, and the brown-headed cowbird. Among the rarest are the whooping crane and Kirtland's warbler, each with a population of less than 200. The ivory-billed woodpecker and Bachman's warbler, if not already extinct, are even rarer. Our tallest bird, the whooping crane, stands almost five feet high. The record wingspan, at nine feet seven inches, belongs to the endangered California condor. The heaviest is the male trumpeter swan, which weighs as much as 38 pounds, while the smallest is the Calliope hummingbird, at 2314 inches long and weighing only a fraction of an ounce. Except for the extinct great auk, all North American birds known in historic times have been capable of flight. Indeed, flight is one of the characteristic features of birds, and many of their adaptations are related to this ability. Chief among these are feathers, which, being light and strong, serve the needs of flight very well. The large feathers of the outer wing propel the bird through the air, and the curved flight feathers of the inner wing provide lift. Those of the tail aid in steering by acting as a rudder, while the feathers of the body, known as contour feathers, form a smooth surface that offers little drag, or resistance, to the flow of air. Feathers also provide insulation, important for animals that must maintain high body heat and conserve energy to meet the demands of flying. Other adaptations for flight include an internal system of air sacs that lower the ratio of weight to volume. The air sacs also allow oxygen rich air to pass through the lungs during both inhalation and exhalation, another way of meeting the energy demands of flight. Eggs that develop rapidly and are incubated outside the body also contribute to weight reduction. The reproductive system, moreover, is active and enlarged only during the nesting season; after breeding it shrinks drastically both in size and weight. In addition, birds have a rigid skeleton, which provides a solid base for the powerful breast muscles that drive the wings. Some of the bones are hollow and so help to reduce weight. Finally, birds are equipped with senses- including large, keen eyes- that allow them to operate skillfully in the air. Birds have many different flight styles, from the effortless gliding and soaring of vultures, hawks, and eagles to the hovering flight of hummingbirds. Petrels, shearwaters, and albatrosses take advantage of subtle air currents over the ocean, conserving energy by riding on small updrafts over the waves, just as larger birds make use of updrafts over open country or mountainsides. Woodpeckers, starlings, and finches fold their wings during flight, which results in a bounding flight style. Finally, many birds fly with steady, powerful wing beats, often in wedge-shaped formations that allow each bird to ride on the turbulence of the one in front of it. Flight in many cases is important in obtaining food. Swallows, swifts, and night jars capture insects in midair, and hummingbirds use their hovering abilities to get at the nectar in flowers. Hawks and eagles soar over vast areas searching for prey, and flycatchers dart out from perches to snap up passing insects. The bills of birds reflect their methods of foraging and so show many adaptations. Hawks and owls use their hooked bills for tearing flesh. The conical bills of finches, sparrows, grosbeaks, and buntings are ideal for crushing seeds. Hummingbirds and some sandpipers use their long, slender bills for probing, while the bills of flamingos and many kinds of ducks are specially formed for filtering food from water. The fish catching herons, the anhinga, and the northern gannet, in turn, have spear-shaped bills, and woodpeckers have chisel like bills that are ideal for hacking holes in tree trunks. A number of other birds such as crows and jays, noted for their varied diets, have all-purpose bills. Habitats are varied, too, for no other group of animals has been so successful in reaching and adapting to so many different environments. From the highest mountain peaks to expanses of ocean thousands of miles from any coastline, birds have found ways of obtaining sufficient food and, in many cases, of nesting. Except for fish, the vertebrate that lives closest to the North Pole in winter is the common raven, which ranges all the way to northern Greenland and the islands of the Canadian Arctic. Many species make their home in America's harshest deserts, and even the most barren salt flats have their pairs of snowy plovers. Because birds are conspicuous and attractive, concern for their well being has always been important in conservation movements. They are easy to see and count, and any drop in their populations is easily detected. Birds thus provide an early warning system, often the first indication we have that something is wrong with the environment. Declines in ospreys, bald eagles, and peregrine falcons provided a clue that DDT and similar chemicals, all of them potentially harmful to humans, were building to dangerous levels in wetlands. As a result of this research with birds, these chemicals are now controlled or banned. Today, declines in migrant songbirds in North America's woodlands signal the destruction of the tropical rain forests where these species spend the winter. Birds thus are not merely conspicuous and beautiful. They are valuable allies in our efforts to save our planet.

Birding (Recreation)

Bird-watching is a popular hobby. Many birders assist organizations in monitoring bird populations through annual counts.

Bison

Bison bison

When Europeans first reached North America, bison by the tens of millions roamed the continent. Most lived on the Great Plains, where several tribes of Native Americans hunted them for meat. Their hides were used for clothing and shelter, and their horn and bone for utensils. Buffalo, as these magnificent grazers are sometimes called, are unmistakable-with their huge, horned head, massive neck, and high, humped shoulders. A thick, dark, shaggy cape of hair, often matted and mudcaked, hangs from the head, neck, and forelegs. Bulls stand about six feet tall at the shoulder and can weigh more than a ton, while cows average about 900 pounds. During most of the year, cows and calves live in family groups, but bulls join them during the summer to compete for harems that range from 10 to as many as 70 cows. Slaughtered for sport, food, and as part of a campaign to subdue the Native Americans, the bison were eventually reduced to near extinction. By 1890, fewer than 1,000 of the animals had survived. Now protected in parks and reserves, bison number about 50,000 and are a treasured part of our natural heritage.

Bittern

At home amid the reeds and cattails of freshwater and brackish marshes, American bitterns are skilled camouflage artists whose streaky brown plumage helps them blend into their surroundings. Whenever they sense danger, these masters of deception all but disappear by stretching their necks and long bills skyward, mimicking the vegetation. They even waver gently when breezes ripple the reeds. American bitterns, at two to three feet long, are the larger of the two North American species, which are related to the lankier, longer necked herons. Thanks to their bellowing springtime calls, they are also known as thunder-pumpers and bog bulls. Their smaller cousins, least bitterns, are only about one foot long and utter a more subdued cooing note. Both species build clumsy nests on the ground near water and lay clutches of three to five eggs. They feed on a wide variety of aquatic animals, including fish, frogs, tadpoles, and insects. Though sometimes seen flying low over marshlands, these secretive birds seldom fly any great distances except during migration.

Bitterroot

Lewisia rediviva

Though it grows only three inches tall, bitterroot nevertheless makes a bright display on arid western mountain slopes from late April into July, for each plant produces a virtual bouquet of spectacular pink to whitish blooms. Native Americans no doubt admired the show, but they did not pick the flowers. They harvested the thick fleshy roots instead and, after paring away the bitter red bark, roasted them like potatoes or boiled them in soups and stews.

Bittersweet

Celastrus

Many people cherish bittersweet as a highlight of the autumn landscape, for it is then that the orange husks of its showy fruits burst open to reveal the bright red seeds within. They may look inviting, but despite the plant's name, bittersweet fruits are not edible. Two species of these twining vines are common across much of the United States. The native American bittersweet thrives in moist, shady spots from Quebec to North Carolina and west to New Mexico. It rambles happily over stone walls and fences, and up shrubs and trees to a height of 60 feet. The other kind, oriental bittersweet, has escaped from gardens and become naturalized along the eastern seaboard. Its fruits are similar to those of the American species, but the clusters are smaller and hidden among the foliage.

Bivalve

A mollusk whose shell comprises two halves.

Black bass Micropterus

Several species of freshwater bass, known collectively as black bass, are native to cooler streams in eastern North America. Unrelated to striped bass or the sea bass, they are members of the sunfish family-and most are just as pugnacious as their smaller kin. Because they are such strong, tenacious fighters, the two best-known species-largemouth bass and smallmouth bass-have been introduced into lakes and rivers all across the country. They are in fact among the most popular of our freshwater game fish; armies of anglers try to deceive them with a seemingly endless array of artificial lures. Largemouth bass may grow to three feet in length and weigh more than 20 pounds-twice the size of smallmouth bass. Even so, the two fish are often mistaken for one another since their coloring-olive above with silvery undersides-is so similar. The best distinguishing feature is the mouth, which on largemouth bass extends back beyond the eye. During the heat of the day, bass stay in deeper water, swimming among the rocks and preying on crustaceans and small fish. In the evening, they move into the shallows to feed on insects and other creatures near the water's edge.

Blackberry

Rubus

It seems only fair that wild fruits as delectable as those of the blackberries should be well-guarded, hidden among thickets of thorny canes. Blackberries, though, are a tangle in more ways than one. Botanists argue endlessly about the number of species there are-one count runs to 122. They probably will never agree, since blackberries cross easily with their close relatives the raspberries and dewberries to produce a continual stream of new hybrids. The denizens of field and forest do not worry about the scientific status of the fruit; they are too busy eating it. Animals from chipmunks to grizzly bears rely on blackberries as a major part of their summer diet. Some of these foragers even view the thorns as an asset- many small birds rely on them as protection for their nests.

Blackbird

Of the five kinds of blackbirds found in North America, the best known and most widely distributed are red-winged blackbirds (or redwings), named for the males' bright red wing patches, bordered with a band of yellow. Nesting in marshes across most of North America, the males stake out their breeding territories with a con-ka-ree call familiar to many as one of the earliest signs of spring. In winter, the redwings and other blackbirds gather in such enormous flocks (sometimes numbering in the millions) that they threaten crops and even destroy the trees on which they roost. Tricolored blackbirds resemble redwings, but the males' wing patches have a white border. They are found only in California and Oregon and live year-round in huge, dense colonies. Yellow-headed blackbirds, ranging from the Great Lakes to the Pacific, often breed in the same marshes as redwings. But the two do not compete for living space, since yellow-headed blackbirds tend to nest over deeper water. The other two species, rusty blackbirds and Brewer's blackbirds, lack any patches of red or yellow. Both nest in trees or shrubs near water; the rusty prefers conifers in northern forests and bogs, while the Brewer's often breeds in western towns and parks. The females of all the blackbirds, drab compared to the males, take charge of nest building and incubation. They fashion sturdy, cupshaped nests, firmly anchored to reeds, bulrushes, or branches, and lay an average of four to six eggs. In most cases, the males have more than one mate.

Black fly

Simulium

Only about an eighth of an inch long, humpbacked black flies nevertheless are determined aggressors; attacking man and beast alike, they can inflict painful, sometimes bloody, bites. Their yearly cycle begins in early summer, when adult females lay masses of eggs in fast-flowing streams and rivers. The wormlike larvae attach themselves to rocks by means of sucking disks on the ends of their bodies, and they filter bits of food from the water flowing past. Sometimes the larvae are so numerous that their densely packed bodies look like mossy mats on the rocks. Eventually encasing themselves in cocoons, the legless wrigglers are transformed into adult flies that go swarming through the north woods- much to the dismay of summer campers. Common examples of these noxious pests are the Adirondack black fly, the buffalo gnat, and the white-stockinged black fly.

Black rat

Rattus rattus

Along with its cousin the Norway rat, this aggressive, adaptable rodent has been man's uninvited companion for centuries. The two rats, both immigrants from the Old World, are similar in appearance, but black rats have longer tails, larger ears, more-pointed noses, and darker fur. Unlike the more widely distributed Norway rat, black rats in the United States are restricted mainly to the southern states and seaport cities. Living in or near buildings, they reproduce rapidly and feed by night, usually on human food supplies. Good climbers that like to nest above ground, black rats tend to occupy the upper floors of buildings, while Norway rats prefer ground floors, basements, and sewers. Both species carry diseases, but the black rat is especially notorious for its role in bringing the bubonic plague to medieval Europe.

Black widow spider

Latrodectus mactans

The most poisonous spider in North America, the female black widow produces a powerful venom that causes severe pain and occasionally even death. Shiny black, she is easily recognized by the red hourglass-shaped mark on the underside of her pea-sized abdomen. (The harmless male is less than half the size of the female.) Although the black widow spider ranges across much of the country, it is most common in the south and is usually found in damp, dark places. It earned its name from the female's habit of eating the male after mating, despite the fact that such cannibalism also is practiced by many other kinds of spiders.

Bladderwort

Utricularia

Carnivorous plants with no roots and, in some species, no true leaves, the bladderworts grow in swamps and ponds, where they feed on small animal life. Scattered among the stems and leaves are tiny bladders that function as traps. A watertight door seals the bladder's entrance, and glands pump out any water inside to create a partial vacuum. When an animal touches trigger hairs on the door, the seal breaks and a stream of water rushes in, along with the hapless prey.

Blazing star

Liatris

The nomadic Indians of the northern plains used to wait anxiously each year for the late summer blossoming of the blazing stars. They knew that the appearance of the purplish spikes of thistlelike flower heads, also called gayfeathers, coincided with the ripening of the corn in the fields of neighboring tribes and so marked the beginning of a time of feasting. Though blazing stars of several species grow as far east as the Atlantic Coast, these hardy perennials are uniquely suited to life on the prairie. One kind, for instance, sends its roots a yard or more into the soil during its first season of growth, making the modest above-ground seedling almost invulnerable to drought.

Bleeding heart

Dicentra

Set amid lacy, finely cut foliage, the pink, heartshaped blossoms of the eastern and western wild bleeding hearts look for all the world like old-fashioned valentines. Just as descriptively named are their near relatives: Dutchman's breeches, which resembles trousers hung out on a line to dry, and the western steer's head, which looks uncannily like a skull with horns. But beware; despite their charm, several of these plants are also known as staggerweed because of the stupefying effect their toxic foliage has on unwary deer and cattle.

Blenny

Living in tidepools and other shallow waters, blennies are a diverse group of small, slender marine fish. Most are only a few inches long, with a spiny back fin extending from head to tail, and many have branched tentacles and "hairs" on their heads. Some of them, known as the scaled blennies, are predators, while the scaleless combtooth blennies use their teeth to scrape algae from rocks and coral. Some of the blennies use their two front fins as limbs for crawling along the bottom and can even pull themselves out of the water to bask on spray soaked rocks.

Blizzard

Although any heavy snowstorm is commonly called a blizzard, in its strict sense the term refers to a storm with abundant snowfall, wind speeds of 35 miles an hour or more, and temperatures of 20°F or less. Large, dunelike drifts usually form, blocking roads and piling up around buildings, and strong gusts sometimes blow so much snow through the air that visibility is reduced to just a few feet. While storms of this kind most often occur on the northern Great Plains, the most famous blizzard of all blasted the northeast from March 11 to March 14, 1888. Winds during the Blizzard of '88 gusted to 85 miles an hour, and the temperature dropped to zero. In some places snow fell for 48 hours, and in New York City it reached a record depth of 20.9 inches. More than 400 people lost their lives as a result of the storm. The Blizzard of '88 was fed by moisture from the Atlantic Ocean, but the Great Lakes spawn blizzards, too. One of the worst in modern times struck Buffalo, New York, on January 28, 1977. Driven by 70-mile-an-hour winds, snow fell for three days and, with nearly 3 feet of snow already on the ground, drifts reached heights of 30 feet. The death toll was 29, including several people who were trapped in stranded cars.

Bloodroot

Sanguinaria canadensis

Cherished as a harbinger of spring, bloodroot is among the first flowers to appear in eastern woodlands. Its blossoms, pure white or pinkish, are each borne singly at the end of a stem, with the stalk enfolded in a large blue-green leaf. In 1612, Captain John Smith, leader of the Jamestown settlement, commented on bloodroot, noting that it bore a root "the bignesse of a finger and as red as blood." The color was in the sap, which Indians throughout the plant's range, from New Brunswick to Florida and west to Oklahoma, used as a dye to paint their faces, clothes, and weapons. In more recent times, scientists found that an extract of the root helps control dental plaque, and it is the basis of a toothpaste and oral rinse now offered for sale.

Blowhole

When tides are high and seas strong, spectacular fountains of spray can sometimes be seen shooting through vents in the cliffs along rocky shores. The openings, called blowholes, are gaps in the roofs of caves carved by the steady assault of battering waves. At high tide the ocean rushes into the caves, and successive surges force jets of water up through the blowholes.

Bluebell Mertensia

Of the many bluebells native to the United States, most inhabit high meadows and rocky slopes on our western mountains. Far more familiar to most of us is an adaptable lowland species, the Virginia bluebell, which flourishes in woodlands and wet fields from New York to Minnesota and south to Alabama. Also widely cultivated in gardens, the Virginia bluebell is a seasonal treat that shows its colors only briefly. Bursting from the soil as a tightly wrapped, bluish clump of leaves on the first warm days of spring, it unfurls its foliage and sends up stalks topped by clusters of pinkish buds that open to porcelain blue, bell-shaped flowers. Then, in just a few weeks, the whole plant withers and hides underground until the following spring.

Bluebird

Sialia

With their bright blue feathers and cheerful songs, our three species of bluebirds are a welcome presence in fields and gardens across the country. The most widespread, ranging from the Atlantic Coast to the Rocky Mountains, is the eastern bluebird, which has a rust-colored breast and throat. The western bluebird, similar in appearance but reddish on its back as well, lives only in the Far West. And the all-blue mountain bluebird prefers the higher elevations of western mountains. Bluebirds feed primarily on insects in summer and berries in fall and winter. Scanning the ground from fence posts or other perches, they dart down and pounce on insect prey. The mountain bluebird uses a more aerial technique; it often catches insects on the wing or, hovering in midair, drops down to snatch insects it has spotted on the ground. Found mainly in areas with scattered trees, all three bluebirds are hole nesters. They commonly take over abandoned woodpecker nests, but the mountain bluebird sometimes chooses rocky crevices as well. Like most hole nesters, they willingly accept bird houses. In many areas the bluebirds have declined in numbers. Biologists believe this is due in part to human activities. But the main factor seems to be competition with other hole-nesting birds, especially those two imported aliens, the house sparrow and the starling.

Bluebonnet

Lupinus

The much-beloved symbol of Texas, these wild lupines are expansive as only Texans can be, their spikes of clear blue blossoms mirror the sky for miles along Texas highways from spring into early summer. (Of the four species of bluebonnets found in Texas, the official state flower is the little Lupinus subcarnosus.) A simple device helps these prairie wildflowers succeed in the difficult southwestern climate: their seeds have such a hard coat that they can lie dormant through years of drought and sprout only when rainfall returns. Early settlers called the bluebonnets "buffalo clover," and in fact, they are related to the clovers. Like other legumes, they take nitrogen from the air and fix it in the soil. So this Texas wildflower enriches the land even while cloaking it in beauty.

Blue cohosh

Caulophyllum thalictroides

Named for the bluish cast of its foliage, blue cohosh is a deceptive plant: what appears to be three separate leaves is actually a single, very complex compound leaf attached to the main stem. And the clusters of blue berries borne by the three- to four-foot-tall wildflowers are not really berries at all, but seeds. Each greenishyellow flower produces exactly two, which swell to burst free from the enveloping fruit by midsummer. At one time the blue cohosh's root was used by Indian women. Taken as a tea, this "papoose root" helped to hasten childbirth.

Bluefish

Pomatomus saltatrix

Prized by commercial fishermen as popular tablefare and by anglers as game, bluefish are formidable ocean predators that grow up to four feet long and weigh as much as 20 pounds. The blue-backed, silvery-sided carnivores travel in large schools and swiftly track down and attack other schooling fish such as menhaden, mackerel, herring, and even smaller bluefish. Bluefish are found off the Atlantic coast, where they travel toward Florida in winter and north again in summer, following the movements of their favorite prey. Slicing easily through flesh with their razor-sharp teeth, these frantic feeders often eat until full and then continue the slaughter, leaving a floating trail of blood and fish parts in their wake. On forays inshore, they have been known to nip bathers caught amid their prey. The young, sometimes called tailors or snappers, begin life in estuaries and bays. Forming schools at an early age, they soon begin to hone their predatory skills on shrimp, anchovies, and other small prey.

Blue moon

A genuine rarity in the night sky, a blue moon occurs only when smoke and dust particles form a layer in the air. The dusty air screens out all colors except blue from sunlight. And since moonlight is actually reflected sunlight, the moon at such times takes on a bluish cast.

Boa

Compared to their awesome tropical relatives, North America's two native boas are small, rather mild-mannered snakes. Like all constrictors, however, they coil tightly around their prey until it suffocates, then swallow the victim whole. The 18-inch rubber boa of the Far West looks and feels like rubber. It is also called the two headed snake because its blunt tail looks much like its head; when threatened, it rolls up in a ball and, hiding its head inside, lifts its tail toward its attacker. The three-foot rosy boa, with brown to reddish stripes, lives in deserts of the Southwest. Both snakes feed on rodents but also climb small trees in search of nesting birds.

Bobcat

Felis rufus

The most widespread of our wildcats, bobcats are at home in a broad range of habitats; these versatile hunters are found from western chaparral and deserts to eastern forests and southern swamps. In general appearance they resemble tawny, oversized tabby cats with prominent, tufted ears. The "bob" in their name refers to their short tails, a feature shared with their close relative the 1ynx. Masters of the slow stalk, bobcats can also playa waiting game, crouching motionless before pouncing on prey. Scavengers in lean times, they much prefer fresh red meat. Cottontail rabbits are a favorite prey, supplemented by squirrels and mice. At about 20 pounds, bobcats are small compared to mountain lions; even so, they can kill deer many times their size.

Adult bobcats are solitary and seldom meet except to mate, which is done with much loud caterwauling. Reared in dens in rocky crevices, caves, or hollow trees, even as kittens they display the instincts of hunters.

Bobolink

Dolichonyx oryzivorus

In their flight south for the winter, bobolinks travel from the northern United States and Canada all the way to Argentina, a marathon of some 5,000 miles. Their flight note-a metallic sounding pink-can be heard by night as the migrant flocks pass overhead. In the past, hordes of southbound bobolinks descended on the once abundant rice fields of the Carolinas, where the so-called ricebirds were slaughtered as pests. In the summer, bobolinks settle in open grasslands, where they feed on insects and seeds. The males, black except for a tawny nape and white on the wings and back, court their mates with a delightful bubbling song as they flutter through the air.

Bobwhite

See Quail.

Body whorl

The last whorl of the spire of a snail.

Bog

Often thought of as bleak and even threatening places, bogs are actually rich and highly specialized environments. In North America, most bogs are relics of the last Ice Age. As the glaciers retreated, they left chunks of ice buried in rocky debris; when the ice melted, steep-sided ponds were formed and later filled by rain and snow. Too poor in oxygen and nutrients to support most kinds of life, these pockets of moisture offer ideal havens for sphagnum moss. This primitive plant needs no soil, only water, to thrive, and once established, it forms a floating mat that gradually spreads across the surface of the pond. As the mat slowly thickens, it deposits a substantial layer of dead, compressed organic material-peat-on the bottom of the pond.

Because both peat and sphagnum are acidic, bogs can support only acid-tolerant plants. Larch, black spruce, and white cedar typically take root in the moss around the bog's margin; cranberries, bog rosemary, and labrador tea spring up on the floating sphagnum mat itself; and water lilies hold sway in the open water at the center. Many plants that cannot compete on dry land find a haven in bogs, which are excellent places to hunt for the rare lady slippers and white-fringed orchids. And carnivorous plants, which live on insects, thrive on the sphagnum mat. Few fish can survive in the oxygen-poor waters, but frogs, ducks, moose, wolves, and lynx all take refuge in the remote fastness of bogs.

Bonefish

Albula vulpes

Up to three feet long with deeply forked tails, slender, silvery bonefish are found along both the Atlantic and Pacific coasts. They can often be seen as they probe shallows near the shore, nudging the sandy bottom with their snouts in search of shellfish, worms, and other food. Bonefish are a great favorite with anglers because of the vigorous fight they wage on the hook. But after losing the tug-of-war, they usually are tossed back alive, since their flesh is filled with so many bones.

Boneset

Eupatorium perfoliatum

Tall, robust, and crowned with fuzzy, flattopped flower heads, boneset is a familiar sight in the East when it blooms, from late summer into autumn. A white-flowered herb that favors damp meadows, it was recommended by pioneer herbalists for the treatment of fevers and similar ailments. Feverwort, ague-weed, and sweating plant-other old names for boneset- all testify to its medicinal reputation. Even the name boneset refers not to its virtues in healing broken bones, but in curing "breakbone fever," a type of influenza. As recently as 1900, country people still used the plant as a cough and cold remedy, and every farm had a bunch of bone set hanging up to dry in the attic or woodshed.

Borage

Borago officinalis

Ever since ancient times, it has been claimed that this sprawling annual herb could drive away sadness and make men merry. And almost certainly it did when taken as traditionally recommended - in a tankard of wine. Though hairy, the young leaves are rich in vitamin C and, with their cucumberlike flavor, make a tasty addition to salads. Bees are attracted to the plant's flowers-five-pointed stars of blue or purple that produce a generous supply of nectar.

Boundary

The edge between different habitat types. If distinctive, a boundary can be considered a separate edge habitat or ecotone. Boundaries that are readily crossed by an organism are called permeable, those that are crossed reluctantly are called semipermeable, and those that are not crossed are called impermeable.

Bowfin

Amia calva

Often called living fossils, bowfins are the sole survivors of a once widespread family of prehistoric fish. And they demonstrate their survival skills even today: by gulping air at the surface, bowfins thrive in sluggish, oxygen-poor water that few other fish can tolerate. Up to 30 inches long, they are mottled green with a dark spot near the tail and a long fin down the back. Also known as dogfish, grindles, and mudfish, bowfins are found in quiet, plant-choked lakes and streams across most of eastern North America.

Boxfish

A built-in suit of armor-bony plates fused into a protective case-gives boxfish their name. Also called trunkfish, these chunky residents of temperate and tropical seas move about sluggishly, propelled by fins and tail that poke through openings in the rigid case. Boxfish are easily approached by divers as they putter around seagrass beds and coral reefs. Some, such as the smooth trunkfish of the Atlantic coast, use a water-pistol technique to feed: they shoot a stream of water from the mouth, aiming it at the sandy bottom to dislodge small worms and crustaceans that might otherwise remain hidden. Certain species contain a toxin that, if released in an aquarium, can kill every other animal in the tank. Indeed, the boxfish itself sometimes succumbs to its own poison.

Box turtle

Terrapene

When box turtles sense danger, they not only retract their head, legs, and feet like other turtles, but close up their shells as well. A hinge divides the underside into two halves that can be folded up against the rim of the upper shell, sealing the creature in so snugly that not even a knife blade can be inserted between the shells.

Found only in North America, box turtles are five to eight inches long, with yellow or orange markings on their dark backs. They are more at home on land than in water, with the eastern box turtle living in woodlands and meadows and its western cousin preferring the prairies of the south central states. Active by day, box turtles cool off on hot afternoons by soaking in puddles or resting in mounds of damp leaves. In winter, these expert diggers can hibernate as deep as four feet below the ground. If removed from their home territories, box turtles can find their way back using the sun as a navigational aid. But if left alone, they spend their entire lives on just a few acres. And their lives are long indeed; box turtles have been known to survive for more than a century.

Brachiopod

Known mainly by their fossil remains, brachiopods flourished hundreds of millions of years ago when much of North America was covered by shallow seas. Some 30,000 fossil species have been found in sedimentary rocks throughout the country, and a few kinds still survive today. Encased in two saucerlike shells, brachiopods are also called lamp shells because of their fancied resemblance to ancient Roman lamps. Most species live attached to the sea floor by an upright fleshy stalk, relying on movement of the water to bring them food.

Bract

A small leaflike or scalelike structure beneath a flower.

Braided stream

Networks of interlaced channels that repeatedly divide and then rejoin each other, braided streams create striking patterns of land and water. They tend to form where wide, shallow, slow-moving rivers become choked with sediment, forcing the water to find new paths as constantly shifting sandbars block the channel. Melting glaciers, which release huge amounts of eroded debris, frequently produce intricate braided streams, with rivulets of meltwater weaving across one another. Farther downstream, if the slope becomes steeper, the numerous diverging smaller streams often reunite into a single main channel.

Breccia

Formed of coarse, angular rock fragments that have been naturally cemented together, breccias resemble gravelly, manmade concrete. Although they can be produced by any geologic process that breaks up existing rocks, they most commonly result when rock debris- from a landslide, for instance-is dumped in a valley and buried beneath additional layers of sediment. Eventually the rock fragments are compacted and cemented together as smaller grains fill the gaps between them. The very similar sedimentary rocks called conglomerates are made up of pebbles that have been rounded and worn through long transport by streams, rather than the sharp, angular fragments found in breccias.

Breeding Bird Atlas

Bird Biology Avian Conservation term.

See Atlas.

Breeding Bird Census (BBC)

Bird Biology Avian Conservation term.

A census program in North America that uses the spot-mapping method during the breeding season.

Breeding Bird Survey (BBS)

Bird Biology Avian Conservation term.

A cooperative program of the U.S. Fish and Wildlife Service and the Canadian Wildlife Service for monitoring population changes in North American breeding birds by using point counts along roads.

Breeding dispersal

Movement of individuals that have reproduced between successive breeding sites.

Brittle star

With five spiny arms radiating from a small central body, brittle stars resemble their relatives the sea stars, or starfish. Unlike sea stars, however, brittle stars have arms that are long, thin, and flexible, with a snakelike appearance that has prompted their alternate name, serpent stars. The arms are used for moving across the sea floor and for passing food to the mouth, which is located on the underside of the inch wide central body. If an arm is grasped, the creature escapes by allowing it to snap off; hence the name brittle star. Later a new arm grows in place of the lost one. Congregating by the thousands on the deep ocean floor, brittle stars also live in shallower waters along the Atlantic, Pacific, and Gulf coasts. Since they prefer to stay hidden under rocks, in seaweed, or buried in sand, these retiring little invertebrates are seldom seen.

Broad-leaved trees

Oak, beech, ash, hickory, maple-these and other broad-leaved species are the trees that dominate our temperate forests. The secret of their success is the efficiency of their foliage, for leaves are factories that use energy from the sun to manufacture sugars. And since the typical broad-leaved tree boasts four times the leaf surface of a comparable needle-leaved tree such as a pine, the broad-leaved tree is a much more effective solar collector. In addition, most broadleaved trees are deciduous- that is, in contrast to the evergreen conifers; they shed their leaves each fall. This not only protects them from winter cold but also keeps them from drying out, since moisture is easily lost from the broad leaves. The two classes of trees also differ in their methods of reproduction. Broad-leaved trees are flowering plants that enclose their seeds in fruits, while the needle-leaved trees bear their seeds naked and unprotected in cones.

Bromeliad

Spanish moss drooping from the branches of a live oak in the Deep South may not seem to have much in common with pineapples on the greengrocer's shelf. Yet both are members of the same strange plant family-the bromeliads. Some 15 species of these tropical and subtropical plants are native to the continental United States, where they range from coastal Virginia south to Florida and west to Texas. Most of our bromeliads, like Spanish moss, are epiphytes, plants that cling to the branches of trees and shrubs. Their roots never touch the ground, but instead serve mainly to attach the plant to its host. Unlike the dangling threads of Spanish moss, most of our native bromeliads form rosettes of stiff, upright leaves with cuplike bases that collect water. And in contrast to the minute flowers of Spanish moss, most bear conspicuous, brightly colored flower stalks. Not all bromeliads are tree dwellers. Some make their homes more conventionally on the ground-the pineapple, though originally native to Brazil, grows so well in Hawaii's volcanic soils that it has escaped from plantations and run wild through the Kona region.

Brood parasitism

An Animal Behavior term, this means the system in which the young are raised by individuals that are not their parents. Usually, as in the Brown-headed cowbird or European cuckoo, the hosts are of a different species and all young of the parasite species are raised in this way. Brood parasitism may also occur within a species, some females laying eggs in the nests of others.

Brood parasitism (interspecific)

Bird Biology Avian Conservation term.

The laying of eggs by an individual of one species in nests of other species with subsequent care for the parasite young provided by the hosts.

Brown creeper

Certhia americana

Camouflaged by its barklike, streaked, and spotted plumage, the brown creeper is a small and inconspicuous bird that spirals up tree trunks in search of food. Held in place by sharp claws and a stiff, proplike tail, it uses its slender, curved bill to probe for insects and spiders hidden in crevices in the bark. The brown creeper usually begins foraging at the foot of a tree, works its way up the trunk, and then swoops down to the base of the next tree. When alarmed, it spreads its wings and flattens its body against the tree, making itself almost invisible. Brown creepers depend on bark not only for food and concealment, but for their homes as well. Nests are occasionally built in cavities but most often are hidden behind loose strips of bark. Although their usual call is a single lisping note, in the nesting season brown creepers deliver a melodic song more like that of a warbler.

Bryozoan

Commonly known as moss animals because of the plantlike appearance of many species, bryozoans are tiny invertebrates that live in colonies encrusting rocks, shells, boat bottoms, and other surfaces in both salt and fresh water. Each member is encased in a protective capsule, hard in many species but jellylike in others, and each case has an opening through which the animal extends its tentacles to capture food. The colonies assume a variety of forms. Some resemble seaweed fronds and become dry and brittle when washed up on shore; others grow in bushy tufts on coastal rocks. One freshwater species forms spongelike mats; another lives in colonies that look like strings of snail eggs.

Bovids

The common term for the family of Animals named Bovidae, which includes hoofed Animals that have horns which are never shed and are not branched. Horns are present on both sexes. This group includes the Wildlife species bighorn and thinhorn sheep and mountain goat, and the domestic species cattle, sheep and goats.

Browser

An Animal that feeds on leaves, twigs or shoots.

Brow tine

Projection on an antler.

Bryozoan

Buckeye

Aesculus

Ohio claims one species of buckeye as its symbol, but in fact these American relatives of the imported horse chestnut range east to Pennsylvania, south to Florida, and west to Texas, with a California representative as well. One of the great beauties of late spring, buckeyes bear upright clusters of white, yellow, cream, or even pink flowers. The blooms are followed by thickhulled burs that split in early summer to disgorge large, fleshy seeds with coats like polished mahogany. These may look like chestnuts, but they are bitter to the taste and poisonous. Resourceful Indians, however, still managed to get a meal from the buckeyes by pulverizing the seeds and leaching out the poison.

Buffalo

See Bison.

Buffalo grass

Buchloe dactyloides

Only two to six inches tall, buffalo grass forms a fine, dense, gray-green turf that spreads across portions of the Great Plains like a natural lawn. Indeed, it once covered such vast expanses from Minnesota to Montana and south to Texas and New Mexico that the whole region was known as the short grass prairie.

As the name suggests, buffalo grass was a favorite food of our native bison and furnished herds of millions with nourishing winter forage. The grass was nearly as important to the pioneers who went west to tame the plains. They used blocks of the thick, durable turf to build their snug sod houses. Virtually immune to insects and disease, buffalo grass tolerates extremes of temperature and needs little water. For these reasons it is winning new popularity in the plains states as a lowmaintenance lawn.

Bug

While all insects are commonly referred to as bugs, the term actually applies to just one group-the true bugs. More than 40,000 species of these insects are found worldwide, with some 4,500 of them living in North America. They range from tiny bedbugs to the giant water bugs, aquatic insects that sometimes are more than two inches long. A few characteristics distinguish the true bugs from other insects. Almost all have two pairs of wings. The forewings are thick and leathery near the base and thin and membranous near the tip; the hind wings, used for flying, are completely membranous. Unlike the many insects that bite and chew, bugs have beaklike mouthparts, which they use to pierce the skin of plants or animals and then suck out the juices. In addition, bugs undergo an incomplete metamorphosis. The young, called nymphs, molt several times and develop into adults without passing through a pupal or resting stage-quite different from the complete metamorphosis of beetles.

Bulb

A fleshy, underground structure found in certain plants and comprising leaf bases and next year's bud.

Bulbil

A small, bulblike structure.

Bulk Water Removal (Water)

The removal and transfer of water out of its basin of origin by human-made diversions (e.g., canals), tanker ships or trucks, and pipelines. Such removals have the potential, directly or cumulatively, to harm the health of a drainage basin.

Bullfrog

Rana catesbeiana

Named for their loud, deep-throated croaks, bullfrogs live in the shallows of permanent bodies of fresh water across most of the continent. Up to eight inches long with smooth, greenish brown backs, tan bellies, and powerful hind legs, they are our largest frogs. On spring nights, males shatter the stillness with their booming mating call, a resounding jug-a-rum. While the notes may be jarring to human ears, they attract female bullfrogs in large numbers. After mating, the females lay clusters of as many as 20,000 eggs and attach them to underwater vegetation. The eggs hatch into tadpoles, which, depending on the climate, take one to three years to develop into adults. Hunting mostly by night, bullfrogs prey on insects and other small animals. They can be caught quite easily if dazzled by the beam of a flashlight, and will often "play dead," only to spring back to life and escape at the first opportunity. Many are captured in the wild and raised commercially both for their tasty leg meat and for use as laboratory animals.

Bullhead

See Catfish.

Bullsnake Pituophis melanoleucus

At five to nine feet in length, bullsnakes are among the largest snakes in North America. Their massive bodies are yellow or tannish, marked with dark blotches. Though harmless to man, they can make a tremendous fuss when disturbed, vibrating their tails like rattlesnakes and hissing loudly. Larger specimens even make snorting sounds like those of a bull-hence their name. Powerful constrictors, bullsnakes feed mainly on gophers, rats, and mice and so are protected by farmers in both barn and field. Known in the West as gopher snakes, they are called pine snakes in the East.

Bunting

A number of small, plump, finchlike birds with stout, seed-crushing bills are known as buntings. Some, related to cardinals and grosbeaks, are brilliantly colored. The others, more closely akin to sparrows, wear more somber hues. The brightly tinted buntings are birds of brushy areas. The females, tan or greenish, build their nests well hidden in thickets, while the males flaunt their colors as they sing from conspicuous perches. The male indigo bunting, a rich metallic blue, is one of the few birds that fill the air with song at midday; it performs its recitals well into August. Another, the lazuli bunting, is bright turquoise with orange on the breast. But the most brilliant of all-some call it our most beautiful bird-is the painted bunting. A dazzling patchwork of red, blue, and green, the painted bunting used to be called the nonpareil- French for "unequaled." The drabber buntings prefer open country and nest on the ground. The well-named snow buntings, mainly white with dramatic black accents, winter in the northern states and move about in flocks. In spring they head north for the arctic tundra, where males help the females rear their young. Males of the lark buntings, in stark contrast to snow buntings, are almost completely black, except for a large white patch on each wing. Birds of the Great Plains, they gather in enormous flocks in winter, roaming about in search of seeds.

Burdock

Arctium

Coarse, invasive weeds up to eight feet tall with large, rhubarb like leaves and clusters of purplish, thistle like flowers, burdocks thrive in fields and pastures across much of North America. Two factors have guaranteed their spread despite all efforts to eradicate them: the vigor with which they thrust their thick taproots into the earth (even through compacted, uncultivated soil), and their finesse as hitchhikers. Each bur of 10 to 25 seeds is surrounded by a stubble of tiny hooks that cling tenaciously to any passerby. Tangled in the fur of animals, the seed heads may ride for weeks and miles before dropping off to colonize new territory-and so ensure the burdocks' success.

Bur reed

Sparganium

Well-known to both bird watchers and duck hunters, these freshwater marsh plants are much favored by migratory waterfowl. The long, ribbonlike leaves of the bur reeds, which may rise shoulder high above the water, furnish ducks and other animals with cover in which to hide and nest, while the tough, spiky seed balls serve as an important food source. The plants, in turn, are benefited by the birds; migrating ducks sow the partially digested seeds of bur reeds at stops all along their route.

Burying beetle

Nicrophorus

The undertakers of the insect world, burying beetles specialize in the interment of dead mice, voles, birds, and other small animals. Usually less than an inch long, these glossy black insects with orange-red markings first locate a dead animal with their sense of smell. A mating pair then teams up to push it to soft ground, where the beetles burrow beneath the carcass until it sinks a few inches below the surface. After the pair has covered the body with soil, the female lays eggs on the corpse, which becomes both larder and nursery for the offspring. Burying beetles are also called sexton beetles, recalling the fact that in the past the duties of church sextons included the digging of graves.

Bushtit

Psaltriparus minimus

Tiny, grayish birds with stubby bills and long tails, bushtits spend most of the year in flocks of 20 or more birds, traveling through brushy woodlands in the West. Twittering, acrobatic fliers, the birds call constantly to one another with soft lisping notes as they dart among small trees and shrubs foraging for insects.

Their nest, built over a period of weeks, is a hanging, baglike structure made of twigs, moss, and lichens and held together with spiderwebs. Both members of a pair build the nest, incubate the eggs, and tend the young. Bushtits often raise more than one brood per year, with the young from the previous clutch remaining to help with the new arrivals.

Buteo

Well-equipped for hours of soaring, buteos are hawks with broad, rounded wings and fanshaped tails. Their effortless flight lets them scan vast areas of countryside for prey and migrate for long distances by riding on rising currents of warm air. Found throughout North America, many of the buteos-such as the red-tailed, the rough-legged, and Swainson's hawks-prefer open country, while the broad-winged and the red-shouldered hawks frequent wooded areas.

Butte

Flat-topped and steep-sided, the towering red sandstone buttes of Monument Valley on the Utah-Arizona border are familiar to many as the scenery in western films. One tall, slender butte known as the Totem Pole has the same dimensions as the Washington Monument; at sunset it casts a shadow that extends for miles across the desert floor. Nearby are two massive stumps called the Elephant's Feet, which look like the fossil remains of some ancient behemoth. The buttes are the lonely remnants of a vanished plateau that once stood high above the present valley floor. Attacked by wind and water for countless centuries, most of the rock has long since been worn away. Only the slender, scattered buttes, protected by erosion-resistant caps, remain standing today.

Butter-and-eggs

Linaria vulgaris

Also known as toadflax, these charming wildflowers look so much like their cultivated cousins, the snapdragons, that admirers sometimes transplant them into their gardens. Up to three feet tall and topped with jaunty spikes of flowers, butter-and-eggs thrives in fields and on roadsides throughout most of North America. Each pale yellow blossom has an orange lobe on its lower lip that both marks and blocks the entrance to its nectar supply. Since the sweet liquor is hidden at the end of a long spur, only long-tongued insects, such as bumblebees, can get at it. After drinking their fill, they emerge from the blossom thoroughly dusted with pollen, ready to fertilize the next plant they visit.

Buttercup

Ranunculus

Shiny yellow five-petaled buttercups are a conspicuous sight throughout the country, adding a bright splash of color wherever they spring up. Also called crowfoot because of the shape of their leaves, these wildflowers are fond of moist areas, and a few kinds even grow in water. One species, the tall buttercup, is a favorite with children, who hold the blossoms under each other's chin in a test that supposedly reveals their fondness for butter. Water crowfoot, which grows underwater, sends up creamy white blossoms that unfold above the surface. Despite their innocent appearance, some buttercups contain an acrid, toxic juice that can cause dizziness and even death in livestock. Fortunately, most grazers eat buttercups only as a last resort. Once having tasted the weeds, however, farm animals sometimes develop a perverse liking for it and return repeatedly for more, even after suffering from its ill effects. The juice of some kinds, while not as dangerous to humans, can blister the skin.

Butterfish

Silvery, schooling ocean fish with high, thin bodies that from the side seem almost round, butterfish look a bit like shiny, oversized silver dollars. (Some, in fact, are known as dollarfish.) Six to 12 inches long, with tiny mouths and deeply forked tails, they live in temperate to tropical waters along the Atlantic and Pacific coasts. Among the more common species are harvestfish, found in Atlantic waters, and the Pacific pompano; both are valued as food fish. Showing a marked tendency to seek shelter beneath floating objects, young butterfish often take up residence under the bells of jellyfish. One, the man-of-war fish, lives relatively unscathed amid the poisonous stinging tentacles of the notorious Portuguese man-of-war. When grown, however, butterfish abandon the protection of their floating, jellylike umbrellas and travel in schools.

Butterfly

Among the most beautiful members of the insect world are the butterflies. Together with moths, they make up the order Lepidoptera, from the Greek lepus, meaning scale, and pteron, meaning wing. The order is well named, for butterflies and moths are distinguished from all other insects by the minute scales that cover their wings. The differences between butterflies and moths are usually conspicuous. Butterflies ordinarily fly by day and are brightly colored, while moths have dull colors and fly by night. Butterflies tend to rest with the wings folded up over their backs, and moths rest with the wings fanned out. There are, however, notable exceptions to these "rules," and the only sure way to recognize a butterfly is by examining its antennae. Butterfly antennae have a knob at the tip; on moths they are feathery or finely pointed. Nearly 700 species of butterflies are found in North America, and they vary widely in shape, color, and ornamentation. Some, such as the skippers, are dull, stocky, and mothlike in appearance. The checkerspots and fritillaries, in contrast, have elaborate, boldly colored wing patterns in orange, yellow, and black. The blues, coppers, and metalmarks not only are colorful but have an iridescent glow. The buckeyes, pearly eyes, and satyrs are ornamented with eyespot patterns- prominent black spots or colored concentric circles on the wings. Other butterflies are known for the unusual shapes of their wings. The anglewings have jagged, irregularly shaped wings. Swallowtails and daggerwings have daggerlike extensions on their hind wings, while the hairstreaks have thinner, more hairlike "tails." The particles of "dust" that rub off the wings of a captured butterfly or moth are actually tiny scales. Arranged like shingles on a roof, they account for the variety of colors and patterns on butterfly wings. In some species the scales are colored by pigments. In others, they are grooved in such a way that the play of light on their surfaces produces the effect of color. The iridescence on the wings of blues and coppers is caused in this way, and their metallic glint is accentuated by a thin film of oil on the scales. Wing scales also playa role in the mating of butterflies, which rely on scent to attract and locate the opposite sex. Glands at the base of some scales produce a distinctive aroma, which is diffused through tufts of very fine hairs at the tips of the scales. As if to confirm his amorous intentions, a male sometimes brushes these hairs over the antennae of the female. The patterns on butterflies' wings play a significant role in their survival. Many have wings that so closely mimic the leaves, twigs, or bark they rest on that they are nearly invisible to predators. Wings with eyespots and other patterns mislead predators, encouraging them to bite in nonvital areas. And bright colors, though conspicuous, often startle would-be predators or deter them in other ways. The brightly colored monarch, for instance, is highly toxic. Once a predator learns this, through trial and error, it will leave the monarch alone. The nontoxic viceroy, nearly identical in appearance to the monarch, survives by capitalizing on mistaken identity. In the course of its life, a butterfly undergoes a complete metamorphosis, drastically changing in form and appearance. The four stages in its life cycle consist of the egg; the caterpillar, or larva; the chrysalis, or pupa; and finally the adult butterfly, or imago.

The adult female lays a few to several hundred sticky eggs: depositing them on the leaves or stems of plants best suited to the food needs of the caterpillars. Some butterflies lay their eggs singly, others in chains or large clusters. The shapes of the eggs, which are best observed with a magnifying glass, vary with the species; some are simple, smooth spheres, while others have unusual shapes and may be elaborately ornamented, with fluted, ribbed, or pitted surfaces. Unless the egg is meant to survive the winter, as in some species, the caterpillar normally hatches within a week and begins gorging on food. During the larval stage the caterpillar must eat as much as it can to sustain it through the noneating pupal stage. To avoid being eaten themselves, many caterpillars are well camouflaged, and those that are not are often conspicuously colored, relying on their unpleasant taste or an armor of spines to make them difficult for predators to swallow. After about a month of eating and several molts to accommodate its increasing size, the caterpillar settles into a suitable spot to pupate. It may hang from a plant by a silken thread, attach itself to a stem with a girdle of silk, or remain on the ground. After a few days the caterpillar's skin shrivels and is cast off, leaving the chrysalis, or pupa. The outside of the chrysalis, though usually blending in with its surroundings, also shows the rudimentary outlines of the developing butterfly's wings, eyes, and legs. Eventually the chrysalis splits open, and the adult insect pulls itself free, climbing onto a twig or leaf to rest while its wings expand and dry. Soon it flies off to begin life as an adult butterfly, a life that will last an average of two weeks but may continue for many months. The adult butterfly survives on plant nectar, which it drinks through its long, tubelike tongue, or proboscis. The nectar provides the energy needed for flight and for the butterfly's last and most important function: reproduction. Once a male and female of the same species have found each other, they begin an aerial courtship that involves elaborately choreographed movements such as fluttering, diving, and spiraling. Mating itself begins on a branch or other perch and may continue in the air. Finally, some days after mating, the female lays her eggs, and the complex and astonishing life cycle of the butterfly begins all over again.

Cabbage butterfly Artogeia rapae Common in fields and gardens across the country, cabbage butterflies are serious agricultural pests whose larvae feed on cabbage, mustard, cauliflower, and other crop plants. Accidentally introduced to North America in the 1860's, they have since become the most common butterfly in many areas; they can even be seen fluttering over the scattered patches of greenery in cities. Not the most colorful of their kind, cabbage butterflies have white forewings tipped with black. Dark spots, one on the male and two on the female, dot the wings near the bottom edge. The caterpillars, which hatch from eggs laid on plant leaves, are bright green with yellow stripes.

Butterflyfish

Like butterflies in a flower garden, these dainty, disc-shaped fish flash with bright colors as they flutter across reefs of rock or coral. Though they prefer shallow tropical seas, a few hardy species venture as far north as New England. Many, like the foureye butterflyfish, have dark bands that mask the eyes and dummy "eyespots" toward the rear of the body; would-be predators mistake tail for head and lunge at the less vulnerable end of the fish. With tiny, pouting mouths lined with bristly teeth, butterflyfish feed on coral polyps, tubeworms, and algae. The longsnout butterflyfish of Florida can insert its slender nose between the spines of sea urchins to extract prey. Other species are living vacuum cleaners, nibbling parasites from the skins of infested fish.

Butterwort

Pinguicula

Lying flat on the ground, the butterworts' rosettes of greenish-yellow leaves glisten in the summer sun. Their sheen results from drops of liquid secreted by glands on the upper surfaces. This sticky secretion gives the leaves a greasy feel; hence the name butterwort. It also serves a vital purpose: it transforms the leaves into a kind of natural flypaper designed to trap any small insects that land on them. The leaves then secrete a digestive juice, extracting nitrogen and other vital nutrients from their prey. Found in bogs and other damp places, the carnivorous butterworts make a lovely display from spring into summer as they wave their colorful, spurred blooms atop delicate stems.

Buttonbush

Cephalanthus occidentalis

Although it is fairly widespread across the country, few people know this handsome shrub, for buttonbush hides in swamps and along the drowned margins of ponds and streams. At summer's end, however, a rich aroma reveals its presence; it is then that the buttonbush bears its creamy, sunburst-shaped, richly fragrant flower heads, which provide a welcome feast of nectar for bees and other insects. The name buttonbush derives from the spherical seed heads, up to an inch across, that follow. Hanging from the barren branches all winter long, they look a bit like buttons dangling from a tattered coat.

Cactus

Characterized by fleshy stems and an armament of spines, the cacti are a richly varied plant family. Of the 2,000 species included in the group, all but 1 are native to the New World, and some 1,200 are indigenous to North America alone. They range from the tiny, buttonlike peyote to the sentinel-like saguaro, which grows up to 60 feet tall. The most notable common characteristics of the cacti are their many adaptations for surviving drought. Their bodies are filled with soft, porous tissue that absorbs water and holds it like a sponge, allowing them to store moisture in wet periods for use through the ensuing dry seasons. Some of the cacti are ribbed with accordion-like pleats that enable them to expand as they fill with water. To minimize the amount of moisture lost by evaporation through the skin, most cacti produce no leaves and have a waxy, waterproof outer covering. Even their shapes - globes, cylinders, and barrels-help guard against dehydration, since they are the forms that allow for the greatest volume with the least surface area. When the rare rain does fall, some of the cacti respond by sending out shallow networks of hairlike roots to tap the moisture, then shed the new growth when the soil dries. The cacti's spines also play a vital role in survival. More than mere protection against grazers, they cast enough shadow to help shade the plants and keep them cool. (The layer of air trapped under the spines may be 20°F cooler than the outside air temperature.) By slowing the circulation of air, the spines also help minimize the drying effect of wind. In some cases, they even function as water collectors; moisture from fog or light rains condenses on downcurved spines, gradually collecting into drops that fall directly on the roots.

Caddisfly

Found in ponds and streams across most of the country, caddisfly larvae are freshwater aquanauts. Those of some species tend silken nets that they spin to entrap food, but many others move about in search of their meals, secure in the protection of mobile homes that they build around their own bodies. The cases are usually tubular, with only the larva's head and legs projecting from one end. Building materials, held together by silk or glue, range from sand grains to plant stalks and pieces of shell. As they approach maturity, the caddisworms seal up their cases and pupate inside. Eventually they are transformed into delicate, winged, mothlike insects of the night.

Caldera

Far different from the small craters found atop volcanic mountains, calderas are huge circular depressions that result when a volcano completely destroys itself. They usually are formed when an extraordinarily violent eruption spews out so much lava that the magma chamber beneath the volcano becomes empty, causing the top of the mountain to collapse into itself. A well-known relic of such an event is Crater Lake in the Cascade Mountains of Oregon. The six mile-wide expanse of water fills a caldera left behind by the titanic explosion of Mt. Mazama, an ancient volcano. Almost 2,000 feet deep, Crater Lake is the deepest in the United States. Only Wizard Island, a small volcano rising above the water's surface, gives a hint of the fiery mountain that once stood where the lake is now.

California poppy

Eschscholzia californica

In late April, when the hillsides of southern California blaze with countless millions of these golden blossoms, it is easy to understand why early explorers sometimes called the area "the land of fire." Borne one to a stem atop mounds of finely cut, blue-gray foliage, the cup-shaped flowers of the California poppy usually have four petals and range in color from brilliant yellow to deep orange. The elongated pods that follow the bloom explode when they mature, scattering seeds for several feet. The official flower of California, this delightful native poppy is at its best there. But it is widely cultivated as a garden flower as well and has established itself in the wild as far afield as Australia.

Camas

Camassia

Before the arrival of white settlers in the West, these showy members of the lily family were so plentiful that their starchy bulbs were a staple food of several Indian tribes. Five species of camas flourished in damp meadows throughout much of the West, with one, the wild hyacinth, found as far East as Pennsylvania. Explorers described vast expanses of starry blue, white, and purple blossoms clustered atop wandlike stems that rose two to three feet from tufts of grassy leaves. Nowadays the common camas, or quamash, sometimes still colors whole meadows, but the other camases have been wiped out in many areas, the result of overgrazing and cultivation of the land.

Camouflage

Whether hunters or hunted, many animals make use of camouflage to escape enemies or deceive prey. In most cases they rely on color or pattern to blend into their surroundings, but shape and posture can also play a role. The green snakes, for instance, all but disappear as they slither through the grass, and the mottled brown woodcock is nearly invisible on the forest floor. Fawns, brown and spotted, are inconspicuous in sun-dappled woodlands, while on open beaches plover chicks, as well as the eggs from which they hatch, are colored like the sand and pebbles around them. Another form of deception, called countershading, is practiced by animals with dark backs and light undersides. When seen from above, the dark backs of fish such as bass and mackerel blend in with the dark water; when seen from below, their light bellies are indistinguishable from the sunlit surface. Many birds with dark backs and white breasts wear a similar disguise. Other animals actually change color to match their surroundings. Flounders and the chameleon-like anoles, for example, change to blend with their backgrounds when they move from one place to another. Ptarmigans, ermines, and snowshoe hares, in contrast, change color with the seasons. During the summer they wear dark, earth-colored feathers or fur. But in winter, their warm-weather colors are replaced by suits as white as snow. In the insect world, many grasshoppers, katydids, mantids, and others are as green as the plants they rest on, and moths and caterpillars often are patterned like dead leaves, bark, or other vegetation. But the real professionals in the camouflage act are the ones that pose as inedible objects. Walkingstick insects are easily mistaken for twigs, and many of the treehoppers look exactly like thorns.

Camouflaged

An Animal Behavior term, this is used to describe color and patterns of Animals which blend with their background, thereby minimizing the risk of predation or, in the case of predators, enabling undetected approach to prey.

Campion

Lychnis

Hardy members of the carnation family, campions are most commonly found in cool northern regions. The white campion, however, ranges as far south as South Carolina. Opening only at night, its inch-wide blossoms are white, making them more visible to the moths on which they depend for pollination. Its day-blooming relatives, such as red campion and ragged-robin, have more-colorful flowers in shades of red and pink. The name campion is also applied to a number of catchflies, similar wildflowers that belong to another genus.

Endangered and Threatened species term.

Plants and animals that have been studied and the U.S. Fish & Wildlife Service has concluded that they should be proposed for addition to the Federal endangered and threatened species list. These species have formerly been referred to as category 1 candidate species. From the February 28, 1996 Federal Register, page 7597: "those species for which the Service has on file sufficient information on biological vulnerability and threat(s) to support issuance of a proposed rule to list but issuance of the proposed rule is precluded."

- A term no longer in use, having been replaced by the term "candidate species" which uses the same definition.

- A term no longer in use. Previously referred to species for which the Service had some indication that listing as threatened or endangered might be warranted, but there were insufficient data available to justify a proposal to list them.

- A term no longer in use. Previously referred to species which once were category 1 or 2 candidate species, but for which subsequent data indicated that listing as threatened or endangered was not appropriate.

Canine

The domestic dog and its wild, meat-eating relatives, such as wolves, coyotes, and foxes, are all canines. Common characteristics of the wild canines are long, pointed snouts, triangular ears, and bushy tails. Lean, muscular, and longlegged, they are good runners, well suited for the pursuit of prey. They also are intelligent animals, with keen senses of hearing and smell.

Cannibalism

An Animal Behavior term, this describe eating members of an Animal's own species. It has been reported in many species but is relatively uncommon, except in Animals subjected to stress or high population density.

Canyon

A mile deep in places, the Grand Canyon in northern Arizona covers an area the size of Delaware. From the rim, the river that created the awesome abyss can barely be seen. Snaking across the bottom of the gorge, however, the Colorado River continues to slice downward through the rock. Its power to erode is evident in the river's muddy water, which has been carrying away tons of silt, sand, and gravel for some 20 million years. The river was not the only agent involved in deepening the canyon, however. At the same time that it was cutting downward, upheavals of the earth's crust were raising the Colorado Plateau through which the river had to carve its pathway to the ocean. In the process, layers of rock representing a billion years of geologic time have been exposed. The stepped appearance of the canyon walls results from the fact that the different kinds of rock vary in their ability to withstand erosion. Although the many canyons carved into the brightly colored rocks of the Colorado Plateau are among the most beautiful, canyons are common throughout the West. They occur in arid regions where rivers deepen gorges faster than their steep sides can be reduced by weathering.

Cap

A structure seen in fungi under which spore-bearing structures, usually gills or pores, are suspended. The top of a mushroom.

Capsule

A structure within which seeds are formed in flowering plants and spores develop in mosses and liverworts.

Capture-recapture method

A procedure involving the distinctive marking of individuals and their subsequent recapture (or sighting) to estimate population size and other population parameters.

Caracara

Polyborus plancus

Large, dark, long-legged, and long-necked, with a distinctive black crown and red, naked face, the crested caracara looks and behaves somewhat like a vulture, although in fact it is related to the falcons. It gets its name from its harsh, cackling cry and makes its home on open scrublands in Florida, coastal Texas, and southern Arizona and New Mexico. In flight this splendid bird can be identified by its long, broad wings with conspicuous white patches. It is more commonly seen on the ground, however, walking in a regal manner or feeding, alongside vultures, on carrion. A brash bully that is not above stealing food from vultures, the caracara also captures frogs, lizards, and other small prey.

Carapace

The hard, upper surface of a crustacean's shell. Protecting the bodies of creatures as diverse as crabs, insects, and turtles, an animal's carapace is a rigid case covering all or part of its back. On turtles, the carapace is the domed upper shell and is composed of a bony layer overlain by hard, horny plates. The carapace of insects and crustaceans, such as crabs and shrimp, is made of a tough, waterproof substance known as chitin. As with turtles, this enveloping armor protects the animals from predators and prevents moisture loss. But it has another function as well: whereas turtles have an internal skeleton of bones, the carapace of insects and crustaceans serves as part of their external skeleton.

Cardinal

Cardinalis cardinalis

Bright crimson plumage and a regal crest make the northern cardinal unique and unmistakable. Its stout, cone-shaped bill identifies the bird as a seedeater, and indeed the cardinal is a familiar sight at feeders everywhere east of the Great Plains as well as in parts of the Southwest. Originally confined to the southern states, the nonmigratory cardinal is gradually expanding its range northward into Canada. Aggressively territorial, cardinals sing with a variety of loud, clear whistles. Females, though more subdued in color than the males, have the same distinctive crest and are just as vocal. Nesting in shrubs and thickets, the birds often raise more than one brood a year, with the male caring for the young while the female begins the next brood.

The pyrrhuloxia, a close relative of the northern cardinal, lives in desert scrub in the Southwest. Also known as the Texas cardinal and the parrot-bill, it is mostly gray, with a few prominent patches of red, but nevertheless looks much like its more brightly colored cousin. Both the male and female share in building a tidy, cup-shaped nest in thorny desert scrub, where they raise just one brood each year.

Cardinalfish

Found near coral reefs in warm or tropical seas, most cardinalfish, true to their name, are vivid red. Despite their bright color, however, the tiny fish - most are just one to four inches long - are often difficult to spot. During the day they elude predators by hiding in crevices, caves, burrows, and even in or on other animals. Some species, for instance, dwell among the spines of sea urchins, the tentacles of sea anemones, and between the valves of certain clams. Brownish rather than red, the sponge cardinalfish lives in tube sponges, while the conchfish inhabits the snaillike shell of queen conchs. At night, the cardinalfish emerge from their hiding places and hunt for small prey.

Caribou

Rangifer tarandus

Like their old-world relatives, the reindeer, caribou are stocky deer of the Far North, with the biggest males weighing as much as 700 pounds. In contrast to most other deer, both sexes have many-branched antlers, though the males' are much larger. Big round hooves ease their passage as they roam across bogs, snow, and soggy tundra. The hollow outer hairs of their coats keep them warm and help make them buoyant (caribou are excellent swimmers), while dense underfur insulates them. Two races of caribou are found in North America. Woodland caribou live year-round in northern evergreen forests across much of Canada. Barren ground caribou, on the other hand, are migratory and travel in herds that sometimes number in the tens of thousands. They winter in forests just south of the tree line and in spring head north for the Arctic tundra, a journey of up to 800 miles. Following the same routes year after year, they feed along the way on grasses, sedges, and the abundant lichens known as reindeer moss. Calves born on the trek follow their mothers when just hours old.

At summer's end, the herds turn south again. Males battle with each other during the autumn mating season, with the winners establishing and jealously guarding harems. The herds then spend the lean winter months in the forest, browsing on willow and dwarf birch and pawing through the snow with their sharp-edged hooves to reach buried lichens.

Carnivore

To the taxonomist, the term carnivore refers to land-dwelling mammals in the large order that includes such diverse creatures as dogs, cats, weasels, and bears. But in a broader sense the word can be applied to any animal - from birds and fish to reptiles and insects-that feeds on other animals. Herbivores, in contrast, are animals that feed mainly on plants, while omnivores eat both plant and animal matter. Carnivores have adapted to capturing and eating food in a variety of ways. Hawks and owls, for instance, are equipped with hooked, flesh-tearing beaks, while the specially hinged jaws of snakes enable them to swallow their prey whole. Other animals, such as cats, rely on agility and speed to outmaneuver their victims.

Carnivorous

A carnivorous creature is any mainly or exclusively meat-eating organism; alternatively. a member of the order Carnivora, many of whose members are carnivores.

Carnivorous plants

More than 40 species of carnivorous plants are native to the United States, and like their hundreds of relatives around the world, they all thrive on adversity. Although they manufacture most of their food in their leaves just as other plants do, their ability to trap and digest insects and similar prey has enabled them to flourish in habitats where few other flowering plants are able to survive. Most carnivorous plants live in bogs or swamps, where the highly acidic soil lacks vital mineral nutrients and so is too poor to support most vegetation. The carnivores are able to flourish in such places because of the extra nitrogen, phosphorus, and trace elements they derive from their animal prey. In general, carnivorous plants are of two kinds: those with active traps and those with passive ones. The best known of the active trappers is the Venus flytrap, which has specially adapted leaves that snap shut like bear traps on unwary insects. Passive traps are used by the pitcher plants, which drown their prey in pools of liquid, and by the sundews and butterworts, which secrete sticky fluid on their leaves, turning them into a kind of natural flypaper. The aquatic bladderworts consume any small animals that are sucked into their bladderlike underwater traps. Because of their unique adaptation to one kind of environment, many carnivorous plants have severely limited ranges. The Venus flytrap, for example, occurs naturally in only one small area of North and South Carolina. On richer soils, few of the carnivores can compete with less specialized but more vigorous plants.

Carp

Cyprinus carpio

Hardy and adaptable fish, carp thrive in almost any freshwater environment, from weed-infested lakes and rivers to polluted ponds and backwaters. Asian natives, they were introduced to North America from Europe, where they are commonly cultivated for food. Many think the introduction was a mistake, however, because carp frequently displace more desirable fish. Since they feed by rooting on the muddy bottom for small animals and plants, they often destroy the eggs of other species, as well as the vegetation that the young fish need for cover. Carp are stout-bodied fish with short, fleshy whiskers near the mouth. Their large, coarse scales are dark on the back and tinged with bronze on the sides. Although they average about 15 inches in the wild, carp raised in captivity may grow to 3 feet and live for 40 years. Some anglers value carp for sport. The fish are normally caught with rod and reel, but when large numbers are found in shallow water, carp are sometimes shot with bow and arrow.

Carpal

Bird Biology Avian Ecology term. The area on a bird's wing corresponding to the "wrist" joint.

Carrying Capacity

The constant number that, left to itself, a natural population will achieve in a given ecosystem. The idea there is a constant number is, according to some ecologists, an unwarranted assumption. See Balance of Nature. The maximum number of individuals that can use a given area of habitat without degrading the habitat and without causing social stresses that result in population reduction.

Caste

An Animal Behavior term, this is used to described individual members of a species which are adapted to perform a particular task, both by their structure and their behavior. Usually applied only to social Insects such as Honeybees and Termites.

Catalpa

Lush and green, with large, heart-shaped leaves throughout the summer, catalpas have an exotic, almost tropical look. But the trees are at their best when covered with big, upright clusters of showy white flowers in late spring and early summer-a time when few other trees are in bloom. Attractive and fast-growing, they have been valued as shade and ornamental trees ever since 19th-century settlers began planting them in parks and gardens. As a result, both of our native species-the northern catalpa, which was once confined to a small area of the Midwest, and the southern catalpa, once found only near the Gulf Coast-now are common in all but the coldest states. The trees also are known as Indian beans because of the long beanlike pods that develop after the flowering season. Turning brown, they hang on the trees all winter long before splitting open and shedding their seeds the following spring. The leaves of the northern species are fed upon by caterpillars of the catalpa sphinx moth. Green and horned, the larvae eventually mature into colorful and convincing mimics of the hummingbird.

Catastrophe

An event that causes sudden decreases of population size or the entire elimination of subpopulations.

Catastrophism

Biological Philosophy term. One side of a nineteenth-century geological argument about the forces that have shaped the earth. Catastrophism proposes that the earth was shaped by sudden, cataclysmic upheavals (such as the "Flood" or "Deluge" of Noah in the Bible) and that the laws of nature in the periods between these cataclysms are not the same, that is, "uniform." The issue is this: if the laws are not uniform, we cannot really see back beyond the last major cataclysm and so cannot reliably talk about millions of years in the past. Compare Uniformitarianism.

Catbird

Oumetella carolinensis

An uncanny, catlike mewing announces the presence of the gray catbird even before the black-capped, slate-gray bird itself emerges from the underbrush where it usually hides. Like its close relative the mockingbird, the catbird is a talented mimic. Its renderings are not as varied or as accurate as the mockingbird's, but its often melodious, sometimes squeaky phrases clearly suggest the songs of other species. Breeding across most of North America from southern Canada to the Gulf States, the catbird is a friendly creature that is welcomed in suburban yards and gardens. Both males and females incubate the four to six shiny, greenish-blue eggs in a cuplike nest of twigs. In spring, the catbird feeds almost exclusively on insects and provides a valuable service by eating the destructive caterpillars of the gypsy moth.

Catchfly

Silene

Widespread members of the pink or carnation family, the catchflies are so called because crawling insects sometimes get caught in the sticky hairs on their stems. Unlike the carnivorous plants, however, the catchflies do not consume insects as food. The stickiness instead serves as a barrier that prevents crawling insects from pilfering the flowers' sweet nectar, which is reserved for the flying insects that distribute pollen. Known by a variety of names, some of the catchflies are called campions because of their resemblance to their near relatives, the true campions, while still others are called pinks.

Caterpillar

A larval stage of a butterfly or moth. The wormlike larvae of butterflies and moths, caterpillars got their name from a word meaning "hairy cat"-and many are hairy indeed. The wooly bear, the larva of the Isabella tiger moth, has a thick coat of black hair with an orange band on its midsection that supposedly predicts the length of winter. Such bristly surfaces discourage predators; some caterpillars further protect themselves by secreting irritants from special glands. Smooth-skinned caterpillars include the inchworm, which moves by alternately hunching and stretching its body, and the striped larva of the monarch butterfly.

Catfish

Whiskerlike feelers, or barbels, around their mouths give the catfish their name. Living on the bottoms of lakes, ponds, and slow-moving streams, they use the taste- and touch-sensitive feelers to help locate their food, which includes fish, insect larvae, crustaceans, and a wide variety of other creatures. Catfish have no scales, but some of their fins are armed with sharp spines that can cause painful injuries. The most abundant of the North American catfish are the bullheads. Popular with anglers, they average 10 inches in length but can grow much bigger. The largest American species, the blue catfish of the Mississippi River system, grows to five feet and weighs as much as I50 pounds. The channel catfish, slender by comparison, reaches four feet but weighs only 30 pounds. Popular as food fish, catfish are raised on commercial fish farms in the South.

Catkin

A flowering structure of certain trees and shrubs. Found on a variety of deciduous trees and shrubs, from willows to oaks and birches, catkins are flower clusters pared down to the bare essentials. On pussy willows they are the small silvery tufts that stand erect like furry candle flames, signaling winter's end; on hickories they dangle like long, fuzzy pendants, each one containing dozens of individual flowers along its length. Because most depend on the wind for pollination, these tiny flowers lack petals and sepals-any structures that might impede air circulation. And most catkins appear in early spring, while the branches are still bare. Often the male (pollen-producing) and female (seedproducing) flowers are borne on separate catkins and sometimes on separate plants.

Cattail

Typha

The tall, sturdy stalks with cigar-shaped tips that give cattails their name are a common sight in marshlands all across the continent. Shooting upward in the spring, they wave the cattail's densely packed flowers aloft where the wind can catch their pollen and carry it far and wide. A single flower head may produce more than 140,000 seeds, each of them equipped with its own parachute of down to help it sail away to new territory. If a seed lands on well-watered soil, it can develop in a single season into a patch of cattails 10 feet across.

Cattails have been used in remarkably varied ways. Indians and pioneers wove the leaves into baskets and chair seats, and cattail fluff once served as stuffing for quilts and mattresses. The pollen makes a tasty flour substitute, and the cooked roots are as nutritious as rice.

Caudal fin

The tail fin of a fish.

Causation

An Animal Behavior term describing the immediate causes of behavior and the mechanisms by which they act. Studies of causation investigate factors such as how external stimuli and internal factors, such as hormones, affect behavior and the neural structures involved in its production.

Cave

Festooned with iciclelike stalactites, rosettes of mineral crystals, and other exotic formations, caves encompass some of North America's most fascinating scenery. Usually found in areas underlain by thick layers of limestone, they are formed when slightly acid water seeps through cracks in the soluble rock and dissolves ever larger openings. Caves sometimes develop into complex systems of rooms and winding passageways, which can be many miles long and extend deep into the earth's interior. Among the best known of these hidden underground worlds is Carlsbad Caverns in New Mexico. Its "Big Room" covers 14 acres and has a ceiling that, at its highest, could accommodate a 30-story building. Once filled with moving water, the chambers at Carlsbad eventually were raised above the water table and now are relatively dry. Kentucky also is riddled with caves. The largest, Mammoth Cave, has miles of interconnecting rooms linked by twisting passageways. With streams still running through its lowest levels, this remarkable cave system continues to grow. Missouri, too, is pitted with hundreds of caverns. One of them, the labyrinthine Mark Twain Cave near Hannibal, was made famous by Twain's novel Tom Sawyer.

Cave animals

Though dark and mysterious, caves nevertheless are home for a rich variety of animal life. Owls roost by day in crevices near the entrances, while phoebes and swallows build mud nests on the walls. Pack rats nest on the floor, venturing outside at night to forage and look for objects to add to their collections of debris. Deeper inside the cave are the permanent residents, including fish, crayfish, salamanders, spiders, and beetles. In their world of perpetual night, high humidity, and nearly constant cool temperatures, these creatures have developed a number of special adaptations. Many fish have lost all pigmentation and are as white as alabaster. Most cave fish are blind as well, with mere traces of eyes, or none at all; highly developed senses of touch, smell, and hearing compensate for their lack of vision. Many of the crayfish, salamanders, millipedes, and other creatures of the cave also are colorless and blind. The best known of all cave dwellers are bats, which roost in the caves by day and emerge at night to feed on insects. The roosting bats often are so numerous that they form a dense canopy across the ceiling. And when they leave at dusk, they come out in huge clouds that darken the sky. Carlsbad Caverns in New Mexico were discovered by a cowboy who spotted a cloud of bats. Bracken Cave in Texas, another notable roost, is home to an estimated 20 million bats.

Cecropia moth

Hyalophora cecropia

Often seen fluttering near bright lights, the cecropia moth is popular with collectors. Its velvety brown wings, with a span of about five inches, are brightly patterned with white and reddish bands and spots. The adults do not eat, but the larvae-green, with spiny red, yellow, and bluish tubercles-feast on the leaves of many trees and shrubs. Found in cities, suburbs, and rural areas, cecropia moths range from the Atlantic Coast to the Great Plains.

Cedar

The coniferous evergreen that the ancient Greeks called kedros was made famous by King Solomon, who used its timber for the temple at Jerusalem. He chose the cedar for its reddish, aromatic, rot-resistant lumber. While the true cedars are old-world species, a number of our native evergreen trees have similar wood and were dubbed cedars by the early settlers. This has resulted in a great deal of botanical confusion. The eastern red cedar and southern red cedar, for example, are actually junipers, and the western red cedar, also known as giant arborvitae, is really a thuja. The Atlantic white cedar belongs to yet another genus. Adding to the confusion, a rare tree native to Florida, a relative of the yews, is called stinking cedar because its leaves release a fetid odor when bruised. This use of the word cedar for so many conifers illustrates how misleading common plant names can be. For although all our cedars are evergreens with durable, aromatic wood, none are closely related to Solomon's tree.

Celandine

Chelidonium majus

One of the earliest spring wildflowers in the northeast, celandine unfurls its bright green, deeply cleft foliage before the last snow melts, and opens its small, four-petaled yellow flowers by late April or early May. Farther south the plant is virtually evergreen, especially when it grows in a sheltered spot at the foot of a sundrenched wall. A member of the poppy family, celandine has orange sap that oozes from any cut stems. And as with many of the poppies, the sap has been used medicinally, though in this case to clear the eyes, not cloud the senses.

Census (noun)

Bird Biology Avian Conservation term.

A count of all individuals in a specified area over a specified time interval.

Census (verb)

Bird Biology Avian Conservation term.

The act or process of counting all individuals within a specified area and estimating density or a total population for that area.

Census efficiency

Bird Biology Avian Conservation term.

Proportion of actual population density that is assessed by a census.

Centipede

Unlike some of their tropical relatives, which can be as much as a foot long, our centipedes are rarely more than an inch in length. Even so, they are agile predators that run down insects, spiders, and earthworms. Though their name suggests that centipedes have 100 legs, the actual number varies from fewer than 40 to more than 340. One pair of legs is located on each body segment; they walk by moving the legs in neatly coordinated, rhythmical waves. Centipedes hide in dark, damp places under rocks, logs, and in leaf litter during the day and come out at night to hunt. They use their long, sensitive antennae to locate prey, and then paralyze it with their poison claws. Although most species are harmless to humans, some of the larger southern centipedes can inflict painful bites.

Century plant

See Agave.

Cephalopod

Squid, cuttlefish, octopuses, and the nautiluses all are cephalopods. Their name, from the Greek for "head-feet," refers to the fact that their grasping armlike tentacles grow out from the head. Like clams and snails, cephalopods are mollusks, but only the nautiluses have external shells. Cuttlefish and squid have only rudimentary shells imbedded in their bodies, and the octopuses have no shells at all. Among the most extraordinary features of the cephalopods are their "camera" eyes, with lenses that can be focused, like human eyes-an asset in capturing prey. Highly mobile, the cephalopods are jet propelled, moving about by expelling water through a muscular siphon in their bodies.

Cephalothorax

The fused head and thorax found in spiders.

Cerci

The paired appendages at the hind end of an insect's body.

Cervid

The common term for the family of Animals named Cervidae, which includes hoofed Mammals that have antlers. They are all ruminants. These include Deer, Elk, Moose, and Caribou.

Chaining

An Animal Behavior term describing sequences of behavior in which actions occur in a series, each one leading to the next. Within an Animal, this may be because one activity brings the Animal into the situation where the next is stimulated. Chaining may also occur between Animals, for example in courtship, where each partner often responds to the previous action of the partner in a series that leads to mating.

Chalk

The white, powdery variety of limestone from which blackboard chalk is made, chalk is composed of the remains of microorganisms that once drifted near the surface of the sea. When they died, their calcium carbonate skeletons rained down to the ocean floor and accumulated over the course of millions of years into layers many feet thick. Compacted into rock, the beds eventually were uplifted and exposed on the surface. The most famous chalk formations are the White Cliffs of Dover along the English Channel, but chalk beds were also deposited in shallow seas that once covered parts of North America, and can be seen in Alabama and Kansas.

Chamomile

Two common herbs are called chamomile, and they have much in common. Both have feathery, pale green foliage; pretty, daisylike flowers; and when crushed, a sweet, applelike aroma. Both, moreover, came to our shores in the baggage of European immigrants and have a long history of use among herbalists. Chamomile tea, brewed from the dried flowers of either kind, still is taken as a gentle, pleasant remedy for insomnia and upset stomach. The smaller of the two species, usually called true or Roman chamomile, grows only about nine inches tall and is the more fragrant of the two. The other, wild or German chamomile, at two to three feet in height, towers over its smaller cousin.

Chaparral

Taking its name from a Spanish word for scrub oak, chaparral is a specialized plant community made up of broad-leaved evergreen shrubs. Growing in dense thickets up to 15 feet high, it is found in hot, dry foothills from Arizona and Baja California northward through coastal California to southern Oregon. In addition to scrub oaks, the plants include manzanitas, chamisos, hollyleaf cherries, and dozens of other species. Although seemingly impenetrable, these tangles of vegetation are havens for hosts of animals, from lizards and packrats to wrens and thrashers. As part of the chaparral's natural cycle, thousands of acres fall victim to wildfires every year in the wake of the hot Santa Ana winds.

Chaparral biome

The Chaparral biome is found in a little bit of most of the continents. On the North American continent, it is found on the west coast of the United States.

Lay of the land: The chaparral biome has many different types of terrain. Some examples are flat plains, rocky hills and mountain slopes. It is sometimes used in movies for the "Wild West".

Chaparral is characterized as being very hot and dry. As for the temperature, the winter is very mild and is usually about 50 degrees F. Then there is the summer. It is so hot and dry at over 100 degrees that fires and droughts are very common.

Fortunately, the plants and animals are adapted to these conditions. Most of the plants have small, hard leaves which hold moisture. Some of these plants are poison oak, scrub oak, Yucca and other shrubs, trees and cacti.

The animals are all mainly grassland and desert types adapted to hot, dry weather. A few examples: coyotes, jack rabbits, mule deer, alligator lizards, horned toads, praying mantis, honey bee and ladybugs.

Char

Salvelinus

Prized by anglers and gourmets, the beautifully speckled chars are relatives of salmon and trout. In fact, both the brook trout and the lake trout are actually chars; they differ from true trout in having smaller scales and paler spots. Chars thrive in cold, clear waters across North America and spawn every autumn in the gravelly shallows of lakes and streams. The largest char, the lake trout, occasionally reaches 100 pounds, though most are caught before they reach 10 pounds. The brook trout is generally smaller but also puts up a challenging fight when caught. Other chars include the Arctic char, which inhabits northern waters and mountain lakes, and the Dolly Varden trout of the West.

Chemical (Industry)

Chemical industries are those involved in the importation, manufacture or sale of substances that are produced by or used in a reaction involving changes in atoms or molecules

Chemistry (Water)

The basic chemistry of water is hydrogen and oxygen, however unpurified water may also contain natural and human-made chemical pollutants.

Cheating

An Animal Behavior term, this is used to describe behavior believed to have evolved because the Animal showing it gains at the expense of other individuals. For example, male Scorpion flies present prey to females before mating, but some males cheat by mimicking females, flying off after accepting the gift and using it in their own courtship.

Cherry

Though modest compared to the splendid show put on by the ornamental cherries grown in parks and gardens, the spring flowering of our several native species nevertheless is a pleasant reminder of the progress of the season. The clusters of delicate, five-petaled, white flowers, like flurries of snow, contrast nicely with the shiny, reddish bark on the twigs. And the fruits that follow, though tarter than the imported cherries we grow in orchards, make tasty jams and jellies, as well as providing food for a wide variety of wildlife. The tallest and most valuable of our wild species is the black cherry, common in forests and fields throughout the East. Reaching a height of 100 feet, it is especially prized for its rich, reddish wood, which is second only to black walnut for fine cabinet work, decorative paneling, and musical instruments. Another species, found across the northern states and in the mountains south to Georgia and Colorado, is the pin cherry. It is also known as fire cherry because of the speed with which it follows in the tracks of forest fires. Its roots halt erosion, and its fallen leaves add humus to the soil, preparing the way for the forest's return. The most widespread of all the natives, the chokecherry is a common sight in hedgerows across most of the country. Its dangling clusters of pea-sized fruits are a boon to birds. Like some of the other wild cherry trees, though, its leaves can be a bane to any livestock that eats them; when the leaves wilt, a normally harmless substance contained in them is converted into the deadly poison cyanide.

Chert

A variety of quartz also known as flint and hornstone, chert is a dense, fine-grained sedimentary rock that has been valued for thousands of years. As early as the Stone Age, humans discovered that it can quite easily be chipped into sharp-edged tools and weapons. The first mineral to be deliberately mined, chert was fashioned into spearheads, knives, scrapers, and many other implements. In more recent times the rock again was used for weaponry when another of its properties, the ability to produce sparks, gave it a role as the firing device in flintlock rifles. Most commonly found as round nodules within other sedimentary rocks, chert also occurs in extensive, layered beds.

Chestnut

Castanea dentata

No tree was more esteemed by our early settlers than the American chestnut. Its soft but durable timber was used for cabins, rail fences, and furniture. And the sweet, glossy nuts, encased in spiny burrs, were a nutritious food for wild and domestic animals as well as for humans. Growing rapidly to a height of 100 feet, with a trunk up to 8 feet in diameter, the chestnut was king of the forest from Maine to Florida and westward almost to the Mississippi. Billions of the trees flourished throughout this range; in the Appalachian Mountains alone, their lanceshaped, coarsely toothed leaves shaded untold millions of acres. When the clusters of creamy flowers opened in June and July, the hills had the look of a rolling, foam-capped sea. Then, in 1904, a fungal blight appeared in New York City on chestnut trees imported from China. Within 50 years its spores had blown west, killing all but a few isolated specimens. Those that survived had been planted in western states, far beyond the tree's natural range. For decades, sprouts kept springing up from stumps of fallen chestnuts, but many of these too succumbed to the tragic blight. Valiant attempts were made to crossbreed the American chestnut in hopes of developing trees resistant to the fungus. But the experiments took decades and had mixed results. In recent years, however, plant pathologists have detected a weaker strain of the fungus, one that competes with the blight and enables infected trees to heal. By inoculating wild trees with this less virulent parasite, they hope to restore the American chestnut to its rightful domain.

Chickadee

Parus

Familiar inhabitants of woodlands and gardens and frequent visitors to feeders, chickadees are among our best-known songbirds. All are active, gregarious, friendly little creatures, with dark caps, black bibs, and gray or brown backs. Named for their cheerful "chickadee-dee-dee" calls, they also make a variety of piping and whistling sounds. While searching in trees for insects and insect eggs, these spirited acrobats often hang upside down from branches as they probe the bark with their bills. Chickadees nest in cavities in dead wood, in abandoned woodpecker holes, and sometimes in birdhouses. Both male and female share in incubation and all the duties of caring for the young. After the fledglings leave the nest, they gather in small, chattering flocks that roam the woods in winter foraging for food. The common species across the northern states and Canada is the black-capped chickadee; the nearly identical Carolina chickadee lives in the southeastern states. The mountain chickadee, with a distinctive white eyebrow, makes its home in the western mountains, and the ruddy chestnut-backed chickadee is found in humid forests and parklands along the Pacific coast. The boreal chickadee, also a northern bird, is the most drably colored of the group. During the winter months, if food supplies run short, flocks of these "brown-caps" sometimes stray well to the south in search of seed.

Chickweed

Stella ria media

Found in lawns and gardens all across the continent, chickweed grows in a sprawling tangle of stems. Commonly regarded as a nuisance, it is a persistent weed that often remains green throughout the winter; its tiny white starlike flowers bloom even when there is snow on the ground, yielding a continual crop of round, reddish-brown seeds. The plant appeals to a variety of animals, however, and the popularity of its seeds with birds both wild and domestic has given chickweed its name. Some people also eat the plant; its tender little leaves and stems, when tossed in salads or served as a hot vegetable, are a tasty substitute for spinach.

Chicory

Cichorium intybus

So common are the chicory's sky-blue, asterlike flowers by mid-July that it would be hard to imagine American roadsides without this tall, branching perennial. Yet it is not a native plant; its first reported appearance on this continent came in 1785, when Governor Bowdoin of Massachusetts imported its seed from Holland. He may have had a taste for the rosettes of tender, dandelionlike leaves the plant produces in its first year of growth; these are still grown for use as a salad green. But it is more likely that he planned to harvest the fleshy taproots, roasting and grinding them to flavor his coffee as the Creoles of Louisiana do today. Unlike many foreign weeds, chicory, which prefers dry soils, has never become a serious pest on farmlands.

Chinook

Mainly a winter phenomenon, the chinook is a warm, dry wind that sometimes rushes down the eastern slopes of the Rocky Mountains. Spilling onto the northern plains, it can cause temperatures to rise dramatically. On January 22, 1943, for instance, the temperature at Spearfish, South Dakota, jumped 49 degrees- from _4°F to 45°F -within a matter of minutes. Because such winds can rapidly melt any snow cover, chinooks are often called "snow eaters."

Chipmunk

Tamias

Small, striped, ground-dwelling squirrels, chipmunks are widespread across much of North America. The reddish-brown eastern chipmunk is found nearly everywhere east of the Great Plains; the least chipmunk is the most common of more than a dozen smaller, paler western species, which thrive in deserts as well as forests. Active by day, these bold and curious rodents tend to be most conspicuous in the fall, when they dart about in search of food for the coming winter. They stuff their roomy cheek pouches with seeds and nuts, which they then cache in their underground nests. And they live up to their scientific name, Tamias, which derives from a Latin word for treasurer: in three days, one eastern chipmunk took in 5 quarts of hickory nuts, 2 quarts of chestnuts, and about 24 quarts of shelled corn; the hoard of one of the western species contained over 67,500 items. During the winter, chipmunks sleep for long periods, waking regularly to feed. In the spring they emerge to mate, and a litter of two to six young is born about a month later.

Chiton

Insect term. The primary component of the external skeleton of crustaceans and insects.

Chiton

Molluscan term. Often exposed at low tide as they cling to seaside rocks, chitons are primitive, oval-shaped mollusks covered by eight overlapping plates. By day a large muscular foot on the underside holds them firmly in place; at night they creep about feeding on algae scraped from the rocks with a rasping, tonguelike organ. While most are only an inch or two long, one Pacific species grows up to a foot in length.

Chlorophyll

The green pigment found in plant tissue and essential for photosynthesis.

Cholla

Opuntia

A large and varied group, the chollas include cacti that sprawl in tangles several yards across but only a foot or so high, as well as others such as the jumping cholla that are branching, treelike, and grow up to 15 feet tall. All, however, are studded with a fearsome armament of spines, which are often up to 21/2 inches long. The spines protect the cactus wrens and thrashers that nest among the cholla's thorny branches. Pack rats also gather fallen joints of the cholla's cylindrical stems and build imposing, intruder-proof nests that are up to two feet high and eight feet across. For the cacti themselves, the spines function as much for reproduction as for defense. They catch on passing animals, which pull away short sections of the stems and carry them off to new locations; eventually the pieces drop to the ground and take root as new plants.

Christmas Bird Count (formerly "Census") (CBC)

Bird Biology Avian Conservation term.

An annual project, in the Americas, involving a one-day count in December of the individuals of all species observed within a circle that is 15 miles (24 km) in diameter.

Chuckwalla

Sauromalus obesus

A large, dark, stout-bodied lizard that sometimes reaches nearly a foot and a half in length, the chuckwalla lives on dry rocky hills in southwestern deserts. It is active during the day, appearing on rocky ledges early in the morning and basking in the sun until its body temperature rises to about 100~. Then, climbing about in creosote bushes, a favorite food plant, it forages for buds, fruit, flowers, and leaves. When threatened by predators, the slow-moving chuckwalla escapes by slipping into crevices among the rocks and inhaling large quantities of air; swelling up until it nearly doubles in size, the lizard becomes so securely wedged in place that it is almost impossible to dislodge.

Cicada

One of nature's most intriguing spectacles is provided by periodical cicadas, insects that emerge from the ground at 17 -year intervals in the North and on a 13-year schedule in the South. Appearing in huge numbers, the cicadas first shed their nymphal skins, which can often be seen clinging to trees and other supports like ghostly duplicates of the insects themselves. Then the cicadas move higher into the trees, where they mate, lay eggs, and-most notably- sing. Males serenade females by vibrating membranes on the sides of the abdomen. Their loud trills and soft buzzes, produced by throngs of insects, make up a deafening chorus. After mating, females insert their eggs in twigs, and the hatched nymphs later drop to the ground, burrow into the soil, and begin sucking juice from the tree's roots. After years of feeding in the dark, the nymphs tunnel to the surface, emerge as adults, and repeat the cycle. Often erroneously called locusts, cicadas are not related to true locusts, which are a kind of grasshopper. The periodical cicadas look like giant, broad-headed flies with bright red, bulging eyes and four transparent wings. Like their relatives the aphids and leafhoppers, they have mouthparts adapted for sucking plant juices. Similar to the periodical cicada are the dogday cicadas of the Northeast and the grand western cicadas of the Southwest. Both differ from the periodical cicadas in their greenish color and their much shorter life cycles, which span just one or two years.

Cinquefoil

Potentilla

The name cinquefoil means "five-leaf," and many of these perennial wildflowers and shrubs do indeed bear leaflets in groups of five, spread out like the fingers of a hand. Sometimes, however, the number varies; the shrubby cinquefoil, a dense, four-foot plant that ranges from Alaska to New Jersey, may bear leaflets in groups of 3 or 7, while other species have as many as 15 leaflets per leaf. The flowers, however, are more consistent in their arithmetic. The petals, usually yellow but occasionally white or crimson, always number five, and the many stamens invariably occur in multiples of five. The plants' generic name means "little potent one" and refers to the supposed medicinal properties of silverweed, one of the commoner species.

Circadian rhythm

An Animal Behavior term, this is used to illustrate a rhythm which is about one day in length, found in many aspects of behavior and physiology. Circadian rhythms often appear even in Animals kept under constant conditions, but they then usually "free run" at a length which diverges from 24 hours. In Nature, this intrinsic rhythm is entrained by the cycle of light and dark and so matched precisely to the 24-hour rhythm of the earth's rotation.

Cirque

Common features on glaciated mountains, cirques are steep-walled, basin-shaped hollows carved into the slopes. They were formed at the heads of glacier-filled valleys; plucking away blocks of underlying rock, the moving tongues of ice gradually excavated the hollows. With the glaciers now gone, the bottoms of the basins are often filled with the picturesque little mountain lakes known as tarns.

CITES

Endangered and Threatened species term.

The 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora, restricting international commerce between participating nations for plant and animal species believed to be harmed by trade.

CITES species

Species (675 as of this writing) listed under the 1975 Convention on International Trade in Endangered Species (CITES), which is administered by the United Nations Environment Programme. Such species cannot be commercially traded as live specimens or wildlife products because they are endangered or threatened with extinction.

Clam

Living on the bottom of oceans, rivers, and lakes, clams spend most of their time buried in mud or sand. Their soft bodies are protected by hinged, two-part shells of various shapes, depending on the species. The shell can be opened and closed, allowing a muscular foot to protrude. The foot propels the animal across the bottom by expanding and contracting in such a way that the clam alternately anchors the tip in the sand and then pulls itself forward. Clams eat and breathe by drawing water into the shell through a fleshy tube called the siphon, then passing it across their gills and expelling it through another tube. They feed on microscopic bits of food that become trapped in mucus on the gills. Since clams have no need to move about in search of prey, they can remain buried indefinitely on the bottom. Many of the clams are popular as seafood. One of the commonest kinds along the Atlantic coast is the quahog, or hard-shelled clam, which is often served in chowder and on the half shell. Another, the eastern surf clam, grows up to nine inches across. Soft-shelled clams, with shells that are more fragile than those of other species, are known familiarly as steamers.

On the Pacific coast, the eight-inch Washington clam, or gaper, can squirt a three-foot stream of water when disturbed. Another, the pismo clam, may live for 25 years. And the geoduck (pronounced "gooey duck"), sought as a delicacy, can weigh as much as 12 pounds. Freshwater clams, called river mussels, are less well known and less palatable than their marine cousins. Darker on the outside than sea clams, they are often harvested for their pearly inner shells, which are used for making buttons.

Clamworm

Well known to fishermen who often use them as bait, clamworms once were thought to prey on clams because they were sometimes found in empty clam shells. In fact, most of these marine worms live in burrows or under rocks and snatch small animals that pass within their reach. During the mating season, some species swarm to the surface and perform a kind of nuptial dance as they spawn. The larvae drift for a time with the plankton, then settle to the bottom for the rest of their lives.

Clarkia

Some three dozen species of these charming annuals ornament the western states. Growing up to three feet tall, the clarkias tend to prefer dry open areas such as the slopes and foothills of the Sierra Nevada and the Coast Ranges. An outstanding attraction of these four-petaled wildflowers is suggested by one of their colloquial names, farewell-to-spring. Blooming at the onset of hot weather, the clarkias open their pink, lavender, or white blossoms after most other wildflowers have faded and the turf has begun to brown with drought.

Classification

Biological Philosophy term. Linnaeus classified all known plants and animals and devised a system of naming plants and animals. The system assigns a two-word Latin name to each organism: the first word is the genus; the second, often descriptive, is the species name. For example, the house cat has the scientific name Felis domesticus; the lion, is Felis leo. He became interested in classification while studying the stamens and pistils (male and female sex structures) of flowers. He used the numbers of these structures to classify all known flowering plants in his Systema Plantarum (1753). His Systema Naturae (1758) classifies more than 4,000 animals, even human beings. Linnaeus first gave humans the scientific name Homo sapiens.

Classification

In order to study nature, scientists have classified the life forms in nature, or put them into groups. Organisms are classified according to how closely they are related. Large groups are broken down into smaller and smaller groups. A kingdom is the largest unit of classification. There are five kingdoms in nature. One of those kingdoms is Animalia, or the animal kingdom.

There are two main groups of animals: vertebrates and invertebrates. Vertebrates are a subgroup of the Phylum Cordata, or animals that have a spinal chord. These include fish, amphibians, reptiles, birds and mammals. You might not think it, but invertebrates, or animals without a spinal chord, make up most of the animal kingdom. These include sponges, jellyfish, worms, arthropods (insects, shrimp, spiders), mollusks (snails, clams, octopuses), and echinoderms (sea urchins, sea stars).

Organisms in the animal kingdom consist of many different species. Some animals most familiar to us are mammals, birds, fish and insects.

Animal cells don't have the rigid cell walls that plant cells have. Most animal bodies are made up of organized cells that are specialized to perform a specific task. Other cells are organized into even more specialized organs. Most animals are capable of moving relatively fast, unlike plants. Most animals reproduce sexually.

All told, around 9 or 10 million species of the kingdom Animalia inhabit the earth; the exact number isn't known. Most of them are in the Arthropod phylum, or animals with jointed legs, like insects and crustaceans. In fact, some scientists believe that if we were to identify all species in the tropical rain forests, the ranks of Arthropoda would be over 10 million species.

Clay

An extremely fine-grained earthy material that can be molded when moist but hardens when dried or fired, clay is an important component of soil. It also is a valuable resource that has been used for centuries in architecture and industry. Its numerous applications range from the manufacture of bricks, fine china, and high technology ceramics to the coatings that give book papers their whiteness and glossy shine.

Clean-Up (Water)

Cleaning up a chemical spill in water involves trying to physically contain the spill and prevent it from coming into contact with sensitive ecosystems, as well as removing the pollutant itself through the use of such technologies as oil skimmers or the introduction of a degrading substance.

Clematis

Most of the wild clematises, like their cultivated cousins, are vines. Their leafstalks coil around the twigs of neighboring shrubs and so help hoist the plants up into sunlight. The most common species in the East is virgin's bower, a vine that scrambles over streamside brush. Its other common name, old-man's beard, was inspired by the clustered fruits, each one tipped with a long silky plume. A few of the clematises are not vines at all, but upright, earthbound wildflowers. Typical of the nonclimbing sorts is the pine-hyacinth of Florida. Its knee-high stems bear as many as three blue or lavender bells in late winter.

Click beetle

Noisy little acrobats, click beetles are also known as skipjacks and snapping bugs-and with good reason. When threatened, the inch long insects drop to the ground and play dead. If they happen to land upside down, they arch their backs, then snap them straight-an action that launches their bodies into the air with an audible click and, with luck, lands them on their feet again. One of the largest, commonest, and most conspicuous North American species, the eyed click beetle is easily recognized by the pair of large eyelike spots on its back. The larvae of click beetles-hard and wiry-are called wireworms. Burrowing through the soil and feeding on seeds and roots, many of them are serious agricultural pests.

Climate

The difference between weather and climate is, in effect, the difference between days and decades. Weather, which changes daily, includes such things as the temperature, wind, rain, snow, and cloudiness at a particular time and place. An area's climate, in contrast, is the average pattern of weather that occurs there over tens or even hundreds of years. Among the factors influencing a region's climate are its latitude, its distance from the sea, and the existence of mountain barriers. Widely varying conditions in North America result in such extremes as the humid, subtropical climate of southern Florida and the hot, dry climate of the southwestern deserts. Although in the course of a human lifetime climate appears to be fixed, it can in fact change. Some 20,000 years ago, for example, much of North America was covered by glacial ice-and many scientists believe that such ice ages recur in cycles. In more recent times, the amount of carbon dioxide in the atmosphere has been increasing as a result of the burning of fossil fuels. Preventing the escape of heat from the earth the so-called greenhouse effect-this build-up of carbon dioxide could, over a long period of time, cause a gradual warming of climates all around the world.

Climate Change (UF Global Warming)

Human activities are altering the chemical composition of the atmosphere through the build-up of greenhouse gases that trap heat and reflect it back to the earth's surface. This is resulting in changes to our climate, including a rise in global temperatures and more frequent extreme weather events.

Climate change

Changes in the global climate system in response to physical feedbacks, chemical feedbacks, and changes in terrestrial and aquatic systems caused by humans and nature.

Climate facts

The sun's rays hit the equator at a direct angle between 23 ° N and 23 ° S latitude. Radiation that reaches the atmosphere here is at its most intense.

In all other cases, the rays arrive at an angle to the surface and are less intense. The closer a place is to the poles, the smaller the angle and therefore the less intense the radiation.

Our climate system is based on the location of these hot and cold air-mass regions and the atmospheric circulation created by trade winds and westerlies.

Trade winds north of the equator blow from the northeast. South of the equator, they blow from the southeast. The trade winds of the two hemispheres meet near the equator, causing the air to rise. As the rising air cools, clouds and rain develop. The resulting bands of cloudy and rainy weather near the equator create tropical conditions.

Westerlies blow from the southwest on the Northern Hemisphere and from the northwest in the Southern Hemisphere. Westerlies steer storms from west to east across middle latitudes.

Both westerlies and trade winds blow away from the 30 ° latitude belt. Over large areas centered at 30 ° latitude, surface winds are light. Air slowly descends to replace the air that blows away. Any moisture the air contains evaporates in the intense heat. The tropical deserts, such as the Sahara of Africa and the Sonoran of Mexico, exist under these regions.

Climax

An assumed final state of stability in the reconstitution of a destroyed ecosystem. The endpoint of a successional sequence; a community that has reached a steady state under a particular set of environmental conditions.

Climax community

Ecologists have long recognized that any plant community-the association of species growing on a given site-tends to change over time in the process of natural succession. Eventually, however, a state of equilibrium is reached; the species are so finely attuned to each other and to the overall environment that changes cease. This stable, self-perpetuating mix of vegetation is called the area's climax community. Only a change in climate, a catastrophic event such as a forest fire, or more often, man's interference will alter the vegetation.

The nature of the climax community is determined by climate, soil, and other environmental factors. The abundant precipitation and mild winters of central North Carolina, for instance, foster an oak/hickory climax-a hardwood forest dominated by those trees. And Oklahoma's hotter summers, colder winters, and periodic drought result in a tallgrass prairie.

Cline

A geographic gradient in a measurable character, or gradient in gene, genotype, or phenotype frequency.

Clingfish

Shaped more or less like tadpoles, these scaleless, broad-headed bottom dwellers are made for the sedentary life: on their undersides, the pelvic fins are fused into suction discs that enable clingfish to get a grip on rocks, oysters, and other hard surfaces, and so steady themselves against the ebb and flow of the tide. Even when plucked from the water, they sometimes hold fast to their moorings. Clingfish are most common in tropical seas, but the hardy skilletfish-named for its fryingpan shape- is often seen in oyster beds as far north as New Jersey. In the West, the northern clingfish, large at six inches, ranges all the way to Alaska and lives in kelp beds.

Clintonia

Bride's bonnet is the common name of the western clintonia, and the one or sometimes two dainty white blossoms that top its 18-inch stems in early summer would indeed be suitable adornment for a bride. Also called queen cup, this graceful perennial produces bright blue berries, a characteristic it shares with a clintonia found in northern California and Oregon. The bluebead, or dogberry, of northeastern forests and bogs also bears blue fruits. The only nonconformist is the speckled wood lily of eastern mountains; its berries are pitch black.

Cloud

Everyone, no doubt, has marveled at the sight of billowing, cottonlike clouds drifting slowly overhead and changing constantly in size and shape. Substantial as they may seem, however, these fantastic sky sculptures are nothing more than water vapor made visible. They form when warm air rises and cools, causing the water vapor in it to condense into tiny droplets or ice crystals. And these droplets and crystals are what we see as clouds. Based on their appearance, clouds are classified into three basic types: cumulus, or heaped; stratus, or layered; and cirrus, or wispy. The shapes of clouds are significant because they can help us predict coming changes in the weather. Fleets of mile-high, puffy, cumulus clouds, for instance, indicate fair weather. If very large cumulus clouds develop and their domes rise five miles or more into the sky, their tops often spread out into the shape of an anvil. Such ominous-looking clouds are described as cumulonimbus (nimbus means rain) and usually foretell impending thunderstorms and heavy rain. Stratus clouds form when there is little wind and a warm front flows across a wedge of colder air. Uniform in appearance, these layered clouds often lie close to the ground and may produce drizzle or light rain. In contrast, wispy cirrus clouds, also known as mares' tails, form at very high altitudes and are composed of ice crystals; advancing ahead of a front, they usually indicate the approach of rain or snow.

Clover

Trifolium

Distinguished by their three-part leaves and dense, fragrant flower heads, clovers are a familiar element in many American landscapes; they thrive in lawns, fields, vacant lots, roadsides virtually everywhere. Although we have several native species, almost all the common cultivated clovers are imports that have long since spread across the country. White clover and crimson clover, from Europe, were introduced as forage crops; both are also valued as honey plants. Red clover, another immigrant and the state flower of Vermont, is one of the more important species grown for hay. In lawns, however, the clovers are sometimes regarded as pests. But turf purists who try to eradicate them do so at their own expense, since clovers, like other members of the pea family, have nodules on their roots that host nitrogenfixing bacteria. These valuable microorganisms enrich the soil by converting atmospheric nitrogen into a form usable by plants-and nitrogen is the major active ingredient in most lawn foods. Appreciating their value as natural fertilizers, farmers often sow clovers in their fields to be plowed under as "green manure."

Clubmoss

Despite their name and sometimes mossy appearance, clubmosses are not mosses at all. Growing in woodlands, bogs, and meadows, many of these low-growing evergreens, such as ground pine and running cedar, have narrow, scalelike leaves and are topped by erect, clublike cones. Looking much like miniature conifers, they are, in fact, related to ferns and horsetails. They are the descendants of huge prehistoric trees that flourished hundreds of millions of years ago-in the forests that later were transformed into tremendous coal deposits. Clubmosses spread mainly by means of long, wiry stems that creep across or just under the ground and send up new shoots every few inches, but they also reproduce by means of spores. The clublike structures atop the plants-or in some species, the tiny sacs at the base of the leaves-produce the fine, yellow, dustlike spore granules that are dispersed by the wind. When the spores settle to the earth, they develop into tiny plants that live hidden underground for years before emerging as adults.

Coal

One of our most important and abundant mineral resources, the coal that we burn today had its beginnings hundreds of millions of years ago in vast prehistoric swamps. Forests of gigantic, fernlike trees up to 100 feet tall and 6 feet in diameter flourished in these wetlands, along with amphibians 8 feet long and dragonflies with 2-foot wingspans. When the plants died, their remains accumulated into layers many feet thick and gradually decomposed into peat. Layers of sediment eventually were deposited over the peat, and heat and pressure transformed it into coal. Fern fronds and other fossils from the prehistoric forests are often found preserved in coal seams-compelling evidence of their origin as living plants. Variations in conditions produced different kinds of coal in different areas. Ugnite, the type most like peat, is soft, crumbly, and brown. Bituminous, or soft, coal-by far the most abundant sort-is dull black and harder than lignite. Anthracite, produced by tremendous pressures generated by folding of the earth's crust, is extremely hard, black, and shiny; almost pure carbon, it burns the most efficiently of any coal.

Coarse-grained

Referring to qualities of the environment that occur in large patches with respect to the activity patterns of an organism. This results in the organism's ability to select usefully from among qualities.

Coati

Nasua narica

A lively relative of the raccoon, the coati ranges just north of the Mexican border into southern Arizona, New Mexico, and Texas. Foraging by day with its long, striped tail held high, this 15to 25-pound mammal eats almost anything, from prickly pears to tarantulas. It probes the earth with its nimble snout in search of grubs and roots but also takes small prey such as scorpions and lizards. Leaping into trees like troops of monkeys, coatis feast as well on eggs, nuts, and especially, fruit. An agile climber, it uses its tail as a balancing pole on the way up and as a holdfast on the way down. Females and young males feed, nap, groom, and play in boisterous bands of a dozen or more. Adult males, however, are loners and join the groups only during the breeding season. Some seven weeks after mating, the females retire to tree nests or rock dens and give birth to four to six kits. There they remain until, about five weeks later, the noisy young are brought forth and introduced to high-spirited coati society.

Cobia

Rachycentron canadum

With no close kin among any fish in the sea, the cobia is one of a kind. Sleek and fast-moving, it has a long, dark body, a pointed snout, and a line of short spines in front of the dorsal fin. While they are usually one to four feet long and weigh 30 to 50 pounds, specimens more than five feet long and weighing as much as 100 pounds have been hooked. Traveling alone or in small schools, cobias rove warm inshore waters and are often seen hovering beneath larger fish, boats, buoys, and other floating objects. Most prefer the balmy Gulf of Mexico, but during the summer some cobias travel north to brave the cooler waters off New England. Voracious predators, their keen appetite for crustaceans has earned them the nickname crabeaters.

Cockroach

With a lineage of some 350 million years, cockroaches are obviously born survivors. Voracious eaters, they feed on almost anything, including paper, soap, and glue. Usually dark brown or black, with a flattened oval body, cockroaches are creatures of the night that, with few exceptions, scuttle frantically away from light. Body hairs that are sensitive to air currents and sound vibrations warn them of approaching danger; long legs and lightning reflexes help them dash to safety. While many species have wings, most household varieties do not fly. Fifty-five species of cockroaches are found in North America. Luckily, only five of them are household pests; the majority live outdoors in plant litter, woodpiles, and crevices. The giant palmetto bug of Florida, at more than two inches in length, is North America's largest cockroach. More common and much smaller is the Croton bug, or German cockroach, which is found in urban dwellings all around the world.

Codfish

Abundant and valuable food fish-annual catches amount to tens of thousands of tonsseveral members of the codfish family are prized for their tasty flesh. The premier member of the family, the Atlantic cod, has in fact been so vital to the Massachusetts economy since colonial days that a large carving of the fish is prominently-and proudly-displayed in the State House in Boston. Dark-spotted, with three back fins and a single chin whisker, Atlantic cod live in cold waters and probe the ocean bottom for a variety of foods. Active predators, they eagerly devour other fish, squid, and shellfish, often swallowing the shells along with the flesh inside. The average cod hauled in by fishermen weighs less than 25 pounds, but they can grow to great size; the record holder was a hefty 200-pounder. Other important members of the codfish family include the Pacific cod, found in waters off the northwest coast; haddock, which live in the north Atlantic and are among the most valuable of all food fish; tomcod and pollock, found off both coasts; and the burbot, a freshwater codfish found in northern lakes.

Coitus

Sexual intercourse, also called coitus, or simply sex, is to have sex is the human form of reproduction. In humans this is performed relatively frequently, and primarily for sexual pleasure rather than in response to a seasonal stimulus. To engage in sexual intercourse, the erect penis is inserted into the vagina and one or both of the partners move their hips to move the penis backward and forward inside the vagina to cause friction, and an increasingly rapid back and forth motion, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasms are achieved. Penetration by the hardened erect penis is also known as intromission, or by the Latin name immissio penis.

Coltsfoot

Tussilago farfara

One of the earliest of spring flowers, coltsfoot seems intent on getting a head start on the season: its yellow, dandelionlike blooms open atop scaly 4- to 18-inch stems, then wither and set seed before any leaves appear. Because of this two-stage growth pattern, herbalists called the plant son before the father. When the large, roundish leaves do unfurl, they explain coltsfoot's common name; toothed along the edge, they are shaped more or less like a hoofprint.

Columbine

Aquilegia

Their delicate blue-green leaves and dainty flowers may have an appearance of great fragility, but columbines are tough. Blue columbine, for instance, the state flower of Colorado, climbs well above timberline on its native peaks, while the yellow-blossomed Chap line's columbine sprouts from desert cliffs in New Mexico. Even the red and yellow wild columbine of eastern North America ventures out of its preferred moist woodlands to colonize rocky crevices and ravines. Although the color varies from species to species, the form of the flowers remains the same: each of the five petals extends backward in a long, pointed tube, or spur. Our ancestors likened the blooms to five birds perched around the edge of a fountain, and the plant's name derives from the Latin for "like a dove."

Comb jelly

Sometimes seen dotting sandy beaches after storms or drifting at the surface in quiet lagoons, comb jellies look like small, transparent blobs of gelatin. No relation to the true jellyfish, they are named for the eight rows of comblike projections that circle their body like lines oflongitude on a globe. Moved in unison, the combs propel the creatures weakly through the water. By day, sunlight reflects off the moving combs, producing an iridescent glint; at night the animals sometimes glow in the dark with a lovely greenish or bluish light. Most comb jellies feed by sweeping tiny planktonic organisms into their mouth with their long, sticky tentacles. Common species include the sea gooseberry, less than an inch in diameter, and the pinkish, two-inch sea walnut.

Comfort movements

An Animal Behavior term, this is used to refer to a varied group of activities including grooming, scRatching, shaking, stretching and yawning.

Comfrey

Symphytum officinale

An immigrant from Europe that now grows wild on roadsides and in waste places, comfrey is abuzz with activity when it blooms, for bees find its dangling clusters of pink, blue, or yellowish bell-shaped flowers irresistible. The plant's large, hairy leaves supplied generations of countryfolk with salad greens and pot herbs, and they were traditionally used in a variety of herbal remedies. Unfortunately, however, while the foliage is rich in protein, vitamins, and minerals, the plant has also been found to contain a cancer-causing alkaloid, particularly in its long, black-skinned root. No longer recommended for internal use, the leaves nevertheless can be crushed and safely applied to wounds as a soothing poultice.

Common name

The nonscientific name of an animal or plant most widely used and accepted by the scientific community.

Commons

Biological Philosophy term. "The global commons": Those resources we all have to use to survive but which we do not have to pay for. The term is based on the idea of the village commons: a plot of land owned by no one where all had the right to graze their stock. Because its use was without cost, people overused it, not respecting its fragility or limits or expending any effort or resources to preserve it. The inevitable result was the destruction of the commons. By application, the "global commons" are threatened with overuse precisely because we do not figure in a cost for them. There is a cost, of course, that we are paying all the time, in the diminution or damaging of the commons.

Commensalism

An Animal Behavior term, this is used to explain an association between two species such that one of them benefits without appreciable cost to the other. Examples are Scavengers, and predatory Fish that live in shoals of harmless ones so gaining Camouflage from which they can attack prey.

Community (Action and Learning)

All of the people living in a specific locality or members of a group that share a particular interest.

Community

A group of organisms, generally of wide taxonomic affinities, occurring together. Many will interact within a framework of horizontal and vertical linkages such as competition, predation, and mutualism.

Competition

An interaction between members of two or more species that, as a consequence either of exploitation of a shared resource or of interference related to that resource, has a negative effect on fitness-related characteristics of at least one of the species.

Compliance (Law)

Compliance means conformity with the law. Government ensures compliance with legislation through two types of activity: promotion and enforcement.

Composting (Recreation)

Using decomposing vegetable matter, including table scraps, grass clippings, leaves, peat and soil to fertilize the soil. Composting reduces the amount of waste sent to landfill, and helps put valuable nutrients back into residential and commercial gardens.

Compound eye

The eye structure typical of insects and some other invertebrates comprising numerous cells and lenses, not a single lens.

Conch

Found in warm, shallow tropical seas, especially off the Gulf Coast and southern Florida, conchs (pronounced "conks") are large, spiral-shelled marine snails. Docile plant eaters, conchs move quickly across the sandy bottom by means of a horny, clawlike plate attached to the end of the muscular foot. By digging the claw into the sand and quickly contracting a muscle, conchs can actually leap or somersault. Queen conchs, prized by collectors for their beautiful pink shells, are up to a foot long and weigh as much as five pounds. Florida fighting conchs, about four inches long, are particularly agile leapers, hence their name. Conch flesh is used in fritters and chowders, and the shells are occasionally fashioned into horns for signaling.

Conditioning

An Animal Behavior term, this is used to define learning by association. In classical conditioning, two stimuli are associated so that the second comes to elicit a response formerly only elicited by the first. In Instrumental or OperAnt conditioning, the Rate of a response is raised or lowered by its association with Reinforcement.

Condor

Gymnogyps californianus

With a nine-foot wingspan-the greatest of any North American land bird - the California condor used to be a master of the sky. Now rare and seriously endangered, this extraordinary vulture once soared high above the land, gliding 10 miles at a time without flapping its wings. Thousands of years ago the birds ranged east as far as Florida, feeding on the carcasses of once-plentiful large mammals, but by the middle of this century, the huge, cliff-nesting birds were confined to the mountains of southern California. Raising only one young every other year and beset by habitat loss, food shortages, and contamination of their food with pesticides and poisons, their numbers dropped to fewer than 40 by 1975. In the mid-1980's the remaining wild birds were captured and placed in zoos, where only a few young have so far been successfully hatched. Researchers are trying to build up a population of captive-bred condors and hope eventually to return them to the wild.

Cone

The structure bearing reproductive elements of conifers.

Conference

Endangered and Threatened species term.

The consultation process required for Federal actions that are likely to jeopardize the continued existence of a species proposed for listing or result in the destruction of adverse modification of proposed critical habitat.

Conflict

An Animal Behavior term, this is used to explain a situation when an Animal with an approximately equal tendency to do two things at once is said to be in a Motivational conflict. Thus, a hungry Animal beside whose food a frightening object is placed is in an approach-avoidance conflict. In such a balanced state, Animals often show other, seemingly irrelevAnt, behavior (see Displacement Activity). Many courtship displays are thought to have arisen from such actions produced as a result of conflict.

Coneflower

The cheerful, golden yellow rays encircling a dark, domed center have fixed the name blackeyed Susan in the minds of flower lovers all across the continent. But the black-eyed Susan is just one of many coneflowers, members of the sunflower family with petallike ray flowers that surround a thimblelike cone of disc flowers. The prairie coneflowers, found on the Great Plains and eastward, have drooping yellow ray flowers, and their cones give off a licoricelike aroma when crushed. The purple coneflowers, also native to the plains, have more bristly cones. Their lovely, magenta flowers are prized by gardeners.

Conglomerate

Naturally cemented jumbles of rounded stones, conglomerates are a type of sedimentary rock. The pebbles they contain usually were worn smooth as they were rolled and bounced along by fast-flowing water in ancient streams. When the stones eventually came to rest, the spaces between them filled with smaller grains and the mass was gradually cemented together to form the potpourri referred to as a conglomerate.

Conifer

A tree that bears its reproductive structures in cones. The scaled cones that protect the seeds of conifers come in a variety of shapes and sizes and are one of the main distinguishing characteristics of these trees and shrubs. Their needlelike leaves are another feature common to conifers, although cedars and junipers, for example, have flat, scalelike leaves instead. Most also are evergreen: the exceptions are the larches and bald cypresses, which lose their needles in winter.

An ancient order of plants, the conifers developed millions of years ago, long before the first broad-leaved trees. Their stately descendants include our oldest trees (the 4,600-year-old bristlecone pines), our biggest (the giant sequoias), and our tallest (the California redwoods). Cones not at tips of branches Bracts between cone scales. Broad-leaved trees are better adapted to temperate climates, however. The conifers are dominant in northern regions where the evergreens' ability to make and store food year-round is a major advantage. Because needles are better at retaining water than broad, flat leaves, conifers also thrive in hot, dry areas and often on poor, rocky soils.

Connectedness

The structural links between habitat patches in a landscape; can be described from mappable features.

Connectivity

A parameter of landscape function that measures the processes by which a set of populations are interconnected into a metapopulation.

Conserve

Endangered and Threatened species term.

Carrying out actions to improve the health of a species so it no longer needs to be listed as threatened or endangered.

Conservation

Environmental conservation is a general term that refers to the preservation of the natural environment-including wildlife, habitat, and the ecosystems they are a part of.

Conservation

Endangered and Threatened species term.

From section 3(3) of the Federal Endangered Species Act: "The terms "conserve," "conserving," and "conservation" mean to use and the use of all methods and procedures which are necessary to bring any endangered species or threatened species to the point at which the measures provided under this Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transportation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking."

Conservation

Biological Philosophy term. The "wise use" of natural resources, managing nature rather than preserving it as untouched wilderness. Gifford Pinchot of the U. S. Forest Service is the name associated with wise use; John Muir is associated with the rival policy focusing on preservation of wilderness. Aldo Leopold was a student in the Pinchot tradition, but seems to have arrived at a balance between the two.

Consort relationship

An Animal Behavior term, this is used to describe a temporary Pair Bond between a male and a receptive female as found, for example, during mating season.

Constant-effort mist netting

Bird Biology Avian Conservation term.

A capture method, standardized over space and time, used for counting numbers of birds captured in mist nets.

Endangered and Threatened species term.

All Federal agencies must consult with the U.S. Fish and Wildlife Service (or National Marine Fisheries Service) when any activity permitted, funded, or conducted by that agency may affect a listed species or designated critical habitat, or is likely to jeopardize proposed species or adversely modify proposed critical habitat. There are two stages of consultation: informal and formal.

Consummatory act

An Animal Behavior term, this is used to define an act that terminates a behavior sequence and leads to a period of quiescence. Opposed to the Appetitive Behavior that leads up to it; thus, food seeking ends in eating, and mating in ejaculation.

Contact

A single field record of an individual by sight or sound (syn. detection, cue, registration, observation).

Contact call

An Animal Behavior term, this is used to refer to any sound which serves to keep members of a pair or social group in touch with one another. Contact calls are commonly produced by moving Animals, especially where visibility is poor.

Contamination (Water)

Water is considered contaminated if it contains chemical or biological pollutants that are harmful to human health or the environment.

Continental Divide

Gentle rivulets, rushing streams, and mighty rivers-all are affected by a line of high ridges in the Rocky Mountains that we call the Continental Divide. To the west of the line water flows toward the Pacific Ocean; to the east it flows into the Atlantic or the Gulf of Mexico. Marking the boundary between two drainage systems, the Continental Divide, sometimes called the Great Divide, continues north through Canada and south into Mexico. Lesser divides can also be traced. One, near Duluth, Minnesota, runs from east to west, separating the water flowing north into the Great Lakes and the St. Lawrence River from the water that flows south into the Mississippi.

Cottaging (Recreation)

Many people spend their summers at cottages located on the shores of lakes and rivers. Good cottagers make an effort to reduce their impact on the surrounding environment, particularly the sensitive aquatic ecosystem, by using non-polluting boats and innovative composting toilets.

Cooperation

An Animal Behavior term, this is used to define the situation in which Animals assist one another for mutual benefit. Thus, Animals in groups may assist one another in predator detection because they have more pairs of eyes. They may also be able to Catch larger prey through coopeRative hunting, as in certain Predators.

Coot

Fulica americana

Noisier and more quarrelsome than their relatives the rails, American coots are known for their unmelodic medleys of cackles, grunts, and croaks. Ducklike water birds, they are slaty gray with a white bill, red eyes, and lobed toes that facilitate both swimming and walking on muddy shores. The birds take flight awkwardly, spattering water as they run across the surface trying to lift off. Feeding on aquatic plants, insects, worms, and snails, coots often gather in dense flocks on open water. The young have a remarkable means of escaping danger: at the first warning from an adult, chicks dive underwater and grasp a plant stem in their bill, anchoring themselves to the bottom until the danger has passed.

Copepod

Tiny (the largest are no bigger than a grain of rice) but incredibly abundant, copepods playa vital role in oceanic food chains. These small, shrimp like crustaceans feed on microscopic plants and are in turn consumed in vast quantities by other invertebrates, as well as by fish and even whales. The copepod's body, enclosed in a protective shell like that of a shrimp, is equipped with two pairs of antennae and several pairs of flattened limbs. The limbs, in fact, give the copepod its name, which is derived from Greek words meaning "oar foot." In addition to the marine copepods, freshwater species live in ponds and quiet streams. Easily captured with a fine net, they can be observed with a hand lens.

Copper

A shiny, pliable, orange-red metal that is easily shaped and immune to rust, copper has been pounded into tools and implements since ancient times. It still is widely used for utensils, coins, and roofing. (The familiar greenish patina on copper roofs prevents further corrosion.) An excellent conductor of heat and electricity, copper also is used for pots, pans, wire, and tubing. In addition, it can be combined with other metals to form the alloys brass and bronze. Copper is sometimes found in its pure form (called native copper); on Michigan's Keweenaw Peninsula, it occurs in masses weighing up to several tons. More often, copper is mined as an ore, from which the metal is extracted.

Copperhead

Agkistrodon contortrix

up to 41/2 feet long, the copperhead is a poisonous snake named for the coppery color of its head. It lives in rocky, wooded areas from Massachusetts to Texas, where the chestnut-brown hourglass pattern on its back keeps it well camouflaged among fallen leaves. Copperheads are related to cottonmouths and rattlesnakes and, like those other pit vipers, have heat-sensitive organs on their faces that are used to locate warm-blooded prey. In addition to small mammals, they feed on lizards and frogs, which are killed by venom delivered through sharp, hollow fangs. Fortunately, their bite, though painful, is seldom fatal to humans.

Coprophagy

An Animal Behavior term, meaning the eating of feces. This is importAnt in some Animals to transmit organisms, which help to break down food, from one individual to another, such as from adult to offspring. Eating its own feces may also improve the efficiency with which an Animal utilizes its food. It is sometimes practiced by Rabbits and Picas.

Copulation

Copulation is the union of the external genetalia of two animals for the purpose of sexual activity and subsequent reproduction. The two individuals may be of opposite sexes or of the same sex. Animals initially lived only in water and reproduced by reproducing in the water. Certain animals started migrating from oceans to the land during the epoch about 450 million years ago, necessitating internal fertilization to maintain the developing offspring in a liquid medium.

Coquina

Oonax variabilis

Less than one inch long, the glossy-shelled Florida coquina is a pretty wedge-shaped clam found in the surf zone of sandy beaches from New York to Texas. Coming in a variety of pastel hues, these dainty little mollusks burrow into the sand with each receding wave, then resurface to feed on the next incoming wave. Despite their small size, coquinas make an excellent chowder, and their shells, compacted into rock, are used as a building material in parts of Florida.

Coral

Relatives of sea anemones and jellyfish, the stony corals are tiny invertebrates found in warm, shallow tropical and subtropical seas. Some live as solitary individuals, but most form large colonies. Each animal, called a polyp, is usually only a fraction of an inch long, and its tube-shaped body is fixed at one end to a limestone cup formed of its own secretions. At the other end is a mouth leading to a gullet, and around the mouth are tentacles used to sting small prey. Less common than the stony corals, soft corals have horny or leathery skeletons. Colonies of the stony corals grow in size by building on the skeletons of their ancestors. Different species develop characteristic and sometimes wonderfully exotic forms, as suggested by such common names as brain coral, lace coral, star coral, and elkhorn coral. Individual polyps reproduce by forming buds, each of which matures into a new polyp alongside the old one. The same corals also reproduce sexually; the fertilized eggs hatch into free-swimming larvae that, unlike the buds, can swim off on their own to begin new colonies.

Coralbean

Erythrina

Covered with showy spikes of tubular, brilliant scarlet blossoms, these handsome shrubs and small trees stage a dramatic show each year from late spring through early summer. The flowers are followed by pods of attractive, but poisonous, shiny red beans. The most familiar species are the eastern coralbean, which ranges from North Carolina to Texas, and the southwestern coralbean, native to the dry, rocky soils of Arizona and New Mexico. The buoyant, light wood of a Hawaiian coralbean is used for the manufacture of surfboards, floats, and similar items.

Coral reef

Individual coral polyps, the marine animals that spend their lives anchored in self-made limestone cups, are relatively small. Colonies of these little creatures, however, have created the largest structures ever produced by any living thing; generation after generation builds upon the limestone remains of their ancestors, forming underwater reefs that can continue to expand indefinitely. Found in warm, shallow seas off the coast of Florida and farther south, coral reefs support an incredible variety of life. Snails, crabs, and spiny lobsters creep through crevices in the coral rock. Starfish, worms, and parrot fish "graze" on the living polyps. And everywhere there are sea fans, sponges, and other exotic creatures. Divers have long been enchanted by coral reefs, where they marvel at the intricate formations of the corals themselves and the astonishing array of brightly colored fish that flit through these incredible underwater seascapes. Among the most fascinating reef dwellers are the small, low-profile cleaner fish, at whose "stations" the larger fish patiently wait in line to be nibbled free of parasites.

Coral snake

To recognize the difference between the colorfully banded, poisonous coral snakes and harmless look-alikes such as the scarlet kingsnake, generations of southern children have been taught a helpful ditty: Red next to black, a friend of Jack; Red next to yellow can kill a fellow. For only on coral snakes do the red and yellow bands touch each other. In fact, the snakes are seldom even seen; our two native species are mainly nocturnal and spend most of their time hiding under logs or in burrows. When people do encounter the smallish, handsomely banded reptiles, the snakes tend to be docile and bite only if handled. Sometimes called harlequin or candystick snakes, coral snakes live in a variety of locations and habitats, from dry, rocky slopes and canyons in the Southwest to pine woods and wet hammocks in the Southeast.

Cormorant

Phalacrocorax

Long-necked, duck-sized, and glossy black, cormorants are fast and efficient water birds. Diving underwater, they paddle furiously with their webbed feet and seize fish in their long, sharply hooked bill. Unlike most aquatic birds, they do not have water-repellent feathers and so can often be seen perched on rocks or pilings with their wings spread out to dry. Found along seacoasts and on inland lakes and rivers, cormorants are highly social; they sometimes form communal fishing groups that include hundreds or even thousands of birds. Assembling into long lines, they herd a school of fish toward the shallows and snatch those feeding near the surface. Cormorants also breed in colonies, building crude, bulky nests on rocky cliffs or in treetops.

The most widespread of the six North American species and the only one likely to be seen far inland is the double-crested cormorant, named for the pair of curly plumes it wears on the sides of its head during the breeding season. Others include the Brandt's and pelagic cormorants of the Pacific coast and the great cormorant, found along the Atlantic coast.

Corridor

A spatial linkage that facilitates movements of organisms among habitat patches in a landscape.

Cornetfish

Fistularia

Long, slender fish that sometimes reach a length of six feet, cornetfish have an elongated, tubular snout and a whiplike filament trailing from their tail fins. These near relatives of trumpetfish occur mostly in the West Indies, but in summer are found further north. Camouflaged by their vertical stripes and dark color, they swim just below the surface and stalk prey near corals and grassy seabed flats. They drift slowly toward unsuspecting small fish and feed by quickly sucking prey into their tiny mouth. The blue-spotted cornetfish ranges from Nova Scotia to Florida and the Gulf of Mexico. The less common red cornetfish travels only as far north as Virginia.

Cosmopolitan

Meaning that it is usually found worldwide in suitable habitat.

Cotton grass

Eriophorum

Despite their name, the cotton grasses are not grasses at all but members of the sedge family. In bloom from summer into fall, they bear tiny flowers amid tufts of long, cottony white hairs atop their triangular stems. Found in bogs and moist meadows all the way north to the Arctic Circle, the cotton grasses often grow in dense stands, their tufted white flower heads looking like unseasonable snow covering the land.

Cottonmouth

Agkistrodon piscivorus

Often spotted on branches overhanging water, cottonmouths are highly venomous snakes whose bite can be quite dangerous. When threatened, the snake rears its chunky head and gapes to display the cottony white interior of its mouth-hence the name. Also called water moccasins, they are closely related to the copperhead and infest swamps, rivers, lakes, and rice fields in the southern states. From two to six feet long, the cottonmouth has a broad flat head and stout body, either unpatterned or marked with dark, ragged blotches. Uke other pit vipers, cottonmouths have deep, heat-sensitive facial pits that detect warm-blooded prey. They also feed on frogs and insects.

Cotton rat

Sigmodon hispidus

One of three rats native to the United States, the hispid cotton rat is an agricultural pest noted for its destruction of cotton crops. It also devours sugarcane, alfalfa, and sweet potatoes and eats insects, birds' eggs, and carrion as well. With grizzled fur and a short, scaly tail, the cotton rat occurs mainly on farmlands of the Southeast. Although primarily nocturnal, it is sometimes seen along roads during the day, where it quickly disappears into weeds, ditches, or its own well-made runways. One of the world's most prolific mammals, the cotton rat begins to breed at six weeks of age and produces several litters each year. Predators such as cats, hawks, and snakes, however, help control its population.

Cottontail

See Rabbit.

Cottonwood

Populus

Found in almost every region of the country, cottonwoods are named for the parachute of cottony down attached to each of their seeds. When the tiny fruits burst open in late spring, the seeds drift away by the millions and collect in fluffy white windrows. Favoring damp soils in low-lying areas, these fast-growing members of the willow family may add four to five feet to their height annually. They peak at an early age, however: cottonwoods begin to decline when about 75 years old, and very few live more than a century.

During its relatively short lifespan, the eastern cottonwood may reach a height of 150 feet. Though settlers in the East paid little attention to it, on the prairie, where it was often the only tree around, the eastern cottonwood was treasured by pioneers. In the Pacific Northwest the black cottonwood is the largest broad-leaved tree; old accounts describe specimens 225 feet tall, with trunks 8 feet in diameter.

Cougar

See Mountain lion.

Count (noun)

Bird Biology Avian Conservation term.

The act or process of enumerating. The number or sum total obtained by counting.

Countershading

An Animal Behavior term, this is used to describe an aspect of camouflage in which an Animal is paler colored in less brightly lit areas, usually the underside, so that it appears to be uniform and is less easily detected.

Cowbird

Molothrus

Named for their habit of feeding among grazing cattle, cowbirds are best known as opportunists that raid the nests of other birds-not to take eggs, but to leave them. Both the bronzed cowbird of the Southwest and the more widespread brown-headed cowbird lay their eggs in the nests of other songbirds, such as warblers, vireos, and flycatchers, and then abandon them to be raised by foster parents. While such behavior may seem easier than incubating eggs and feeding nestlings, brood parasitism is costly for both the cowbird and its victims. Many species thwart the cowbirds by removing their eggs, burying them beneath a new nest lining, or abandoning the nest altogether. As a result, female cowbirds must lay many more eggs than other birds do. And the cowbirds that do hatch crowd out and starve some of the rightful nestlings. Most experts believe that the cowbirds' nest parasitism accounts for the decline of such songbirds as the endangered Kirtland's warbler in Michigan and Bell's vireo in California.

Cowrie

Cypraea

Noted for their glossy shells, brilliant colors, and intriguing patterns, these handsome snails have long been prized by collectors. On Pacific islands, royalty once wore golden cowries as symbols of rank. Although the cowries live mainly in tropical seas, a few species are found off our southern shores. The chestnut cowrie, about two inches long, inhabits rocky coasts and inlets in California, and the four-inch measled cowrie lives in bays and inlets in southern Florida.

Coyote

Canis latrans

"Ufe span, if lucky, about 13 years," one text says of the wide-ranging coyote, and certainly few animals have needed more luck to reach old age in the face of human persecution. For centuries coyotes have had an exaggerated reputation as ruthless predators of domestic livestock, especially sheep and poultry. Although studies show that these midsize wild dogs feed mainly on rabbits, ground squirrels, small rodents, and carrion, the truth is that they eat almost anything. In the South they have even been known to feed on watermelons and persimmons. Despite man's poisons, traps, and guns, coyotes have not merely survived; they have actually expanded their range as well. Their distinctive nocturnal yaps and howls now are heard from the suburbs of Los Angeles to the farmlands of New England. Coyotes mate in winter, and in spring the females give birth to litters of 4 to 10 tiny, helpless pups that grow with astonishing speed. Beginning at three weeks to take food provided by their fathers, they reach independence in the fall, when most disperse in search of home territories-and mates-of their own.

Coyness

An Animal Behavior term, this is used to describe the reluctance to mate, as is often found in newly formed pairs. In females, coyness may serve to ensure that the male is fully committed to her and will assist in care of young; in males it may ensure that young are his Rather than of any previous male.

Crab

Among the most familiar seashore creatures, crabs are easily identified by their broad backs, formidable pincers, and their habit of scuttling sideways on four pairs of walking legs. Adapted to a variety of habitats, they can be seen racing across the sand, burrowing into muddy salt marshes, and crawling across the sea floor. A few kinds live mainly on land, but all crabs must return to the water to reproduce. The eggs, which the females carry on their undersides, hatch into tiny free-swimming larvae that go through several molts before settling to the ocean bottom and developing into adults. Most crabs are scavengers and eat a variety of foods, which they seize in their pincers. Lady crabs and other swimming crabs have oarlike tips on their last pair of legs, enabling them to move swiftly through the water. The nocturnal ghost crabs run across beaches with astonishing speed, then burrow into sand above the high-tide line. Fiddler crabs are well known for the males' one enormously oversized pincer, which they brandish to court females and to fend off competing males. Blue crabs, one of the most important commercial species, are found in bays and estuaries all along the Atlantic coast. The soft-shelled crabs listed on seafood menus are usually blues; their shells are edible because the crabs have just molted.

Crab Spider

Masters of camouflage, some of the crab spiders can change their color to match the flowers on which they wait for passing prey. Once settled in, they grab any insect that comes close, poison it with their bite, and enjoy a meal. Uke their namesakes, crab spiders can easily and nimbly scuttle sideways. Although they do not spin webs, the females produce silken sacs to protect their eggs. They usually die, however, before the young emerge.

Cranberry

Vaccinium

Low, creeping vines with tough, wiry stems, cranberries flourish in bogs and other moist, acidic soils from Labrador to Alaska and south to North Carolina. Though Indians of the northeast relished the fruit, there is no proof that cranberries were served at the first Thanksgiving in 1621. By 1663, however, a recipe for cranberry sauce appeared in a Pilgrim cookbook, and in 1677 colonists sent 10 barrels of the crimson berries to King Charles II. Valued mainly for their fruits, cranberries nevertheless provide a colorful display over the seasons. In summer the vines are dotted with pretty pink flowers, which are followed in the fall by plump red berries; and in winter the leathery, oval leaves turn from dark green to blazing scarlet.

Crane

Grus

The two North American members of the ancient crane family are birds of open wetlands, plains, and prairies. The whooping crane, standing more than four feet tall, is the giant of our waders. It is also one of the most endangered of birds. In the 1940's the entire population of whoopers totaled fewer than two dozen. Now, however, with strict protection and careful management, the majestic white cranes are slowly increasing in number. Each spring the growing flock migrates from its winter home in Texas to its nesting ground in northern Canada. Sandhill cranes-regal, gray, and three to four feet tall-are more numerous than whoopers but also depend on shallow wetlands anri open prairies for survival. In an experiment begun in 1975, sandhill cranes that nest in Idaho have served as foster parents to eggs and young of captive-bred whooping cranes.

Cranes mate for life and may live for 30 years. Their remarkable calls can be heard a mile away, but even more compelling are the musical duets sung by mated pairs. The most striking aspect of crane courtship, though, is their dancing. Male and female bow low to each other and then bound high in the air, like bouncing balls, in the annual mating rite. Some native Americans copied the dance as part of their ceremonies. And one biologist, caring for a captive female whooper, induced her to lay an egg by repeatedly joining her in this courtship dance.

Crane fly

Tipula

Long-winged and long-legged, crane flies are often mistaken for huge mosquitoes. They are harmless, however; the adults feed only on nectar or, in some species, nothing at all. Walking and flying slowly and rather awkwardly, crane flies are usually found in dense vegetation or near water. They also are attracted to buildings, where, after dusk, clouds of them are frequently seen swarming about lights. The tough-skinned larvae, called leatherjackets, live in damp soil or shallow ponds and are often used as bait.

Crater

Formed at the summit of volcanoes or by the impact of meteors crashing into the earth from outer space, craters are steep-walled, circular depressions. Meteor Crater in Arizona, nearly a mile wide and 600 feet deep, is one of the best known of its type. The gaping hole was formed in prehistoric times when a meteor some 80 feet in diameter, traveling at more than 30,000 miles per hour, collided with the earth. Much more common are volcanic craters. Almost all volcanoes have small craters around their vents, caused by the slumping of molten lava at the end of an eruption. Later eruptions, such as the one that rocked Washington's Mount St. Helens in 1980, can destroy the summit and greatly enlarge the crater. Calderas, in contrast, are deep, broad basins often several miles in diameter, usually formed by the collapse of a volcanic cone into its empty magma chamber after an especially violent eruption.

Crayfish

Also called crawfish and, sometimes, crawdads, crayfish are freshwater crustaceans that look very much like miniature lobsters. Common in streams and quiet ponds, they grow to three or four inches in length. Four pairs of walking legs allow them to move in any direction. When danger threatens, however, they flex powerful abdominal muscles and dart abruptly backward, out of harm's way. Feeding on vegetation and a variety of small animals, crayfish in turn are prey for birds, turtles, raccoons, and otters. Some species live in deep burrows with a water-filled chamber at the end that serves as a refuge in times of drought. A few inhabit damp meadows and have earned a reputation as crop-eating pests. Crayfish are popular menu items, particularly in the Mississippi River basin. In Louisiana, residents and visitors alike savor such local favorites as crayfish bisque.

Creation

Biological Philosophy term. The idea is both philosophical and religious. Philosophically, the notion of an original creative act is not inherently antipathetic to evolution or to physics, nor is it refutable by science (see the conclusion of Hawking's Brief History of Time along with Harrison's Masks of the Universe). It is, however, a matter of belief, not science. Religiously, however, the Western notion of creation roots itself in the first two chapters of Genesis; and these accounts are, of course, incompatible with scientific accounts, though early scientists tried valiantly to reconcile scientific discoveries with a literal interpretation of Genesis.

Creationism or Special Creation

Biological Philosophy term. Creationism affirms that God created each form of life as it is, and denies the idea that the various forms of life evolved from earlier forms.

Creation Science

Biological Philosophy term. The claim that special creation is not merely a belief but a scientific hypothesis, a rival hypothesis to evolution.

Creosote bush

Larrea tridentata

The most common shrub of our southwestern deserts, the creosote bush is superbly adapted for survival. It sends out roots in two directions: a taproot reaches down to find deep hidden reserves of water, while a network of shallow roots quickly absorbs any rainfall at the surface. It also secretes an herbicide into the surrounding soil, killing any seedlings that might compete for moisture. A waxy coating on the leaves helps protect the creosote bush against dehydration, but in periods of extreme heat or drought it simply sheds its normally evergreen foliage, then sprouts new leaves when the weather becomes more moderate. And while some desert animals, such as the chuckwalla, thrive on the creosote bush's leaves and twigs, most mammals are warned off by an acrid odor that inspired the plant's nickname, stinkweed.

Crepuscular

An Animal Behavior term, this is used in describing Animal species that are active at dawn or dusk or both. Desert Animals are commonly crepuscular because hot and dry days and cold and dark nights are hostile.

Crevasse

An ever-present peril on glaciers, crevasses are gigantic vertical cracks that form in the slowly moving rivers of ice. Sometimes dozens of feet wide and more than ISO feet deep, they usually are caused by stresses that develop as the ice passes over obstructions or begins to descend steep slopes. Crossing a crevasse field on a glacier can be extremely hazardous, especially when a cover of snow hides the narrower gaps. Sometimes, however, the wider gaps can be crossed safely where wind-blown snow has formed bridges over the chasms.

Cricket

The subject of a great deal of superstition, crickets have been regarded as signaling both good fortune and bad. Having a cricket in the house brought good luck, while harming one was believed to cause all manner of woes. The most common of these familiar chirping, hopping insects are the black field cricket and the similar brown house cricket. The latter, an old-world import, thrives in American homes on food crumbs and even on bits of fabric. Smaller and pale green, the snowy tree cricket is known mostly by its sounds. Rubbing their wings together, the males sing in unison on summer nights and unwittingly tell us how warm it is: adding 40 to the number of times they chirp in 15 seconds yields the approximate temperature in degrees Fahrenheit.

Crinoid

Although they look like showy flowers of the sea, crinoids actually are invertebrate animals related to sand dollars and starfish. The two types of crinoids-sea lilies and feather starstrace their ancestry back to fossil forms that lived hundreds of millions of years ago. Sea lilies, the more flowerlike of the two, live atop long slender stalks that are permanently attached to the ocean floor, and use their feathery arms to strain food from the surrounding water. Feather stars, on the other hand, break free of their anchoring stalks as they mature, and use their arms to swim about in shallow water.

Critical habitat

Endangered and Threatened species term.

Specific geographic areas, whether occupied by listed species or not, that are determined to be essential for the conservation and management of listed species, and that have been formally described in the Federal Register.

Crocodilian

The closest living relatives of the long-extinct dinosaurs, crocodilians include alligators, caimans, crocodiles, and a single species of gavial. While the American alligator is quite plentiful in southeastern swamps and bayous, the American crocodile is an endangered species found only in southern Florida. In appearance, crocodiles differ from alligators in having narrower, more pointed snouts and bigger teeth that show more prominently even when the mouth is closed.

Crossbill

Loxia

Crossed at the tips, the distinctively twisted beaks of crossbills look at first glance like a handicap. In fact, they are delicate tools that serve very well for removing seeds from the cones of pines and other conifers. The birds use the crossed tips to pry the cone scales apart, then deftly extract the seeds with their tongue. Our two species of crossbills-white-winged and red-are primarily birds of northern forests. In years when cone crops fail, however, large flocks of cross bills often wander far beyond their normal range. Red crossbill males are brick-red, with dark wings and tail, and tend to favor pine seeds. Snowy wing bars highlight the rosier whitewinged crossbills, which prefer the seeds of spruces and hemlocks and often fly to the ground to open fallen cones.

Crow

Corvus

Bold, brash, mischievous, and black from beak to toe, crows are big, imposing birds with a three-foot wingspan. Adapting to a variety of habitats and resourceful in securing food, they also are extremely intelligent. Crows raiding cornfields, for example, have an uncanny ability to tell the difference between a farmer's gun and such harmless articles as brooms or sticks. Crows adopted as pets have actually learned to count and utter coherent phrases. And they solve the problem of cracking mollusks such as clams by carrying them into the air, then dropping them on rocks to smash the shells. Omnivorous in their eating habits, crows also devour eggs, worms, berries, insects, fish, grain, and animals killed on roadways. The familiar caw of the common crow is heard throughout the country in parks, farmlands, woods, and suburbs. Our other two crows, both slightly smaller than the common crow, are the fish crow of the Atlantic and Gulf coasts and the northwestern crow, which lives along the north Pacific coast from Washington to Alaska. More sociable than the common crow, they forage year-round in groups. Like all crows, they nest in pairs, but in winter they often gather by the thousands to roost.

Crustacean

Hard-shelled crabs scurrying along seashores, sowbugs living under logs, fairy shrimp swimming in temporary ponds---all are crustaceans. Like their relatives the insects, spiders, and scorpions, they have jointed legs and external skeletons, which they shed periodically as they grow.

The largest American crustacean is the Alaskan king crab. A record specimen measured six feet two inches from claw tip to claw tip. Although crustaceans are found in oceans from polar regions to tropical climes, they are not limited to the sea. Tiny brine shrimp, for instance, thrive in the ultrasalty waters of the Great Salt Lake, while others, such as crayfish, inhabit fresh water. A few specialized types live in the outflow of natural hot springs, and some, such as the land crabs of southern Florida, are terrestrial air-breathers.

Some of the crustaceans are pests. Crayfish riddle dikes and levees with their burrows; land crabs devour crop plants; and barnacles on the hull of a ship can cut its speed in half. But others, including lobsters, crabs, and shrimp, are valued human foods. And as a link in marine food chains, copepods and other tiny members of the class are swallowed up by a vast array of sea creatures, from arrow worms to whales.

Crypsis

An Animal Behavior term, see Camouflage.

Cryptic

Meaning colored to blend in, providing camouflage.

Crystal

Disparate as they may seem, salt, snowflakes, gemstones, metals, and sugar all have one thing in common: they are made up of crystals, as are most nonliving substances. Crystals are characterized by symmetrical atomic structures whose orderly patterns are repeated again and again, often yielding beautiful shapes. Some crystals, such as quartz, are large and conspicuous, but in most substances they are much too small to be seen with the naked eye.

Cuckoldry

An Animal Behavior term, this is used to describe the situation in which the female of a pair mates with males other than her partner. It is not infrequently observed, and mate-guarding by males is thought to have evolved as a device to avoid it and the possibility of the male rearing young which are not his own.

Cuckoo

Coccyzus

Unlike the brash character that leaps out of clocks to announce the hour, the cuckoos of North America are shy birds. Both the blackbilled cuckoo and the yellow-billed cuckoo prefer to hide in thickets at the edges of forests and orchards and are more likely to be heard than seen. (A third species, the mangrove cuckoo, lives only along the Florida coast.) Nest building is not one of the strong points of these slim, long-tailed birds; they raise their young on crudely assembled platforms of sticks and twigs. From the moment of hatching, the chicks are studded with stout quills that finally open into feathers just before the birds are ready to begin flying. The cuckoos' voracious appetite for insects, especially hairy caterpillars, makes them welcome allies in the fight against such pests as the gypsy moth. Tent caterpillars, which veil trees with their big cobweblike nests, are also a favored food. Yellow-billed cuckoos, in fact, have been known to consume more than 300 of these destructive larvae in a single meal.

Culture

The totality of ways of acting and thinking which a group acquires by experience and interpretation and then passes down by teaching and training. Roughly, culture is the learned human behavior which is passed on, as opposed to the instinctual behavior which evolves.

Cultural evolution

An Animal Behavior term, this is used to describe the changing of behavior as it passes from one geneRation to another through learning. Single individuals may learn new habits and, if these are copied by others, the change may spread and persist in the population without any genetic alteRation being involved.

Culture

An Animal Behavior term, this is used to describe a set of patterns of behavior which are reproduced geneRation after geneRation through learning, as well as the products of those behavior patterns, such as tools and works of art in Humans (see also Tradition).

Currant

Ribes

Valued for their tart, juicy berries, which are used in jams, jellies, and pies, currants are low to midsize shrubs that prefer cool, moist climates. Their arching branches, with lobed, maplelike leaves, bear clusters of tiny, bell-shaped yellow-green flowers that mature into shiny red, black, or amber fruits. Unfortunately, however, currants are host to a fungus called blister rust that attacks the eastern white pine and a number of other pines prized for their timber. Thus, while many species of wild currants are native to North America, they have been systematically eradicated from many areas.

Cusk-eel

Long, slender, and snaky, cusk-eels resemble true eels but have a pair of feelers (actually modified fins) under the chin. Although they are not common, cusk-eels are found in temperate and tropical seas around the world. The spotted cusk-eel, a dweller in deep water off the west coast, ranges from one to two feet in length; the striped cusk-eel of the east coast averages just six inches. To hide from predators, these shy and secretive fish back into rock crevices or burrow tail-first into sandy bottoms.

Cyclone

See Hurricane.

Cypress

Cupressus

Perched on rocky cliffs above the Pacific, their crowns flattened and their trunks contorted by driving winds, Monterey cypresses seem the perfect symbol of persistence. But their romantic beauty is rare indeed, for the trees' entire wild population is restricted to two groves in Carmel, California. In fact, all of our native cypresses, evergreens with scalelike foliage, woody cones, and fragrant wood-prefer dry, austere habitats in the Far West. The Modoc cypress, for example, flourishes in lava fields of the Siskiyou Mountains in northern California and Oregon, while the Arizona cypress is found only in arid canyons of the Southwest.

Cypress swamp

There's a sense of age and mystery about a Cypress Swamp as one meanders through a 100-foot canopy of trees that can reach an age of over 1,000 years. Such swamps were prevalent during the age of mammoths. But today, these swamps are populated with woodpeckers, raccoons, flying squirrels, owls, bee hives, and frogs. Reptiles are also common, including Snakes, Turtles and Alligators, but of course, no Dinosaurs remain.

Dabbling Ducks

Some ducks are not capable of completely submerging. Instead, they will merely tip their head down and their backside into the air. This allows them to feed on shallow plants.

Daddy long legs

Familiar to almost everyone, the daddy longlegs has a plump, oval body supported by eight long, threadlike legs. (The biggest of North America's 200 species boasts a three-inch leg span.) Although they are related to spiders, daddy longlegs lack silk glands and so spin no webs. They are not poisonous but can defend themselves by emitting a foul odor. Usually found in damp places, they feed on small insects, spiders, carrion, plant juices, and even each other. In the North most daddy longlegs hatch in the spring and die after the females lay their eggs in the fall. In the South they often hibernate. Because they mature in late summer and are often seen at harvest time, they are also known as harvestmen.

Daisy

Leucanthemum vulgare

Relatives of the florist's chrysanthemums, oxeye daisies are among the first wildflowers that most children learn to recognize. Their cheerful flower heads-bright yellow central disks encircled by haloes of white, petallike ray flowers-embellish fields and roadsides from coast to coast. Growing up to three feet tall, daisies have narrow, jagged leaves that when young are tender enough to be eaten in salads. When older, however, they become so pungent that even grazing cattle shun them.

Dall Sheep

Ovis dalli

Another species of North American wild sheep is called Dall or Dall’s Sheep or the Thinhorn Sheep. Dall sheep are smaller than Bighorns and have more slender horns. They live in Alaska and in the Yukon Territory and British Columbia provinces of Canada. They range in color from white in the northernmost part of their range to almost black in the southernmost part. Dark brown or black Dall sheep are also called Stone or Stone’s Sheep or Fannin Sheep.

Damselfish

Brilliantly colored and adorned with stripes, spots, and bars, damselfish are among the most striking of the small reef fish. Characterized by a single nostril in front of each eye (most fish have Damselfish, pugnacious reef dwellers, are known for launching aggressive attacks against much larger foes.) they are found in tropical and some temperate seas. Despite their name, these colorful fish are anything but delicate damsels. Daring warriors instead, they aggressively defend their home ground-a patch of kelp or coral or a crevice in the rocks- from other reef fish, spiny sea urchins, inquisitive barracudas, and even snorkelers and scuba divers. The sergeantmajor, named for its stripes, often travels in small platoons as far north as New England. Pacific coastal waters from southern California southward are the domain of the ferocious garibaldi. Not only does the bright orange male zealously defend its nest, but the nest site is often passed from one generation to the next

Damselfly

Flashing with brilliant metallic hues of green, blue, violet, and other colors as they dart through the summer air, damselflies are beautiful, slender-bodied insects. They often are mistaken for dragonflies, but while at rest, most damselflies fold their wings parallel to their body, while dragonflies hold them straight out. Like dragonflies, damselflies are found around water; they prey on mosquitoes and other small insects, which they trap in a cage formed by their legs. Damselfly nymphs are aquatic predators that usually creep along the bottom, but they can also scull through the water, using their three feathery gills as oars.

Dandelion

Taraxacum officinale

Though gardeners might find it difficult to believe, North America used to be almost entirely free of dandelions. Once it had been imported by early colonists, however, the familiar yellow-flowered weed proceeded to do some colonizing on its own, its downy seeds floating off and eventually taking root across the continent. Fecundity is one reason for the dandelion's success. Its flower heads contain as many as 200 individual florets, each of which sets seed without need for pollination. The blossoms, moreover, release ethylene gas in the late afternoon, which poisons competing plants. And the dandelion's hollow stem contains a bitter white sap that effectively discourages grazing animals.

Darter

Little minnowlike fish that range from one to nine inches in length, darters are named for their habit of darting swiftly from one resting place to the next. More than lOO species live in streams and lakes east of the Rockies, where they feed on a variety of small aquatic animals. Many of the darters are brightly colored, with the males' hues becoming particularly intense during the breeding season. Common species include the widespread]ohnny darter; the sand darter, which burrows into sandy stream bottoms and leaves only its eyes and snout exposed to detect prey; and the celebrated snail darter, which made news in the 1970's when concern over destruction of its habitat delayed completion of a dam.

Dayflower

Commelina

Thriving in shady dooryards, roadsides, and woodland clearings, dayflowers furnish a pretty show of three-petaled blue flowers from May to October. When the blooms open, the two larger, upper petals arch back to expose the nectar and invite visits from pollinating bees. After a few hours, the petals wilt, wrapping a moist blanket around the flower's pistil and stamens. This allows for self-pollination, so that even without the help of bees, fertile seed is assured.

Daylily

Hemerocallis

Roadside wildflowers of beauty and elegance, daylilies are hardy perennials that long ago escaped from cultivation. Both the orange and the yellow daylily, the latter lemon-scented, bloom in loose clusters atop four-foot stalks. Though each trumpet-shaped flower lives only a day, as the name suggests, the plants produce a succession of blossoms over several weeks. Resistant to insects and disease, daylilies also are extremely resilient: their fleshy, fibrous roots easily survived the long ocean voyages of the settlers who introduced them, and they have since become established in the wild as far west as Texas.

Death camas

Zigadenus

Aptly named, the death camases are poisonous in every part. They can easily be distinguished from their edible relatives, the true camases, when in bloom. On death camases, the spikes of small, six-pointed flowers are greenish yellow, white, or bronze, while most of the true camases have blue flowers. In early spring, however, the differences are not so apparent, since all are simply tufts of grasslike leaves. Indians, who used to gather camas bulbs for food, occasionally made fatal mistakes in identification. Even today, the death camases sometimes poison sheep and cattle on the western mountains and plains.

Deceit

An Animal Behavior term, see Cheating.

Decomposer

When a plant or animal dies, hosts of other organisms feed on its remains. The most numerous of these decomposers are bacteria and fungi, indispensible recyclers that break down organic compounds into simpler components and so return vital nutrients to the environment. A host of small animals, from earthworms to insects, also feed on the remains. The wood-gnawing larvae of bark beetles, for instance, tunnel beneath the bark of rotting logs, where they in turn become hosts to the parasitic larvae of tiny wasps. Termites, too, may consume the wood but must rely on microscopic protozoans in their bodies to actually digest the fibers. Thus a single rotting log on the forest floor can be a thriving metropolis of interrelated life.

Deciduous

A woody plant that sheds its leaves in winter.

Deciduous Forest

Dominated by lofty and elegant broad-leaved trees that shed their foliage in autumn, deciduous (as opposed to evergreen) forests flourish in moist, rich soils over much of the eastern United States. Oaks, maples, beeches, birches, and other tall trees, their crowns merging into a continuous canopy, spread their leaves in the sunlight to manufacture food. Squirrels, hawks, and owls nest in the treetops, insects feed on the leaves, and birds in turn feed on the insects. Below the canopy is an understory of shade-tolerant trees. Deer wander among the low-growing ferns and scattered shrubs on the sun-dappled forest floor, woodcocks probe the soil for worms, and bears search for wild berries. The forest floor is also a place where decaying logs and leaves are broken down by insects, worms, fungi, and bacteria, renewing the soil by releasing vital nutrients. With the cool of autumn, the green leaves tum to yellow, orange, and red, and for a short time, especially in New England, the forests are ablaze with colors that rival those of the most dazzling flowers. By winter, most of the leaves have fallen to the forest floor, leaving bare branches silhouetted against the sky. In spring, before the canopy of leaves has had a chance to fill in again, the sun-drenched forest floor is carpeted with a tapestry of wildflowers.

Deciduous forest biome

Deciduous forests can be found in the eastern half of North America. The average annual temperature in a deciduous forest is 50° F. The average rainfall is 30 to 60 inches a year.

In deciduous forests there are five different zones. The first zone is the Tree Stratum zone. The Tree Stratum zone contains such trees as oak, beech, maple, chestnut hickory, elm, basswood, linden, walnut, and sweet gum trees. This zone has height ranges between 60 feet and 100 feet.

The small tree and sapling zone is the second zone. This zone has young, and short trees. The third zone is called the shrub zone. Some of the shrubs in this zone are rhododendrons, azaleas, mountain laurel, and huckleberries. The Herb zone is the fourth zone. It contains short plants such as herbal plants. The final zone is the Ground zone. It contains lichen, club mosses, and true mosses.

The deciduous forest has four distinct seasons, spring, summer, autumn, and winter. In the autumn the leaves change color. During the winter months the trees lose their leaves.

The animals adapt to the climate by hibernating in the winter and living off the land in the other three seasons. The animals have adapted to the land by trying the plants in the forest to see if they are good to eat for a good supply of food. Also the trees provide shelter for them. Animal use the trees for food and a water sources. Most of the animals are camouflaged to look like the ground.

The plants have adapted to the forests by leaning toward the sun. Soaking up the nutrients in the ground is also a way of adaptation.

A lot of deciduous forests have lost land to farms and towns. Although people are trying to protect the forests some poachers are trying to kill the animals in the forests. The animals are losing their homes because of people building their homes.

Deer

Odocoileus

Our only animals with antlers, North America's deer include three giants-moose, caribou, and wapiti, or elk. The most widespread and abundant members of the family, however, are the alert, elegant bucks, graceful does, and dappled fawns of the white-tailed and the mule deer. Especially common throughout the East, the delicate white-tailed, or Virginia, deer prefers woodland edges but can also be found in many suburban areas. Up to 3V2 feet tall and weighing as much as 250 pounds, it is a fleet, elusive creature that, when frightened, flashes the white underside of its tail like a banner. The stockier, long-eared mule deer lives in the West on forested mountain slopes as well as in deserts and chaparral. The black-tailed deer of the Northwest is a subspecies of the mule deer. Both white-tails and mule deer browse by day and on moonlit nights on the buds and twigs of trees, feeding on tender grass, berries, and acorns when they are available. During hard winters they barely subsist on the meager food that is available, and starvation is common. In fall, the antlered males battle other bucks for mates. Some seven months later, first-time mothers generally give birth to a single fawn, while older does commonly bear twins. The young have spotted coats that provide camouflage when they crouch motionless on the forest floor or in tall grass. And they are scentless, which further protects them from predators.

Deer family

Hoofed Mammals that have antlers. They are ruminants and have no upper incisors. These include the Deer, Elk, Moose, and Caribou.

Deer mouse

See White-footed mouse.

Deep time

Biological Philosophy term. The discovery that the universe has been around for more than the few thousand years recorded in the Bible, that it has been in existence for billions of years.

Deforestation

Removal of trees from a forested area without adequate replanting or natural regeneration.

Delayed Implantation

Many animals, in particular the weasels and bears experience a delay in the reproductive process. After mating, the fertilized embryo may float freely in the uterus for up to six months without significant development. At the end of this period (which varies with each species), if the female is healthy, the egg will implant and begin to develop. However, if she is in poor condition, the egg may simply be reabsorbed by the body. This allows more control over population than other animals for whom pregnancy is a one-way street.

Delist

Endangered and Threatened species term.

The process of removing an animal or plant from the list of Endangered and Threatened Wildlife and Plants.

Delta

Formed at the mouths of rivers or streams, where the water slows and drops its burden of sand, silt, and clay, deltas are often triangular in shape and take their name from their resemblance to the Greek letter delta. Not all are wedge shaped, however: some are rounded, and some, like the Mississippi River's, are pronged like bird feet. The size and shape depend on the size of the river, the amount of sediment it carries, and the currents where it empties. The Mississippi River, with a delta that covers hundreds of square miles, dumps more than 5 million tons of sediment each year into the Gulf of Mexico, extending the delta another 200 feet into the Gulf annually. Other notable examples include the Red River delta, formed where the river flows into Lake Winnipeg, and the Colorado River's delta in man-made Lake Mead.

Deer mouse

See White-footed mouse.

Delta

Demographic parameters

Bird Biology Avian Conservation term.

Fecundity and mortality parameters used to predict population changes, such as number of eggs laid per clutch, the frequency at which clutches are laid, the survivorship of eggs and young in the nest and to the age at first reproduction, and the subsequent survival of the adults throughout their lifetime.

Density

The number of units (e.g., individuals, pairs, groups, nests) per unit area.

Density-dependent

Having influence on individuals in a population in a manner that varies with the degree of crowding in the population.

Density-independent

Having influence on individuals in a population in a manner that does not vary with the degree of crowding in the population.

Desert

A Hot and Dry Desert is, as you can tell from the name, hot and dry. Most Hot and Dry Deserts don't have very many plants. They do have some low down plants though. The only animals they have that can survive have the ability to burrow under ground. This is because they would not be able to live in the hot sun and heat. They only come out in the night when it is a little cooler.

A Cold desert is a desert that has snow in the winter instead of just dropping a few degrees in temperature like they would in a Hot and Dry Desert. It never gets warm enough for plants to grow. Just maybe a few grasses and mosses. The animals in Cold Deserts also have to burrow but in this case to keep warm, not cool. That is why you might find some of the same animals here as you would in the Hot and Dry Deserts.

Deserts cover about one fifth of the Earth's land surface. Most Hot and Dry Deserts are near the Tropic of Cancer or the Tropic of Capricorn. Cold Deserts are near the Arctic part of the world.

Hot and Dry Deserts temperature ranges from a low of 70 to 80 degrees in the summer during the day and goes upward from there. The extreme maximum temperature for Hot Desert ranges from 110 to 130 degrees. Cold Deserts temperature in winter ranges from 30 to 40 degrees and in the summer it ranges from 70 to 80 degrees.

The precipitation in Hot and Dry Deserts and the precipitation in Cold Deserts is different. Hot and Dry Deserts usually have very little rainfall and/or concentrated rainfall in short periods between long rainless periods. This averages out to under a few inches a year. Cold Deserts usually have lots of snow. They also have rain around spring. This averages out to as much as 10 inches of rain or more in a year.

Hot and Dry Deserts are warm throughout the fall and spring seasons and very hot during the summer. the winters usually have very little if any rainfall. Cold Deserts have quite a bit of snow during winter. The summer and the beginning of the spring are barely warm enough for a few lichens, grasses and mosses to grow.

Hot and Dry Deserts vegetation is very rare. Plants are almost all ground-hugging shrubs and short woody trees. All of the leaves are replete (packed with nutrients). Some examples of these kinds of plant are Turpentine Bush, Prickly Pears, and Brittle Bush. For all of these plants to survive they have to have adaptations. Some of the adaptations in this case are the ability to store water for long periods of time and the ability to stand the hot weather.

Cold Desert's plants are scattered. In areas with little shade,about 10 percent of the ground is covered with plants. In some areas of sagebrush it reaches 85 percent. The height of scrub varies from a few inches to several feet at the most. All plants are either deciduous and more or less contain spiny leaves.

Hot and Dry Deserts animals include small nocturnal (only active at night) carnivores. There are also insects, arachnids, reptiles, and birds. Some common examples of these animals are lizards and snakes. Cold Deserts have animals like Antelope, Ground Squirrels, Jack Rabbits, and Kangaroo Rats.

Desert pavement

Long before humans were paving roads, wind and water were at work paving parts of deserts with mosaiclike expanses of closely packed rock fragments known as desert pavement. These barren, windswept areas result where finer particles of sand and soil have been carried away by erosion, leaving the surface covered with a solid armor of rocks. Though we usually think of deserts as sandy places, rocky areas sheathed with desert pavement, such as those found in parts of California's Death Valley, are actually far more common than sand.

Desert poppy

Kallstroemia grandiflora

In late summer the desert poppy spreads brilliant coverlets of bloom over dry, sandy flats and slopes from western Texas to southern California. Bright orange and bowl-shaped, the fivepetaled blossoms are two inches across and grow on sprawling hairy stems. Later in the season the handsome flowers are followed by seedfilled fruits with long beaks and spiny, swollen bodies that look like miniature replicas of medieval maces. Though not poppies at all, these tough annual wildflowers are also known as Arizona poppies and summer poppies.

Desert pavement

Desert poppy

Kallstroemia grandiflora

Desertion

An Animal Behavior term, this is used to describe the situation in which one partner leaves parental care to the other at some stage after mating. Whole species may show the same pattern: eg female alone caring (Ducks) or male alone (someFishes). In other cases, desertion occurs occasionally where the deserted partner can rear young alone and the deserter can find a new mate. The term is also applied to desertion of offspring by adults which may occur after disturbance or in adverse conditions.

Design

Biological Philosophy term. An argument for the existence of God. Here, for instance, is Thomas Jefferson's version: "I hold (without appeal to revelation) that when we take a view of the universe, in its parts general or particular, it is impossible for the human mind not to perceive and feel a conviction of design, consummate skill, and indefinite power in every atom of its composition. The movement of the heavenly bodies, so exactly held in their course by the balance of centrifugal and centripetal forces, the structure of our earth itself, with its distribution of lands, waters and atmosphere, animal and vegetable bodies, examined in all their minutest particles, insects mere atoms of life, yet as perfectly organized as man or mammoth, the mineral substances, their generation and uses, it is impossible, I say, for the human mind not to believe that there is, in all this, design, cause and effect, up to an ultimate cause, a fabricator of all things from matter and motion, their preserver and regulator while permitted to exist in their present forms, and their regenerator into new and other forms." (Letter to John Adams)

Detectability

Bird Biology Avian Conservation term.

A measure of the conspicuousness of a species equal to the proportion of actual units (individuals, territorial males, etc.) observed on a given area.

Detection distance

Bird Biology Avian Conservation term.

The distance from the observer at which the individual or cluster of individuals is seen or heard (the radius in point counts and the lateral or perpendicular distance in transect counts).

Devil's walking stick

Aralia spinosa

Sometimes growing as a 40-foot tree, the devil's walking stick more often has just a single stem some 15 feet tall, topped by a parasol of huge, twice-divided leaves. Up to three feet long, they are the biggest leaves borne by any native shrub or tree. Also known as Hercules' club, the devil's walking stick is armed with a fearsome array of thorns, which even bristle from the leaf stalks. In summer the plant's forbidding aspect is softened by huge clusters of little greenish flowers that, by autumn, turn into small black berries. Ranging from New York to east Texas, the deviI's walking stick often forms dense thickets along streambanks and other low-lying areas. The devil's walking stick, despite its fearsome armament of spines, is sometimes eaten by hungry white-tailed deer. The small, five-seeded black berries, however, are ignored by all but a few mammals and birds.

Dew

When the sun goes down at the end of the day, objects near the ground begin to cool off and chill the warmer air that surrounds them. As the air cools, it becomes more saturated with the water vapor it contains, because cool air cannot hold as much moisture as warm air can. When the air reaches the temperature at which it is completely saturated with water vapor-its dew point-some of the vapor condenses as dew, glistening drops of water that appear on grasses, flower petals, spiderwebs, and other outdoor surfaces. (If the dew point is below freezing, the excess moisture freezes directly onto surfaces and is called frost.) Most likely to form on calm, clear nights, dew is an important source of moisture for many desert plants.

Dewberry

See Blackberry.

Dewlap

A pendant of hair-covered skin that hangs from under the throat of an Animal, e.g., the Moose.

Dialect

An Animal Behavior term, this is used to describe the variation of social signals within a species from one locality to another. Described for vocalizations of Birds and Frogs, and for the waggle dance of the HoneyBee. The term is sometimes restricted to cases where variation shows sharp boundaries between populations giving a mosaic of signal forms.

Diamond

The hardest of all natural substances, diamonds are formed from carbon that was dissolved in molten rock and cooled under enormous pressure. Looking like glassy, irregular pebbles, they can be cut and polished to produce gems. Most, however, are not of gem quality and are used instead as industrial abrasives. The only Significant diamond field in the United States is in Arkansas, but diamonds scattered by glaciers and streams have been found near the Great Lakes, in the Appalachians, and in California.

Diatom

Among the most abundant of all living things, diatoms are so tiny that as many as 20 million of these one-celled plants can live in a single quart of seawater. Unlike other algae, they have shelllike cell walls made of silica and come in a bewildering variety of shapes-round, square, needlelike, triangular, starlike, and more.

Golden brown in color, diatoms live in both salt and fresh water. They sometimes form slimy films or jellylike lumps on underwater stones and sticks, but most float free in the plankton. Key links in aquatic and marine food chains, they are eaten in countless numbers by planktonic animals that are in turn the food of larger creatures of the sea. After death the empty shells of diatoms accumulate in deposits of diatomaceous earth, valued as an ingredient in scouring powder and other abrasives; as a filter; and as a filler in paints, plastics, and other products.

Dinosaur

Dominating the earth for 140 million years, dinosaurs were the largest land animals that ever lived. The earliest of these giant reptiles appeared more than 200 million years ago, and the last of them mysteriously disappeared some 65 million years ago. In North America, dinosaurs lived mainly on the plains and badlands just east of the present-day Rocky Mountains, in the Southwest, and on the coastal plain between the Appalachian Mountains and the sea. Among the hundreds of species that flourished here were the fearsome three-horned triceratops; the stegosaur, with a deadly spiked tail used in selfdefense; and the 75-foot, 30-ton brontosaur ("thunder lizard"). The largest dinosaur, the seismosaur ("earthquake lizard"), was up to 120 feet long and weighed perhaps 100 tons. Its fossil remains were discovered by hikers in New Mexico in 1986. Preying on these herbivores were a variety of awesome carnivores, notably the Tyrannosaurus rex ("tyrant lizard king"), which was 40 feet long, 18 feet high at the hip, and had a huge head and a mouth filled with 6-inch-long daggerlike teeth.

Dipper

Cinclus mexicanus

Stocky, gray, short-tailed songbirds that favor waterfalls and cold rushing mountain streams of the Far West, American dippers earn their living in an extraordinary way. Undaunted even by water too turbulent for humans to stand in, they fearlessly plunge in and pump their wings to reach the bottom, where they stride along the streambed in search of food. Small fish and insect larvae are their main prey.

Also known as water ouzels, dippers have big feet and thick plumage that is waterproofed by oil from large preen glands. Flaps over the nostrils, and transparent membranes that close over the eyes complete their diving outfits. The dippers' fluid song, often delivered from streamside boulders, can be heard even over the roar of rushing water. The birds always build their domed nests near waterways. Some even raise their families behind the curtains of waterfalls-one reason why the young must be accomplished swimmers when they leave the nest.

Direct competition

Bird Biology Avian Conservation term.

The exclusion of individuals from resources by aggressive behavior or use of toxins.

Disc florets

Small flowers found at the centre of the inflorescence of members of the daisy family.

Discrimination

An Animal Behavior term, this is used to describe the ability of an Animal to distinguish between two stimuli. Thus, Gulls prefer to sit on brown egg models Rather than on red ones and so must be able to distinguish between them. Many psychological studies have examined the processes of discrimination learning whereby Animals can be trained to make such distinctions.

Disease (Wildlife)

Bird Biology Avian Conservation. Birds, like any animals, are subject to illness, and the migratory nature of many species makes it hard to control the spread of contagious diseases, such as avian cholera. Avian botulism, which is contracted by eating poisoned maggots, occurs naturally and is a leading cause of bird death, especially in migratory waterfowl.

Dispersal

The movement of organisms away from the place of birth or from centers of population density.

Dispersion

The pattern of spacing of individuals in a population. The nonaccidental movement of individuals into or out of an area or population, typically a movement over a relatively short distance and of a regular nature.

Displacement activity

An Animal Behavior term, this is used to describe seemingly irrelevAnt behavior, such as grooming or nest building, sometimes shown by courting or fighting Animals. It is thought to be shown where more relevAnt behaviors are thwarted or in conflict. Such actions are often hurried or incomplete and some are considered to have been the original behavior from which certain Displays evolved.

Display

An Animal Behavior term, this is used to describe movement pattern used in communiCation. These are often striking, stereotyped and species-specific, especially during courtship and aggressive behavior. Displays may also function between species (see also Distraction Display).

Disruptive coloration

An Animal Behavior term, this is used to describe color patterns which break up the outline of an Animal and other features of its body so that it is very hard to pick out when motionless.

Distraction display

An Animal Behavior term, this is used to describe a Display with which Mother Birds lead predators away from their broods by feigning injury.

Distinct population segment

If it satisfies the criteria specified in the February 7, 1996, Federal Register, pages 4722-4725, a portion of a vertebrate (i.e., animals with a backbone) species or subspecies can be listed. The criteria require it to be readily separable from the rest of its species and to be biologically and ecologically significant. Such a portion of a species or subspecies is called a distinct population segment.

Disturbance

Any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment.

Diurnal

Meaning active during daylight hours.

Diversity

Bird Biology Avian Conservation term.

Typically used in relation to species, a single index that incorporates the number of species and relative abundances of species (evenness). For example, a collection is said to have high diversity if it has many species and their abundances are relatively even. There are many types of diversity:

Point diversity--for a small or microhabitat sample within a community regarded as homogeneous

Pattern diversity--as change between parts of the internal pattern of a community

Alpha diversity--for a sample representing a community regarded as homogeneous (despite its internal pattern)

Beta diversity--as change along an environmental gradient or among the different communities of a landscape

Gamma diversity--for a landscape or set of samples including more than one kind of community

Delta diversity--as change along climatic gradients or among geographic areas

Epsilon diversity--for a broader geographic area, including differing landscapes

Diving Ducks

Some waterfowl are able to dive completely below the surface, allowing them to feed in much deeper water than dabbling ducks.

Dobsonfly

Long, fearsome-looking insects with a five-inch wingspan, male dobsonflies have a daunting pair of jaws: an inch long on some species and gracefully curved, they look like crossed sabers. (The females' jaws are much smaller.) During their brief two-week existence as adults, these fluttery fliers sometimes are seen congregating around outdoor lights. After mating, they lay waxy clusters of eggs on leaves or branches above rapid streams. When the larvae hatch, they drop into the water and spend two years or so as ravenous aquatic predators, lurking under stones and gobbling up small prey. Known as hellgrammites, dobsonfly larvae can inflict painful bites on swimmers. They are, however, relished by bass and prized by anglers as bait.

Dock

Rumex

Found on roadsides and in fields and gardens from coast to coast, docks are ubiquitous members of the buckwheat family. Thanks to long, penetrating taproots, they also are among the most persistent. Leaves vary with the species, but most docks look alike in flower and seed. In June they send up tall stems topped with spikes of small greenish flowers, which by September yield an abundant crop of reddish-brown, threesided fruits. All parts of the plants are avidly consumed by wildlife.

Dodder

Cuscuta

A threadlike parasite that twines around other plants, dodder is a nuisance that sucks the juices from ornamentals and valuable crop plants. Each seed sends up a thin stem that attaches itself to a nearby plant, penetrating the host's tissue and drinking in its sap. Dodder's own roots then wither, leaving the parasite with no attachment to the soil. Its leafless stems are light orange, lacking the chlorophyll that enables other plants to make their own food. Dodder does bloom like a normal plant, however, bearing dense clusters of tiny, bell-shaped, white or yellow flowers. Its seeds can lie dormant for five years, but once they sprout, each can produce a half mile of coiling stems in just four months.

Dogbane

Apocynum

Despite their sinister name, our several species of dogbanes are of little threat to dogs. Nor, despite their poisonous milky sap, are they any threat to grazers: the juice is so bitter that animals generally avoid the plants. From June to September, all the dogbanes are arrayed with clusters of pink or whitish flowers. The tallest species, a five-foot plant sometimes called Indian hemp, has especially stringy bark that Indians used for making rope and fishnets.

Dogtooth violet

Erythronium

The dozen or more wildflowers known as dogtooth violets all are members of the lily family and are among the first to bloom in spring. In the East the common species is the trout lily, named for its mottled green leaves. Often growing in large patches, each plant bears a single yellow bloom atop a four- to eight-inch stem. Of the several western dogtooth violets, one of the best known is the glacier lily, a white-flowered species found near snow fields.

Dogwood

Comus

Virginia and North Carolina both claim the dogwood as their state flower, but in fact the white spring blooms beloved from Maine to Texas are not flowers at all. Their four notched "petals" are actually bracts, modified leaves that surround the real flowers-the cluster of tiny greenishyellow blossoms at their center.

Dogwood is useful and lovely-the bark was substituted for quinine during the Civil War. Seldom exceeding 30 feet in height, the flowering dogwood of the East is overshadowed by the Pacific dogwood of the West, which grows up to 60 feet tall. Four to six white bracts encircle its flower clusters, and it sometimes blooms twice a year. Both trees, unfortunately, are susceptible to a fungus disease that in recent years has caused an epidemic of deaths among these beautiful ornamentals. Well known-and easily recognized-among the smaller species is the red osier dogwood, a shrub with blood-red bark that adds a welcome note of color to winter landscapes. Another, silky dogwood, is a spreading species with purplish twigs that favors streambanks and similar moist places. Notable berry producers, the dogwoods rank high among trees and shrubs as a source of food for wildlife.

Dolomite

Composed of calcium carbonate, dolomite is nearly identical to limestone-with one crucial difference. It contains magnesium, which makes it harder and less soluble than limestone and therefore more resistant to weathering. Most dolomite was formed when magnesium-rich water seeped into preexisting limestone and replaced some of the rock's calcium with magnesium. Dolomite is used as a building stone, a lining for furnaces, and in smelting.

Dolphin

Often seen cavorting off the bows of moving ships, schools of dolphins move in graceful arcs as they leap above the waves. These playful, intelligent mammals are actually small, toothed whales, whose beaklike snouts distinguish them from their blunt-nosed relatives, the porpoises. With a highly varied repertoire of whistles, clicks, and chirps, dolphins can signal to each other and even carry on conversations. They also produce ultrasonic sounds, which they use for navigation and locating prey. Using their teeth to capture and hold prey rather than to chew it, dolphins feed on fish and squid, swallowing them whole. Like other whales, dolphins breathe through a blowhole on the back and sleep while floating near the surface. Found off both the Atlantic and Pacific coasts, the eight-foot common dolphin has a black back, white belly, and yellowish stripes on its sides. The larger bottle-nosed dolphin is 9 to 12 feet long and mostly gray in color. Famous for its ability as a performer, the bottle-nosed dolphin thrives in captivity, is easily trained, and has made innumerable appearances in films and aquarium shows.

Dolphinfish

Coryphaena hippurus

Though no relation to the acrobatic marine mammals known as dolphins, dolphinfish also are well known for their agile antics: lightning speed, dramatic leaps, and ferocious fighting ability make them a favorite with deep-sea fishermen. Unmistakable in appearance, dolphinfish are up to 6 V2 feet long, with a dorsal fin that tapers all the way from their blunt head to their forked tail. The fish also are brilliantly colored, with deep blue and green on the back and bright golden flanks (which no doubt inspired their other name, dorado). Roaming in schools, dolphinfish feed on squid, crustaceans, and especially, flying fish, which they often pursue by leaping above the waves.

Dominance

An Animal Behavior term, this is used to describe the situation in which one Animal dominates another in fights or in access to resources such as sitting positions, food and mates. DominAnts are often older or stronger, but fighting may not be involved in encounters because subordinates frequently defer. In some social groups, relationships may be consistent and clear enough for Animals to be placed in a linear dominance hierarchy in which each is dominated by those above it and dominates those below.

Dorsal

The upper surface.

Dorsal fin

One or more fins along the backbone of a fish, dolphin or whale.

Douglas fir

Pseudotsuga

Towering, majestic trees that sometimes reach heights of more than 300 feet, Douglas firs are exceeded in size only by the redwoods and giant sequoias. The largest specimen on record stood 385 feet tall and had a trunk 15 feet thick. On the tallest trees, the trunks soar straight up for 100 feet or more and are crowned by a compact pyramid of branches covered with flattened needles and pendulous cones. In 1825, botanist David Douglas, for whom the tree is named, failed in his first attempt to collect seeds because his shotgun would not shoot high enough to dislodge a cone. Unmistakable in appearance, the cones have three-pointed, ribbonlike bracts projecting from between their scales. Though the biggest trees are found in coastal forests from British Columbia to northern California, Douglas firs range through much of the West. Prized as ornamentals and for Christmas trees, they also are one of our most valuable timber trees.

Dove

Known for their gentle, cooing calls, doves have been symbols of peace and love since ancient times. Stocky, small-headed, and usually brown or gray, they scuttle along on short legs with their heads bobbing back and forth. Although there is no technical distinction between doves and pigeons, doves tend to be smaller, more graceful birds with pointed tails, while pigeons are larger and have fan-shaped tails. Doves nest on flimsy platforms of twigs and usually lay two pale, unmarked eggs. The newly hatched young are fed pigeon milk, a substance that looks like cottage cheese and is produced in the parents' crops. Mature doves feed mainly on seeds and fruit and are among the few birds that can drink without lifting their heads to let the water run down their throats. The most widespread species is the mourning dove, whose repeated coos add a poignant, mournful note to forests, deserts, suburbs, and even cities from coast to coast. Because of it abundance and fast flight, the mourning dove is a popular game bird in many states. So is the white-winged dove, which lives in the Southwest. The sparrow-sized common ground-dove is found in southern grasslands, and the similar Inca dove prefers to nest in deserts.

Dragonfly

Quick and agile fliers, dragonflies are long, slender insects equipped with two pairs of gauzelike wings that shimmer in the sunlight. Although our largest species has a wingspan of nearly six inches, fossils reveal that some of their ancient ancestors were five times that size. Dragonflies are usually seen hovering over ponds and quiet streams, where they hunt for mosquitoes and other insects. Gathering their legs together to form a sort of basket, they scoop up their victims as they dart through the air. Even as aquatic nymphs, immature dragonflies are accomplished predators. Their hinged lower jaws, armed with sharp hooks at the end, can shoot out with lightning speed to snatch tadpoles, small fish, and insects. After one or more years, the homely nymphs emerge from the water and begin their lives as graceful, winged adults.

Drinking Water

Water that is pure enough for drinking.

Drive

An Animal Behavior term, this is a psychological term applied to supposed moving forces underlying the appearance of behavior. For example, the hunger drive, sex drive and social drive. The term has fallen from use as the causes of behavior have Been analyzed in more detail and different factors have Been found to affect different aspects of behavior without the need for motive forces affecting each of them to be postulated.

Drizzle

Associated with gloomy days and low-lying clouds, the form of precipitation we call drizzle is neither mist nor rain but something in between. It is made up of water droplets that are

just large enough to drift slowly downward. They are not so small that they float in the air as do the tiny particles of mist or fog. Nor are they so large and heavy that they fall rapidly like rain. And unlike rain, which is associated with high, turbulent clouds that tend to pass quickly overhead, drizzle usually continues to fall over longer periods of time.

Drought

When the amount of precipitation in a region drops far below its normal level over an extended period of time, the resultant shortage of moisture is called a drought. In their severest form, droughts can cause a succession of calamities and take an enormous toll on life, land, and the economy. Streams and reservoirs dry up; crops wither and perish; animals starve or die of thirst; the soil turns to dust and is carried away by the wind; and grass and forest fires rage out of control. In the 1930's, for example, the Great Plains were devastated by one of the worst droughts in history. Crops failed, much of the land was ruined, and families were forced to abandon their homes forever.

Drum

Also known as croakers, drums are named for the low-pitched sounds they make by contracting muscles next to the swim bladder. The family includes about 160 species of mostly oceanic fish, though not all of them croak, because not all are equipped with the swim bladder that serves to amplify the sound. The various species range from 1 to 100 pounds in weight, but all have in common a conspicuous notch dividing the dorsal fin into two parts. Found mostly in shallow coastal waters, the drums are popular commercial and sport fish. Millions of red drums, or channel bass, are caught off Florida every year, and black drums and spotted seatrout are sought from New England to the Rio Grande. Off the west coast, the white seabass, up to four feet long, also is prized by fishermen. Other drums include the weakfish and kingfish, found in the Atlantic, and the freshwater drum of the central states.

Drumlin

Relics of the Ice Age, drumlins are long, low, oval-shaped hills composed of glacially deposited rock debris. Molded into their characteristic streamlined form as ice sheets moved over the debris, they lie with their long axis in line with the direction of the ice's movement. Up to 150 feet high and half a mile long, drumlins often occur in groups on flat plains, where they look like schools of giant leaping porpoises. Among the most famous drumlins is Bunker Hill in Boston, but groups of them can also be seen elsewhere in eastern Massachusetts, in Wisconsin, and in New York State.

Duck

Web-footed waterfowl with waterproof feathers, ducks are birds of oceans, lakes, rivers, and ponds. In contrast to their larger cousins, geese and swans, they generally have shorter legs and necks and broader, flatter bills; and instead of trumpeting or honking, they quack or whistle. Male ducks are more brightly colored than females, but after mating they molt into drab browns similar to the females' plumage. Most species build down-lined nests on the ground near the water's edge, but a few kinds nest in cavities in trees. Unlike geese and swans, ducks do not mate for life; once the eggs have been laid, the males abandon the females and troop off to molt and congregate with other males. Our many kinds of ducks fall into several groups based on appearance and feeding habits. Most familiar are the freshwater dabbling ducks such as mallards, black ducks, teals, and wigeons. Dabblers feed by filtering small plants and animals from the surface or by tipping tailup to pull underwater plants from the bottom. Diving ducks are found on both fresh and salt water. Some, such as canvasbacks and redheads, are mainly vegetarians, while scaups, eiders, scoters, goldeneyes, and buffleheads dive for shellfish and crustaceans. Mergansers are streamlined divers that seize fish with their long, sawtooth-edged bills. Oldsquaws, the deepest divers, can descend to depths of 200 feet. Other ducks include ruddy ducks, which are chunky, broad billed, and stiff tailed, and the whistling ducks of southern marshes, longlegged, long-necked birds with shrill calls.

Duckweed

Of the more than 300,000 known species of flowering plants, the duckweeds are the smallest; one kind is so tiny that a dozen individuals could fit on the head of a pin. Found in still, warm waters, duckweeds are simple, free-floating fronds that have no stems or leaves, and in a few species lack roots as well. Their tiny flowers rarely produce seeds. Duckweeds propagate instead by developing buds that break off and grow into mature plants. Extremely prolific, duckweeds sometimes multiply so rapidly that they completely cover a pond's surface.

Dudleya

Plants of harsh places where little else can survive, dudleyas of various species cling to seaside cliffs in California, hide under the scrub on coastal mountain ranges, and poke up from desert slopes in the Southwest. The plants lie withered and dormant through the summer's heat, but winter rains revive their tidy rosettes of succulent leaves, and in spring they send up stalks of pretty yellow, red, or white flowers. One of the better-known species is the powdery dudleya, a yellow-flowered plant of coastal cliffs that is named for the mealy white coating on its leaves. Another widespread species, canyon dudleya, produces red to yellow flowers; it brightens rocky outcrops in California's Sierra Nevada and the coastal mountain ranges.

Duetting

An Animal Behavior term, this is used to describe the calling of some pairs of Birds, notably Whooping Cranes and Canada Geese, where calls of two members of the pair arc so close together and coordinated that the sequence sounds like the song of a single Bird. Duetting may help to maintain the pair bond as well as having a function in territorial advertisement.

Dumping (Ocean)

The disposal of waste into an ocean.

Dune

Unstable monuments to the combined action of wind and time, dunes are hills of sand found in deserts and along shorelines. Formed in much the same way as snowdrifts, they build up when wind, slowed by an obstacle such as a rock or plant, drops its load of sand on the leeward side. The resultant mound gradually increases in size, in some cases reaching hundreds of feet in height. Some dunes are anchored by vegetation; others migrate many feet each year. In the United States, notable seashore dunes are found on Cape Cod in Massachusetts, and along the Oregon coast. On the shores of Lake Michigan, many dunes are piled 500 feet high and extend for miles. Some of the tallest inland dunes in the country occur at Great Sand Dunes National Monument in Colorado, where they reach heights of more than 700 feet.

Dust devil

On hot, still days when the midday sun blazes down in arid regions, air near the ground heats up and begins to rise. As air rushes in to replace it, the rising air starts to spin. Dust, sand, leaves, and debris also are pulled up into what then becomes visible as a slender, wavering dust devil. Looking like tiny tornadoes, dust devils may rise hundreds of feet. But because they are small and easily disturbed by surface winds, they seldom last more than a few minutes.

Dust storm

Sweeping across the land-often for hundreds of miles-dust storms are strong, dust-laden winds that smother animals and plants, bury crops, and reduce visibility to nighttime darkness. Destructive and awesome, they occur in arid regions with little protective vegetation and in areas where drought has reduced the soil to powdery dust. As winds sweep across the ground, particles are stirred up and held aloft, forming great dark walls that can reach heights of 10,000 feet or more. Although dust storms have always been part of the American scene, the worst occurred on the Great Plains in the 1930's. During those Dust Bowl years, 50 million acres of farmland were destroyed.

Dusty miller

Artemisia stelleriana

A common plant on eastern seashores, dusty miller sports little yellowish flower heads in summer. But its outstanding feature is its felty gray-green foliage, which does indeed have a dusty look, as if it had been sprinkled with flour. The covering protects the leaves from drying out in sun and wind, so that it flourishes even at the ocean's edge. An import from Asia, the plant is cultivated for its attractive foliage. But since escaping from the garden, this perennial has proven an important stabilizer of beaches. As sprawling stems take root across the dunes, they cast a silvery net that slows the shifting sands.

DVD

DVD (sometimes called "Digital Versatile Disc", or "Digital Video Disc") is a modern media format that can be used for recording, storing and playing information, including Computer files, Audio and Video - including movies with high video and sound quality. DVDs resemble a small, shiny round record, and the much more common CDs - as their physical dimensions are the same 4.72 inches or occasionally 3.15 inches in diameter, but they are encoded in a different format and at a much higher density. Different sizes of DVD hold different quantities of information. Two commonly used sizes are DVD5 and DVD9. An "average" DVD holds about 5.7 GB of information.

Eagle

Bold and proud in appearance, eagles have symbolized power since ancient times. Like other hawks, they have keen eyesight, hooked beaks, and long, curved talons for seizing prey. The two North American species, the bald eagle and golden eagle, are similar in size, with eight-foot wingspans, but otherwise differ in several ways. Despite its fierce appearance, the bald eagle, our national bird, is a rather timid hunter. Usually found near water, it feeds mainly on fish, which it often steals from ospreys. Its nest, or aerie, generally built in tall trees, is enlarged year after year and may be as much as 9Y2 feet wide and 20 feet high. In the 1960's bald eagles were reduced in numbers by DDT but have made a comeback since the pesticide was banned.

The golden eagle, which nests on cliffs in western mountains and across Canada, is a bolder hunter than the bald eagle. It captures prey in long swoops and sometimes attacks animals larger than itself. In the past, thousands of golden eagles, thought to be a threat to livestock, were shot from airplanes. Since 1962, however, federal law has protected them.

Earth

This place we live, Planet Earth, is the third planet, and 93,000,000 miles from the sun. It is estimated to be over 4.5 billion years old.

The planet rotates once every 23 hours, 56 minutes, and 4.09 seconds. It makes one full revolution around the sun every 365 days, 6 hours, 9 minutes, and 9.45 seconds. Earth's axis is tilted at a 23.5° angle.

Earth has a total surface area of 196,800,00 square miles. Approximately 57,300,00 square miles, or 29% of the total surface area is land. Water covers approximately 139,500,000 square miles, or 71% of the total surface area.

The highest temperatures on Earth have reached 136° F (58° C) at Al Asisiyah, Libya. Temperatures of - 128° F (-89° C) have been recorded at Vostok station in Antarctica.

The atmosphere is a thin, gaseous layer of air that envelops the planet. Its inner layer is called the troposphere and reaches only 11 miles above sea level. It contains most of the planet's air, which consists of nitrogen (78%) and oxygen (21%). The stratosphere, or outer layer, stretches 11-30 miles above sea level and contains ozone (O3). Ozone filters out most of the sun's harmful ultraviolet radiation.

More than 99% of earth's atmosphere is less than 50 miles (80 km.) high. However, particles of the atmosphere are found 1,000 miles (1,600 km.) in space above the planet's surface.

Earthquake

Among the most dreaded of natural phenomena, severe earthquakes are terrifying events. Their awesome force can topple buildings, buckle bridges, rupture highways, and cause catastrophic loss oflife and property. Fortunately, the most powerful quakes are rare. Of the million or so earthquakes that occur around the world every year, the vast majority are too small to be detected except by sensitive instruments. In the United States, about 700 a year are strong enough to be felt, but most cause no more rumbling than a passing truck.

The earth's crust consists of about 20 gigantic, slowly moving plates. As the plates collide, grind past, or sink below one another, stress builds up along their edges. Finally, the pressure becomes so intense that the crust suddenly gives way, sending shock waves in all directions at thousands of miles per hour. The slippage temporarily relieves the stress, but it also causes the earth to tremble and crack. The largest, most destructive quakes tend to originate near socalled subduction zones, regions where one plate is being pushed beneath the edge of the adjoining plate. When earthquakes occur on the ocean floor, the shock waves can produce swift and devastating tidal waves known as tsunamis. Earthquakes can also be triggered by volcanic eruptions, and some have even been generated by human activities. Pumping liquids into oil fields to force petroleum to the surface, for instance, has resulted in small quakes when the injected fluids lubricated fissures in the bedrock, causing slippage. The magnitude of earthquakes is usually measured on the Richter scale, devised by a California geologist. Each successive whole number on the scale represents a tenfold increase in the force of the earthquake's shock waves. For example, a magnitude of 7 on the Richter scale is 10 times greater than a magnitude of 6, and 100 times greater than a magnitude of 5. The most powerful earthquake to strike North America in recent times, the Alaskan quake of 1964, registered 8.4 on the Richter scale. One of our earliest recorded earthquakes took place in Plymouth, Massachusetts, in 1638. Luckily, none of the Pilgrims were hurt, though houses shook and dishes were shattered. In 1755, another quake that struck New England was felt from Nova Scotia to South Carolina. A far more devasting earthquake centered on the little frontier town of New Madrid, Missouri, at two in the morning on December 16, 1811. As the terrified settlers ran from their cabins, they watched helplessly as the ground heaved and split, spewing gravel and sand into the air. Churning with waves, the Mississippi River overflowed its banks, and bluffs along the river collapsed into the water. In the next few months, two more major earthquakes struck the same area, totally leveling New Madrid. The second was so powerful it caused church bells to toll in Washington, D.C., and stopped clocks in Charleston, South Carolina. This time, the Mississippi reversed its course and then rushed into a newly created depression in the ground, forming gigantic Reelfoot Lake. The earth-shaking shocks continued almost daily for two years. In 1886 a violent earthquake hit Charleston, South Carolina, killing 60 people and destroying much of the city in just 70 excruciating seconds. As in the Missouri quakes, the ground split open, casting silt and water 20 feet into the air, a phenomenon that occurs when powerful shock waves suddenly rip through loose, watery soil. Tremors from the devastating earthquake were felt as far away as Canada.

The Pacific Coast, where two of the earth's giant shifting plates meet, is the continent's leading earthquake zone. More than half of the quakes that strike the lower 48 states occur in California because of its extensive, branching system of faults. The largest of these is the San Andreas fault, where the Pacific Plate slides northwestward against the North American Plate at about two inches per year. Visible on the surface, the fault stretches nearly 700 miles through southern and central California. San Francisco, built astride the San Andreas fault, has a long history of earthquakes. The most violent of these, estimated at 8.25 on the Richter scale, occurred in 1906. It struck at about five in the morning with a roar that survivors compared to a thousand runaway trains. Streets rippled and heaved, water and gas mains ruptured, cornices fell from swaying buildings, wooden houses collapsed, and even massive structures built of stone and brick disintegrated. Dozens of fires sprang up from the broken gas mains and live electric wires, and whole sections of the city went up in flames. The devastating Good Friday earthquake in Anchorage, Alaska, struck on the afternoon of March 27, 1964. At 8.4 on the Richter scale, the quake released energy equivalent to 12,000 Hiroshima-type atomic bombs. Fissures sliced through the city, and entire neighborhoods sank 30 feet below the surface. Nearly 2,000 miles away, a tsunami hit Crescent City, California, drowning 12 people and demolishing the town.

Earthworm

Cylindrical, segmented, legless animals, earthworms move with the help of tiny bristles, called setae, on each body segment. They feed on decaying organic matter in the soil and deposit the residue on the surface as granular castings. Charles Darwin considered earthworms to be among the most important creatures on earth because they encourage plant growth by mixing and aerating the soil as they burrow through it. He estimated that the worms on a single acre of land bring as much as 18 tons of soil to the surface each year. Although they often appear after storms, earthworms do not rain down from the heavens as was once thought: they simply are forced to flee from their water-filled burrows.

Earwig

Inch-long insects with fierce-looking pincers at the rear of their bodies, earwigs trace their name to the superstition that they crawl into the ears of sleeping people. They are, in fact, nocturnal but are harmless to humans. Earwigs do, however, hide in cracks and crevices by day and, because they sometimes cause an unpleasant odor, can be household pests. Those in the West and South sometimes damage cultivated plants.

Echolocation

Bats, porpoises, and a few birds are among the animals that use echolocation to navigate and locate prey. For bats, cave dwellers that live in a world of darkness, this system of sonar provides a means of capturing flying insects even on the inkiest of nights. As they flutter through the air, bats emit short bursts of high-pitched sounds that bounce off objects around them and are reflected back to their large ears. These echoes enable the bats, in effect, to "see" pictures in sound. Porpoises emit clicking sounds whose echoes tell them about the location, size, and shape of prey, and some cave-dwelling birds navigate by means of high-pitched calls.

Echolocation

An Animal Behavior term, this is used to describe orientation by emitting high-pitched sounds and locating the positions of objects by the way in which they reflect the sound. Echolocation is used mainly by bats, but also by Dolphins.

Ecocline

A geographical gradient of vegetation structure associated with one or more environmental variables.

Ecology

Biological Philosophy term. The scientific study of the interrelationship of all life-forms and of their dependency on their environments. By inference: the scientific study of the ties that bind humankind to the natural world. The word is derived from the Greek oikos, a dwelling place. It was coined in German, Oekologie, in 1832 by Ernst Haeckel, a leading German proponent of Darwin. It was "Anglicized at the Madison, Wisconsin, Botanical Congress of 1893”.

Ecology (Ocean)

Ocean ecology deals with the relations of ocean-dwelling organisms to one another and to their physical surroundings.

Ecological community

A set of interacting natural populations.

Ecological effects characterization

The identification and quantification of the adverse effects elicited by a stressor and, to the extent possible, the evaluation of cause-and-effect relations.

Ecological risk assessment

A process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. Ecological risk assessment may evaluate one or many stressors and ecological components.

Ecological risk characterization

A process that uses the results of the exposure and ecological effects analyses to evaluate the likelihood of adverse ecological effects associated with exposure to a stressor.

Economics

The study of how human beings allocate limited resources to produce various commodities and how those goods are distributed for consumption among members of society.

Ecosystem

The totality of components of all kinds that make up a particular environment; the complex of biotic community and its abiotic, physical environment. A local ecological community: coral reef, prairie, alpine, etc. Dynamic and interrelating complex of plant and animal communities and their associated nonliving (e.g. physical and chemical) environment.

Ecosystem Approach

Endangered and Threatened species term.

Protecting or restoring the function, structure, and species composition of an ecosystem, recognizing that all components are interrelated.

Ecotone

A habitat created by the juxtaposition of distinctly different habitats; an edge habitat; a zone of transition between habitat types or adjacent ecological systems having a set of characteristics uniquely defined by space and time scales and by the strength of the interactions(see Boundary).

Ecosystem

A biological community of interacting organisms and their physical environment.

Education (Action and Learning): The process of providing intellectual, moral and social instruction to an individual or group of people, particularly in a formal, prolonged manner. There are many programs and projects aimed at incorporating environmental education into school curricula.

Eden

Biological Philosophy term. The mythic place where Adam and Eve lived before their "fall" into sin, which some interpret as their discovery of self, of consciousness, of self-consciousness, and so, their alienation. It is connected to the Pastoral Ideal.

Edge effect

Changes in a community due to the rapid creation of abrupt edges in large units of previously undisturbed habitat and the tendency for increased variety and density of organisms at community or habitat junctions.

Edge species

Species preferring the habitat created by the abutment of distinctive vegetation types.

Eel

Anguilla rostrata

Long, slender, snakelike fish, American eels have a ribbonlike look as they undulate through the water. They are found in lakes, ponds, rivers, and streams all along the eastern seaboard, but they migrate to the Sargasso Sea in the Atlantic Ocean to spawn. There each female lays as many as 20 million eggs, which the males cover with milt. This prodigious effort is the final act of the adults, for they die before the eggs hatch. The young drift with the currents toward the coast and gradually metamorphose from flat, transparent, leaf-shaped larvae into elvers, miniature, light-colored versions of the adults. The journey to the shore takes about a year; once there, the males remain near the river mouths while the females continue upstream, sometimes slithering across mud flats and wet grass on their way to inland lakes and ponds. When fully grown, from 8 to 20 years later, the eels begin their long swim back to the Sargasso Sea.

Eelgrass

Zostera marina

One of the few flowering plants found in the sea, eelgrass is named for its long, ribbonlike leaves that sway gently with the currents. Growing in dense stands in shallow waters along the Atlantic and Pacific coasts, it was long regarded by fishermen as little more than a propeller-fouling pest. Then in 1931 a mysterious blight virtually wiped out the eelgrass beds. When the thriving bay scallop fishery also collapsed, ecologists realized that the beds are in fact vital nurseries, not only for scallops but for a host of other creatures, too. The subsequent starvation of thousands of brants demonstrated the importance of eelgrass to these geese as well. Fortunately, the eelgrass eventually recovered and once again fulfills its vital role in coastal ecology.

Egret

See Heron.

Eider

Stocky ducks of northern climes, the eiders are best known for their down. Famed for its softness and superb insulating qualities, it has for centuries been harvested from their nests to make eiderdown bedding and parkas. Common eiders, at 27 inches and nearly five pounds, are the largest North American ducks. They winter along the north Atlantic and Pacific coasts and migrate farther north each spring. Feeding on mollusks and crustaceans, these expert divers routinely plunge to depths of 60 feet. The other three species-king, spectacled, and Steller's eiders-all dwell somewhat farther north year-round. Or so it is assumed, for the wintering grounds of the spectacled eider remain largely unknown to this day.

El Niño

El Niño is a warm surface current that usually appears in the Pacific Ocean off Ecuador and Peru around Christmas, and lasts about three months. Every three to seven years it remains for as long as a year-and-a-half as part of a southern oscillation. In North America, this contributes to warmer temperatures along the Pacific coast and weaker hurricanes on the Atlantic.

Elder

Sambucus

Famous for its fruits, which are made into elderberry jam, pie, and wine, the common elder of the East is a shrub up to eight feet tall. In contrast, the treelike blueberry elder of the West often grows 20 feet tall with a trunk 2 feet wide. In summer the elders bear broad clusters of creamy flowers, which are followed by red or purple fruits. A favorite with wildlife, the fruits often are so abundant that the plants' stems break under their weight. All elders, in fact, have brittle wood and pithy twigs that are easily hollowed out to make whistles and drinking straws.

Electrocommunication

An Animal Behavior term, this is used to describe communication by means of electric fields and pulses generated by one individual and detected by others. ElectrocommuniCatlon is used by some Fish in courtship and aggressive encounters.

Elk

See Wapiti.

Elm

Ulmus

Practically every town east of the Rocky Mountains seems to have its Elm Street, for in the post-Civil War building boom, people found the American elm to be an ideal shade tree. Fastgrowing and up to roo feet tall, the graceful vase-shaped trees formed cathedrallike gothic arches over hot roadways; they prospered even in the compacted streetside soil; and they tolerated both drought and periodic flooding. Since the 1930's, however, the trees have been decimated by the deadly Dutch elm disease. Caused by a fungus that is spread from tree to tree by elm bark beetles, the fatal ailment arrived on these shores with a shipment of logs infested with fungus-carrying beetles. One estimate puts the death toll of the last half century at roo million trees. Other shade-producing elms include the hard-wooded rock, or cork, elm and the slippery elm. Like all the elms, they produce small, winged fruits and have elongated, oval leaves with typically lopsided bases. Unfortunately, they too are susceptible to Dutch elm disease.

Elytra

The hard horny forewings of a beetle, which cover and protect the hindwings.

Emancipation

An Animal Behavior term, this is used to describe a suggested process whereby movements shown during Displays have become divorced from their original controlling mechanisms during Ritualization. Thus, grooming and drinking movements acting as signals during courtship may no longer require Motivation to groom or to drink before they appear.

Emergency Response (Action and Learning)

An emergency response is an action carried out in a particular community or region to protect human health and the environment from the impacts of an environmental emergency, such as a forest fire or a chemical spill.

Empiricism

Biological Philosophy term. In its naive form, the belief that one can examine "the facts" without any beliefs or assumptions at all to guide the examination and a hypothesis will emerge. In most cases it appears that scientists begin with a theory, test it empirically, find it wanting, and move toward new theory.

Endangered

Endangered and Threatened species term.

The classification provided to an animal or plant in danger of extinction within the foreseeable future throughout all or a significant portion of its range. Species that are much reduced in number and could disappear in part or all of their range.

Endangered species

Plants and animals whose populations have dwindled to such low levels that they are threatened with extinction are known as endangered species. In some cases species have become so specialized in their requirements that even the slightest change in the environment imperils their existence. In modern times, however, the threats more often result from human interference. In the last century, bison were so ruthlessly slaughtered that they were nearly wiped out before efforts were undertaken to save theI)l from extinction. Even more sinister than hunting and trapping is the destruction of habitat. The elimination of forests and wetlands to build suburbs and shopping malls, and the fouling of whole ecosystems with pollutants and pesticides have taken a devastating toll on wildlife. Before it was banned, for instance, DDT threatened such birds as bald eagles and peregrine falcons by causing them to produce eggs with abnormally thin shells. From the Florida golden aster and the Santa Cruz cypress to the wood stork, the red wolf, and the magnificent blue whale, the list of endangered species is a long one.

Endangered Species Act

1973 Act of U.S. Congress, amended several times subsequently, that elevates the goal of conservation of listed species above virtually all other considerations. The act provides for identifying (listing) endangered and threatened species or distinct segments of species, monitoring candidate species, designating critical habitat, preparing recovery plans, consulting by federal agencies to ensure that their actions do not jeopardize the continued existence of listed species or adversely modify critical habitats, restricting importation and trade in endangered species or products made from them, restricting the taking of endangered fish and wildlife. The act also provides for cooperation between the federal government and the states.

Endangered and Threatened species term.

Federal legislation intended to provide a means whereby the ecosystems upon which endangered and threatened species depend may be conserved, and provide programs for the conservation of those species, thus preventing extinction of native plants and animals.

Endangered species permit

Endangered and Threatened species term.

A document issued by the Service under authority of Section 10 allowing an action otherwise prohibited under Section 9 of the Endangered Species Act.

Endemic

Bird Biology Avian Conservation term.

Confined and native to a certain region. Confined to a geographical area such as an island, state or country.

Endemic species

Endangered and Threatened species term.

A species native and confined to a certain region; having comparatively restricted distribution.

Endpoint

A characteristic of an ecological component that may be affected by exposure to a stressor; a characteristic of valued environmental entities that are believed to be at risk. Distinguished are two types of endpoints:

Assessment endpoint--an explicit expression of the actual environmental value that is to be protected.

Measurement endpoint--a measurable response to a stressor that is related to the valued characteristics chosen as the assessment endpoints.

Energy

Anything that can be efficiently converted into heat or motion to provide power to run machines and vehicles and to supply heat and light is a source of energy.

Energy (Industry)

The energy industry includes businesses that produce power through such means as hydroelectricity and nuclear energy, as well as those that extract and refine energy-producing fossil fuels. Others are involved in the development of alternative energy sources, such as solar and wind power, and fuel cells.

Energy consumption

Energy consumption refers to the amount of energy used by an object, system or process to carry out a particular function.

Enforcement (Law)

Enforcement embodies those activities that compel adherence to legal requirements. These activities include inspection and monitoring; investigation of violations; issuance of notices to individuals or businesses to require them to correct improper practices; issuance of tickets for violations; seizure of wildlife, or their parts and products, and any item that may have been used to commit the offence; and prosecution.

Engram

An Animal Behavior term, this is used to describe the memory trace within the brain, the nature of which is as yet unknown. Many electrical, chemical and anatomical studies of the brain are aimed at discovering its form.

English sparrow

See House sparrow.

Environment

The surroundings on which animals and humans depend for life, especially, but not exclusively, the inanimate environment: air, water, topsoil, weather, wetlands, ozone shield. Physical and biological surroundings of an organism, including the plants and animals with which it interacts.

Environmental assessment

Carrying out an environmental assessment means determining or estimating the value, significance or extent of damage to a particular ecosystem or aspect of it.

Environmental characterization

The prediction or measurement of the spatial and temporal distribution of a stressor and its co-occurrence or contact with the ecological components of concern.

Environmental emergencies

An uncontrolled, unplanned or accidental release of a substance into the environment that may affect human life or health or the environment of which human health depends. These emergencies include those resulting from human activities as well as ones created as a side effect of a natural hazard (forest fires, spills, leaks)

Environmental gradient

A continuum of conditions, such as the gradation from hot to cold environments.

Environmental monitoring

Monitoring, or making systematic geo-referenced observations of the environment-such as measuring water level or counting trees-is essential to detecting changes in ecosystems over time.

Epigamic selection

An Animal Behavior term, this is used to describe sexual selection based on the choice of one sex by the other, usually of males by females, which has led to enormously elaboRated Displays. Such Courtship Displays are often called Epigamic Displays. The classic example is the Peacock's tail.

Epiphyte

Perched on trees, utility wires, and even buildings, the so-called air plants use their roots only to anchor themselves in place; having no contact with the soil, epiphytes get all their nourishment from wind-blown dust and from minerals in rainwater. Epiphytic ferns, orchids, and bromeliads are plentiful in subtropical Florida, while Spanish moss drapes trees throughout the South. In other areas, mosses, liverworts, and lichens are common epiphytes.

Equitability

Evenness relative to any specific standard or model of species abundance and uniformity of abundance in an assemblage of species. Equitability is greatest when all species are equally numerous (syn. evenness).

Ermine

Mustela erminea

Small and agile, with a lithe and sinuous body, the ermine is a ferocious nocturnal hunter that can slip through even the tightest spaces in pursuit of mice and other small mammals. Sometimes known as the short-tailed weasel, it is 12 to 14 inches long, including its 2- to 4-inch black-tipped tail. Twice a year, ermines molt and undergo a complete color change. Chocolate-brown with white underparts in summer, in winter they turn snow-white except for their black tail tips. The beautiful winter pelts are valued as luxury furs and have traditionally been a symbol ofEuropean royalty. Found as far north as the Arctic and south to New Jersey in the East and New Mexico in the West, ermines live alone in forests and brushy areas-anyplace with an abundance of prey and water. Almost perpetually hungry, they help keep rodent populations in check.

Erosion

Bit by bit, the face of the earth is constantly changed by the never-ending process of erosion. Its agents-water, wind, waves, and ice-all have amazing power to move, sculpt, and scar the land. Falling rain, each drop like a little hammer, pounds away at the soil. Streams and rivers strip off sediment and carry it toward the sea. Waves gnaw at sandy shores and pummel seaside cliffs. Mighty glaciers gouge out valleys and, over time, reshape entire mountain ranges. And in the desert, intermittent downpours deepen gullies, while wind-blown sand scours away the surfaces of solid rock. Erosion does not work alone. Weathering first breaks down the rocks by dissolving them with acidic groundwater, by alternate freezing and thawing, and by other means. The smaller pieces can then be moved from place to place. The results of this slow but steady change can be harmful. Millions of tons of topsoil are lost from farmlands every year. But erosion has also created some of our most spectacular sceneryfrom the Grand Canyon, etched into the Colorado Plateau, to the sheer cliffs along parts of the Pacific coast, created by the pounding waves.

Erratic

When the massive ice sheets of the last Ice Age moved slowly across the land, they carried along pieces of bedrock and deposited them far south of their places of origin. Such rocks, called erratics, often differ dramatically from the surface on which they rest in their new surroundings. As a result, they have provided geologists with important clues as to the routes taken by the longvanished ice sheets. These well-traveled relics of the Ice Age range in size from mere pebbles to building-size boulders that weigh tens of tons.

Esker

Steep-sided winding ridges made up of sand and gravel, eskers are remnants of the last Ice Age. The ridges of debris were deposited by streams of water that snaked through passages in and under glaciers, and were exposed when the ice melted. To modem eyes some of the narrower eskers look like railroad embankments. Eskers can be seen in parts of New England as well as in other northern areas that were covered by the great ice sheets. Many of them, however, have long since disappeared, mined for the sand and gravel they contained.

Estimator

A function of sample data that describes or approximates a parameter.

Estivation

The hot-weather equivalent of hibernation, estivation is a state of dormancy that allows animals, particularly those that dwell in the desert, to survive in times of excessive heat and drought. During such periods, the animals become torpid, their breathing and heart rates are reduced, and the need for oxygen and water are greatly diminished. Many insects and snails estivate, as do spadefoot toads and fish that live in ponds subject to drying out. Estivators sometimes wrap themselves in moisture-retaining cocoons; others burrow into the ground while waiting for rain. A few mammals, such as ground squirrels, also become dormant in the hot summer months, but scientists disagree as to whether their metabolic slowdown can be described as true estivation.

Estrus

An Animal Behavior term, this is used to describe the state in female Mammals when they are receptive to a male or "in heat."

Estuary

When, over the course of time, coastal land subsides or the melting of glaciers causes sea levels to rise, the mouths of rivers are drowned, producing bodies of mixed salt and fresh water called estuaries. They may be broad and shallow, like Chesapeake Bay (America's largest estuary), or narrow and deep, like an Alaskan fjord. Many of our great port cities- New York, Baltimore, San Francisco-were built on estuaries, particularly those with protected bays. While an estuary may look placid on the surface, it is in fact a battleground of opposing forces: the river current, laden with soil and other sediments, drives seaward, only to be rebuffed by the relentless tides. A battleground might seem an unlikely setting for a nursery, but the estuary's brackish waters are just that-a rich reproductive habitat for marine life.

Ethogram

An Animal Behavior term, this is used to describe an inventory which lists and describes all the behavior patterns shown by a species.

Ethology

An Animal Behavior term, this is used to describe the biological study of behavior.

Eucalyptus

Native to Australia, where they are called gum trees, eucalypti are famous for being the sole food source of koala bears. In the 1850's these attractive evergreens were first introduced to California, where, because of their amazing vigor and tolerance for dry soils, they were widely planted both as ornamentals and in reforestation projects. The blue gum is the tallest and most vigorous species, attaining heights of 50

feet in five years and 180 feet at maturity. On some eucalypti the bark is shed in flakes, giving the trees a mottled appearance, while on others it peels off in shaggy strips. The leathery, lanceshaped leaves contain aromatic oils used in medicines, deodorants, and perfumes, and the wood is used for lumber and fuel.

Eusociality

An Animal Behavior term, this is used to describe the form of society found in some social Insects in which there is coopeRation between individuals and division of labor. For example, some individuals are more or less sterile and others primarily engaged in reproduction. (See Caste.)

Eutrophication

As a lake evolves over time, it becomes enriched with nutrients in a natural aging process called eutrophication. The nutrients, released by the decay of plants and animals, stimulate even more growth and decay, causing silt and organic remains to accumulate on the bottom. Over thousands of years, the lake is transformed into a marsh and finally into dry land. Man-made pollutants, however, speed up the process, causing lakes to age prematurely. The nutrients in sewage and fertilizers foster the rapid growth of algae, which, when they die and decay, use up so much oxygen that fish and other animals literally suffocate. And so, ironically, the lake chokes to death from its own excessive fertility.

Evening primrose

Oenothera

Though the evening primroses favor sunny sites such as roadsides and vacant lots all across America, most of them reserve their blooms for the evening hours. The four-petaled flowers open at sunset and wilt the next morning, a schedule that suits the night-flying moths they depend on for pollination. The blossoms' light colors-yellows, pinks, and whites-show up in the dark, and a sweet lemon fragrance adds to their allure. The most abundant species, the common evening primrose, has six-foot stems that help its inch-wide flowers stand out against the night sky. The Missouri evening primrose, less than one foot tall, compensates for its modest stature with bolder flowers-bright yellow saucers three inches across.

Evenness

The uniformity of abundance between species in a community.

Everglades

Called pa-Hay-Okee-the grassy river-by the Seminole Indians, Florida's Everglades are a 4,000 square mile wetland extending from Lake Okeechobee south to Florida Bay. Most of the Everglades is a vast, nearly flat expanse of sawgrass, a sharp-edged sedge that grows 10 to 15 feet tall. Ponds and channels of open water lace the sawgrass prairie, and here and there the monotony is interrupted by small stands of treesbald cypresses in low places, and virtual jungles of mahoganies, gumbo-limbos, and other tropical species on the hammocks, low islands that rise only a foot or two above the water level. Where the marsh meets the ocean, it is fringed with a broad belt of mangroves, salt-tolerant trees that protect the land from the ravages of wind and waves. And everywhere there is wildlife. Teeming with a staggering variety of species, the Everglades serve as a sanctuary for many rare plants and animals. Ibises, egrets, and other long-legged waders fish in the shallows, while bald eagles roost in the cypress trees. Alligators, deer, marsh rabbits, bobcats, and even the endangered Florida panther all find a haven in this unique waterlogged wilderness.

Evergreen

A tree or plant that retains its leaves throughout the year.

Evergreen forest.

Trees.

Evolution

Biological Philosophy term. A scientific explanation of the development of life from the earliest one-celled animals to the variety of species we see today. The major assertion here is not that there is variation within a species--which is obvious--but that variation can be so fundamental that a new species arises. The mechanism of evolution is Natural Selection. This process does not lead inevitably toward greater complexity or to "higher" forms of life. To say it does is to give Teleology, purpose, to an accidental process. The larger brain of the shark does not indicate, as Louis Agassiz thought, that the shark is a later, higher form of marine animal than fish with smaller brains.

Evolutionarily stable strategy

An Animal Behavior term, see StRategy.

Excess Nutrients (Water)

Excess nutrients such as nitrogen and phosphorus compounds come mainly from municipal sewage and farm runoff containing fertilizers and animal waste. When these nutrients are introduced to lakes, rivers, and marine environments, they can cause excess growth of aquatic plants, which then die and decay, depleting water of dissolved oxygen and killing fish (a process called eutrophication).

Exotic

This term, related to wildlife, usually refers to an alien or introduced species.

Exploitation

The removal of individuals or biomass from a population by predators or parasites.

Exploitation competition

Competition in which two or more organisms consume the same limited resource.

Extinct

The disappearance of plants and animals from the face of the earth is an ongoing process in the life of the planet. Scientists, in fact, estimate that perhaps 90 percent of all the species that have ever lived are now extinct. Mammoths and mastodons, saber-toothed tigers, and countless other creatures have long since died out and are known to us only as fossils. Gone too are all the dinosaurs, victims of a mysterious mass extinction that took place some 65 million years ago. In modem times, however, the pace of extinctions has increased alarmingly. All too often human activity has been to blame, both directly through wanton slaughter and indirectly through destruction or degradation of habitat. Unless vigorous steps are taken to protect and replenish them, more and more endangered plants and animals are doomed to slip into the eternal oblivion of extinction.

Extinct species

Endangered and Threatened species term.

A species no longer in existence.

Extinction

The disappearance of a species, which is always irreversible. The complete disappearance of a species from the earth. The total disappearance of a species from an island (this does not preclude later recolonization).

Extinction

An Animal Behavior term, this is used to describe the process whereby learned behavior ceases to be performed when no longer appropriate. In a Rat, the response of bar pressing to obtain food will slowly decline when the reward is withdrawn; Dogs will cease to salivate to the bell announcing food if it is often rung without food appearing.

Extirpation

The elimination of a species from an island, local area, or region.

Extirpated species

Endangered and Threatened species term.

A species no longer surviving in regions that were once part of their range.

Extractive reserves

Conservation areas that permit certain kinds of resource harvesting on a (theoretically) sustainable basis.

Falcon

Falco

With pointed wings and streamlined bodies, falcons are fast-flying, open-country birds of prey that specialize in catching other birds in flight. Most seize their prey in steep power dives, or stoops, but some also drop to the ground to catch small mammals, insects, and lizards. Unlike hawks, which use their talons to kill their prey, falcons do in their victims with a quick bite on the back of the neck. Falcon nests are simple affairs with little or no lining, usually placed on ledges or in the old nests of other birds. The females lay three to five eggs, which, like the hatchlings, are tended by both parents. The peregrine falcon, clocked at speeds of 175 miles an hour, is the fastest of the falcons. Once found across most of North America, it has declined drastically in numbers because of pesticide residues in the ducks, pigeons, and shorebirds that it feeds on. The prairie falcon lives in dry regions of the West, where it often skims low and flushes birds from the ground. Merlins, small falcons of savannas and open woodlands, prey on songbirds, which they often overtake in swift horizontal attacks rather than downward stoops. The American kestrel, our smallest species, takes more insects and mammals than birds, and hovers as it scans the ground for prey. While most falcons raise only one brood each year, kestrels produce a second in years when mice and voles are abundant.

Fall

Autumn (also known as Fall) is one of the four temperate seasons. It is the transition from Summer into Winter. Autumn is the season during which most crops are harvested and is when most deciduous trees lose their leaves. It is also the season where days rapidly get shorter and cooler, the nights rapidly get longer, and of gradually increasing precipitation in some parts of the world.

Astronomically, some Western countries consider autumn to begin with the September equinox, in the end of September and to end with the December solstice in the Northern hemisphere and the June solstice in the Southern hemisphere. Such conventions are by no means universal, however. Meteorologists count the entire months of March, April and May in the Southern hemisphere, and September, October and November in the Northern hemisphere as autumn.

Although the days begin to shorten after the Summer equinox, it is usually in September (Northern Hemisphere) or March (Southern Hemisphere) when twilight becomes noticeably shorter and the change more abrupt in comparison with the more lingering ones of summer.

Autumn is often defined as the start of the school year, since the children usually begin in early September or early March. Either definition, as with those of the seasons generally, is somewhat flawed because it assumes that the seasons are all of the same length, and begin and end at the same time throughout the temperate zone of each hemisphere. Many ancient civilizations computed the years by autumns, because of Autumn's association with the transition from warm to cold weather, and its related status as the season of the primarychange from one year to the next. The concept of Autumn has dominated the downward cycle in themes and popular images of death and rebirth in many societies. In Western cultures, personifications of Autumn are usually pretty, well-fed females adorned with fruits, vegetables and grains that ripen at this time. Most ancient cultures featured autumnal celebrations of the harvest, often the most important on their calendars. Still extant echoes of these celebrations are found in the late-Autumn holidays of the harvest.

One such holiday with its roots as a full moon harvest festival is the holiday of "tabernacles" (huts wherein the harvest was processed and which later gained religious significance), the many North American Indian festivals tied to harvest of autumnally ripe foods gathered in the wild, the Chinese and many others had similar rituals. The predominant mood of these autumnal celebrations is a gladness for the fruits of the earth mixed with a certain melancholy linked to the imminence of harsh weather. Remembrance of ancestors is also a common theme.

Autumn in poetry has often been associated with melancholy. The possibilities of summer are gone, and the chill of winter is on the horizon. Thoughts and skies turn to grey. And yet it is a very beautiful season of color and is greatly enjoyed. Virtually everywhere that deciduous trees are found, colored autumn is a lovely spectacle. and it is most famously noted in two regions of the world: most of Eastern Canada and also the Eastern region of the United States are famous for the brilliance of their "fall foliage," and a seasonal tourist industry has grown up around the few weeks in autumn when the leaves are at their peak. Some television and web-based weather forecasts even report on the status of the fall foliage throughout the season as a service to tourists. Fall is an alternative word for the season of Autumn.

False hellebore

Veratrum

Stately summer-blooming perennials, the false hellebores bear plumes of green, yellow, white, or purplish star-shaped flowers atop stems three to seven feet tall. The delicacy of the blooms provides a pleasing contrast with the plants' broad, boldly pleated leaves, which clasp the stem at their bases. Members of the lily family, the false hellebores are unrelated to the true hellebores, which are old-world relatives of buttercups. And although one western species is known as skunk cabbage, the false hellebores are in no way related to the malodorous wetland plants of that name. All the false hellebores are believed to be poisonous and are occasionally fatal to grazing livestock. Yet the same toxic alkaloids also have the power to heal; they are used in medications for treating hypertension.

Fang

Operating something like hypodermic needles, fangs are the specialized teeth that poisonous snakes use to inject venom into prey. Modified salivary glands produce the poisons, which kill the snakes' victims and assist in digesting them. When a snake is ready to strike, toxins secreted by the glands pass into the hollow fangs, where they are injected into the victim. Some snakes, such as copperheads, have fangs in the front of the mouth that fold back when not in use. On other snakes the fangs remain erect. A third group delivers venom with grooved fangs at the rear of the mouth.

Fannin Sheep

Ovis dalli

A form of mountain sheep. See Dall Sheep.

Fault

Caused by tremendous pressures deep within the earth, faults are fractures in bedrock where the rocks on one side have slipped past those on the other. Faults range in length from a few feet to many miles, and the movement along them may occur a bit at a time or-at high levels of stress-in dramatic, devastating leaps. North America's most famous fault is the San Andreas fault, which slashes across California. It marks the boundary between two of the giant plates that make up the earth's crust, and sudden slips along its length have caused major earthquakes. Other faults are found far from plate boundaries. But no matter where they lie, most are created as the moving plates jostle one other, straining the rigid bedrock until it snaps and thrusts blocks of rock up or down, right or left, along the fracture. So-called fault-block mountains, such as the Sierra Nevada in California, formed when a crustal block was heaved up and tilted along a fault.

Fecundity

Rate at which an individual produces offspring, usually expressed only for females.

Federal action agency

Endangered and Threatened species term.

Any department or agency of the United States proposing to authorize, fund, or carry out an action under existing authorities.

Feedback

An Animal Behavior term, this is used to describe the modifiCation of behavior in response to its consequences. In negative feedback, the consequences slOwly suppress the behavior, as when grooming removes the irritation that caused it. Positive feedback has the opposite effect leading to more of the behavior, for example where sexual stimulation leads to more sexual behavior and so on until terminated by ejaculation.

Feldspar

The most common group of minerals in the earth's crust, feldspars are the main components of many types of rocks and occur in a range of colors. One kind provides the fleshy pink tone that characterizes some of the granites. Another variety, labradorite, displays a rainbow of colors and can be polished into gemstones, as can milky white moonstone and the green variety called Amazon stone. When decomposed by weathering, feldspars form clay, which can be used in the manufacture of glass and ceramics.

Feral

Escaped from domestication. Feral individuals may be descendants of the original escapees. Feral means that a species has returned to the wild.

Fern

An ancient class of plants that dominated the earth hundreds of millions of years ago, ferns are indeed rather primitive looking. Most have delicate, feathery leaves, or fronds; grow close to the ground; and prefer damp, shady areas. When the young leaves, aptly called fiddleheads, first appear, their tips are tightly coiled, and they gradually unfurl into mature fronds. The small dark spots on the undersides of the fronds are clusters of spore sacs that eventually burst open and scatter dustlike spores to the wind. When the spores land, they develop into tiny intermediate plants that reproduce sexually, and it is their offspring that grow into the familiar spore-producing fern plants. Of our 300 species of ferns, two of the more common and typical examples are the elegant ostrich fern and the ubiquitous bracken. Some of the others are nonconformists. The walking fern, for example, sprouts new plantlets at the tips of its long, narrow leaves and reroots itself as it "walks" across the soil. The shoestring fern, an epiphyte that never touches the ground, has yard-long strap-shaped fronds, which dangle like ribbons from rough-barked trees in Florida and Georgia. Other mavericks include ferns that float and a few climbing vines.

Ferret

Mustela nigripes

A secretive but inquisitive member of the weasel family, the endangered black-footed ferret is one of our rarest mammals. This slim-bodied, shortlegged native of the Great Plains is an appealing creature with a black mask across its eyes and with dark feet and a dark tail tip accenting its yellowish coat. The ferret feeds on ground squirrels, mice, and ground-nesting birds, but its favorite prey is the prairie dog, whose underground burrows it takes over as its home. Active at dusk and by night, the ferret makes chattering sounds and hisses when alarmed. With the decline of prairie dogs-considered pests by farmers, who have waged constant war against them-the black-footed ferret's very existence has been threatened. By the 1980's, the last known wild colony was on the brink of extinction. Its plight prompted an intensive captive breeding program aimed at saving the ferrets and returning them to their native plains.

Fiddler crab

Uca

Low tide on sandy or muddy seashores and in salt marshes brings out fiddler crabs in droves. Emerging from their burrows, where they find protection from fish and other predators, the little crustaceans scuttle sideways across the surface, feeding on algae and other plant material. Then, when the tide comes in, the fiddlers head back for the safety of their burrows and carefully plug the entrances. Male fiddlers are easily recognized by their one greatly enlarged pincer, or claw, which they wave about in self-defense and as part of their courtship rituals. The crabs are named for the males' habit of moving the oversized claw back and forth with a sawing motion that looks much like a fiddler fiddling.

Filefish

With bodies flattened from side to side and a single spine projecting, unicorn-style, from the top of their heads, filefish are strange-looking creatures that were named for the sandpaperlike texture of their scales. Usually found near wharves and reefs along the Atlantic coast, filefish swim along slowly, stopping now and then to munch on sea fans, algae, sponges, and even stinging corals. They often hover head down as they forage, and can change color to blend with their surroundings.

Film

Film is a term that encompasses motion pictures as individual projects, as well as the field in general. Many other terms exist for an individual motion picture, including picture, picture show, photoplay, flick, and most commonly, movie. Additional terms for the field in general include the big screen, the silver screen, the cinema, and the movies.

Films are produced by photographing images in a rapid sequence on a long roll of perforated plastic-like material. This resultant product comprises a series of individual frames, and each is literally only a single still photograph, but when these images are shown rapidly in succession, the illusion of motion is given to the viewer. Flickering between the single frames not seen due to an effect known as "persistence of vision", whereby the eye retains a visual image for a fraction of a second after the source has been removed. Also of relevance is what causes the perception of motion; a psychological effect. Film is considered by many to be an important storage medium for historic and scientific events; Quite amazingly, films entertain, educate, enlighten and inspire audiences. The visual elements of cinema need no translation, giving the motion picture a universal power of communication. Any film can become a worldwide attraction, especially with the addition of additional soundtrack editing changes that translate the dialogue. Films are also artifacts created by specific cultures, which reflect those cultures, and, in turn, affect them.

Filter feeding

An Animal Behavior term, this is used to describe a method of feeding used by some Animals whereby they filter small particles from the surrounding medium as they move through it, as in Whaless, or as it moves past them, as in barnacles.

Finch

In addition to finches and goldfinches, the finch family includes the pine siskin, the redpolls, the cross bills, and the evening and pine grosbeaks. Seedeaters all, most of the finches have stout, conical bills that are ideal for crushing such fare. Many finches even feed seeds to their nestlings. (Most other seed-eating birds raise their young on a diet of insects.) And one, the American goldfinch, delays nesting until late summer when seeds are most plentiful. Most of the finches are birds of open woodlands or fields. Rosy finches, however, nest on alpine and arctic tundra, and house finches, once exclusively southwestern birds, now thrive in eastern cities. The eastern birds are descendants of caged finches that were released in 1940. In winters when northern seed crops fail, finches sometimes fly south in exceptionally large numbers. Pine siskins, for instance, may roam from Canada and the northernmost states all the way to the Gulf Coast in search of food.

Fine-grained

Referring to qualities of the environment that occur in small patches with respect to the activity patterns of an organism. This results in the organism's inability to distinguish qualities usefully.

Finger lake

During the last Ice Age, tongues of glacial ice sometimes advanced along north-south river valleys, gouging them out and greatly deepening them. When the ice later retreated, it sometimes left small moraines that dammed the ice-gouged hollows and created long, narrow lakes. Such lakes are called finger lakes after the most famous examples of their kind, the Finger Lakes of western New York.

Fir

Abies

Though a few other evergreens are called firs, our nine species of true firs are unmistakable. Their cones, unlike those of other conifers, stand upright on the branches; the axis of each cone, moreover, remains attached to the tree after its seeds and scales are shed, leaving an erect pencillike spike. The firs also are known for the blisters of aromatic resin that collect under their bark. It is this sticky substance that gives the popular Christmas tree, the balsam fir, its pleasant holiday fragrance. While the balsam fir ranges across much of the Northeast and Canada, and the equally widespread white fir grows from California to the Rockies and south into Mexico, some of the other firs have more limited ranges. The Fraser fir, for example, survives only on the highest peaks of the Appalachians, and the bristlecone fir is confined to canyons in California's Santa Lucia Mountains.

Firefly

Also called lightning bugs, fireflies are actually small, slow-flying beetles that brighten the sky with their blinking lights on summer evenings. Each species has its own characteristic pattern of flashes, which the insects use for finding mates. The males fly about flashing a signal from a light organ on the abdomen, and females hiding on vegetation respond with flashes that announce their readiness to mate. Some females can also mimic the signals of other species: males fooled by this apparent invitation fly down, only to be eaten by the deceptive temptress. After mating, the females lay eggs on moist ground. The larvae, sometimes seen glowing on damp lawns, prey on snails and small insects.

Fireweed

Epilobium angustifolium

Often the first plant to grow in fire-scorched areas, fireweed adds a striking note of color as it springs to life from charred soils. Useful as well as beautiful, it produces seeds by the thousands, each one equipped with a tuft of silken hairs that allows the seeds to drift for long distances on the wind. After settling to the ground, the seeds lay dormant, sometimes for years, until fire strips away the shade and sunlight warms the soil, enabling them to germinate at last. Taking nutrients from the ashes, fireweed spreads a mat of roots through the soil, protecting it from erosion until shrubs and trees reestablish themselves. Found from Labrador to Alaska and south to California, Arizona, South Dakota, and North Carolina, fireweed stages a spectacular show when it comes into bloom. From July to September, spires of showy four-petaled magenta-pink blossoms top its six-foot stalks, which are lined with willowlike leaves. The flowers are followed by slender pods, which soon burst open to launch their downy seeds.

First-year bird:

Bird Biology Avian Conservation term.

A bird in its first 12-16 months (or until its second prebasic molt).

Fish

A cold-blooded, limbless, vertebrate that lives wholly in water and has fins, internal gills, and skin with a glandular secretion that decreases friction. By far the most numerous of all our animals with backbones, fish are cold-blooded, waterdwelling creatures that breathe through gills. Beyond that basic definition, however, it is difficult to generalize. Almost anyone would recognize a carp or a tuna as a fish: like most of their kind, they have paired gills, fins for swimming, and scale-covered bodies that are tapered at both ends. But fish come in an enormous array of shapes and sizes, ranging from less than half an inch to more than 40 feet and weighing from less than an ounce to thousands of pounds. Fish also display vastly different characteristics. They are as varied as the pancake-flat flounder, with its oddly placed eyes; the batfish, which uses its fins for walking across the ocean loor; and the bizarrely shaped seahorse. There are fish armed with swords, others with fishing lures, fish that produce electricity, and even fish that can crawl about on land. And fish live in nearly every imaginable watery habitat, from mountain lakes to murky ocean depths and from steaming hot springs to frigid polar seas.

The vast majority of the 2,000 or so North American species are bony fish, meaning their skeletons are made primarily of bone. These most advanced of all fish are usually equipped with gas-filled swim bladders, used for controlling buoyancy. Other fish, such as sharks, rays, and skates, have skeletons of cartilage rather than bone. Lacking swim bladders, they must remain constantly on the move to keep from sinking. The most primitive fish-the eellike lampreys and hagfish-lack jaws and instead have sucking mouths lined with teeth. The bony and the jawless fish usually reproduce by spawning, with the males fertilizing the eggs after the females have released them into the water. On the other hand, sharks and rays mate, and in most cases the females bear live young.

Fish Stocks (Ocean)

The supply or quantity of fish acquired or allowed to accumulate for future use.

Fisher

Martes pennanti

A brownish-black, bushy-tailed member of the weasel family, about the size of a small fox, the fisher is a stong, aggressive, agile hunter active by night. It lives in dense forests across northern North America, where it roams widely over a home territory of up to 10 square miles. Although the fisher occasionally eats fish, its diet consists primarily of rodents, porcupines, and snowshoe hares. Running, swimming, and climbing trees in pursuit of prey, it can track with the persistence of a wolverine, fend off dogs, and kill animals as large as deer and lynx. Solitary for most of the year, fishers pair off with mates from January through April. Well before giving birth to one to four blind, helpless young, the females make dens in hollow trees, logs, or under rocky ledges. Overtrapped in the past for its handsome pelt, the fisher is now protected and is valued for its role in controlling porcupine numbers.

Fishing (Recreation)

The catching of fish, either as a job or a hobby.

Fitness

An Animal Behavior term, this is used to describe the measure of an individual's genetic contribution to the next geneRation. The term Inclusive Fitness is used to refer not only to the fitness an individual achieves through its own reproductive efforts, but also the Improved Fitness it achieves through assisting relatives to reproduce. Animals are thought to behave in such a way as to maximize their inclusive fitness.

Fitness

Bird Biology Avian Conservation term.

The average contribution of one allele (i.e., one form of a gene) or genotype to the next generation or to succeeding generations, compared with that of other alleles or genotypes. It may be either an absolute value, measured by the number of progeny per parent, or it may be relative to some reference genotype.

Fixed action pattern

An Animal Behavior term, this is used to describe any stereotyped movement pattern found in more or less identical form throughout a species, at least among Animals of similar age and sex. Their relative fixity makes such movements especially useful in classifying Animals and in analyzing behavior. As they are not as fixed as originally thought, the term Modal action pattern has Been proposed as preferable.

Fjord

As Ice Age glaciers moved slowly down existing river valleys on their journey to the sea, they carved deep into the bedrock and excavated the spectacular inlets that we know today as fjords. Although fjords are relatively shallow at their entrances, farther inland they may reach depths of 4,000 feet. Distinguished by dramatically soaring walls, these unique waterways often have waterfalls cascading down their sides, which further enhance their beauty. Although fjords are most often associated with Norway (the word itself is Norwegian), many spectacular examples can be seen in Alaska, especially at Kenai Fjords National Park on the state's rugged southern coast. A setting of breathtaking beauty, the park is home to seals, sea otters, sea lions, and a host of seabirds. But Somes Sound, on the picturesque coast of Mount Desert Island in Maine, is the only fjord in the lower 48 states.
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Flamingo

Phoenicopterus ruber

A bird that has come to symbolize not only Florida but all things tropical, the greater flamingo is unmistakable with its exotic pink plumage, stiltlike legs, and graceful, swanlike neck. Standing three to five feet tall, it feeds by dipping its curved bill upside down in brackish water, then using its thick, fleshy tongue to force mud and water through sievelike structures on the bill that strain out algae, tiny shellfish, and other small animals. Gregarious birds, flamingos live in large colonies on isolated lagoons, where they build moundlike nests of mud and where each pair raises a single chick. The few truly wild flamingos that tum up in Florida come from colonies in the Bahamas. The ones most often seen there are not wild at all, but the semidomesticated denizens of parks and gardens.

Flatfish

In contrast to other fish, the bottom-dwelling flatfish-flounder, sole, halibut, and the likeswim on their sides. They begin life swimming upright like "normal" fish, but then something peculiar happens: one eye begins to migrate across the head toward the other eye, and in some species the mouth becomes twisted as well. The body also develops the typical flattened, oval form of adult flatfish and becomes colored on the eyed upper side and pale on the eyeless underside. Once the transformation is complete, flatfish sink to the bottom of the sea, where they often lie partially buried in mud or sand. Frequently covered with spots and blotches, they are perfectly camouflaged. Some flatfish can even change their color to match almost any background. Active predators, they dart quickly upward to snatch unwary crustaceans, squid, and smaller fish. While flatfish average a foot or two in length, some kinds are much larger. The Atlantic halibut can be more than eight feet long and weigh some 700 pounds, and the Pacific halibut is nearly as big. The most beautiful flatfish, the peacock flounder of warm Florida waters, is named for the brilliant blue markings on its body. Another, known as the windowpane, is a remarkably thin-bodied flatfish that ranges from Canada to South Carolina. Unlike its relatives, most of which are featured on seafood menus, the windowpane is simply too flat and meatless to be valued as a food fish.

Flatworm

Simple, soft-bodied invertebrates, flatworms fall into three main classes: the mostly free-living turbellarians and the parasitic tapeworms and flukes. The best-known turbellarians are the freshwater planarians. Less than an inch long, these worms have been much studied because of their remarkable regenerative abilities; if cut in two, the rear end of a planarian grows a new head, while the head end grows a new rear. The parasitic tapeworms, which absorb food through their body walls, live inside other animals. Beef tapeworms, which mature in the human intestine, can be as much as 30 feet long. They may weaken their hosts by competing for food but usually cause no damage. Many of the parasitic flukes, in contrast, cause serious diseases. The sheep liver fluke, for instance, inhabits the bile ducts of sheep and cattle and is responsible for the disease known as liver rot.

Flax

Unum

Once grown on every farm, flax was so valued in colonial America that authorities required every household to produce a certain quota of flax yam and offered prizes to those who wove the homegrown fiber into linen cloth. Now, however, flax cultivation is limited to California and the Pacific Northwest, where it is no longer grown for fiber, but for the flaxseeds that yield the linseed oil used in linoleum, oilcloth, paints, and varnishes. Imported from Europe, where it had been used for making rope, fishnets, and fabric since ancient times, flax has escaped from cultivation and now survives in fields and waste places as a graceful annual wildflower up to three feet tall. Clusters of small five-petaled sky-blue flowers open as early as February in some parts of the country, and blossoming continues until September, adding cheerful splashes of color to the sandy, well-drained sites the plant favors. Several native flaxes also grow throughout the country, including a yellow-flowered species found in Eastern woodlands and a copper-colored variety that thrives from Texas to Canada.

Flea

Tiny blood-sucking insects that live on dogs, cats, rodents, birds, and humans, these wingless pests can move easily through hair and feathers. Equipped with powerful leg muscles, fleas also can leap indiscriminately from one host to another. The dog flea, one-tenth of an inch long, can jump seven inches high and more than one foot horizontally. Dog fleas, translucent, wingless, and almost microscopic, are nonetheless a bane to animals and humans alike. As they move from animal to animal, fleas help spread a number of ailments. The dog flea, for example, is involved in the transmission of the dog tapeworm. Another, the oriental rat flea, is notorious for its role in spreading the dreaded bubonic plague.

Fleabane

Erigeron

Whether low and sprawling or growing up to three feet tall, the fleabanes all bear daisylike flowers in shades of white, pink, purple, blue, or more rarely, yellow or orange. Found from coast to coast in habitats that range from moist meadows to dry rocky slopes, the plants might easily be confused with asters, except that most of the fleabanes bloom earlier, in summer rather than the fall. Their name recalls a time when pungent fleabanes were hung in homes to drive away fleas. Today some of them serve a similar purpose, with oil of fleabane being used as an ingredient in insect repellants.

Fledge

This is the term used to describe a nestlings first flight, usually when it leaves the nest.

Fledging success

Bird Biology Avian Conservation term.

The average number of offspring fledged (i.e, raised until they leave the nest) per female; percentage of hatchlings that fledge.

Flicker

See Woodpecker.

Flint

See Chert.

Flood

Among nature's most destructive phenomena, floods occur when heavy rains or rapidly melting snow cause streams or rivers to overflow their banks and spill water on land that is normally dry. A river flood of this sort may mean little more than a mild soaking of the surrounding land, or it may result in a major disaster in which people, homes, bridges, and everything else are swept away. In mountainous areas, torrential downpours sometimes result in the massive and rapid runoff of flash floods, which often strike without warning. In 1972 a flash flood in Rapid City, South Dakota, killed more than 200 unwary people.

Floods also occur in coastal areas, when hurricanes batter the shore and swamp low-lying areas with storm-driven walls of water. Even more frightening are tsunamis, tidal waves generated by earthquakes on the ocean floor; they pummel everything in their path as they submerge the coast beneath mountainous waves.

One of our worst floods, in 1889, was caused not by nature but by human neglect. A dam burst near Johnstown, Pennsylvania, and sent a raging torrent into the valley below, sweeping away homes, locomotives, and everything else in its way. More than 2,000 people lost their lives in the disaster.

Flooding (Water)

An overflowing of water beyond its normal confines, and especially over land. Flooding may occur as a result of heavy rainfall and, in spring, as the result of a sudden melting of ice and snow.

Flood plain

The flatlands bordering a river and composed of sediments deposited by the river are called its flood plain. When a river is moving swiftly, particles of sand and silt are carried along in suspension, but when the river overflows its banks in flood, the water immediately slows down and drops its load of sediment, forming the plain. The flood plains of young streams may be only a few feet wide, while those of older, meandering rivers like the Mississippi can stretch for miles.

Floret

A small flower.

Floristic

Referring to studies of the species composition of plant associations.

Flounder

See Flatfish.

Flower

Whether large and showy or small and inconspicuous, all flowers serve the same purpose: they produce the seeds that enable flowering plants to perpetuate their kind. While their structure varies from species to species, the basic design includes one or more female organs, called pistils, at the center; these are surrounded by male organs, called stamens, and then by rings of petals and sepals. The sepals, usually green, enclose the bud before the flower opens. The petals, often colorful, serve to attract pollinators such as bees and butterflies. Each stamen consists of a pollen-bearing structure (the anther) atop a slender stalk (the filament). The pistil has a sticky or fuzzy top, called the stigma, which traps pollen. Once a grain of pollen has landed on the stigma, a tube grows down the necklike style into the ovary, where the plant's egg cells, or ovules, are fertilized and develop into seeds. There are countless variations on this basic plan. Besides differences in the number, size, shape, and arrangement of the various parts, for example, some species have separate male and female flowers or even male and female plants.

Flowering plant

From grasses and wildflowers to towering trees, flowering plants far outnumber such nonflowering types as conifers, ferns, and mosses and truly dominate the earth today. Despite differences in size, shape, and habitat, all flowering plants are similar in the way they reproduce. In contrast to the seeds of conifers, which are borne unprotected on the scales of cones, the seeds of flowering plants are enclosed within ovaries that, sometimes along with other floral parts, develop into fruits.

Fly

Distinguished by having just one pair of wings (most insects have two pairs), the true flies nevertheless are able fliers. The adults of some species drink nectar and other liquids, some kinds suck blood, and others eat nothing at all. The larvae of many flies are known as maggots and feed on dead and decaying organic matter.

Perhaps the best-known member of the group is the house fly, a pest that breeds in filth and transmits such diseases as typhoid fever and cholera. Mosquitoes also are true flies. The females are the ones that bite, with various kinds transmitting malaria, yellow fever, and other illnesses. The black fly, another pest, has a vicious bite that is all too familiar in wooded areas of the Northeast in early summer. Flies can, however, be useful as well. Some kinds parasitize insect pests and help keep them under control. Many are eaten by larger animals. Because of their impressive reproductive potential, flies have found their way into the research laboratory: geneticists are quick to point out that significant advances have been made in the field of heredity by studying the characteristics of succeeding generations of fruit flies.

Flycatcher

Nearly three dozen species of flycatchers, including the kingbirds, the phoebes, and the wood pewees, are found in North America. They earned their name from their habit of darting from perches to snatch passing insects in flight. Alert and upright in posture, the birds flit swiftly out to snap up prey, often with an audible click of their broad, flattened bills. Ranging up to 16 inches in length, most flycatchers are rather drab and nondescript, clad in olive, brown, or dull gray. One exception is the male vermilion flycatcher, which is bright red and black. Another, the scissor-tailed flycatcher, is pale gray with pinkish sides and very long outer tail feathers. Besides being beautiful, the scissortail is notable for its courtship ritual. The male flutters downward in an intricate flight pattern, concluding his descent with several neatly executed somersaults. The scissortail and most other flycatchers build cup-shaped nests, generally in the open but sometimes in tree cavities or crevices in rocks. All species are territorial, with the kingbirds even attacking crows and hawks that trespass on their turf.

Flying fish

Often taking to the air in swarms, silvery, bulletshaped flying fish can sail above the sea at 35 miles per hour. By spreading their enlarged pectoral (forward) fins like wings and sculling with their tails, they become airborne and glide above the waves, sometimes for hundreds of feet. They fly not to amuse themselves but to escape predators such as tuna and dolphinfish. Each species is dubbed either monoplane or biplane, depending on whether its members use just the pectoral fins alone or both the pectoral and pelvic (rear) fins to glide. Among the more common biplanes are the Atlantic and the California flying fish. The latter, at 18 inches, is one of the largest members of the family and is considered excellent eating.

Flying squirrel

Big-eyed and covered with soft velvety fur, these charming creatures of the treetops do not actually fly, as their name implies, but glide from tree to tree. Launching themselves from limbs, flying squirrels spread out the folds of skin that extend along each side between front and hind legs, and sail through the air. Using their broad tails as rudders, they can glide for 150 feet. Strictly nocturnal, flying squirrels love old, rotten trees with plenty of cavities and snags. Some build nests ofleaves and lichens, but most prefer to use old woodpecker holes as dens and nurseries. Sociable creatures, they frequently share their dens with other squirrels. About 10 inches long, including the tail, the southern flying squirrel inhabits broad-leaved and mixed forests throughout the eastern half of the country. Its larger relative, the northern flying squirrel, is found in evergreen forests in the northern states and Canada, as well as farther south in the mountains.

Flyway

Bird Biology Avian Conservation term.

A broad-front band or pathway used in migration.

Flyway

On their seasonal flights to and from their breeding grounds, many migratory birds travel along well-defined north-south routes known as flyways. Broad in some places and narrow in others, these paths provide links between feeding areas, where the birds can stop to rest and refuel. The four main flyways in North America are the Atlantic Flyway, along the Atlantic Coast; the Mississippi Flyway, which follows the Mississippi Valley; the Central Flyway, more or less parallel to the Rocky Mountains; and the Pacific Flyway, along the Pacific Coast. Ducks, geese, and swans are the birds that most commonly use these migratory corridors. For these waterfowl, the flyways connect important marshes, lakes, and wildlife refuges. Other birds, such as shorebirds, also rely on feeding areas along the routes-stopovers that are essential for their survival. The loss of even one feeding site (to development, for instance, or to pollution) could interfere with migration, because the next stop on the route might be too far away for the hungry, tired birds to reach.

Fog

The dense, ground-hugging clouds of suspended water droplets known as fog can cover the land like clammy shrouds. They often occur on calm, clear nights when the ground cools, chilling the air above it enough for water vapor in the air to condense into visible droplets. Fog may also result when cold air passes over warm water, causing a steamy cloud to form. Conversely, it can form when warm, moist winds blow over chilly land-along a seacoast, for example-or a cool ocean current. In many areas, dense fogs pose a hazard to motorists and sometimes cause delays at airports.

Fold

Caused by movements in the earth's crust, folds are bends in rock layers. Although rocks are rigid, if enough pressure is applied they become plastic and can be bent or warped without breaking. The resultant rumples vary greatly in size. Some folds are mountainous in scale and extend for miles. Others are gentle ripples only a few inches long. Folds that sag downward are called synclines; those that arch up are known as anticlines.

Food chain

Bird Biology Avian Conservation term.

A feeding sequence, such as seed-to-songbird-to-raptor, used to describe the flow of energy and materials in an ecosystem.

Food web

An abstract representation of the various paths of energy and material flow through populations in the community.

Fool's gold

See Pyrite.

Foraminiferan

Single-celled, mostly marine animals found in all oceans, foraminiferans are best known for their beautiful, elaborately structured shells, which in most species are composed of calcium carbonate. Threadlike extensions of the body protrude through tiny holes in the shells, enabling the animals to move and feed. When the creatures die, their shells sink to the bottom. So numerous are they that their remains form an ooze covering about 30 percent of the ocean floor. And so abundant have they been over the past 420 million years that in many areas foraminiferan fossils are the major component of massive deposits of limestone and chalk.

Forecasts (Weather)

Predictions of the weather for the next few hours or days made by using computer models to analyze atmospheric data. Long-range weather forecasts, which are more general and less accurate, are also made for future periods of several months.

Forest

A forest is an area with a high density of woody growth, as a wilderness area or, historically, a wooded area set aside for any number of reasons. Many forests have been cut and eliminated by mankind. There are many definitions of a forest, based on various criteria. These plant communities cover large areas of the globe and function as animal habitats, constituting one of the most important aspects of wildlife preservation.

Although often thought of as carbon sinks, mature forests are approximately carbon neutral with only disturbed and young forests acting as carbon sinks. Nonetheless mature forests do play an important role in the global carbon cycle as stable carbon pools, and clearance of forests leads to an increase of atmospheric carbon dioxide levels.

Forests can be found in all regions capable of sustaining tree growth, at altitudes up to the very tops of mountains and they thrive except where natural fire frequency is too high, or where the environment has been impaired by natural processes or by human activities. As a general rule, forests dominated by (broadleaf forests) are more species-rich than those dominated by evergreens (conifer, montane, or needleleaf forests), although exceptions exist (for example, species-poor aspen and birch stands in northern latitudes). Forests sometimes contain many tree species within a small area (as in tropical rain and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid montane coniferous forests). Forests are often home to many animal and plant species.

These existence of these wildlife populations per unit area is high compared to other vegetation communities. Much of this biomass occurs below-ground in the root systems and as partially decomposed plant humus. In a forest the branches and foliage of separate trees often meet or interlock, although there can be gaps of varying sizes within an area referred to as forest. A woodland has a more continuously open canopy, with trees spaced further apart, which allows more sunlight to penetrate to the ground between them.

Forest fragmentation

Patchwork conversion and development of forest sites (usually the most accessible or most productive ones) that leave the remaining forest in stands of varying sizes and degrees of isolation.

Forest-interior species

Species that tend to avoid edge habitats and that require large tracts of forest habitat for nesting and foraging.

Forestry (Industry)

The management of forests for wood, water, wildlife, forage, and recreation. Due to wood's economic importance, forestry has been chiefly concerned with timber management, especially reforestation, maintenance of existing forests, and fire control.

Forget-me-not

Myosotis

Flourishing along stream banks and in other moist locations across the country are several kinds offorget-me-nots, among them the familiar five-petaled sky-blue flower with the bright yellow eye at its center. Erect or sprawling plants no more than two feet tall, these delightful wildlings bear their dainty nosegays of blue, white, or occasionally pink blooms from late spring until early fall.

Formal consultation

The consultation process conducted when a Federal agency determines its action may affect a listed species or its critical habitat, and is used to determine whether the proposed action may jeopardize the continued existence of listed species or adversely modify critical habitat. This determination is stated in the Service's biological opinion.

Fossil

Each one a bit of evidence in the mystery of life's past, fossils are remnants of plants and animals that have been preserved from prehistoric times. Most were formed when dead plants or animals were quickly buried, protecting them from scavengers. Since flesh and other soft parts usually decayed before they could be preserved, the most common fossils are teeth, bones, shells, and other hard parts. The majority of fossils are petrified, or turned to stone. In some cases dissolved minerals simply filled the tiny air spaces in bones or shells, strengthening the original object. In other cases all of the original animal or plant gradually dissolved and was replaced bit by bit by minerals. Natural molds were formed when entire organisms disappeared after sediments hardened around them. If minerals later filled the mold, the result was a natural cast-an exact replica of the organism. Flat objects such as leaves or feathers often left thin molds called prints. Fossils of insects are often found in amber, or fossilized resin, where they were trapped in ancient times. The footprints of dinosaurs and other extinct animals were sometimes preserved in hardened mud and clay. In rare instances, the entire bodies of mastodons and other large animals were preserved in ice or tar. Fossils are found only in sedimentary rocks, such as limestone, sandstone, and shale. While erosion sometimes exposes them on the surface of the earth, most collectors know that manmade quarries and road cuts are among the best places to hunt for these clues to life long ago.

Four-o'clock

Mirabilis

Named for their habit of blooming as the day wanes, the four-o'clocks are handsome, brightly colored wildflowers. The Southwest claims the greatest variety, including the sweet fouro'clock, which flaunts six-inch tubular blossoms of white or pink atop sticky three-foot stems. Another one-the Colorado, or desert, fouro'clock- is a sprawling annual that yields spectacular displays of two-inch purplish trumpets.

Fox

Traditional symbols of cunning and craftiness, foxes are, in fact, agile, intelligent, and above all, adaptable creatures. Bushy-tailed, long-snouted members of the dog family, they are quick and skillful hunters that eat a broad range of wild fare, including insects, rabbits, berries, and all sorts of rodents. The most common and widespread of the North American foxes are red foxes. Surprisingly small under their luxurious, usually flame-red coats-on the average, about 10 pounds-they hunt in fields and along woodland edges with catlike stealth. Gray foxes, also widespread but most common in the South, are unusual in their ability to climb trees-a rarity in the dog family. The Great Plains and arid Southwest are home to the tiny kit foxes, nocturnal hunters distinguished by their oversized ears. The Arctic foxes, in tum, live in the Far North. Brown or gray during the summer months, they spend their time hunting on the tundra; in winter they tum white and move out onto the pack ice, scavenging in the wake of polar bears.

Foxglove

Digitalis

Pretty but poisonous, the foxgloves are powerful medicinal plants. An extract of their leaves, digitalis, is one of the most effective medicines for certain heart diseases. During their first year of growth, these robust biennials form lush rosettes of ground-hugging, wrinkled, tongue-shaped leaves. Then, in their second season, they send up tall stalks lined with lovely bell-shaped flowers. The common foxglove, native to Europe, was introduced by physicians in the 1700's; its spires of purpleflecked rose or white blossoms now brighten shady spots across most of North America, particularly in the Pacific states.

Fractal dimension

An index of the complexity of spatial patterns.

Fractal geometry

A method to study shapes that are self-similar over many scales.

Frequency

Bird Biology Avian Conservation term.

The number of plots, stations, counts (visits), or intervals in which a species is detected; when expressed as a fraction of the total sampled, it becomes relative frequency.

Freshwater

Water that is not salty, found in inland bodies of water.

Fritillary

Boldly patterned with dark spots on the upper sides of their wings and, in many cases, with silvery spots on the undersides, the tawny to orange fritillaries include some of North America's most striking butterflies. The larger kinds, known as the greater fritillaries, are so named for their broader wingspans; they flit over meadows and bogs, visiting thistles and other flowers. One of the more common species, the great spangled fritillary, is found from Canada south to Georgia, New Mexico, and central California. The lesser fritillaries are small, swift fliers that range as far north as the Arctic.

Frog

Smooth-skinned, tailless creatures with bulging eyes and powerful hind legs adapted for leaping and swimming, frogs are the most familiar of our amphibians. They are found from the Arctic to the tropics, and range in size from tiny cricket frogs, sometimes a mere half inch long, to bassvoiced, eight-inch bullfrogs. Most have thin, moist skin and must live in or near water; others live on land but return to the water to breed.

In spring the males raucously summon the females with a variety of mating calls, each species sounding its own particular notes. After joining them in the water, the females lay eggs by the hundreds or even the thousands. Covered with a protective, jellylike coating, the fertilized eggs hatch into tadpoles a week to a month later. The tadpoles undergo an amazing transformation as they develop from long-tailed, round-bellied, gill-breathing larvae into tailless, strong-limbed, lung-breathing adults. Bullfrog tadpoles take up to three years to develop into frogs, but most species take just a few months. Although frogs begin life as vegetarians, they are voracious carnivores as adults. Skilled hunters, they devour huge quantities of insects, as well as spiders, earthworms, and other small creatures, which they catch with their long sticky tongues. Cold-blooded animals, many of the frogs hibernate in winter by burying themselves in mud at the bottom of ponds.

Frogfish

Plump, round-bodied inhabitants of warmwater seas, frogfish are intricately camouflaged anglers. They entice their prey-usually small fish-within range of their wide mouths by waving a wormlike lure from the end of their "fishing rod," actually a modified spine on the dorsal fin. Most frogfish rest quietly in place on the ocean floor or crawl about with the help of armlike pectoral fins. The sargassumfish, one of the best-known species, in contrast, lives not at the bottom of the sea but instead drifts near the surface amid floating forests of sargassum weed. Looking very much like the algae in which it dwells, it creeps among the plants, stalking other inhabitants of the sargassum weed. Sargassumfish have the ability to inflate their bodies by swallowing water or air, most likely as a means of preventing predators from extricating them from their seaweed world.

Froghopper

See Spittlebug.

Frond

A leaflike structure found in some lower plants.

Front

Associated with changing weather, a front is the moving boundary between two air masses of different properties. If the advancing air mass is colder than the one it is replacing, the leading edge of colder air is called a cold front; if the air is warmer, the leading edge is called a warm front. Cold fronts move rapidly, as the denser, heavier cold air drives a wedge under the warm air. Most cold fronts cause brief showers and gusty winds, followed by clear skies and cool, dry conditions. Warm fronts move more slowly, with the advancing warm air gradually sliding up over the heavier, low-lying cold air. They bring layered clouds and longer, steadier rains, which are usually followed by clearing skies and warm, humid air. When a fast-moving cold front catches up with a slowly advancing warm front, the result is an occluded front. The warm air, now surrounded by colder air, is forced aloft. Trapped over a trough of cool air, the warm air produces rain that lasts for hours.

Frost

The delicate ice crystals that tum grass to silvery white, create feathery patterns on windowpanes, and lend a magical quality to other surfaces are known as frost. It is formed-usually on cold, cloudless nights-when air saturated with moisture comes in contact with belowfreezing surfaces near the ground. Unlike frozen dew, which occurs when dewdrops freeze after a fall in temperature, frost is formed from water vapor that has crystallized directly into ice without passing through the liquid stage.

Fruit

Fruit are seeds together with their surrounding tissues. Botanically speaking, acorns, cucumbers, bean pods, and even grains of wheat all are fruits. The mature seed-bearing structures of flowering plants, fruits develop from the flowers' ovaries and, sometimes, associated floral parts. They can be sweet and fleshy, like apples and cherries, or dry and papery, like milkweed pods. Fruits are classified according to their structure. Simple fruits, for example, develop from a single ovary, while complex fruits derive from more than one. Those with stony pits, such as peaches and plums, are called drupes; pods, like those of peas and beans, are legumes; and the winged fruits of maples and elms are known as samaras. Apples and pears are called pomes; their edible flesh is actually swollen stem tissue. So is the ripe flesh of a strawberry; the seeds on its surface are in fact tiny individual fruits called achenes.

Fruit fly

Tiny insects that lay their eggs on fruit or decaying vegetation, fruit flies of various kinds are found all over the country. The Mediterranean fruit fly, for example, is a serious pest that periodically infests citrus crops. The well-known vinegar fly, Drosophila melanogaster, in contrast, has benefited humanity, for it has proved to be an ideal subject for the study of heredity.

Fulmar

Fulmarus glacialis

Stocky seabirds that look like thick-necked gulls, fulmars spend most of their lives gliding over far northern seas. They feed mainly on fish and squid but also trail fishing boats to scavenge for cast-off wastes. Like their relatives the petrels, fulmars have tubelike nostrils atop their beaks. When disturbed, they regurgitate a thick, smelly oil and spit it at enemies. The name fulmar, in fact, means foul gull.

Fumarole

Often hissing with steam, fumaroles are vents in the earth that emit water vapor, carbon dioxide, and other volcanic gases. They are found in volcanic areas such as Yellowstone National Park, where molten magma lies relatively close to the surface. The discharge from some fumaroles is mainly steam; in others the water vapor carries along a mixture of volatile, sometimes noxious, gases escaping from the lava.

Function

An Animal Behavior term, this is used to describe the function of an attribute, such as a behavior pattern, is its selective advAntage. This is the way in which it confers on its possessors greater survival and reproductive success than if they did not have it, and thereby persists in the population.

Functional response

The change in an individual predator's rate of exploitation of prey as a result of a change in prey density.

Funding (Action and Learning)

Money provided for a particular use. The government provides funding to a wide range of community groups and individuals to carry out projects aimed at protecting, conserving or restoring the environment.

Fungus

Molds, mildews, yeasts, and the familiar mushrooms all are fungi. Although they have traditionally been considered plants, fungi differ in so many ways that some scientists now place them in a separate kingdom. Unlike green plants, for example, fungi have no chlorophyll to make their own food and so must absorb nutrients from other organisms, living or dead. Most fungi are microscopic, but even those that yield mushrooms or other visible structures consist mainly of underground masses of fine cottony threads. A mushroom is the fungus's fruiting body and exists solely to make spores that, scattered by wind and water, develop into new fungi. Many of the fungi form partnerships with plants. Lichens, for instance, consist of algae and fungi that live in close association. Other fungi are attached to the roots of living plants, providing them with mineral nutrients and receiving food in return. Many plants, such as orchids, cannot survive without the help of fungi. Fungi also cause diseases, including ringworm, athlete's foot, and the rusts and smuts that afflict many crop plants. But mostly they are beneficial. Fungi enrich the soil by assisting in decay; they cause the fermentation that results in alcohol; they produce antibiotics and other life-saving drugs. And of course, many mushrooms are good to eat.

Gabbro

A dark, coarse-grained igneous rock, gabbro forms by slow cooling and crystallization of magma deep within the earth. Common in the Adirondack Mountains of New York, it often contains the green mineral olivine, as well as feldspar and large amounts of iron-rich minerals such as pyroxene. Sometimes sold under the name black granite, gabbro is widely used as a building stone, and it is especially popular for decorative facings.

Gaia Hypothesis

Biological Philosophy term. Gaia is the Greek goddess, Earth. James Lovelock and Lynn Margulis have proposed the idea that "the biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling the chemical and physical environment".

Galena

The shiny blue-gray mineral known as galena is the principal ore of lead. It forms impressive cubic or eight-sided crystals, and fine specimens have been uncovered in Oklahoma, Kansas, Missouri, and Illinois. (Galena, Illinois, was named for the extensive deposits of ore that gained it prominence as a 19th-century lead mining center.) Often found in limestone, many galena deposits also contain silver and are frequently mined for that metal as well. Extracting lead from galena is a simple process; pioneers, in fact, simply tossed lumps of the ore into hot fires to obtain lead for bullets. Galena was important in the early years of radio, when its crystals were used in crystal radio sets.

Gall

Plant growth induced by another organism, often a gall wasp. The warty or tumorlike growths often seen on the leaves, stems, and other parts of plants are known as galls. Most of them are caused by small insects that lay their eggs in the plant tissue. When the larva hatches from the egg, its presence stimulates the abnormal growth of the tissue surrounding it. The larva is not only protected inside the gall but also feeds on the swollen plant tissue. Chief among the gall-forming insects are gall flies, tiny wasps, midges, and aphids. Bacteria, fungi, and minute worms called nematodes can also stimulate the production of galls, often on the roots of plants. Each gall maker has its own particular host plant and forms galls of characteristic shapes and sizes. Although galls are usually small, crown galls on tree trunks, caused by bacteria, can be as much as two feet across. Most galls cause little damage to their host plants, but others, such as those produced by Hessian flies, can result in serious crop damage.

Gallinule

Porphyrula martinica

At home in freshwater wetlands in the South, the purple gallinule, or marsh hen, is shaped like a chicken. Its brilliant colors, however, make it stand out like a jewel. In addition to its handsome green and purple plumage, the gallinule sports a striking yellow-tipped red bill and a powder-blue shield on the forehead. Illequipped for swift flight, it prefers to wade through reeds and pickerelweed and occasionally climbs into low bushes. Its long yellow toes also enable the gallinule to tread with quiet grace across the tops of lily pads.

Living on the bounty of the marsh, gallinules eat frogs, snails, aquatic insects, eggs, and seeds. They build nests one to five feet above the water in shrubs or other vegetation and raise broods of six to eight young. Their similar-looking cousin, the common moorhen, used to be known as the common gallinule.

Gannet

Morus bassanus

Goose-sized seabirds with stout, pointed bills, northern gannets are renowned plunge divers. Sighting a school of fish-usually herring or mackerel-they hurtle seaward from heights of 50 feet or more and hit the water with a tremendous splash. A reinforced skull and air cells in the neck and breast help absorb the impact.

In winter northern gannets range from Massachusetts to Florida and the Gulf Coast; in summer they gather in the North Atlantic to breed in huge, noisy colonies on seaside cliffs. Gannets mate for life and return to the same nesting spot each year. When one bird arrives at the nest of dried seaweed and debris to relieve its mate on their single egg, it is welcomed with rituals that include the tossing of seaweed. Both birds may bow, point their bills skyward, and strike them like swords against each other. When their young finally takes wing, it spends the next three or four years at sea before returning to shore for the first time to breed.

Gap

Rivers sometimes slice straight across mountain ridges in deep valleys known as water gaps. The valleys usually began forming long ago when the river flowed across a level plain. As the surrounding land was worn away, exposing a layer of more resistant rock, the river etched its course downward through the ridge, forming the defile. The Delaware Water Gap is one of many found in the Appalachians. If the stream is later diverted, leaving the gap dry, it is called a wind gap. The Cumberland Gap is a wellknown example of a wind gap.

Gap analysis

The process of identifying and classifying components of biodiversity to determine which components already occur on protected areas and, conversely, which are un- or underrepresented on protected areas.

Gap formation

The creation of a habitat patch of different characteristics within a larger patch.

Gar

Lepisosteus

Bullet-shaped fish with pointed snouts and rows of needle-sharp teeth, gars have skins covered with thick, diamond-shaped scales so tough that they can deflect spears and arrows. Several species inhabit lakes and rivers of the eastern and central states, and they sometimes venture into brackish coastal waters. They often float in the water with an eerie stillness, springing to life only when prey fish blunder near.

Gars can grow up to 10 feet in length. The largest species, the alligator gar, weighs up to 200 pounds and is one of our most formidable freshwater fish. They are not, however, much sought as sport fish; their flesh, though edible, is not very tasty, and their roe is poisonous.

Gardening (Recreation)

Planting and weeding vegetable and flower gardens is good exercise. Green gardeners use organic methods to control pests, instead of pesticides, and use composted material instead of commercial fertilizers.

Garnet

Glassy, hard, and richly colored, garnets have been prized as gemstones since antiquity. The intensely red variety called pyrope (Greek for "fire-eyed") has even been sold as imitation ruby. Though the garnets valued as gems usually are red or purplish, the crystals also come in shades of orange, yellow, green, and black. Composed of silica and a variety of metallic elements, they get their colors from their differing metallic contents. The crystals, found embedded in various, usually metamorphic rocks, are generally less than an inch across, though a mine at Gore Mountain, New York, has yielded specimens some three feet in diameter. Most of the garnet mined commercially today is used in industrial abrasives for grinding and polishing.

Garter snake

Thamnophis

Marked with three light stripes along the length of their bodies, garter snakes were named for their supposed resemblance to the fancy garters men once wore to support their hose. Garden snake might, however, be a more appropriate name, for these familiar, harmless reptiles thrive in parks and gardens as well as in pastures, meadows, and marshes. With a dozen or so species found from coast to coast, garter snakes are most often seen in early spring, their mating season. Bearing live young instead of laying eggs, they are among the most prolific North American snakes: though litters average fewer than 20, the common garter snake sometimes produces nearly 100 offspring at a time.

Gayfeather

See Blazing star.

Gecko

Named for the geck-o cry of an Oriental species, the geckos are unusual among reptiles for their ability to produce sounds at all. While some bark and others chirp, our commonest species, the banded gecko, simply squeaks in protest when alarmed. A harmless little lizard up to six inches long, it lives in canyons and among the dunes and rocky hillsides of the arid Southwest. Hiding in crevices by day, it comes out at night to feed on insects and spiders, which it captures with lightning-quick flicks of its long, sticky-tipped tongue.

Gemstone

Minerals prized for their beauty, durability, and rarity are known as gemstones. Used since ancient times for jewelry and ornament, they also have been kept as talismans and credited with curing ills as diverse as snakebites and dysentery. Of the 2,500 or so rock-forming minerals, less than 100 are considered gemstones, and only about 20 are of extreme value. When removed from the earth, most gemstones look like nothing more than dull lumps of rock. Their beauty is brought out by cutting, shaping, and polishing. Stones such as amethyst are faceted to reveal their brilliance, or "fire"; others with interesting colors or patterns-opal or cat's-eye, for instance-are polished, not cut. Among the several gemstones found in North America are splendid blue sapphires from Yogu Gulch, Montana, purplish-red tourmalines from California and Maine, and yellow-green peridots from Arizona and New Mexico.

Gene flow

The exchange of genetic traits between populations by movement of individuals, gametes, or spores.

Generalist

Bird Biology Avian Conservation term.

A species with broad food preferences, habitat preferences, or both (see Specialist).

Generation time

Bird Biology Avian Conservation term.

The average age at which a female produces her offspring, or the average time for a population to increase by a factor equal to the net reproductive rate.

Genetic drift

The change in allele frequency due to random variations in fecundity and mortality in a population.

Genome

A full set of chromosomes.

Genotype

The total genetic message found in a cell or an individual.

Gentian

Gentiana

Lovely, brightly colored wildflowers, gentians are relatively rare in the East but are a chief ornament of the western mountains. The Rockies alone host some 20 species, most notably the western fringed gentian. Adopted as the official symbol of Yellowstone National Park, this hardy annual paints moist meadows throughout the summer with a palette of purple-blue blossoms. The four petals on each vase-shaped flower are edged with a fringe that fences out plundering insects, reserving the sweet nectar for pollinating bees. The very similar eastern fringed gentian, a three-foot biennial of sunny meadows, bears up to 100 cerulean blooms in early fall. Another-the closed, or bottle, gentian-has deep blue flask-shaped flowers that never open; bumblebees can shoulder their way in, but if lesser insects follow, they risk entombment.

Genus

A group of similar species.Geode

Hollow nodules of stone with inner cavities that are lined with crystals or layers of minerals, geodes are among nature's surprises, for their beauty is not revealed until they are cut open. They form over long periods of time when cavities in rocks are filled with water containing dissolved quartz or other minerals; the minerals in the water gradually come out of solution and are deposited on the walls of the cavity. If the quartz has few impurities and is deposited relatively quickly, colored layers of fine-grained quartz called agate are formed. Slower deposition results in a lining of beautiful inward-pointing crystals. In North America these delightful oddities are most common in the limestones of the Mississippi and Ohio valleys.

Geographic information system (GIS)

A set of computer hardware and software for analyzing and displaying spatially referenced features (i.e., points, lines, and polygons) with nongeographic attributes such as species and age.

Geranium Geranium

Whether white, pink, or purple, the flowers of the many kinds of wild geraniums found in North America always have five petals, five sepals, and stamens in multiples of five. The leaves are usually lobed or deeply divided. The most distinctive features of the plants, however, are their fruits-long beaklike capsules that have earned some species the name cranesbill. Other well-known species include the pink-flowered herb Robert, widespread in the East, and the dove's-foot geranium, a common weed on lawns in the West.

Geyser

Periodically erupting with explosive bursts of steam and hot water, geysers are one of the great spectacles of nature. Some are notable for the regularity of their eruptions; the world's most famous geyser, Old Faithful in Yellowstone National Park, emits its scalding plume more or less on schedule. With a total of some 3,000 geysers and hot springs, Yellowstone ranks as the world's largest geyser field. Geysers are also found in California. These fascinating natural fountains occur only in areas where pockets of magma, or molten rock, lie close to the earth's surface and heat the overlying rock. Groundwater seeping into a geyser's tube is heated by contact with the rock. The water does not readily come to a boil, however, since an increase in pressure (caused in this case by the weight of the water above it) raises the boiling point of a liquid. Eventually, however, some of the water does reach this elevated boiling point and flashes into steam, forcing water to spill from the top of the tube. With this sudden drop in pressure, superheated water farther down is vaporized, causing the entire column of steam and superheated water to erupt in one explosive jet. As soon as the eruption ends, more water begins to seep into the geyser's tube, setting the stage for the next show.

Giant sequoia

Sequoia dendron giganteum

Among the most massive of living things, the giant sequoias, while not the tallest trees, often weigh more than 1,000 tons. Yet these stately evergreen behemoths sprout from seeds so tiny that 5,500 of them weigh barely an ounce. Remarkably hardy and long-lived, the trees grow only at altitudes of 5,000 to 7,000 feet in a few dozen groves that lie scattered along a 280-mile stretch of the Sierra Nevada's western slope. Sheathed in rich reddish-brown bark that is resistant to both fires and insects, many have lived for 3,000 years or more. Pyramidal in outline when young, the giant sequoias, which have scalelike needles, become craggy and rounded as they age.

Gila monster

Heloderma suspectum

Easily identified by its bold colors and patterns, the Gila monster is a stocky lizard up to two feet long. It has a thickened tail in which it stores fat for use when food is in short supply, and it is covered with small scales that give its skin a beaded look. Native to the deserts of Arizona and New Mexico, the Gila monster and a close relative, the Mexican beaded lizard, are the only venomous lizards in the world. Shy and largely nocturnal, the Gila monster remains hidden by day in rocky crevices or burrows. But by dusk it starts to prowl, preying mainly on small mammals, which are killed by its venom. It also eats the eggs of other reptiles and of birds. The Gila monster is a sluggish creature that usually avoids human beings. But it can, if disturbed, twist its body with surprising speed and deliver a powerful, bulldog-stubborn bite that permits its poisonous saliva to seep slowly from its lower jaw into the victim's wound. Although the Gila monster is widely feared, its bite, though painful, is rarely fatal to humans.

Gilia

Found mainly in the western states, the gilias are a group of some two dozen rather modest wildflowers. Most have delicate, finely cut foliage and trumpet-shaped flowers that flare out with five lobes at the top. The blooms of the bird's-eye gilia, a common wildflower on grasslands throughout most of California, are attractively tricolored in shades of pale blue, dark blue, and yellow. The densely clustered flower heads of blue-headed, or globe, gilia each contain up to 100 individual flowers; with stamens protruding from the trumpets, the rounded clusters look a bit like pastel pincushions. California gilia, found mainly in the Coast Ranges, is quite similar, but its clusters contain fewer flowers and are sometimes fan shaped.

Gills

Many freshwater and marine animals are equipped with gills, specialized breathing organs that take up dissolved oxygen from the water and release carbon dioxide. Gills have thin, membranous walls through which these gases can pass easily, and they are usually filled with blood or body fluids. The gills of fish, tadpoles, and permanently aquatic salamanders are located in the neck region. On fish they are usually protected by hard plates (the gill covers), but they are exposed and feathery on tadpoles and salamanders. On clams, oysters, and other bivalve mollusks, the gills are thin flaps of flesh. Straining food particles from the water that passes across them, they are used for feeding as well as breathing. Other mollusks, including many snails, have feathery gills. The aquatic larvae of many insects, such as mayflies, damselflies, and stoneflies, also are equipped with gills-usually feathery or leaflike structures on the tip or sides of the abdomen. No insects have gills as adults, however. Nor do a host of very small aquatic animals that absorb oxygen directly through the skin and so do not need gills.

Ginkgo

Ginkgo biloba

The sole survivor of an ancient family of trees, the ginkgo is notable for its unusual leaves. Quite different from those of any other tree, they are fan shaped, with the veins fanning out from the narrow end. Bright green in spring, they tum yellow before dropping in the fall. This native of the Far East, also known as the maidenhair tree, probably was saved from extinction by monks who centuries ago began cultivating it in temple gardens in China and Japan. Highly valued as an ornamental, the ginkgo is especially popular in cities because it can tolerate air pollution. Female trees are often destroyed, however, because of the foul odor of their plumlike fruits.

Ginseng

Panax

The celebrated, supposedly man-shaped roots of these low-growing woodland herbs have long been treasured as a cure-all by Orientals, who claim them effective for treating everything from impotence to diabetes. American ginseng, a close relative of the Chinese species, once carpeted our eastern hardwood forests. But centuries of harvesting for export to China, where the root is in great demand, has severely depleted our native stock. A plant of rich, well-drained soils, American ginseng bears three compound leaves that resemble those of the horse chestnut.

Girdle

The oval band surrounding the plates of a chiton.

Glacier

The gentle, rolling hills and fertile soils of the Midwest, the cobbled fields and kettle ponds of New England, and the rugged peaks of the West all are evidence of the actions of one of nature's most potent forces: glaciers. Far from being a thing of the past, these great masses of ice still cover 10 percent of the world's land surface. Some, called valley glaciers, form in hollows on high mountains. Others, known as continental glaciers, are giant ice sheets such as those found today in Greenland and Antarctica. Glaciers form in areas where annual snowfall exceeds melting. As the snow accumulates year after year, it is gradually transformed into ice. Buried under more and more snow, the ice becomes denser still and, when it reaches a critical thickness and weight, begins to move. Most glaciers creep along at only a few inches to a few feet per day, plucking, grinding, and tearing at the land on their relentless journey. They scour the earth and deposit rocks, sand, and debris in a distinctive fashion. Valley glaciers transport huge blocks of rock, sharpen peaks, and widen and deepen valleys, while the great continental ice sheets override hills, incise grooves into bedrock, and leave behind deep lakes and gently sloping mounds of debris. The power of glacial ice is awesome, and so too are its creations. The serrated peaks of the Cascades, sculpted to ragged perfection; the sandy beaches of Cape Cod, the dumping ground of a bygone melting ice sheet; and the Finger Lakes of New York are but a few of the magnificent products of moving ice.

Glasswort

Salicornia

Stripped down to bare essentials, the glassworts consist of little more than fleshy, jointed stems. The leaves have been reduced to clinging scales, and the tiny flowers are practically hidden in hollows on the upper joints. Plants of salt marshes and other saline areas, the glassworts have a pleasantly salty flavor and so are often picked as salad ingredients. Because they can also be pickled, the glassworts are sometimes known as pickle weeds.

Global change

The large-scale alterations in climate, patterns of land and water use, environmental chemistry, etc., especially alterations related to human activities.

Globeflower

Trollius

Attractive members of the buttercup family, globeflowers are widespread across much of North America. The Eastern species, found in swamps and marshes, bears yellow springtime blooms. As the snows melt on mountain slopes, the western globeflowers dot high meadows with flowers that are creamy or greenish white. While abundant in the Rockies, globeflowers are endangered in several Eastern states.

Glowworm

See Firefly.

Glume

A stiffened bract found on a grass flower. See Bract.

Gnat

Troublesome pests in many areas, gnats are any of several kinds of tiny, mosquitolike flies. Some are especially irritating because they form large, marauding swarms that attack humans and animals with annoying bites. The eye gnats, which are attracted to human and animal secretions, are thought to transmit pinkeye and other diseases. The larvae of most species live on plants, and some, such as Hessian flies, pose a serious threat to crops.

Gnatcatcher

Polioptila

Small, active birds, gnatcatchers, as their name implies, feed primarily on tiny insects. Flicking their long tails, they are quite conspicuous as they flit from perch to perch in search of prey. The blue-gray gnatcatcher, the most widespread species, lives in woods and thickets throughout much of the United States. It builds a dainty cuplike nest lined with flower petals, feathers, spiderwebs, and hair and often decorates the outside with bits of lichen.

Gneiss

Coarse-grained and usually marked with altemating light and dark bands, gneiss (pronounced "nice") is a common metamorphic rock. It forms when sedimentary or igneous rocks, such as sandstone or granite, are altered by heat and pressure rearranging and often recrystallizing their minerals. Gneisses are abundant in the Appalachian Mountains in the East and in the Rockies, Cascades, and Sierra Nevada in the West.

Goal-oriented behavior

An Animal Behavior term, this is used to describe behavior directed towards some goal which, when reached, brings that behavior to an end. It is most obvious in, for example, the case of a hungry Rat running a maze to reach food, but can be applied to a variety of behavior patterns, such as mate seeking leading to copulation, and nest building leading to a nest.

Goatfish

Some 50 species of goatfish, or red mullet, are found around the world in tropical and warm temperate seas. Usually traveling in small schools, they are distinguished by the pair of whiskerlike barbels that hang from their chins. Supposedly resembling a goat's beard, the barbels are sensory probes that the fish use to find the bottom-dwelling invertebrates on which they feed. When not in use, the barbels are folded back in special grooves along the lower jaw.

Goatsbeard

Tragopogon pratensis

Bearing flowers that resemble dandelions, the yellow goatsbeard is named for its large, whiteplumed seed heads. Like the purple-flowered oyster plant, a close relative, it was brought to America by colonists who found the flavor of its taproots reminiscent of oysters. Both species have escaped to the wild and become common weeds in many areas. The goatsbeard's alternate names, noonflower and] ack-go- to-bed -at-noon, allude to the fact that its flowers close at midday.

Goatsucker

Named for the ancient belief that their gaping mouths enable these birds to steal milk from goats, the goatsuckers also are called night jars, an allusion to the jarring calls of these nocturnal fliers. The goatsuckers' very large mouths in fact are ideally suited for their diet-insects caught in flight. Typically camouflaged in mottled shades of brown and gray, the birds spend most of the day resting on the ground or perched lengthwise along tree limbs. Perhaps the best-known member of the family is the whip-poor-will, whose name echoes its loud, persistent call. The foot-long chuck-will's-widow, the largest of our goatsuckers, has a similar call but delivers it at a somewhat slower tempo. Another species, the common nighthawk, is more often seen in flight and is notable for its voracious appetite: one hungry bird was shown to have eaten more than 2,000 insects in a single night.

Goby

Members of an enormous family of fish found mainly in tropical and temperate seas, the gobies are a remarkably varied group. A few kinds are transparent, many are brilliantly colored, and most are less than six inches long. Some burrow in the mud, some live on coral reefs, and others cling to slippery rocks, using suction cups formed from their partially fused pelvic fins. Still other species move into the burrows of shrimp and crabs; live in or near tube sponges and feed on parasitic worms; or even hover, unscathed, among the stinging tentacles of sea anemones. Still others spend their time at "cleaning stations: dining on the parasites that they pick from larger fish.

Gold

Perhaps the most versatile and beautiful of all metals, gold has been treasured by mankind since prehistoric times. Its popularity is not a mystery: gold combines rarity with strength, durability, and shimmering beauty. It can be hammered into paper-thin sheets, stretched into wire, and pounded, cut, or molded into shape. Because it is also soft, however, gold is usually mixed with other metals, such as platinum or nickel, when used for jewelry. Gold is found in veins, or lodes, and in placer deposits. Glittering in streambeds, placer deposits consist of flakes and nuggets that were eroded from veins or rocks and then transported to another place. It was the glint of gold in a stream in Georgia that touched off America's first gold rush in 1828. But the real frenzy began in 1849 when, lured by tales of rivers running with gold, prospectors flocked to the West. And it is in the West that most gold is mined today.

Goldenrod

Solidago

Flourishing in fields and clearings all across America, nearly 100 species of goldenrod gild late-summer and autum landscapes with plumes and spires of mellow gold. Though long condemned as the cause of hay fever, the goldenrods in fact are innocent of the charges. The real culprits are ragweed and other plants that bloom at the same time and produce huge amounts of wind-blown pollen. American Indians valued goldenrod as a cure for numerous ailments. (In fact, the plant's Latin name means "to make whole.") Early colonists also gathered leaves of the sweet goldenrod to brew a soothing, aniseflavored tea and used the flowers to produce a rich yellow dye.

Goldenseal

Hydrastis canadensis

The fat yellow roots of goldenseal are marked with leaf scars that do indeed resemble seals stamped into bars of bullion. But those same roots also account for the scarcity of the plant: they were so heavily collected in the past as herbal remedies that goldenseal, once common in eastern woodlands, is now endangered in many areas. A foot or so tall and topped by a pair of maplelike leaves, each stalk bears a single greenish-white flower in spring, which gives way to bright red berries in the fall.

Goldfinch

Carduelis

Noted for their bright colors and cheerful songs, the goldfinches are sometimes called wild canaries. They are small, gregarious birds that prefer open country and, like other finches, feed primarily on seeds. Even the young are fed a diet of regurgitated seeds. The most widespread species by far is the American goldfinch. Common across most of the United States and southern Canada, it tends to nest late in the season, when thistledown is available for lining its tightly woven, cupshaped nest. Breeding males are bright yellow, with a black cap and black wings and tail. The lesser goldfinch, a western species, also has a yellow breast and black cap, but its back varies from greenish to black in different parts of its range. Lawrence's goldfinch, yellow breasted with a distinctive black face patch, is found in California and in areas just north of the Mexican border.

Goose

Honking from on high, clamorous V-shaped flocks of migrating wild geese always are stirring reminders of the changing seasons. Generally larger than ducks, with longer necks and sturdier legs for walking, these widespread waterfowl differ from their smaller cousins in other ways as well. The sexes look alike, making it difficult to tell males from females. Geese are more sociable, migrating and wintering in huge flocks and often nesting in large colonies. While ducks form pairs that last for only a few months, geese usually mate for life, with both parents caring for the young. Geese, moreover, tend to be vegetarians, with short, stout bills that are well suited for grazing on fields, croplands, and even lawns and golf courses. In North America the most familiar species is the Canada goose, with its long black neck and white chin patch. The snow goose is most common in the western states. The greater whitefronted goose, which often flies with snow geese,

can be recognized by its white face and brown plumage. Another common species is the brant, a small, dark, chunky maritime goose that winters along both the Atlantic and Pacific coasts.

Goosefoot

Chenopodium

Found along roadsides and in gardens all across North America, the goosefoots are wild relatives of beets and spinach. Our several species range from one to six feet in height, with the lower leaves on some looking a bit like a goose's foot. Plain but prolific, they bear tiny greenish flowers and produce huge crops of seeds-as many as 50,000 per plant. Indians made flour from the seeds, and the leaves of one kind, lamb's quarters, are still used as a substitute for spinach.

Gopher

See Pocket gopher.

Gopher snake

See Bullsnake.

Gopher tortoise

See Tortoise.

Grackle

Quiscalus

Our three species of grackles are big, glossy members of the blackbird family, with exceptionally long tails. Equipped with stout, all-purpose bills, they are opportunists that eat a wide variety of foods, from grain and grubs to small birds and even minnows. Sociable creatures, they travel in flocks, roost together in winter, and nest in loose colonies. The common grackle, the smallest, most familiar species, is found almost everywhere east of the Rockies. Both sexes are black and richly iridescent. The boat-tailed grackle, a large bird of coastal marshes in the East, is named for its very long, keeled tail. Males are black, but females are a warm brown. The very similar greattailed grackle lives from Louisiana to southern California and ranges northward to the southern Great Plains.

Graded signal

An Animal Behavior term, this is used to describe Animal signals which show differences in frequency or intensity depending on the state of the individual showing them, just as people shout louder the more angry they are. Often, Animal signals show typical intensity.

Granite

A mosaic of colorful, interlocking crystals, including quartz, feldspar, and mica, granite is one of the principal rocks forming the continents. Its name comes from an Italian word meaning "grainy" and refers to the rock's coarse texture. Granite formed as molten magma slowly cooled deep within the earth's crust. Hard, strong, weather-resistant, and taking a fine polish, it is widely quarried for use as tombstones and in construction.

Grape

Vitis

Vinland was what the ancient Vikings called North America, and the name still fits, for wild grapes continue to flourish in thickets and woodlands from Canada to Mexico. Fox grapes, frost grapes, and scuppernongs are among the more familiar, widespread species. Climbing by means of twining tendrils, the pliant vines can clamber up to 100 feet into the treetops. Shading their hosts with their own canopies of leaves, grapevines sometimes kill the trees on which they grow. Catbirds, cardinals, and other birds strip shreds of bark from the vines and weave them into their nests. And in the fall,just as in Aesop's fable, foxes are among the many kinds of wildlife that come to feast on the clusters of tart, juicy fruits.

Graphite

Shiny, black, and greasy to the touch, graphite is one of nature's softest minerals. It is composed of carbon atoms arranged in thin layers that slide easily past one another, and so is an excellent lubricant. When mixed with clay for hardness, it makes up the "lead" in pencils. (Its name is derived from the Greek for "to write.") Graphite is also used for battery electrodes, the cores of nuclear reactors, and a number of other industrial purposes.

Grass

From lawns and pastures to meadows, prairies, and croplands, about half of North America is covered by grasses of various kinds. The cereals that we rely upon for much of our food-corn, rice, wheat, oats, rye, and barley-all are grasses, as is sugar cane. Even more widespread than the cultivated kinds are the wild grasses-some 1,500 species in all-which grow in almost every conceivable habitat, from coastal dunes topped by swaying stands of sea oats to the high mountains of the West, where alpine timothy grows on lofty meadows. Prairie grasses such as buffalo grass and little bluestem once blanketed the Great Plains, thriving in a climate that is too dry to support trees and shrubs. Most grasses have long, bladelike leaves and hollow stems that are reinforced by solid nodes. They spread both by means of seeds produced by their tiny, inconspicuous flowers, and by creeping stems that take root at intervals and send up new plants. The grasses' fibrous roots protect the soil from erosion, and as the plants decay, they help enrich the topsoil.

Grasshopper

Well-known for their extraordinary leaps, grasshoppers are also noted for their summer songs. Depending on the species, they produce the sounds by rubbing rough-edged legs against their wings or by rubbing two wings against each other. The long-horned grasshoppers such as katydids are named for their long antennae. Among short-horned grasshoppers are the lubber grasshoppers, notorious for the havoc that they sometimes produce in the plains states: occasionally erupting in enormous numbers, the insects become the voracious plagues of locusts that swarm over cropland, devouring every plant in sight.

Grasshopper mouse

Onychomys

Unlike most small rodents, which feed on seeds or other plant foods, our two species of grasshopper mice are feisty little carnivores. Inhabitants of western plains and deserts, the stocky, relatively short-tailed creatures move into the burrows of prairie dogs and other animals and come out at night to hunt. They are sometimes called scorpion mice, an allusion to one of their favorite foods. But they also capture insects, lizards, and even small mammals.

Grasslands

From the Rocky Mountains to Indiana and from Canada's prairie provinces to Texas, the heart of North America at one time was dominated by grasslands that stretched as far as the eye could see. Though much of the region now is cropland, pockets of the original prairie still exist. Also known as the Great Plains, this is an area that has always been too dry to support trees, but not so dry as the deserts of the Southwest. The grasslands range from the moist tallgrass prairies of the Midwest to the drier shortgrass prairies farther west, where bison and pronghorns graze. Other wildlife includes small rodents and reptiles, preyed upon by hawks, owls, coyotes, and badgers, and numerous ground-nesting birds. Among the hordes of insects, crickets and grasshoppers sing from the grasses, while bees and butterflies flit from place to place sipping nectar and pollinating an endless array of wildflowers.

Grassland biomes

Grassland biomes are large, rolling terrains of grasses, flowers and herbs. Latitude, soil and local climates for the most part determine what kinds of plants grow in a particular grassland. A grassland is a region where the average annual precipitation is great enough to support grasses, and in some areas a few trees. The precipitation is so eratic that drought and fire prevent large forests from growing. Grasses can survive fires because they grow from the bottom instead of the top. Their stems can grow again after being burned off. The soil of most grasslands is also too thin and dry for trees to survive.

When the settlers of the United States moved westward, they found that the grasslands, or prairies as they called them, were more than just dry, flat areas. The prairies contained more than 80 species of animals and 300 species of birds, and hundreds of species of plants.

There are two different types of grasslands; tall-grass, which are humid and very wet, and short-grass, which are dry, with hotter summers and colder winters than the tall-grass prairie. The settlers found both on their journey west. When they crossed the Mississippi River they came into some very tall grass, some as high as 11 feet. Here it rained quite often and it was very humid. As they traveled further west and approached the Rocky Mountains, the grass became shorter. There was less rain in the summer and the winters got colder. These were the short-grass prairies.

Grassland biomes can be found in the middle latitudes, in the interiors of continents. They can have either moist continental climates or dry subtropical climates. In Argentina, South America, the grasslands are known as pampas. The climate there is humid and moist. Grasslands in the southern hemisphere tend to get more precipitation than those in the northern hemisphere, and the grass tends to be the tall-grass variety.

In tropical and subtropical grasslands the length of the growing season is determined by how long the rainy season lasts. But in the temperate grasslands the length of the growing season is determined by temperature. Plants usually start growing when the daily temperature reached about 50° F.

In temperate grasslands the average rainfall per year ranges from 10-30 inches. In tropical and sub-tropical grasslands the average rainfall per year ranges from 25-60 inches per year. The amount of rainfall is very important in determining which areas are grasslands because it's hard for trees to compete with grasses in places where the uppers layers of soil are moist during part of the year but where deeper layer of soil are always dry.

The most common types of plant life on the North American prairie are Buffalo Grass, Sunflower, Crazy Weed, Asters, Blazing Stars, Coneflowers, Goldenrods, Clover, and Wild Indigos.

Some common animals in the grasslands are Coyotes, Eagles, Bobcats, the Gray Wolf, Wild Turkey, Fly Catcher, Canadian Geese, Crickets, Dung Beetle, Bison, and Prairie Chicken.

Grayling

Thymallus arcticus

Deep, cold lakes and chilly, rushing northern streams are home to the American, or arctic, grayling, esteemed as a sport fish and admired for its beauty. Varying from silvery to brownish in color, these handsome relatives of trout are adorned with high, colorful saillike back fins. Although graylings once ranged south to Utah and Wyoming, they are now scarce in the western states. But they remain plentiful in Canada and Alaska, where prized five-pounders are regularly caught. Game fighters, they rise readily to artificial flies.

Grazer

An Animal that feeds on growing grass or herbage.

Great Chain of Being

Biological Philosophy term. A complex of ideas about nature: that all creatures were created at the moment of original creation, that nature is harmoniously designed, that creatures are arranged in a hierarchical order from lowest to highest, that all the species that could be created have been created; that none have died out or can die out and no new ones can arise. This represents a kind of ecology or economy of the natural world: the completeness of nature is crucial to the understanding of nature. "Nothing incomplete is beautiful ... [nature must be] the perfect image of the whole of which all animals--both individuals and species--are parts" (Lovejoy citing Plato's "Timaeus,"). This is the central conception that motivated objections to evolution. Jefferson, for instance, insisted that nature is complete in this way.

Great Lakes

A group of five connected freshwater lakes-Superior, Michigan, Huron, Erie and Ontario-located in eastern-central North America along the Canada-United States border. The lakes, which cover 246,000 square kilometres, are the continent's largest source of fresh water.

Grebe

Among the most skillful of all diving birds, grebes not only plunge headfirst underwater; they also can sink slowly out of sight by compressing their feathers and driving out trapped air, thus making themselves less buoyant. Grebes, in fact, are so well adapted to life in the water that they seldom fly, and many birders have never seen one on the wing. Most of the grebes are noted for their elaborate courtship dances. Mated pairs build floating, raftlike nests anchored to marsh plants, where both parents tend the clutch of two to eight chalky, plant-stained eggs. Feeding on a wide variety of aquatic life, grebes also eat large quantities of their own feathers. Besides lining the stomach and protecting it from damage by fish bones and shell fragments, the feathers apparently slow down the bones' passage through the digestive system, giving them more time to dissolve. The long-necked western and Clark's grebes are the largest of the seven North American species. Others include the somewhat smaller rednecked grebe, the wide-ranging pied-billed grebe, and the handsomely plumed horned and eared grebes of western prairie marshes.

Greenbrier

Smilax

Woody vines that inch their way upward by clinging with twining tendrils to any available supports, the dozen or so greenbriers-most of them armed with thorns-create impenetrable tangles along eastern streams, roadsides, and woodland edges. They bear rounded clusters of tiny greenish-white flowers, which mature into hard, red to black berries. One species, the carrion flower, is thornless but armed instead with a repugnant odor.

Greenhouse effect

The greenhouse effect is the phenomenon whereby certain gases that absorb and trap heat in the atmosphere cause a warming effect on earth.

Like the glass on a greenhouse, the small amounts of carbon dioxide and water vapor in the atmosphere allow solar rays to warm the earth but prevent heat from radiating back into space. This so-called greenhouse effect has helped maintain life-sustaining temperatures on earth since the atmosphere formed. In recent years, however, a dramatic increase in the burning of fossil fuels has raised the amount of carbon dioxide in the air, intensifying the greenhouse effect. As a result, some experts fear that temperatures around the globe will rise, disrupting climates everywhere.

Greenhouse Gases

Greenhouse gases are gases that absorb and trap heat in the atmosphere and cause a warming effect on earth. Some occur naturally in the atmosphere, while others result from human activities. Greenhouse gases include carbon dioxide, water vapor, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrofluorocarbons and perfluorocarbons.

Greenling

Found in cool coastal waters from California to Alaska, greenlings are popular game fish with colorful markings. The brownish kelp greenlings, for instance, are daubed with blue spots on the males and reddish-brown spots on the females. Fishermen seek greenlings for their flesh, which, though greenish, is very tasty. While most are less than two feet long, the fivefoot, 100-pound lingcod is big enough to be harvested commercially.

Grosbeak

Named for their stout, conical bills, grosbeaks are attractively colored, finchlike songbirds. The rosebreasted grosbeak of the East has been dubbed the potato-bug bird by farmers, who appreciate its voracious appetite for harmful beetles. The closely related black-headed grosbeak lives west of the Rockies, while the South is home to the blue grosbeak, which incorporates into its nest such varied materials as com husks and strips of plastic. The two remaining grosbeaks nest in northern coniferous forests, where seeds are plentiful. The evening grosbeak, famous for raiding bird feeders, actually finds most of its food in the wild. And flocks of pine grosbeaks, which are fond of evergreen seeds, have been known to strip trees of their cones.

Ground beetle

Emerging at night from under logs and litter, ground beetles dash about frantically as they search for insects, slugs, and other small prey. Many of our 3,000 or so species are patentleather black, but others shine with color. Some climb trees to devour gypsy moth caterpillars, and others can extract snails from their shells. When annoyed, those known as bombardier beetles make an audible pop as they expel a foul fluid that instantly vaporizes into a noxious gas.

Ground cherry

Physalis

Their name to the contrary, these wild fruits of fields, waste places, and open woodlands are kin not of cherries but of tomatoes. Low, branching annuals, the ground cherries are adorned in summer with bell-shaped white or yellow flowers, which mature into plump, usually golden berries, each one enclosed in an inflated, papery husk. Though the cherry-sized fruits are prized by country people for use in jams and pies, the leaves and unripe fruits are poisonous.

Groundsel

Senecio

Preferring moist, rich soils, many of the groundsels have become troublesome weeds of barnyards, fields, and gardens. Their name, in fact, is thought to be derived from an Old English word meaning "ground swallower." Members of the sunflower family, most groundsels have small yellow daisylike flowers, and their tiny airborne fruits, equipped with tufts of silken down, are distributed far and wide at the whim of the wind. A number of species, such as common groundsel, have a history of use in herbal medicine. Another, threadleaf groundsel, is notorious in the West as one of the most poisonous of all range plants.

Ground squirrel

Spermophilus

Sprightly cousins of the tree squirrels, ground squirrels are true groundlings; most of them dwell in subterranean burrows that are complete with sleeping chambers and grass-lined dens to accommodate large litters offast-growing young. The labyrinths also provide snug quarters in which the squirrels can hibernate,

particularly at times when food is scarce. A hibernating squirrel typically curls up into a ball, a position that is ideal for conserving heat; as its body temperature and heart rate plummet, the squirrel slips into a deep torpor. Ground squirrels in the Arctic hibernate for up to eight months of the year, while other species that dwell in arid regions become dormant during the hot months of summer. More than a dozen species of ground squirrels live in the western and midwestern states. Inhabiting meadows, rocky hillsides, prairies, and deserts, they feed by day on greenery, seeds, and insects. Ever alert as they forage, the jaunty little rodents regularly rise up on their haunches to survey their surroundings. When threatened by enemies-including eagles, hawks, coyotes, and badgers-they signal their fellows with a sharp, distinctive warning whistle and then run for cover themselves.

Ground water

Beneath the surface of most of the world's land area lies an unseen reservoir of water. Renewed constantly by rain and melting snow, this socalled ground water fills the spaces between particles of soil, sand, and gravel, as well as pores and cracks in the bedrock. The top of the watersaturated area, which may be near the surface or far underground, is called the water table. Ground water sometimes flows onto the surface in springs and riverbeds. In many areas, from New]ersey in the East to the deserts of the Southwest, ground water tapped by wells is the main source of water for drinking, irrigation, and household and industrial use. Although it is less easily contaminated than surface water, ground water is nevertheless subject to pollution. Chemical fertilizers, sewage, and gasoline that leaks from underground storage tanks are but a few of the contaminants that can foul this precious resource.

Grouse

Chunky and chickenlike, grouse are grounddwelling birds that normally take to the air only to escape enemies. Relying instead on their remarkable camouflage, they usually sit tight until predators come dangerously close, then take off with an explosive whirring of wings. The family, which includes ptarmigan and prairie chickens, is renowned for the spectacular shows the birds put on during the spring mating season. The forest-dwelling ruffed grouse stands on a log and drums the air with his cupped wings, producing a deep booming sound that can be heard more than a mile away. Even more elaborate are the rituals of the western sharptailed grouse, sage grouse, and prairie chickens. Males gather at special dance grounds, called leks, where they strut, bow, stamp their feet, and spread their tails like fans, all the while making booming sounds that are amplified by brightly colored air sacs on either side of the neck. Favorite game birds, grouse are admired by hunters for their crafty last-minute escapes. But some kinds, such as the spruce grouse, present less of a challenge: they tend to simply stand in place staring at the hunters.

Grunion

Leuresthes tenuis

Small silvery fish found off the coast of southern California, grunions are best known for their remarkable spawning behavior. Every two weeks from March through]une, when the full or new moon brings the tides to their highest, millions of grunions ride the night waves onto sandy shores. Boring into the damp sand with their tails, the females lay their eggs while the males, curled around the females, quickly fertilize them. The next wave carries the grunions back out to the ocean. So predictable is their spawning that fishermen take advantage of grunion runs and scoop up the tasty fish by the bucketful. Two weeks later, during the next peak tide, the eggs hatch and the fry are washed out to sea. Members of the silversides family, grunions can grow up to eight inches long and have a bluebordered silvery stripe along each side.

Grunt

A large family of colorful warm-water ocean fish, grunts are named for the piglike noises they make, not only while underwater but also after they are caught. The sounds, amplified by their swim bladders, are produced by grinding together powerful teeth in their throats. Ranging in length from six inches to two feet, grunts live in large schools around reefs and weeds and feed on a variety of creatures, from crabs to sea urchins. Several species, including the yellow-striped French grunt, engage in a curious kissing behavior: two fish, with mouths wide open, swim together, touch lips, and then part. Other varieties include the white grunt, an Atlantic food fish, and the California sargo.

Guild

Bird Biology Avian Conservation term.

Two or more co-occurring species' populations that exploit the same type of resources in similar ways. Competition is expected to be especially important within guilds.

Guillemot

Cepphus

Penguinlike birds of the auk family, guillemots nest in rocky crevices along northern coasts. About one foot long, both the black guillemot of the North Atlantic and the pigeon guillemot of Pacific waters are jet black with conspicuous white wing patches and bright red legs. They dive underwater in search of fish, mussels, and other prey and use their wings to paddle. Like other auks, the birds forgo nest building and lay their eggs directly on rocks.

Gull

Whether perched on piers, soaring over surf, or filling the air with raucous, scolding cries, gulls seem virtually synonymous with seashores. Yet the birds, typically white or gray with black markings, are just as likely to be seen inland, where many of them nest and scout for food in fields, marshes, lakes, and garbage dumps. By far the most common species, found on every coastline and on inland lakes and rivers, is the herring gull. An important scavenger, it is also known for its habit of cracking clams open by dropping them on rocks. The largest gull, with a wingspan of more than five feet, is the great black-backed gull of the Atlantic Coast. In mixed gatherings of gulls, this imposing bird always occupies the highest perch and often robs smaller gulls of their food. The California gull, which winters on the West Coast and breeds inland, is the state bird of Utah, an honor it earned by saving the crops of early Mormon settlers from a plague of grasshoppers. Breeding even farther inland, on the Great Plains, is the Franklin's gull; sometimes called the "prairie dove," it builds floating nests in marshes. Another common inland species, the ring-billed gull, is often seen in flocks, gleaning in plowed fields for insects and rodents. Bonaparte's gull (named not for the emperor but for his ornithologist nephew) breeds in forested wetlands and, unlike most other gulls, nests in trees. The laughing gull, found mostly on the Atlantic and Gulf coasts, often follows fishing boats for handouts. The bird is named for its robust ha-ha-ha, which sounds much like human laughter.

Gustation

An Animal Behavior term, this is used to describe the sense of taste. Gustatory stimuli are those received through this sense.

Gypsum

A soft whitish mineral best known for its use in plaster of paris, gypsum is found in many areas in North America. It was usually formed by the evaporation of mineral-laden water in shallow seas and occurs in thick, extensive beds. Other varieties include crystals, lovely reddish rosettes, and a waxy type, called alabaster, that is carved into vases and statuary. Gypsum is also used in the manufacture of such varied products as plasterboard, tile, cement, paper, and paint.

Gypsy moth

Lymantria dispar

Since their introduction from Europe in 1869, gypsy moths have spread throughout the Northeast and turned up as far weSt as Oregon. While the adults do not eat, the caterpillars, marked with red and blue spots, are voracious feeders. Hatching in May, they can strip entire trees of their leaves by the time they spin their cocoons in]uly. Some 10 days later the dusky brown or whitish moths emerge, and in late summer the females lay their eggs, starting the cycle anew.

Habitat

Frequently compared with an address, a habitat is the specific place where a plant or animal lives. A dog's furry back, for instance, is the habitat of fleas, while the moist, shaded forest floor is the place where we would expect to find ferns. A habitat is also a community, like a neighborhood, and includes all the living and nonliving things that make up an area-the plants, the animals, the soil, and everything else that shapes a particular environment. The region or environment where a plant or Animal is normally found. Usually used to refer to the local conditions necessary for the survival of a particular species.

Habitat

Endangered and Threatened species term.

The location where a particular taxon of plant or animal lives and its surroundings (both living and nonliving) and includes the presence of a group of particular environmental conditions surrounding an organism including air, water, soil, mineral elements, moisture, temperature, and topography.

Endangered and Threatened species term.

A plan which outlines ways of maintaining, enhancing, and protecting a given habitat type needed to protect species. The plan usually includes measures to minimize impacts, and might include provisions for permanently protecting land, restoring habitat, and relocating plants or animals to another area. An HCP is required before an incidental take permit may be issued.

Habitat, Core

The place where an animal or plant usually lives, often characterized by a dominant plant form or physical characteristic.

Habitat fragmentation

The alteration of a large habitat patch to create isolated or tenuously connected patches of the original habitat that are interspersed with an extensive mosaic of other habitat types.

Habitat patches

Areas distinguished from their surroundings by environmental discontinuities. Patches are organism-defined (i.e., the edges or discontinuities have biological significance to an organism).

Habitat selection

Preference for certain habitats.

Habitats

An Animal Behavior term, this is used to describe the external environments to which Animal species are adapted and in which they prefer to live, defined in terms of such factors as vegetation, climate and altitude.

Habituation

An Animal Behavior term, this is used to describe a simple form of learning whereby an Animal ceases to respond to a stimulus presented to it repeatedly but which is neither noxious nor rewarding. A property of the nervous system, it is distinguished from sensory adaptation and muscular fatigue: these may lead to similar results, but usually with more rapid recovery when the stimulus is withheld.

Haddock

See Codfish.

Hagfish

Among the most primitive-and homely-of all fish are the hagfish. Like their relatives the lampreys, they lack scales and paired fins; their skeletons are formed of cartilage, not bone. Seldom exceeding two feet, the slimy, eellike creatures have poorly developed eyes, jawless mouths, and fleshy tentacles. Most species burrow into the muddy bottom beneath deep, cold ocean water. Hagfish eat dead or injured fish, using rasplike tongues to bore a hole into the fish's body, then devouring everything but its skin and bones.

Hail

Dramatic but dangerous, hail consists of rocklike lumps of ice that hurtle down from the sky. Hailstones can be as small as peas or as big as grapefruits and are capable of causing tremendous damage. They can break windows, dent cars, ruin crops, and occasionally even kill people. Hail begins as ice pellets that are tossed about in thunderclouds. Kept aloft by powerful updrafts, they accumulate layer after layer of ice on their surfaces until, too heavy to be supported by the updrafts, they fall to earth.

Hairstreak

Named for the fine lines on the undersides of their wings, hairstreaks are brownish, fast-flying butterflies that dart through meadows and forests all across the country. Most hairstreaks also have streamerlike "tails" on their hindwings-a further clue to their identity. Depending on the species, the short, sluglike larvae may feed on leaves, fruits, or small insects. A few kinds have glands that secrete a substance called honeydew, a sweet liquid much craved by ants. The ants, in fact, sometimes tend the caterpillars in their nests, where they "milk" them with gentle strokes on the abdomen.

Halfbeak

Though they are close cousins of the flying fish, haltbeaks never quite become airborne: instead, they skitter along the surface of warm coastal seas, where they feed on small fish and algae. Named for their long, protruding lower jaw, haltbeaks are slender, streamlined fish, with dorsal and anal fins set far back near the tail. A common East Coast species, the foot-long ballyhoo, is often used as bait by anglers trolling for sailfish, marlins, and other game fish.

Halite

Commonly called rock salt, halite is the naturally occurring mineral (sodium chloride) used to flavor food. It is formed by the evaporation of salt water and occurs as clear or colored crystals. Huge deposits are located in Michigan, Ohio, and western New York. Since halite is light and plastic, deep deposits are sometimes squeezed upward by underground forces, causing the rocks above them to arch up into domes. Common in Texas and Louisiana, salt domes are often associated with oil deposits. Though most familiar on dinner tables and on icy roads, halite also has an astonishing range of industrial uses.

Halo

When the sun or moon shines through high, wispy clouds, ice crystals in the clouds can play strange tricks with the light. The most common effect, called a halo, is a bright ring of light that sometimes completely encircles the sun or moon. Variations on the light show, created as the light is refracted and reflected by the ice crystals, include colored halos, double halos, vertical "pillars" oflight, and even bright spots of light on either side of the sun, known as sun dogs or mock suns.

Hammock

In southern parlance, a hammock is an elevated area with fertile soil that supports a hardwood forest. In Georgia the term usually refers to islands in salt marshes, while in Florida the bestknown-and best-preserved-examples are the densely forested islands that rise only a foot or two above the marshes in Everglades National Park. Havens for dozens of plant and animal species, the hammocks are thick with mahoganies and royal palms, festooned with orchids, and alive with a daunting array of tree snails, indigo snakes, and other exotic creatures.

Hanging valley

Tributary valleys that enter a main valley at levels far above that valley's floor are called hanging valleys. Typically, as streams or rivers in hanging valleys flow into the main valley, they tumble down rapids or waterfalls, often producing spectacular scenery. Bridalveil Fall, Ribbon Fall, and other cascades that plummet down sheer cliffs at Yosemite Valley in California, for instance, flow from hanging valleys. Like many others, the hanging valleys at Yosemite are products of glaciation. They were formed by tributary glaciers that flowed into a major valley glacier. Because they were smaller, the tributary glaciers did not cut such deep trenches as the one in the main valley. Thus, when the ice melted, the hanging valleys remained perched above the main valley's floor.

Haplodiploidy

An Animal Behavior term, this is used to describe the genetic system of some Insects, notably Ants and Bees, in which males develop from unfertilized eggs and females from fertilized ones. Thus, males are haploid, having half the number of chromosomes possessed by the diploid females.

Hare

Lepus

Large, long-eared mammals with powerful hind legs, hares are related to rabbits but differ in a number of ways. Unlike the blind and helpless young of rabbits, for example, hares are born fully furred with their eyes open and are soon able to hop about. The most familiar hares are the long-legged jackrabbits, which are often seen bounding across western grasslands and deserts. Their long ears act as antennae, picking up faint sounds, and also help to radiate body heat. Like other hares, they bolt away at the approach of danger, and for short bursts can reach speeds of 35 miles per hour. The snowshoe, or varying, hare of northern and alpine forests and brushlands is brown in summer but turns white in winter. In the fall it also develops dense fur pads on its feet that enable it to leap more easily through the snow. Active by night, it is, like all the hares, a vegetarian, feeding on green plants in summer and on twigs and bark in winter.

Harem

An Animal Behavior term, this is used to describe a group of females guarded by a single male that mates with them and drives off other males attempting to do so, Examples are in Elk and in ElephAnt seals.

Harm

Endangered and Threatened species term.

An act which actually kills or injures wildlife. Such acts may include significant habitat modification or degradation when it actually kills or injures wildlife by significantly impairing essential behavioral patterns including breeding, feeding, or sheltering.

Harvestman

See Daddy longlegs.

Harvest mouse

Reithrodontomys

Though they look very much like house mice, American harvest mice are more at home in fields and grasslands. There they forage by night for seeds and sprouts, often bending stems to the ground to "harvest" the seeds. The mice weave blades of grass into six-inch spherical nests that they build on supports just above the ground. Except for the Northeast, harvest mice are found almost everywhere in the country. But one species, now endangered, lives only in salt marshes around San Francisco Bay.

Hatching success

Bird Biology Avian Conservation term.

Percentage of eggs that hatch.

Hatching-year (HY) bird

Bird Biology Avian Conservation term.

A bird capable of sustained flight and known to have hatched during the calendar year in which it was banded (or seen) or a bird in first basic plumage in its first calendar year.

Hawk

Keen-eyed birds of prey that hunt by day, hawks are most often seen soaring gracefully overhead. But when one of these imposing hunters spots a prospective meal, it swoops down with lightning speed, seizes the animal in its viselike talons, and tears it into bite-sized pieces with its powerful hooked beak. The hawk family includes the accipiters (such as the northern goshawk) and the buteos (such as the red-tailed hawk) as well as eagles, ospreys, marsh-dwelling northern harriers, and the graceful kites. (Falcons, which are often called hawks, differ in several ways and belong to a separate family.) Our largest species is the bald eagle, with a seven-foot wingspan; the smallest, with a wingspan of just under two feet, is the sharp-shinned hawk.

Following a courtship that often includes spectacular displays of aerial acrobatics, most hawks build nests of sticks high in trees. A few, such as the golden eagle, nest on rugged cliffs, while the northern harrier nests on the ground in or near marshes. Hawks eat almost any kind of small animal, from birds to beetles and from rodents to reptiles. Some, however, are more specialized: the snail kite dines only on large snails, and the osprey feeds almost exclusively on fish.

Hawkweed

Hieracium

Though its orange-red flowers add sprightly dashes of color to fields and roadsides in summer, orange hawkweed well deserves its nickname, devil's paintbrush. To gardeners, it and other hawkweeds, such as mouse ear and king devil, are indeed works of the devil, for they are tenacious weeds. Their creeping stems form dense mats of hairy, oblong leaves, and their dandelionlike flowers produce downy seeds that sail on the wind to lawns far and wide.

Hawthorn

Crataegus

The long, needlelike thorns and zigzagging branches of the hawthorns form dense, tangled silhouettes against the winter sky. Then, in spring, the small, prickly trees are covered with coarsely toothed leaves and showy white to pink flowers that resemble apple blossoms. The similarity to apple trees continues in the fall, when the blossoms give way to clusters of small, usually red fruits, called haws, which are eagerly sought by grouse, pheasants, and deer. Many kinds of hawthorns, also known as thorn apples, are found across North America, often forming dense stands in abandoned fields and pastures. Because of their attractive blossoms and bright fruits, the trees make charming ornamentals.

Hazardous Waste

Discarded material which, because of its inherent nature and quantity, requires special disposal techniques to avoid crating health hazards, nuisances or environmental pollution. Hazardous waste can physically be solid, liquid, semi-solid or gaseous.

Hazel

Corylus

Common shrubs or small trees of fencerows and woodland borders, hazels often form dense, twiggy thickets. Their branches, tough and flexible, are sometimes woven into baskets, but the plants are valued mainly for their abundant crops of tasty nuts. Also known as filberts, the fruits are enclosed in distinctive, leafy husks. Those of the American hazel have tattered, ragged edges, while the husks of the beaked hazel are joined in long, tubular snouts.

Health

A person's mental or physical well-being.

Hellbender

Cryptobranchus af/eganiensis

So named, no doubt, because of its grotesque appearance, the hellbender is a flat-headed, wrinkled, dull-colored salamander that grows up to 30 inches long. It is so homely, in fact, that although entirely harmless, it is widely presumed to be poisonous. An ungainly resident of rivers and streams in parts of the East and Midwest, it usually hides under rocks by day and emerges only at night to hunt for crayfish, shellfish, worms, and insect larvae.

Helper

An Animal Behavior term, this is used to describe an individual that assists in the rearing of offspring which are not its own, shown by many Bird species. The helpers are usually elder siblings of the brood.

Hemlock

Tsuga

Slow-growing but long-lived, the hemlocks are softwood conifers that may endure for centuries and reach heights of 100 feet or more. The trees are conical in form, and their drooping branches are covered with short, flattened needles that are dark green above and whitish below. The trees take up to 300 years to reach maturity and, when full grown, cast a dense shade that prevents all but hemlock seedlings from taking root beneath them. Once threatened by overcutting, the eastern hemlock, which flourishes from the Atlantic Coast to Minnesota, was prized by the leather industry for the high tannin content of its bark. The western hemlock is the most common tree of the Pacific Coast rain forests.

Hemlock, poison

Conium macula tum

An imported weed of roadsides, pastures, and waste places, poison hemlock is akin to and closely resembles Queen Anne's lace, or wild carrot. Up to five feet tall, with branching stems and lacy, parsleylike foliage, it bears flat-topped clusters of tiny, dull white flowers from June through August. Unlike Queen Anne's lace, however, the hairless stems of poison hemlock are marked with purple spots and its leaves emit a foul odor when crushed. Well-known as the source of the deadly potion used to execute the Greek philosopher Socrates in 399 BC., poison hemlock contains in all its parts the powerful, often deadly alkaloid coniine. Today this ingredient is extracted for use in sedatives and other medications. Water hemlock, a related weed that flourishes on wet soils, is even more deadly. A single bite of its white, parsniplike taproot has been known to fell a full-grown adult.

Hemoglobin

The red pigment in blood that absorbs oxygen.

Hepatica

Despite their delicate appearance, the hepaticas are in fact quite sturdy: their dainty lavender, pink, or white blooms are among the earliest performers in the annual parade of wildflowers that grace eastern woodlands in the spring. Their broad, three-lobed leaves playa role in the hepaticas' early flowering. Lying flat on the ground throughout the winter, they catch the

Herbivore

Animals that feed primarily on plants are called herbivores and include creatures as diverse as leaf-chewing insects, fruit-eating birds, and wood-boring beetles. Most are specially adapted for their particular diets. Beavers, for example, have chisellike incisors that are perfectly suited for felling trees and gnawing on bark; cattle have flattened molars for grinding food; and seed-eating finches have stout, conical bills that are ideal for cracking seeds. A vital link in all food chains, herbivores convert the energy provided by plants into animal tissue and are in turn consumed by carnivores, or flesh eaters. A herbivorous creature is a plant-eating Animal.

Herb Robert

See Geranium.

Hercules club

Zanthoxylum clava-herculis

Stout thorns sprout from the trunk, branches, and leaf stalks of Hercules club, a shrub or small tree of southeastern coastal plains. On older specimens, warty growths on the trunk give it the look of an ancient weapon, which accounts for the plant's name. Another common name, toothache tree, was inspired by the pungent bark and foliage, which have a long history of use in folk medicine. When chewed, they numb the mouth, temporarily relieving toothache pain. The featherlike compound leaves are nearly evergreen, with the old foliage often persisting until early spring. The tiny greenish flowers appear before the new leaves open, and later give rise to clusters of small reddish pods. As they mature, the pods split open, and a solitary black seed dangles from each one on a thread.

Heritability

An Animal Behavior term, this is used as a measure of the extent to which variation in a behavior pattern, or other characteristic, is due to genetic Rather than environmental causes. Only when heritability is high is selective breeding likely to alter a trait.

Hermit crab

Many a beachcomber has picked up a snail shell, only to find its entrance blocked by the head and claws of a hermit crab. Unlike other crabs, this squatter has a soft, unarmored abdomen and so must use an empty shell for protection. Twisting its body, the hermit crab fits itself into the snail shell; leaving its strong pincers hanging out, it uses its hindmost pair of legs to hold itself firmly in place. When the crab outgrows its borrowed home, it moves into a larger shell, often evicting another hermit crab in the process. Hermits have also been seen pulling live snails from their shells and then eating the former occupants before moving in. Found on both coasts, most species are about an inch long, but the large hermit crab of the Atlantic coast sometimes grows to a length of five inches.

Heron

Elegant, long-legged wading birds with graceful, sinuous necks, herons are widespread across much of North America. The family also includes the egrets, which are simply herons with white plumage, and the closely related bitterns. All herons have long, pointed bills that are used for snapping up fish, frogs, crustaceans, insects, and an occasional bird or mouse. Although they generally nest in colonies, most species hunt alone by day and fly back to their roosts at dusk. The night herons, however, rest by day and work the night shift. Sometimes walking slowly through the water in search of prey, herons may also stand perfectly still and wait for victims to come within reach, then snatch them with quick thrusts of the beak. The great blue heron (which also occurs in Florida in a white form known as the great white heron) has a six-foot wingspan and is our largest species. Equally beautiful are the great and snowy egrets, whose elegant breeding plumes, once sought for hats, nearly caused the birds' extinction. A smaller species, recently arrived from the Old World, is the cattle egret. Unlike most herons, which prefer wetlands, the cattle egret lives in grasslands, where it feeds on insects stirred up by tractors and livestock.

Herring

Clupea harengus

Silvery throngs made up of tens of thousands of herring are found off both the Atlantic and Pacific coasts. Feeding on plankton filtered from the seawater, the foot-long fish are in tum preyed upon by salmon, tuna, seals, and gulls. Because they travel near the surface in such enormous schools, herring are easily accessible to commercial fishermen and are netted by the ton. Among the most valuable of all food fish, herring are marketed fresh, smoked, and pickled, and young fish are canned as sardines. They are also used as bait for catching cod and halibut and are processed for oil and fish meal.

Heterogeneity

The variety of qualities found in an environment (habitat patches) or a population (genotypic variation).

Hibernation

As winter closes in, woodchucks, ground squirrels, and some other animals go into a deep sleeplike state called hibernation. Their temperature, pulse rate, and breathing rate all plummet, and they survive on the energy in body fat. When the weather warms, they slowly reawaken. Other animals, such as raccoons, are inactive in cold weather but are not true hibernators. Their temperature and respiration rate are not greatly reduced, and they can easily be roused.

Hibernator

An Animal Behavior term, this is used to describe the adoption of a state of dormancy in the winter such that heart Rate and temperature fall, and hence, energy requirements are reduced to a minimum. Hibernation enables Animals, such as squirrels, bats and marmots, to survive periods of hostile climate and low food availability.

Hickory

Carya

Synonymous with toughness, the hickories are well known for producing the strongest, most resilient wood of any American trees. Their wood, in fact, is the timber of choice for tool handles but also makes excellent firewood and is especially esteemed as a smokehouse fuel. Common throughout eastern and central North America, all the hickories have long-stalked, featherlike compound leaves. Rough, scaly bark is another common trait, though the shagbark hickory is identified by the long, peeling strips of skin. And all bear oily, hard-shelled nuts enclosed in fibrous green husks. The nuts of one kind, the pecan, are an important commercial crop; those of other species provide a feast for chipmunks, squirrels, and other wild creatures.

Hierarchy

An Animal Behavior term, see Dominance.

Historic range

Endangered and Threatened species term.

Those geographic areas the species was known or believed to occupy in the past.

Hoarding

An Animal Behavior term, this is used to describe the storing of food for later use either in a cache or, as in sCatter hoarding, with each item in a sepaRate place. Mammals, such as Foxes and Squirrels, and Birds, such as Clark’s nutcrackers and Acorn woodpeckers, show hoarding behavior.

Hognose snake

Heterodon

Renowned as a bluff, the nonpoisonous, totally harmless eastern hognose snake puts on quite an act when threatened or surprised. Swelling its body and spreading its neck like a cobra, it hisses fiercely as it lunges and thrashes to frighten the intruder. Then, if the interloper is not deterred, the snake tries another tactic. It writhes convulsively, rolls over on its back, and goes completely limp, playing dead. The ruse usually works, and as soon as the coast is clear, the snake slips away to safety. The western hognose relies on similar but more subdued displays. Both snakes, up to three feet long, are named for their upturned, armored snouts, which they use for digging in the soiL

Hog potato

Hoffmanseggia densiflora

Even for pigs, food is scarce in our southwestern deserts, and the tubers produced by the hog potato's roots furnish welcome fodder. In addition to nourishing many kinds of wild animals-the plant's name in Spanish means "mouse's sweet potato"-the tubers were gathered by Indians when other food was in short supply. Though edible, nutritious, and useful in emergencies, hog potatoes do not provide a very tasty meal.

Bearing dainty compound leaves, the plants in summer produce 16-inch spikes of yelloworange flowers, which give way to beanlike seed pods. While hog potatoes make a pretty show along roads and railways, they can be troublesome pests on farmlands.

Holdfast

A rootlike structure that anchors seaweeds to rocks.

Holly

Ilex

Venturing as far north as Cape Cod, the American holly is a sturdy tree that may reach a height of 100 feet. Like the imported English holly, its spiny evergreen leaves and bright red berries are instantly recognized by almost everyone, thanks to their widespread use as Christmas decorations. Many of our other hollies are less familiar, however, for their leaves are neither leathery nor evergreen, and they lack spines. One such example is possumhaw, a native of the South, which, at 30 feet, is the tallest of our deciduous species. Winterberry, a large shrub that thrives in moist areas, also sheds its foliage in autumn. It is sometimes called black alder because its leaves turn black before they fall.

Home range

An Animal Behavior term, this is used to describe the area which an Animal or group of Animals occupies or visits. As it is not necessarily defended from others, it is distinguished from Territory.

Home range

An area, from which intruders may or may not be excluded, to which an individual restricts most of its usual activities.

Homing

An Animal Behavior term, this is used to describe the ability displayed by many species to return to the same place, usually a breeding area, from a distance, either as part of their normal activities or after displacement in an experiment. Good examples are Fish, such as Eels and Salmon, Turtles and Homing Pigeons.

Honeybee

Apis mellifera

Living together in colonies that number in the thousands, honeybees form complex and efficient societies, with each individual insect performing its preordained role. Preeminent in the colony is the queen, a large, long-lived female bee whose sole mission is to lay eggs. The relatively few males, called drones, exist only to fertilize future queens on special mating flights. The thousands of remaining bees, called workers, are sterile females that perform the colony's day-to-day chores. Toiling industriously, they gather pollen and nectar from flowers, tend the developing larvae, care for the queen, and maintain the nest, or hive. The hive is filled with honeycomb, which is made up of thousands of six-sided cells built with wax secreted by the workers. Honey and pollen are stored in most of the cells; in others the queen lays the eggs, which develop from larvae to pupae to adult bees. Humming from flower to flower, honeybees perform an invaluable service in the natural world. Even as they ensure their own survival by gathering food, they ensure the survival of plants by pollinating their blooms.

Honeydew

A sweet, sticky liquid excreted by treehoppers, aphids, and other sap-sucking insects, honeydew sometimes coats the leaves of plants attacked by these pests. The accumulation can harm the plants by encouraging the growth of mold. While gardeners may disapprove of honeydew, however, ants, wasps, and other insects regard it as an elixir. Ants sometimes approach aphids, tap them with their antennae, then drink the drops of liquid that the aphids excrete in response. Some species even protect the aphids, like herds of cattle, and return regularly to "milk" their charges.

Honeylocust

Gleditsia triacanthos

Even adventurous squirrels avoid climbing the honeylocust, for the tree has clusters of nasty branching thorns on both its trunk and branches. But this fast-growing tree, a native of the Midwest and the South, has a less menacing aspect as well, provided by its delicate, compound leaves and dangling clusters of greenishyellow flowers. The fruits are long, leathery pods that contain the tree's "honey," a sweet pulp that surrounds the beanlike seeds.

Honeysuckle

Lonicera

Attractive shrubs and vines with smooth, oval leaves, honeysuckles are admired for their lovely trumpetlike flowers and sweet nectar. By far the most common is Japanese honeysuckle, a climbing vine with fragrant, white to yellow flowers. Introduced as an ornamental, it has become so pervasive that many regard it as a weed. Trumpet honeysuckle, one of the showiest species, is a woodland vine with beautiful blossoms that are red on the outside and golden within. The tubular blooms are so deep that the plant depends entirely on hummingbirds for pollination. In contrast, mountain fly honeysuckle, a low woodland shrub, bears shallow yellow flowers that are more accessible to insects.

Hoof

Sheep, goats, pigs, cattle, deer, and horses all have hooves, which are essentially large, thick toenails that encase and protect the bottoms of the feet-natural shoes. Made of the same material as claws and fingernails, hooves are derived from the outer layer of an animal's skin. On Single-toed mammals such as horses, the hoof is one continuous sheath. On others, such as sheep and cattle, it is divided into two halves and is called a cleft hoof.

Hop-hornbeam

Ostrya virginiana

Although the dangling papery fruits of the hophornbeam resemble the hops used to flavor beer, its seeds serve instead as forage for ruffed grouse and other wildlife. Ranging across eastern North America, this slow-growing, longlived tree rarely exceeds 30 feet. It is adapted to a wide range of soils and flourishes in shady spots. The hop-hornbeam's bark is rough and shaggy, its leaves toothed, and its timber so hard and tough that the tree is nicknamed ironwood.

Horn

The sturdy headgear of cattle, bison, goats, sheep, and some other mammals, horns serve as more than ornaments. The formidable, paired structures are also weapons used to fend off predators and to joust with males of the same species during the mating season. Horns consist of a core of bone surrounded by a layer of hard fingernail-like material. In contrast to antlers, which are branched and are shed every year, horns are unbranched, permanent fixtures.

Horny

A solid, bony core which is part of the Animal's skull covered by a sheath of hard fibrous horn. The horn sheath grows from the base or skin at the skull. As new growth is formed the old growth is forced away from the skull. The shape that the horn sheath takes is formed by the inner bony core, which also continues to grow. Horns are never shed but continue to grow throughout the Animal's life. Both males and females have horns but may vary in shape or size by sex in some species.

Hornbeam

Carpinus caro/iniana

Rounded ridges spiral up the trunk and limbs of the American hornbean, giving the tree a muscular look that accounts for one of its alternate names- musclewood. Though in fact it is more closely related to the birches, it is also called blue beech because its smooth bluish-gray bark is similar to the beeches'. Thanks to its remarkably hard wood, this small tree of eastern streamsides and bottomlands, like its close relative the hop-hornbeam, is also called ironwood.

Horned lark

Eremophila alpestris

Among the first birds to nest each year, horned larks sometimes begin raising families as early as February. Birds of wide open spaces, they favor fields, prairies, and beaches, where they are often seen in enormous flocks. Although they feed and nest on the ground, horned larks sometimes circle high in the sky, singing a twittering flight song, then plummet earthward once again. Two small feather tufts on their heads, not always conspicuous, give horned larks their name.

Horned lizard

Phrynosoma

Looking a bit like tiny dinosaurs, horned lizards have squat, oval bodies, sharp spines projecting from the back of the head, and rows of pointed scales along their sides. Also known as horned toads, they live in arid and semiarid areas west of the Mississippi River. Protective coloration helps them to blend with their surroundings. When threatened, horned lizards hiss, bite, lower their heads to brandish their spines, and inflate their three- to seven-inch bodies to look larger than they actually are. They can even spurt thin jets of blood from the corners of their eyes. Despite this arsenal of defenses, horned lizards are prey to roadrunners, coyotes, and the occasional snake that risks swallowing the wellarmored body. Able to tolerate higher temperatures than most reptiles, horned lizards forage by day for ants and other insects. At night and when the daytime heat becomes too intense, they burrow into the sand, leaving only their heads exposed.

Horned toad

See Horned lizard.

Hornet

Familiar across North America, hornets are social wasps that build large hanging nests. (The similar yellow jackets build underground nests.) Stout-bodied insects, most are black with yellow or white markings and inflict very painful stings. Hornets chew rotten wood and other plant fibers to form the gray pulp (much like papier-mache) used for nest building. Consisting of tiers of cells, the nests are enclosed in the same papery material. While colonies last just one season, queens overwinter and in spring begin constructing new nests. Adhering to a rigid caste system, female workers, produced in the first broods, assume most of the duties of the nest, with drones appearing in later generations.

Horntail

Though related to wasps and bees, horntails lack the narrow waists and nasty stings of their kin. A projection resembling a hom, at the tip of their elongated bodies, gives them their name. Females also have a sharp ovipositor for drilling into dead trees to lay their eggs. The larvae pupate after tunneling through the wood for up to two years, and emerge as winged adults. The pigeon horntail is the most common species in the East; smoky horntails predominate in the West.

Horse, wild

Equus caballus

Swift, smart, feisty, and free, the wild horses that roam the West today are descendants of the horses brought here centuries ago by Spanish settlers. Also called mustangs (from a Spanish word for "stray"), the horses travel in small bands over plains and grasslands. Stallions battle each other in fierce competition for harems of mares, while the younger males usually congregate in bachelor bands. Tough and hardy, the horses live for about 20 years. Though generally smaller than the average domestic horse, mustangs nevertheless belong to the same species. Often tamed by the plains Indians, who used them to hunt buffalo, wild horses once numbered in the millions. But over the years, so many were hunted or rounded up, to make way for farms and cattle ranches, that their numbers have been drastically reduced.

Horse chestnut

Aesculus hippocastanum According to tradition horse chestnuts long ago were used as a medicine for horses. Hence the name of this old-world tree, which was brought here in colonial times. While the glossy, dark brown nuts do resemble true chestnuts, their meat is bitter and inedible. The two trees are not even closely related. The horse chestnut is instead a close kin of the native American buckeye, which gives Ohio its nickname. Most common in the Northeast and Midwest, horse chestnuts have large, attractive leaves,

with seven leaflets radiating from the end of a single stalk. But the horse chestnuts' chief beauty is the array of upright clusters of showy white flowers that in]une transform the trees into giant candelabras. In September the spiny green fruits fall from the branches and split open to reveal the nuts, which look like polished mahogany.

Horsefly

Tabanus

Known for the painful bites they inflict on animals and humans alike, horseflies are robust, fast-flying insect pests. They are found from coast to coast in fields, forests, and pastures near the ponds and streams where they live as larvae. The males, which feed on pollen and nectar, are harmless. The females, however, have piercing, cutting mouthparts that can penetrate even the toughest hides in order to suck blood. Repeated attacks by horseflies can seriously weaken animals, and their bites can transmit diseases from host to host.

Horseshoe crab

Umulus polyphemus

Little has changed with the horseshoe crabs since they first appeared on earth millions of years ago: every spring these seafaring relatives of spiders and scorpions still head for beaches by the thousands in an ancient spawning ritual, with the males riding ashore atop the larger females. Dome-shelled and dull brown, horseshoe crabs grow to about three feet in length, including their slender, pointed tails. They live in shallow waters all along the Atlantic and Gulf coasts, where they root on the bottom for worms and mollusks. Once ground up by the thousands for fertilizer and still used to bait fish traps, horseshoe crabs are valued for nobler purposes today. Their blood is used in pharmacological research, and scientists study them to learn about the electrical link between eye and brain.

Horsetail

Equisetum

Fossils preserved in coal reveal that the ancient ancestors of present-day horsetails grew to the size of trees. Surviving today as weeds of moist places, the modern horsetails are much more modest, rarely exceeding two or three feet in height. Some are virtually all stem, growing in clumps of hollow green stalks with their leaves reduced to mere sheathes encircling the stems; others bear whorls of branches on the stalks. Producing neither flowers nor seeds, horsetails reproduce instead by releasing spores from special conelike structures. Permeated with silicon crystals, the abrasive stems once were used for cleaning pots and pans and so earned the horsetails their alternate name, scouring rushes.

Hot spring

Ever since antiquity, people have drunk and bathed in the mineral-rich water of hot springs in search of relief from all sorts of ailments. Such springs are usually found in areas where molten rock, or magma, lies fairly close to the surface and heats groundwater that seeps down through cracks and crevices in the overlying rock. Rising back to the surface through natural vents, the steaming water fornls calm pools or steadily flowing streams.

Housefly

Musca domestica

Zigzagging through the air in search of food to light upon, houseflies have been the annoying companions of humans for thousands of years. Suspected of carrying diseases, the insects are attracted to manure and rotting plant and animal matter, where they feed and lay their eggs. Most prolific in warm weather, the housefly develops from egg to maggot to adult in only 10 days, and a single female can theoretically produce millions of offspring in a single summer.

House mouse

Mus musculus

For thousands of years house mice have been uninvited guests in human homes. Choosing warm, dark places to set up housekeeping, the little rodents tear strips of cloth or paper to build their nests, which are often lined with pilfered feathers. Though they usually eat whatever scraps of human food they can find, in lean times they may resort to such fare as glue and soap. House mice also live outdoors, where they feed on plants and are preyed upon by owls, snakes, and other animals. Since the mice can breed at only a few weeks of age, tremendous populations can build up in a short time. On rare occasions, croplands have been known to host more than 80,000 mice per acre.

House sparrow

Passer domesticus

Also known as the English sparrow, the hardy, adaptable house sparrow was imported from Europe in the 1850's and is now abundant in cities, suburbs, and farmlands from coast to coast. Like many other introduced species, it turned out to be a pest--a noisy, aggressive bird that steals the nesting sites of bluebirds, wrens, and other native hole-nesters. Building crude, untidy nests of straw, feathers, and trash, the interlopers raise as many as three broods of young each year.

Hover fly

The nonstinging look-alikes of bees and wasps, hover flies are named for their habit of hovering and darting among flowers in their relentless search for nectar and pollen. Most are brightly patterned with yellow and black; some are slender and narrow-waisted like wasps, while others are plump and fuzzy like bumblebees. Depending on the species, the larvae may live in water, tunnel through flower bulbs, or lodge in the nests of ants or bees. And the larvae of some kinds are gardeners' allies, preying on aphids and other plant pests.

Thus a relative humidity of 50 percent means the air is only halfway to its saturation point; a relative humidity of 100 percent means the air can hold no more moisture.

Humidity

On some days the air is dry and pleasant, while on others it seems sticky and uncomfortable. The difference is due to humidity-the moisture content of the air. Because the amount of water vapor the air can hold before it becomes saturated varies with temperature, the moisture content is expressed in terms of relative humidity-a ratio comparing the amount of water vapor actually present in the air with the amount that would saturate it at the same temperature.

Hummingbird

When European settlers first glimpsed North America's hummingbirds, they were dazzled by their glowing iridescence, incredible speed, and ability to hover before flowers, poised on almost invisible wings. One 18th-century writer called them "the miracle of all our winged animals," and few of us are so blase, even now, that we can ignore such amazing little creatures. Twenty-one species of these exclusively newworld birds have been sighted in the United States. Only one, the ruby-throated hummingbird, lives east of the Mississippi River, and most of the western species venture just a short distance north of the Mexican border. But four, including the diminutive calliope hummingbird, range northward into Canada, and one, the rufous hummingbird, even reaches southern Alaska. As autumn nears, hummers head for warmer climates, with some migrating thousands of miles-an incredible feat for such tiny birds. Most of our hummingbirds are a rich iridescent green above and whitish or buff below. Males usually have a throat patch, or gorget, of bright red, violet, or blue, and in some the color extends to the crown. Exceptions include the magnificent hummingbird, which is black below with a green gorget and a purple crown, and the violet-crowned hummingbird, which has pure white underparts. Females are similar but lack the bright gorgets and crowns.

Beating their wings with powerful muscles, hummingbirds are noted for their ability to hover in midair as they feed. But these aerial acrobats can play other tricks as welL They also are able to fly up and down, shift sideways, and even fly backward. When hummingbirds feed, their wings beat more than 50 times a second as they hover before flowers to probe for nectar and tiny insects with their long, slender bills. As they reach deep

into the blooms, their tubular tongues function like drinking straws. Because of their exceptionally high metabolic rate, hummers feed almost continuously throughout the day. At night they sustain themselves on food stored in their tiny crops, and in cool weather they conserve energy by becoming temporarily dormant.

Fiercely territorial, hummingbirds boldly defend the flowerbeds they have staked out as their own. The males also make spectacular display flights that further proclaim their flowers off limits to others. The ideal territory is a large patch of plants in bloom, but where these are scarce, the birds make the rounds of flowers that are scattered here and there-a so-called "trapline: which is defended as vigorously as a typical territory. A patch of flowers bright with blooms is more than just a source of food, however; for males it is also a means of attracting mates. After building their nests elsewhere, females visit males in their territories. Darting, swooping, and plummeting, the males indulge in the stunning courtship flights that are a vital part of their breeding ritual. Once a pair has mated, the female leaves to carry out the duties of parenthood alone.

All our hummingbirds build tiny cup-shaped nests of plant down, spider silk, and moss, often covering them with bud scales or bits of lichen. The female usually lays two pure white eggs, which hatch after 12 to 18 days, a surprisingly long time for such small birds. Fed on a diet of nectar and insects, the young leave the nest at about three weeks, often spending the last few days perched on the rim. There they exercise their wings, preparing themselves for their lives as fast-flying adults. Just as hummingbirds have adapted to flowers, many flowering plants have come to rely on hummingbirds for pollination. Mostly red or orange, hummingbird blossoms are usually tubular and open during the day. They have little or no scent, since perfume is not needed to attract these little birds. The stamens or pistils extend beyond the petals, where they can touch hovering hummers and transfer the pollen. Lacking the "landing platforms" of plants visited by bees or butterflies, these blooms make their nectar accessible only to hummingbirds. Among the hummingbird favorites in the East are cardinal-flower, trumpet vine, bee balm, and columbine. In the West, Arizona honeysuckle, Indian pink, scarlet larkspur, many paintbrushes, and the bush monkeyflower are adapted to visits by hummers. Since hummingbirds require flowers for survival, it is quite easy to attract these feathered gems to gardens. Even some of the more elusive species can be lured with feeders, glass or plastic containers filled with sweetened water and decorated with the bright red that the birds seem to find irresistible. With the feeder filled, it is easy to enjoy, closeup and firsthand, these delightful sprites thatJohnJames Audubon called "glittering fragments of the rainbow."

Hummingbird moth

Hemaris thysbe

Commonly seen hovering at flowers as it sips nectar through its long tongue, the stout-bodied hummingbird moth does indeed look remarkably like a hummingbird. Also known as the common clearwing because of the large transparent areas on its wings, it has a hairy, dull green body with reddish bands across the abdomen and a fuzzy tuft at the rear. Flitting from flower to flower, the moth feeds during the day in meadows and gardens all across southern Canada, the northern United States, and south to the Gulf of Mexico in the East.

Hummingbird trumpet

Zauschneria

A small shrubby plant of the Far West and Southwest, the hummingbird trumpet enlivens dry slopes and mountain ridges with dazzling displays of bright red tubular blossoms. The nectar-filled flowers open late in the season, providing hummingbirds with energy-rich food as they begin their fall migration. Also known as California fuchsia, the desert plant bears small woolly leaves, while the plants that grow on mountain slopes have less hairy foliage.

Humus

When leaves, branches, dead insects-almost any kind of plant or animal material-fall on warm, moist soil, microorganisms immediately begin breaking them down to their constituent elements. The roots of nearby plants absorb nutrients released by the decay, and carbon dioxide escapes into the air. What remains to enrich the soil is humus. This fine-textured black or brown material promotes healthy plant growth, both by helping the soil retain moisture and by keeping it loose and crumbly so that air can penetrate to roots. As it gradually decomposes, humus continues to benefit surrounding plants with a small but steady supply of nutrients.

Hunting (Recreation)

The practice of pursuing and killing wild animals. To protect wildlife, there are laws governing when the hunting of certain species may take place, as well as the number, size, age and sometimes sex of specimens that may be killed by hunters.

Hunting (Wildlife)

The practice of pursuing and killing game birds is permitted at specific times of the year and in different parts of the country. Conservation hunts are an important means of managing the population of species such as the Snow Goose.

Hurricane

Hurricanes are cyclones of tropical origin, with wind speeds of at least 118 kilometres per hour. The winds in a hurricane rotate inwards to an area of low barometric pressure. This relatively calm centre is called the "eye". Monstrous in both their size and ferocity, Atlantic hurricanes are severe tropical storms that develop over warm oceans. Called typhoons in the Pacific, the giant circular storm systems are also known as tropical cyclones. Their violent winds, which may blow at speeds of more than 150 miles per hour, are accompanied by huge churning waves and torrential rainfall. Seen from a satellite, the swirling clouds of a hurricane resemble a giant pinwheel. At the center is the eye, a low-pressure area about 30 miles in diameter where the weather is eerily calm. The eye is surrounded by a wall of clouds and winds that may spread over an area measuring from 300 to more than 1,000 miles in diameter. Hurricanes usually form over the Caribbean Sea and western Atlantic Ocean in August or September, when the surface of the ocean is warmest. Fueled by heat energy, their power increases as long as they remain over warm water. Those that head for land are prescriptions for disaster, with winds that can smash windows, tear the roofs off buildings, and snap large trees like toothpicks. Ninety percent of the deaths caused by hurricanes, however, result from drowning. The storms' low pressure elevates the level of the sea, and this, combined with huge waves and heavy, pounding rain, causes catastrophic flooding when a hurricane reaches shore. The effects are even worse if a storm hits at high tide. Fortunately, because they are no longer fueled by warm ocean water, hurricanes gradually die out as they move over land.

Hybrid

An individual that is an offspring from different parent species. These individuals are usually not fertile and cannot breed and reproduce. A Mule is a hybrid cross between a Horse and a Donkey.

Hydra

Tiny freshwater relatives of sea anemones, hydras are carnivorous animals with built-in weapons systems. Consisting of hollow central stalks with crowns of tentacles radiating from the top, hydras anchor themselves to stones or plants and wait for passing prey. When tiny insects or crustaceans swim by, stinging cells on the tentacles shoot out poisonous threads, like miniature harpoons, paralyzing the victims, which the hydras then digest.

Ibis

Denizens of shallow marshes, ponds, and coastallagoons, where they stalk a variety of prey, ibises are easily distinguished from other longlegged, long-necked wading birds by their downward-curving bills. At dusk the gregarious creatures form large V-shaped flocks and fly to groves of tall trees, where they roost together for the night. They also nest in colonies. Each pair builds a loose cup of sticks or aquatic plants and tends a clutch of two to four pale blue, green, or buff-colored eggs. Of the three species found in North America, the white ibis-snow-white except for its black wing tips and red bill, face, and legs- inhabits southern marshes and mangroves. The glossy ibis, a medium-size bird with bronzy plumage, is found on the East Coast, occasionally venturing as far north as Canada. Similar-looking except for the band of white circling its face, the white-faced ibis lives on fresh water in the West.

Ice

Frozen water. The formation of ice on bodies of water, such as lakes, rivers and seas, has a profound influence on the shipping industry and plays an important role in our climate system.

Ice (Weather)

Frozen water-used to describe the frozen portion of a body of water, a frozen film of water on a roadway or other surface, and precipitation that is frozen or that freezes on contact.

Iceberg

Massive and menacing, icebergs are floating mountains of ice, sometimes with awesome facades and spires like those of castles and cathedrals. They are formed when huge chunks break off, with a thunderous rumbling, from the ends of glaciers or ice sheets and tumble into the sea. Icebergs present a serious hazard to shipping in such places as the North Atlantic, where most originate in Greenland. Although the largest bergs may tower hundreds of feet into the air, more than 85 percent of their bulk remains hidden below the surface, giving rise to the expression "That's just the tip of the iceberg."

Ice plant

Cryophytum crystal/inum

Covered with tiny, water-filled beads, the stems and leaves of ice plants sparkle like hoarfrost on hot, dry slopes of the southern California coast. They put on a splendid show from March to October, bearing a profusion of pink or white flowers that open only on bright, sunny days. Originally imported from Africa to help control erosion, ice plants also are abundant on dunes, roadsides, salt marshes, and sea cliffs.

Ice storm

Among the most destructive forms of winter weather, ice storms occur when rain falls from warm air into a layer of colder air. As it nears the ground, the water freezes, coating wires, trees, and almost any other object it hits. Also known as silver thaws, the storms result in glittering layers of ice that can be breathtakingly beautiful. But they are also extremely dangerous. Less than half an inch of ice can snap power lines, break branches, and create havoc on roads and highways. If strong winds accompany the storm, the effects on forests can be devastating. And even a thin coating can freeze over the food supply, causing animals to starve. Fortunately, ice storms are usually short-lived. In most cases, the warm air mass that brought the storm slowly displaces the colder air and melts the ice.

Ichneumon

While they rarely sting humans, these relatives of wasps are deadly enemies of the insects that damage trees and crops. The female giant ichneumon, for instance, walks along tree trunks, listening for larvae of the pigeon horntail, a wood-boring insect. When she finds one, she pierces the bark and lays an egg in the horntail's tunnel. The ichneumon larva that hatches from her egg then slowly devours the horntail larva, pupates, and emerges as a winged adult. Other ichneumons parasitize harmful caterpillars, such as the tobacco hornworm, eating them from the inside out.

Igneous rock

Deriving their name from the Latin word for fire, igneous rocks are formed when molten magma cools and crystallizes. Some, such as granites, harden slowly deep within the earth and have a coarse-grained texture. Others, such as basalt, cool rapidly and are finer grained. They form from magma that explodes from volcanoes or oozes out through fissures on the earth's surface. Although often covered by sedimentary rocks or soil, igneous rocks form the bulk of the earth's crust.

Iguana

Some of the hottest, driest areas of the Southwest are home to the large and varied iguana family. The collared and horned lizards, for example, are iguanas, as is the chuckwalla. But our only species that bears the family name is the desert iguana. Unlike most other lizards that return to their burrows when the sun is high in the sky, this iguana is active at midday, often sunning or foraging even when temperatures soar above lOO°F. For relief from the searing heat of the desert floor, it clambers into low shrubs, but at the first hint of danger it scurries into underbrush or into the burrow where it spends the night. Although it resembles a miniature dragon, the foot-long desert iguana prefers eating flowers to breathing fire. The yellow blooms of the creosote bush are its favorite meal, but it also relishes the buds, leaves, and flowers of cacti and other plants, as well as occasional carrion and insects.

Imitation

An Animal Behavior term, this is used to describe the copying of the behavior of one individual by another such that the second acquires a new behavior pattern. Some behavior, such as patterns of Bird song, may pass from geneRation to geneRation in this way, and novel forms of behavior discovered by one Animal may spread rapidly through the population by imitation (see also Cultural Evolution).

Imperial moth facies imperia/is

With a wingspan of four to six inches, the imperial moth is one of the largest in North America. The short-lived, nonfeeding adults have bright yellow wings that are streaked and spotted with purplish brown. Strongly attracted to artificial lights, they sometimes linger near them after daybreak and are eaten by birds. The larvae, four inches long, are horned and hairy caterpillars that feed on the foliage of both broad-leaved and coniferous trees.

Implementation schedule

Endangered and Threatened species term.

An outline of actions, with responsible parties, estimated costs and timeframes, for meeting the recovery objectives described in the species recovery plan.

Imprinting

An Animal Behavior term, this is used to describe a process whereby young Animals learn the characteristics of other individuals, normally a parent, early in life. In filial imprinting, they come to devote their social responses to that individual. Learning about parents and siblings may also influence mate choice through sexual imprinting, the Animal seeking a partner similar to those with which it was reared, but not usually identical with them.

Incentive

An Animal Behavior term, characteristic of a stimulus which makes it pleasAnt or unpleasAnt to an Animal. Thus, to a Rat, sweet solutions have high incentive value and bitter ones have low incentive value.

Incest

An Animal Behavior term, this is used to describe the mating of close relatives, usually of siblings or of parents with offspring. It is seldom found among Animals, partly because the young of one sex or other tend to disperse but partly also because individuals tend to prefer less closely related partners.

Incidental take

Endangered and Threatened species term.

Take, or harvesting (killing), that results from, but is not the purpose of, carrying out an otherwise lawful activity.

Incidental take permit

Endangered and Threatened species term.

A permit issued under Section 10 of the Federal Endangered Species Act to private parties undertaking otherwise lawful projects that might result in the take, or harvesting (killing) of an endangered or threatened species. Application for an incidental take permit is subject to certain requirements, including preparation by the permit applicant of a conservation plan, generally known as a "Habitat Conservation Plan" or "HCP."

Incidental take statement

Endangered and Threatened species term.

A term referring to that part of a biological opinion that exempts incidental take of a listed species from the Section 9 prohibitions.

Incubation

Left alone, a bird's eggs would not hatch, for the embryos must be kept warm if they are to develop. Incubation is the process by which the eggs are maintained at a fairly constant temperature. Usually birds accomplish this by sitting on the eggs and warming them with body heat. Since feathers block the flow of heat from a bird's body, females (which do most of the sitting) molt the feathers on part of the belly to form a brood patch. This bare area, which is well supplied with blood vessels, transfers more heat to the eggs. Ducks and geese pluck feathers from the brood patch, but on most other birds they fall out naturally. During incubation, birds turn their eggs several times a day, both to ensure even heating and to keep the embryos from settling to one side of the eggs. After the eggs hatch, the parents often continue to brood the chicks until they are able to maintain a steady body temperature-anywhere from a few days to a few weeks, depending upon the species. Incubation periods range from 12 days for some of the songbirds to as long as 55 days for shearwaters. Most birds lay one egg a day and do not begin incubating until the clutch is complete. Others-owls, hawks, and herons, for instance, start sitting as soon as the first egg is laid. As a result, their chicks do not hatch in unison, and in lean times the youngest nestlings sometimes starve to death.

Index

The proportional relation of counts of objects or signs associated with a given species to counts of that species on a given area; or counts of individuals (e.g., at a feeding station) reflecting changes in relative abundance on a specified or local area.

Index method

A counting method involving sampling that yields measures of relative abundance rather than density values.

Indicators

Signs or symptoms of changes in the health of an individual or community.

Indicators (Ocean)

Signs or symptoms of changes in the health of the fish stocks in a particular area.

Industry: A commercial undertaking that provides services or is involved in the trade or manufacture of goods.

Indirect competition:

The exploitation of a resource by one individual that reduces the availability of that resource to others.

Indirect effect

The impact on a species caused by affecting the species' competitors, predators, or mutualists; or the impact of toxic chemicals on a species by directly affecting interactions between species. Examples are disruptions in food resources or habitat changes that affect competitive interactions, biomagnification up the food chain, and impacts on populations parasites, symbionts, pollinators, etc.

Inflorescence

The combination of a flower, its bracts and flowering stems.

Informal consultation

Endangered and Threatened species term.

Informal consultation precedes formal consultation and includes any form of communication between the Federal action agency, applicant, or designated non Federal representative and the Service to determine if listed species may occur in the action area and what the effects of the action may be to such species. This phase is often used to develop project modifications or alternatives to avoid adverse effects to listed species, which would then preclude the need for formal consultation.

Inheritance of Acquired Characteristics

Biological Philosophy term. The disproven idea, held by the French evolutionist Lamarck, that characteristics like knowledge or muscular development, acquired during life can be passed on, genetically, to one's children, and thus influence the course of evolution.

Innate behavior

An Animal Behavior term, this is a term which has suffered from a variety of meanings and has, as a result, largely fallen from use. It could be taken to imply that a behavior developed without learning, without practice, without copying from others or even without any environmental influence at all. Criticisms have Been especially directed at this last sense with its suggestion of inflexibility and genetic determinism.

Insect

Astonishing in their number and diversity, the insects of the world outnumber all other animal species by about four to one. North America alone has more than 100,000 kinds, and on

average, a square mile of land is home to more insects than there are people in the world. And this may be only the tip of the iceberg, for scientists discover thousands of new insect species every year. Yet despite their diversity-from beautiful butterflies to chirping crickets to lowly lice-all insects have certain features in common. For one thing, an insect's body always has three parts: the head, thorax, and abdomen. Most insects also have a pair of antennae on the head and three pairs of jointed legs on the thorax. Though a few primitive, soil-dwelling types are wingless, most insects have wings. Usually there are two pairs, attached to the thorax. Flies, however, have only one pair. And on beetles the outer pair of wings are hardened cases that protect the membranous inner pair. Spiders, centipedes, and ticks are often mistaken for insects, but there are basic differences. Spiders, for example, may look like insects, but they have eight legs rather than six, and their bodies are in two parts rather than three. The life cycle of certain insects-among them butterflies, moths, bees, ants, beetles, and flies- involves a remarkable transformation, or metamorphosis, that takes place in four stages: egg, larva, pupa, and adult. Most larvae, such as caterpillars (butterfly larvae) and maggots (fly larvae), are eating machines. As they grow in size, the wormlike larvae shed their skin several times and then pass into the pupal, or resting, stage, in which they are sealed inside a protective covering, such as a cocoon. The pupae of some butterflies are beautifully marked with gold spots and have been given the name chrysalis, which derives from the Greek word for gold. Once the changes of the pupal stage are complete, the insect emerges from its cocoon as a fully formed, winged adult. Many other insects, such as grasshoppers, dragonflies, cockroaches, cicadas, and lice, develop differently, with a life cycle of just three stages: egg, nymph, and adult. In a process called incomplete metamorphosis, the nymphs, which have traces of wing buds, undergo several molts as they increase in size and gradually assume the adult form. Some nymphs-for instance, those of grasshoppers-bear an obvious resemblance to their parents. Others, such as dragonfly nymphs, are homely, voracious predators that live underwater and breathe with gills-a far cry from the beautifully colored, gossamer-winged adults they become. Insects are among the most successful forms of life on earth. For one thing, they are enormously adaptable. Some live in ice-cold water, others in hot springs, salt lakes, or pools of crude oil. They thrive from the frozen polar regions to the tropics, and from deserts to streams. Their small size is helpful too. Insects can hide, build homes, and find food in tiny places that are inaccessible to other animals. And individual insects not only need very little to eat, but they can make a meal of almost anything, from cloth and paper to plaster and glue. Defense against predators is another facet of survival. Insects, for instance, have external skeletons-in effect, hard coats of armor that protect them from injury. When confronted with an enemy, however, most insects escape by flying, jumping, or running away. Others rely on camouflage: walkingsticks, treehoppers, and many moths and caterpillars look exactly like the vegetation on which they rest. Some kinds of insects use weapons to defend themselves. Caterpillars are often armed with poisonous barbs; ants and beetles have sharp, pincerlike jaws; and bees and wasps can deliver powerful stings. Other insects, such as stinkbugs and carrion beetles, emit offensive odors, while earwigs and bombardier beetles can release noxious sprays. Still others survive simply because they are unappetizing. The monarch butterfly, for example, is avoided by birds because of its unpleasant taste. Humans have often wished that insects were not such expert survivors. For thousands of years people have suffered bites and stings, diseases, damaged property, and devastated crops-all thanks to these tiny but ubiquitous creatures. By far the most costly and destructive insects are the agricultural pests. Every year, such important crops as cotton, potatoes, and many fruits are seriously harmed by insects. The damage they do, combined with the cost of controlling them, amounts to many billions of dollars. Without insects, however, the world as we know it would be seriously impoverished. Many thousands of plants would disappear without insects to pollinate them; we would have no silk or honey; and countless kinds of birds, fish, reptiles, and other insect-eaters might simply vanish from the earth.

Insectivore

An organism that feeds on insects. Bats and Shrews are common mammalian Insectivores.

Indian paintbrush

Castilleja

The bright orange, red, yellow, pink, or lavender plumelike flower heads of the Indian paintbrushes look as if they have been freshly dipped into pots of paint. The colorful display, however, is provided not by flowers but by bracts, modified leaves that nearly hide the actual, pale, tubular, two-lipped blooms. Most at home in the West, though a few species do wander to the East, the paintbrushes range from a few inches to five feet in height. Besides the food they manufacture with their own green leaves, these semiparasitic wildflowers also derive nourishment by tapping into their neighbors' roots, a trait that makes them unsuitable for gardens.

Indian pipe

Monotropa uniflora

Rising in ghostly white or pinkish clusters from the shadowed forest floor, the Indian pipe, also known as the corpse plant, is sometimes mistaken for a fungus. It is, however, a true flowering plant, although its leaves, lacking chlorophyll and reduced to mere scales along the stem, are unable to manufacture food. Instead, the Indian pipe's tangled mass of rootlets lives in intimate association with subterranean fungi that take sustenance for both of them from decaying organic matter and the roots of living trees. Each of the Indian pipe's pale, waxy stems is topped in summer by a single nodding cup-shaped flower that does indeed give it the look of a small clay pipe. The closely related pinesap is similar in appearance but is reddish or yellow in color, and each stalk bears not one but several nodding flowers. Often found growing beneath pines and oaks, it too lives in partnership with a fungus.

Indigo

Baptisia

In Colonial times settlers cultivated the native wild indigo as a substitute for the traditional oldworld dye plant. But they also used it to brush flies off their horses and so called it shoofly and horsefly weed. A bushy plant found on sandy soils throughout the East, wild indigo has gray-green compound leaves resembling clover and is covered with pretty yellow flowers from May to September. A pair of taller Midwestern species bear similar blooms. The prairie false indigo produces creamy white flowers. The blue false indigo has flowers of a true indigo-blue, and its sap turns purple upon exposure to the air.

Insight

An Animal Behavior term, this is used to describe learning which involves the appreciation of complex relationships and, at its most sophistiCated, may imply thought and reasoning. It is not clearly distinguished from other forms of learning and its applicability to Animal examples is doubtful.

Instinct

An Animal Behavior term, this term is seldom used now but with many meanings in the past. Most often, it was applied to systems of behavior, like the Drives of psychologists, which were thought by Ethologists to be inborn and fixed, for example reproductive instinct. The term Instinctive Behavior was used in the same way as Innate Behavior and has fallen from use for similar reasons.

Intelligence

An Animal Behavior term, this is used to describe that capacity which enables an individual to learn tasks, reason and solve problems. Such capabilities being based on many attributes, testing of intelligence in Humans is open to numerous biases. In Animals, intelligence is also hard to assess: they may find superficially difficult tasks to which they are adapted easy and other, apparently simpler, tasks much more difficult.

Intention movements

An Animal Behavior term, this is used to describe movements shown by an Animal just before commencing an activity which indiCate to an observer what it is about to do. For example, many Birds crouch down in a hunched posture before taking flight. In many cases such actions are thought to have evolved into signals as they often occur during courtship and aggressive encounters and so indiCate the Animal's intentions to its partner or rival.

Interference competition

Competition in which one species prevents the other from having access to a limiting resource.

Interspecific competition

Competition between individuals of different species.

Intraspecific competition

Competition between individuals of the same species.

Introduced species

Species present in an area due to deliberate release by humans (including reintroductions, transplants, and restocked species) or due to accidental release through escape or indirect assistance.

Invertebrate

Any animal without an internal backbone, or spine, is called an invertebrate. A vast and varied assemblage, such creatures constitute about 95 percent of all animal species, and they range in size and complexity from microscopic protozoans to the 50-foot giant squid. The largest group, the arthropods, includes insects, crustaceans, spiders, and other creatures distinguished by the possession of jointed legs and hard outer coverings. The mollusks, found in almost every habitat, form another large and adaptable group; it includes animals with shells, such as clams and snails, as well as others whose shells are buried in their bodies (squid) or missing altogether (octopuses). Worms, sponges, corals, brachiopods-these and many more creatures are numbered among the invertebrates. Their activities, from pollinating flowers to aerating the soil, are vitally important in the food chain and in every kind of ecosystem.

Iris

Anyone who has ever bought a spring bouquet will recognize these striking flowers and their dramatic swordlike leaves, for the wild irises that adorn our countryside bear an unmistakable resemblance to the cultivated species. Like the florist's blooms, the wildlings-many of them known as flags-flaunt three upright petals and three drooping petallike sepals, which on some kinds sport a fuzzy ridge, or "beard." In spring and early summer the irises put on a spectacular show across much of the country. Violet-colored blue flags dot moist meadows and woodlands in the East, while the similarlooking Rocky Mountain iris is well known throughout the West. In the Southeast, marshes, streambanks, and bayous are enlivened by tall and tawny red flags, and the yellow flag is a familiar ornamental from coast to coast.

Iron

The fourth most abundant element in the earth's crust, iron lacks the shimmering beauty of silver and the lustrous yellow sheen of gold but is nevertheless of inestimable value, for it is the most widely used of all metals. All plants and animals contain small amounts of iron. Humans especially need it for healthy red blood cells, where it plays a crucial role in the transport of oxygen. But iron is also the basis for the manufacture of steel and countless other products. The silvergray shiny metal is extremely malleable; it can be magnetized and is a good conductor of heat and electricity. Iron seldom occurs in its pure state in nature but combines with other elements to form many minerals. When oxidized, it rusts, thus adding magnificent color to rocks.

Jack

Popular as both game and food fish, the jacks are a large family that can challenge even the most experienced angler. Fast swimmers that are apt to head for deep water and shoot straight downward, these fish of tropical and temperate seas display fight and strength far out of proportion to their size. And they are able predators, sometimes herding anchovies and other small fish into dense schools before striking. Ranging in length from six inches to five feet, the jacks have deeply forked tails and, often, an iridescent silvery sheen. Well-known members of the family include the amberjacks, tenacious game fish named for their golden hue; the pompanos, delectable food fish; and the California yellowtails, so prized that their numbers have dwindled. Another, the pilotfish, which travels alongside sharks and ships to pick up scraps, was once thought to lead sharks and whales to food and guide lost ships to land.

Jack-in-the-pulpit

Arisaema triphyllum

A familiar sight in eastern woodlands, the Jackin-the-pulpit is a member of the arum family, which includes such related plants as skunk cabbage and calla lilies. Up to three feet tall, it blooms in early spring, producing distinctive hooded flower spikes. The purple-striped or green "pulpit," called the spathe, arches over "Jack," a fleshy clublike spike-known as the spadix-with many tiny flowers hidden at its base. By fall, after the flowers have passed, the spathe withers to expose a cluster of bright red berries. Also known as Indian turnip, Jack-inthe-pulpit has corms, or bulblike roots, that long ago were cooked and eaten as vegetables by Native Americans. Inedible when raw, the corms were also ground for poultices and dried for a variety of medicinal uses.

Jackrabbit

See Hare.

Jaeger

Stercorarius

Hawklike relatives of gulls, jaegers are pirates of the high seas. Swift and streamlined, with long central tail feathers, they shamelessly bully terns and gulls, grabbing fish from their bills, making them drop hard-won prey, and even forcing them to disgorge fish already eaten. They are also formidable hunters in their own right, equipped with hooked beaks and sharp talons. On their nesting grounds on the Arctic tundra, all three species of jaegers feed regularly on such prey as lemmings and small birds.

Jay

Far more colorful than their larger, somber-hued cousins, the crows, jays are adaptable, aggressive birds that usually live in woodlands and often nest in gardens and backyards. Just as inquisitive as the crows, they are often the first birds to spot predators and sound the alarm. They feed on insects and the eggs and young of other songbirds, as well as seeds and nuts, including acorns, which they thriftily bury for winter use. The handsomely crested blue jay is a familiar bird at backyard feeders in the East, where its nest-robbing habits and raucous cries have given it a reputation as a pest. A western relative, the Steller's jay, inhabits coniferous forests in the mountains. The scrub jay lives in chaparral, pine-oak woodlands, and juniper thickets in the West; an isolated population in Florida is separated from its relatives by more than 1,000 miles. The stocky, crow-shaped pinyon jay likes to travel in large flocks and feeds on the seeds of pinyon pines. Another type, the fluffy gray jay, is a bird of northern spruce and fir forests. It often flies into camps to steal food-a habit that has earned it the epithet camp robber.

Jeopardy biological opinion

Endangered and Threatened species term.

A Service Section 7 biological opinion that determines that a Federal action is likely to jeopardize the continued existence of listed species or result in the destruction or adverse modification of critical habitat.

Jellyfish

These primitive marine animals without backbones or brains are not fish at all but are related to corals, sea anemones, and hydras. Jellyfish have broad, bell-shaped bodies made of translucent gelatinous material. The mouth and four trailing lobes hang from the underside of the bell, and many long, threadlike tentacles dangle from its edge. The tentacles are armed with poisonous stinging cells, which jellyfish use to capture small fish, planktonic animals, and other prey. Since they can also sting humans, they are unwelcome at bathing beaches.

Jellyfish can swim feebly by contracting and relaxing their bells, but for the most part they drift with the currents and winds. Occasionally they swim upside down, their tentacles floating above them. The moon jelly, a species that is common off our Atlantic, Pacific, and Gulf coasts, is 8 to 10 inches in diameter. Another, the by-thewind sailor, is less than four inches across and has a triangular "sail" projecting from the top of its body. The lion's mane, the giant of the clan, is a venomous resident of northern seas. Over 6 feet in diameter, it has tentacles more than 100 feet long.

Jet stream

Giant rivers of air that flow at high velocity about seven miles above the surface of the earth, the jet streams circle the globe from west to east. They blow in narrow bands at an average of 60 miles an hour, though speeds of 300 miles an hour and more have been recorded. Associated with turbulence in the lower parts of the atmosphere, jet streams have a definite effect on weather patterns. These ribbons of wind were first discovered by airplane pilots during World War II. Flying eastward, they found that they could arrive at their destinations well ahead of schedule if they were able to catch a jet stream.

Joe-pye weed

Eupatorium

The curious name of the joe-pye weed honors an Indian healer who, according to legend, used the plants to cure an epidemic of typhus in the Massachusetts Bay Colony. In moist meadows and woodland clearings, they are among the most conspicuous wildflowers of late summer, when their broad, fuzzy clusters of pinkish-purple blooms appear atop stout stems three to seven feet tall. When bruised, the lance-shaped leaves of one species, sweet joe-pye weed, give off an aroma very much like vanilla. The similarlooking spotted joe-pye weed has purple or purple-spotted stems.

Jojoba

Simmondsia chinensis

A hardy survivor that can live for a century,jojoba is a shrub that thrives in the dry, salty soils of southwestern deserts, where rain is scarce and temperatures often soar. The plant grows up to 8 feet tall and gets much of its moisture by sending a taproot 35 feet into the ground. This attractive evergreen has stiff, branching stems and oval, leathery leaves. Its pale greenish flowers are unremarkable, but the acornlike fruits are unique and valuable. Their peanut-size kernels yield a liquid wax that is much in demand for cosmetics and as an industrial lubricant. Very similar to the oil of sperm whales, the substance has been valued as a substitute for whale oil since the great mammals became endangered. Because it resembles boxwood,jojoba is gaining favor in parts of the Southwest as an ornamental shrub. In other arid regions of the world, it has been transplanted to help stabilize soils and stop the spread of deserts.

Joshua tree

Yucca brevifolia

A plant unlike any other, the Joshua tree ornaments the Mojave Desert with picturesque, grotesquely branching silhouettes. It was named by early Mormons, who likened the tree to the biblical Joshua beckoning them to the Promised Land. Starting life as a dense rosette of bluegreen, daggerlike leaves, this oversized member of the agave family sends a single stem 8 to 10 feet into the air. Then, after its first flowering, it begins to spread its branches in characteristically striking patterns. At maturity the Joshua tree may reach a height of 30 to 50 feet, with a trunk 31/2 feet in diameter. From late February to early April, it produces clusters of six-petaled yellowgreen blossoms, fertilized by the night-flying yucca moth. The blooms produce abundant crops of seeds, which Indians used to grind into meal. The tree's wood has been used for everything from paper pulp to surgeon's splints.

Jumping mouse

Named for their habit of moving across the ground with bounding leaps, jumping mice inhabit woodlands and meadows. The small yellowish rodents have long hind legs that enable them to jump up to six feet, and exceptionally long tails that help them maintain balance when leaping. Jumping mice are elusive creatures that hide by day and forage at night for grass seeds, fruit, and insects. Unlike most mice, they do not store food but put on a thick layer of fat in the fall in preparation for six to eight months of hibernation. After emerging in spring, they mate and give birth to a litter of young several weeks later. The woodland jumping mouse of the Northeast prefers brushy areas near water; the meadow jumping mouse is found in some of the northern states and across Canada.

Junco

Small, gregarious birds that resemble sparrows, juncos are found in coniferous and mixed forests and at the edges of woodlands throughout North America. Hopping about on the ground, they forage for seeds in winter and include insects, spiders, and wild fruits in their diet in summer. They also nest on the ground, building well-hidden cups of rootlets, grass, and moss. After nesting, juncos gather in flocks that migrate south or into lowland areas. Tame and trusting, they are welcome visitors at bird feeders. Several races of juncos formerly regarded as separate species are now known as dark-eyed juncos. All have pink conical bills and white outer tail feathers but are otherwise quite variable. The yellow-eyed junco, a second species, lives in the mountain forests of the Southwest.

Juniper

Juniperus

These aromatic evergreens flourish on dry, rocky soils throughout most of North America. Though all junipers have durable, closegrained, soft wood, and pungent, semifleshy cones resembling berries, these trees are a diverse group that varies in form and height. The alligator juniper of the Southwest, for instance, is a spreading tree that reaches heights of 65 feet and has scalelike foliage that overlaps like the shingles on a roof. The widespread common juniper, in contrast, is a sprawling shrub with pointed needles. Cedar chests are made from the wood of another common species, known as eastern red cedar, and the berries of the common juniper are used for flavoring gin.

Juvenile

A newly fledged bird that has not yet acquired adult plumage, a young animal.

Kame

Domelike hills of glacial debris, kames were deposited by streams of meltwater flowing into crevasses or pouring off the leading edges of stagnating glaciers and ice sheets. They range in height from just a few feet to 100 feet or more and are generally composed of a mixture of sand and gravel. Especially common in Wisconsin, Michigan, Indiana, and other areas near the southernmost limits of the vast continental ice sheets of the Ice Age, kames are a good source of sand and gravel for road construction as well as for other purposes.

Kangaroo mouse

Microdipodops

At six inches long, including the tail, kangaroo mice are about half the size of their more familiar cousins, the kangaroo rats. Like their kin, though, they have powerful hind legs that enable them to leap across the deserts and sagebrush flats of the Great Basin in Nevada and neighboring states. Relatively rare, by day the little rodents retreat into burrows among the roots of desert plants and seal the entrances with sand to keep out the heat. They come out at night to feed on seeds and insects but have no need for drinking water, obtaining it instead from their food as it is metabolized.

Kangaroo rat

Dipodomys

Like their Australian namesakes, kangaroo rats have sturdy hind legs and long tails. Agile creatures of the night, they leap gracefully across deserts and dry plains in the West, using their tufted tails for balance. They are gentle, attractive animals, with large heads, large eyes, and tawny, silklike fur. Kangaroo rats stay in their burrows during the heat of day, emerging after dark to forage for seeds, grass, and roots, which they carry back to the nest in fur-lined pouches on their cheeks. Well-adapted to life in the desert, they do not need to drink water. The little moisture that they require is obtained as a by-product of digestion of their food.

Kaolinite

A soft, whitish clay mineral, kaolinite is produced by the decomposition of feldspar and similar materials. As water seeps into soil or rock that is rich in feldspar, the feldspar gradually weathers to form kaolinite. Sometimes called china clay, it is widely used in pottery and ceramics and as a coating and filler in paper products. Our most important deposits of kaolinite are found in Georgia, North and South Carolina, Florida, and Pennsylvania.

Kaspar Hauser

An Animal Behavior term, this is used to describe a boy found in Nuremberg in 1828 who behaved as a child and later claimed to have Been raised by a man in total isolation. He has given his name to the Kaspar Hauser or deprivation experiment in which Animals are reared in isolation and the effect of this on the development of their behavior is noted.

Kaolinite

Katydid

More often heard than seen, katydids fill summer nights with shrill, monotonous music. Best known is the so-called true katydid of the East, which seems to recite its own name over and over again. Their chirping sounds, produced by rubbing one wing against the other, are courtship calls that enable the sexes to find each other and mate. The males' loud serenades are usually answered by the shorter chirps of the female.

Closely related to the grasshoppers, katydids have long, threadlike antennae. Most are green, matching the vegetation on which they rest, and their wings are often ridged and veined to resemble leaves. The insects feed on the leaves and tender twigs of trees and shrubs.

Kentucky coffeetree

Gymnocladus dioicus

Native to the Midwest, where it prefers deep, rich, moist soils, the Kentucky coffeetree is, throughout its range, one of the last trees to leaf out in spring and one of the first to shed its enormous, twice-compound leaves in the fall. In late spring it is covered with large upright clusters of greenish-white flowers, with those on female trees producing broad, leathery, reddish-brown pods. They contain large seeds that pioneers used to brew a coffee substitute.

Kettle

Bowl-shaped depressions, often filled by ponds, are a common sight on the outwash plains of long-vanished Ice Age glaciers. Known as kettles, they usually are quite deep and can be up to a mile in diameter. They formed where blocks of ice were buried in the sand and gravel left behind by retreating glaciers. As the ice slowly melted, the covering debris collapsed, leaving a gently sloping depression on the surface of the land. Many kettle ponds are found in Michigan and Minnesota, on Cape Cod and Long Island, and on other dumping grounds of the great Ice Age glaciers.

Key factor analysis

A statistical treatment of population data designed to identify factors most responsible for change in population size.

Keystone species

A species whose abundance dramatically alters the structure and dynamics of ecological systems.

Kill

To kill means to extinguish and hence cause the death of a living thing. The concept of killing is most general, with no implication of the manner, justification, or purpose of killing, or nature of what is killed. A negative aspect of killing is to kill either immorally, unjustly and without proper reason, or with premeditated intent. A controversial form of killing is to kill a person marked for death by the laws, courts and government of the state, in a manner sanctioned by that state, whether by law or decree. Another negative aspect of killing is to kill a person marked for death, with the intent of furthering ideological or political goals.

Killdeer

Charadrius vociferus

Perhaps the best-known shorebird in North America, this member of the plover family nests in all 49 mainland states and much of Canada. A bird of open places- from pastures and meadows to airports and golf courses- the killdeer is named for its piercing kil-dee call, which it often rings out while in flight.

The killdeer lays its buff-colored, darkblotched eggs in a nest that is nothing more than a shallow depression in the ground lined with pebbles or a few bits of vegetation. Choosing any open stony area, it even nests on driveways and little-used gravel roads. The killdeer is famous for its "broken wing" display. When intruders appear in the nesting area, they are confronted by a creeping, wingdragging, piteously crying adult. Its splayed tail reveals the bright orange rump, a beacon that further distracts potential predators and helps draw them away from the nest full of eggs or tiny chicks.

Killifish

Only a few inches long, the killifish are often confused with minnows. Some of them, in fact, are called topminnows because of their habit of feeding at the water's surface. Equipped with upturned mouths adapted for that purpose, killifish consume large quantities of mosquito larvae and are valued for their role in keeping the insects under control. Of the several dozen species of killifish in North America, most live in the South. They thrive in fresh, salt, or brackish water, and some of the desert dwellers-called pupfish-can

survive temperatures of up to lOO°F. A few killifish, such as mummichogs, are used for bait, while many of the brightly colored kinds, such as pygmy killifish, are popular aquarium fish.

Kinesis

An Animal Behavior term, this is used to describe movement of an Animal which is affected by a stimulus but not oriented with respect to it. Thus, Animals that turn less or move more quickly in the light tend to accumulate in darker places without the direction of the light necessarily affecting them.

Kingbird

Tyrannus

Bold and belligerent, the kingbirds are indeed lords of their domain, as their name Tyrannus implies. When a larger bird, such as a hawk or crow, flies through a kingbird's territory, the fearless little defender immediately takes chase. Scolding the larger bird with staccato squeaks, the kingbird even goes so far as to land on the interloper in flight, pecking at its back until feathers fly and the trespasser is driven away. The kingbirds' aggressive instincts are so strong, in fact, that the birds have even been sighted attacking low-flying airplanes.

Our two most widely distributed species are the black-and-white eastern kingbird and the pale gray and lemon-yellow western kingbird. Like other flycatchers, they feed by swooping out from exposed perches to snatch up flying insects, often with an audible snap of the bill. Especially fond of honeybees, the birds have earned the nickname bee martins. Kingbirds also feed on berries in summer and fall: hovering near shrub dogwoods and elderberry bushes, they dart in repeatedly to nip off the ripening fruits.

Kingfisher

Spirited and able anglers, kingfishers regularly station themselves on branches over lakes or streams and intently eye the water below. When a fish flashes by, the bird plunges into the water and snaps it up with its stout, daggerlike bill. Flying to a nearby perch, it often beats the wriggling fish against a branch, tosses it into the air, and swallows it headfirst. Kingfishers sometimes vary their hunting technique, hovering in midair as they scan the water for fish. Whether perched or on the wing, they frequently fill the air with loud, rattling calls. In summer, male and female kingfishers take turns excavating a nesting burrow up to 15 feet long in a steep sand or gravel bank, usually near a stream or river. They loosen the dirt with their beaks and kick it out with their feet. Then, in a chamber at the end of the tunnel, the female lays her glossy white eggs on a bed of fish bones and scales. The young, fed on small fish, leave the nest when they are some three weeks old. The species seen throughout North America is the belted kingfisher, a chunky, blue-gray bird with a big head and a ragged crest. Two others, the ringed kingfisher and the green kingfisher, are found only in southern Texas in the United States.

Kinglet

Regulus

Tiny, plump, grayish-olive birds, the kinglets are most often seen in trees, flitting restlessly from branch to branch as they pluck insects and their eggs and larvae from the foliage and crevices in the bark. They summer in northern coniferous forests, where they build elaborate, globular nests of moss and spiderwebs, lined with feathers, fur, and plant fibers. Their eggs, up to nine to the clutch, are creamy white with dainty speckles. In winter they range south as far as Mexico and often roam the woodlands in mixed flocks, keeping company with chickadees, brown creepers, and other small birds. The ruby-crowned kinglet is named for the males' red crown patch, though it is visible only when they are excited. About four inches long, these birds produce a surprisingly loud, melodic song. Golden-crowned kinglets are named for the crowns worn by both sexes.

Kingsnake

Lampropeltis

Formidable enemies of both rats and mice, kingsnakes are valued by farmers for keeping down populations of the rodent pests. Since they are immune to the venom of rattlers and copperheads, kingsnakes sometimes feed on these poisonous reptiles as well. They kill by constriction, coiling around their victims and suffocating them, as do their close relatives the milk snakes (so named for their supposed ability to suck milk from cattle).

Kleptoparasitism

An Animal Behavior term, this is used to describe the habit of some Animals, such as the Parasitic jaeger, of living on food stolen from other species.

Knapweed

Centaurea

Adorning fields and roadsides throughout the summer and into fall, the knapweeds are best recognized by their thistlelike flower headstufts of tubular blue, purple, pink, or white florets that emerge from a sheath of prickly bracts. Many species are found across the continent, including a garden favorite, the bachelor's button. The knapweeds range from one to four feet in height, with lance-shaped or divided leaves.

Knotweed

Polygonum

Among the most aggressive, widespread weeds of roadsides, lawns, and cultivated ground, the knotweeds are named for their swollen stem joints. Some, because of their leaves' biting flavor, are also known as smartweeds. Blooming through summer and fall, the knotweeds bear small pink or greenish-white flowers which usually grow in dense spikes. The water smartweed has large pink flower clusters and thrives in ponds and muddy places. Japanese knotweed forms thickets of bamboolike lO-foot-tall shoots and is almost impossible to eradicate. Others-such as lady's thumb, with a dark "thumbprint" near the center of each leaf, and pinkweed, named for its pink flower spikes-flourish in yards virtually everywhere.

Kudzu

Pueraria lobata

Arriving as a gift from Japan at the Centennial Exposition in Philadelphia in 1876, kudzu was once touted as the Savior of the South. With roots that penetrate deep into the soil, the vine promised a solution to the problem of erosion. Its ability to take nitrogen directly from the air and fix it in the soil seemed to make it ideal for restoring fields exhausted by generations of tobacco and cotton culture. And its broad, bright green, three-part leaves were even more nutritious than alfalfa. But kudzu turned out to be too successful, adding a foot of growth each day and sending vines to the tops of tall trees in a single season. While insects, diseases, and colder weather kept kudzu in check in the Orient, the pest flourished in the warm, moist South, smothering 11,000 square miles by the 1980's.

La Niña

La Niña is an extensive cooling of the central and eastern Pacific Ocean that occurs less frequently than El Niño and is its climatic opposite. It occurs when easterly trade winds in the tropics strengthen, intensifying the up-welling of cold waters off the coast of Peru and Ecuador. The effects of La Niña are strongest during the Northern Hemisphere winter, and include abundant snowfall from the interior of British Columbia to the Great Lakes region.

Lacewing

Delicate insects with diaphanous, conspicuously veined wings, lacewings are found throughout North America. Their abdomens are long and slender, and their folded wings resemble tiny tents. Green lacewings live in meadows and gardens, while the less common brown lacewings are more often seen in wooded areas. The larvae of both kinds, like the adults, feed so ravenously on aphids and other soft-bodied insects that they are often known as aphid lions.

Ladybird beetle

Small, round, and colorful, ladybird beetles, or ladybugs, are among our most beneficial and popular insects. Red or yellow with black spots, or black with red or yellow spots, they look like brightly enameled half-peas. They were named after Our Lady, the Virgin Mary, in the Middle Ages. Over the centuries since then, legends about these attractive insects have abounded. Their usefulness, however, is not a matter of folklore: formidable predators, both adults and larvae devour huge numbers of aphids and other harmful insects. Over 150 species of ladybird beetles are found in North America, and almost all are helpful to farmers and gardeners. In the late 1800's an Australian species was imported to combat an insect pest that was plaguing California citrus orchards. The venture proved to be so successful that ladybird beetles are now raised commercially as natural pest controls.

Lady's slipper

Cypripedium

Among the most elegantly beautiful of all wildflowers, lady's slippers are easily recognized by the distinctive slipper-shaped pouch formed by one of their petals. The structure is more than decorative, however. Insects lured into the pouch can escape only through an exit where they are well dusted with pollen, ensuring crosspollination of the plants. These hardy members of the orchid family flourish in bogs and moist woodlands all across the continent. Their lovely pink, yellow, or white blossoms often tempt would-be transplanters. But because the plants cannot survive without the aid of microorganisms in their native soil, they must be admired only in the wild.

Lake

Scattered like jewels across the American landscape, lakes are rich in both beauty and wildlife. Most of these sizable inland bodies of water were formed by glaciers. The icy bulldozers either scarred the bedrock with depressions that later filled with water, or dumped tons of debris in the paths of rivers, creating natural dams. Some lakes occupy volcanic craters, some are man-made, and others were created by the erosion of limestone or movements of the earth's crust. Whether fed by runoff from rain and melting snow or by underground springs, lakes often seem as eternal as the earth itself, but in fact they are short-lived on the scale of geologic time. Some are destined to dry up after a change in climate, and others will be filled with stream-fed sediment. Most shallow lakes, however, expire from eutrification, the process by which the accumulation of organic debris turns lakes into swamps and eventually dry land.

Lamprey

Primitive, scaleless fish that resemble eels, lampreys grow up to three feet long. They lack the jaws, bony skeletons, and paired fins of their more advanced relatives. Most, armed with a circular mouth and horny teeth, live as parasites, attaching themselves to other fish and sucking their blood. Some lampreys live entirely in lakes and rivers, while others venture into the sea. In spring they swim up freshwater streams to scoop out nests and spawn. The wormlike larvae, called ammocoetes, burrow into the mud of riverbeds, where they feed on tiny particles of organic matter. After several years they mature into adults and make their way back to the lake or ocean from which their parents came. Lampreys have at times been used as food; in some cultures, they are a delicacy. But generally they are regarded more as pests, especially in the Great Lakes, where parasitic lampreys killed vast numbers of trout and other fish before measures were devised to keep their numbers in check.

Lanceolate

Meaning lance-shaped.

Landscape

The landforms of a region in the aggregate; the land surface and its associated habitats at scales of hectares to many square kilometers (for most vertebrates); a spatially heterogeneous area; mosaic of habitat types occupying a spatial scale intermediate between an organism's normal home-range size and its regional distribution.

Landscape change

Alteration in the structure and function of the ecological mosaic of a landscape through time.

Landscape complementation

Changes in population caused by the relative distributions of habitat patches containing nonsubstitutable resources in a landscape. Example: increased populations in a portion of a landscape where foraging patches and roosting patches are adjacent, compared with parts of the landscape where these patches are isolated (see Landscape supplementation).

Landscape composition

The relative amounts of habitat types contained within a landscape.

Landscape ecology

Field of study that considers the development and dynamics of spatial heterogeneity, interactions and exchanges across heterogeneous landscapes, the influences of spatial heterogeneity on biotic and abiotic processes, and the management of spatial heterogeneity.

Landscape function

The interactions among the spatial elements, that is, the flow of energy, materials, and organisms among the component ecosystems.

Landscape indexes

Indexes of landscape structure (pattern), including richness, evenness, patchiness, diversity, dominance, contagion, edges, fractal dimension, nearest neighbor probability, and the size and distribution of patches.

Landscape physiognomy

Features associated with the physical layout of elements within a landscape.

Landscape structure

Spatial relationships between distinctive ecosystems, that is, the distribution of energy, materials, and species in relation to the sizes, shapes, numbers, kinds, and configurations of components; composition and extent of different habitat types (landscape composition) and their spatial arrangement (landscape physiognomy) in a landscape.

Landscape supplementation

Changes in populations caused by the distribution of habitat patches containing substitutable resources in a landscape. Example: increased population in a small patch found in a portion of the landscape where residents can easily forage in other nearby similar patches (see Landscape complementation).

Landslide

Terrifying and destructive, landslides occur when soil and rock on steep hillsides come loose and hurtle downward, sweeping away everything in their path. Sometimes landslides are triggered by earthquakes, but more often they are caused by heavy rain that soaks the ground and acts as a lubricant. One of the worst landslides in North America occurred in Montana in 1959, when an entire mountainside, jolted by an earthquake, collapsed into the Madison River gorge. Over two dozen people were killed, and the gorge was heaped with so much debris that it dammed the river and created a new lake.

Language

An Animal Behavior term, this is a term usually applied only to the verbal communiCation system of Humans, but sometimes also applied to aspects of Animal communiCation. That language in Humans can be sharply distinguished from all Animal signals has become increasingly doubtful and an elaboRate definition is required if it is to exclude all Animal examples.

Larch

Larix

Two traits distinguish the larches from all other coniferous trees: their soft, flat needles grow along the twigs in tufts that resemble brushes, and the needles are shed in autumn, leaving the trees naked except for their little upright cones. The eastern larch, or tamarack, which ranges from the Northeast into western Canada, is our most widely distributed species. The western larch, twice as tall at 150 feet or more, is an important timber tree in the Pacific Northwest.

Larkspur

Delphinium

Arranged on slender stalks up to seven feet tall, the showy blue, white, or purple blossoms of the larkspurs each have a long, pointed "spur." Actually a narrow tube, the structure serves as a repository for the nectar that tempts the plant's pollinators, which include bumblebees, moths, and butterflies. Flourishing in a wide range of habitats, larkspurs are found from the moist woodlands of the Northeast to the dry prairies of the plains states and the slopes of western mountains. Because all parts of the plants are poisonous, the larkspurs have earned a sinister reputation in cattle country.

Larva

Soft-bodied, pre-adult stage in the life-cycle of certain insects. At birth or hatching, many animals look like miniature versions of the adults, while others begin their lives as larvae completely different from the adults. The latter must undergo a dramatic transformation, or metamorphosis, before they become fully mature. Larval stages are most common among invertebrates, especially insects and creatures that live in water. Beetle grubs and the caterpillars of butterflies are examples of air-breathing insect larvae. The larvae of other insects, such as dragonflies and alderflies, may spend up to two years in the water, eating voraciously, before they develop into winged, short-lived adults. Marine animals such as sponges, oysters, crabs, and jellyfish also have larval stages. Among vertebrates, some fish produce larvae, but the most familiar examples are the tadpoles of frogs and toads.

Lateral line

A sensory organ along the side of a fish that senses pressure changes

Lava

Molten rock that erupts onto the surface of the earth through volcanos or fissures in the crust is called lava. It can be tllick and viscous or fluid and fast flowing. It also is fiery hot, with temperatures as high as 2200°F. As lava cools, it forms many kinds of igneous rocks. Some are very dense in composition but harden too rapidly to produce visible crystals. Oiliers, like pumice, have a spongy texture and are almost weightless because gases are quickly trapped as the lava becomes solid. Rapid chilling of lava results in obsidian, a black glassy rock. When extruded underwater, lava sometimes solidifies into blobs known as pillow lava. So-called basaltic lavas tend to be more fluid and often pour out of fissures in the earth, burying hundreds of square miles (such as the eastern two-thirds of Oregon and Washington) under thick sheets of rock.

Law

A rule enacted through legislation that prohibits certain actions and is enforced by the imposition of penalties. There are many environmental and wildlife laws aimed at protecting and conserving the environment-some developed because of domestic concerns, and others as a result of international agreements.

Lead

See Galena.

Lead region

Endangered and Threatened species term.

The Fish and Wildlife Service Region that is responsible for coordinating all actions taken to study, propose, list, conserve, and delist a species.

Lead office

Endangered and Threatened species term.

The field office that has been given the responsibility for coordinating all or most actions taken to study, propose, list, conserve, and delist a species within the boundaries of Region 3. If Region 3 is the lead region for a particular species, the lead office has these responsibilities over the entire range of that species.

Leaf

Fundamentally, a leaf is a factory that, by the process of photosynthesis, uses the energy from sunlight to manufacture the sugars and starches that nourish the growth of an entire plant. The flat part of a leaf, its "blade," is actually a highly efficient solar collector, while the veins serve not only as reinforcing ribs but also as a circulatory system. The interior of the leaf, where most of the photosynthesis occurs, is protected on both top and bottom by an epidermis, a tough, wax-coated skin that protects the leaf against dehydration. Pores, or stomata - many thousands per square inch-perforate the epidermis. They can be opened and closed to control the movement of carbon dioxide and oxygen in and out of the leaf. The pores also regulate the escape of excess water, for a leaf serves, too, as an evaporative cooler that keeps the plant from overheating when the temperature rises. The shapes of leaves vary widely from species to species and are among the most reliable clues in plant identification. Needles and scales identify the many different types of conifers, while among broad-leaved plants leaves may be simple (undivided, like those of elms or birches) or compound (composed of numerous leaflets, like the leaves oflocusts and ash trees).

Leafhopper

Tiny, wedge-shaped jumping insects that often are colorfully patterned, leafhoppers feed by sucking juice from the stems and leaves of plants. In the process the host plants, deprived of sap, are stunted and eventually wither. Widespread pests that also cause havoc by transmitting plant diseases, leafhoppers are harmful to a wide range of shrubs, trees, and grasses; apple, bean, potato, beet, and grape crops are particularly susceptible to infestation. The bane of many a gardener, leafhoppers also attack a rainbow of flowers, among them roses, asters, and forsythia. As they sip plant fluids, the insects expel a sweet liquid, called honeydew, that attracts ants, wasps, and flies.

Leaflet

Small, separate segment of a leaf.

Leaf miner

Pale lines winding just beneath the upper surfaces of leaves usually mark the tunnels of leaf miners, the tiny larvae of several kinds of insects, including flies, sawflies, moths, and beetles. When an adult female lands on a leaf, she cuts a hole in its epidermis and deposits an egg in the soft tissue inside. The colorless, wormlike larva that hatches from the egg then gnaws an erratic path through the tissue until, about a week later, it pupates and is transformed into an adult. Though unsightly, the damage done by leaf miners seldom results in serious harm to the host plants.

Leatherback

Dermochelys coriacea

Weighing up to 1,200 pounds, the leatherback is the world's largest turtle. This seafaring giant, named for its dark, Iidged, rubbery carapace, navigates vast distances across the Atlantic and Pacific oceans, swimming strongly with its huge, oarlike forelimbs. While it generally prefers tropical waters, the reptile has been spotted as far north as Canada. Leatherbacks usually mate every other year, with the females then swimming thousands of miles to warm nesting grounds. There they haul themselves ashore at night, dig a hole with their hind flippers, lay 80 to 100 round white eggs, and then return to the sea. The turtles, however, are in dire danger of extinction. Their nests are often plundered, and many adults are killed by acczident. They also drown while entrapped in fishnets or die after eating floating plastic, which they mistake for jellyfish, their primary food.

Leech

Relatives of the earthworm, leeches are generally found in fresh water (though some inhabit moist soil) and live as bloodsucking parasites. Using a sucker at the hind end of the body, they attach themselves to passing animals or humans. Then they pierce the skin and feast on blood with a front sucker. An anticoagulent keeps the victim's blood flowing freely until the sated worm drops off. One such meal can last a leech for months. Used by medical practitioners in the past, leeches are making a comeback, having proved useful for taking up unwanted blood during microsurgery.

Legume

A huge family of flowering plants, the legumes include some 15,000 species of trees, shrubs, herbs, and vines. AltllOugh they exhibit a great deal of variability, all species are distinguished by their pealike fruits-pods that, as they dry, split along both sides to scatter the seeds. Legumes are found almost everywhere, and much of their success is due to their ability to enrich the soil in which they grow. Most species have nodes on their roots inhabited by bacteria that can transform atmospheric nitrogen into nitrates that are usable by plants. As a result, legumes are among the first colonizers of poor or disturbed soils. Second only to the grasses in economic importance, the legumes yield a wide variety of useful products. Because their seeds contain an abundance of protein - two to three times as much as wheat or corn-many legumes, such as soybeans and peanuts, are valuable food crops. Others, including clover and alfalfa, provide nutritious forage for livestock. Some, such as the desert shrub mesquite, are harvested for firewood, and some are used for cabinetmaking and fine furniture. Still others-wisteria and sweet peas, for example-are enjoyed simply for their lovely, sweet-scented flowers.

Lek

Probably derived from a Swedish word meaning "to play," the term lek refers to an area where birds gather communally to enact their courtship rituals. Male prairie chickens and several other grouse, for example, compete for females on the lek by strutting, bowing, and displaying their plumage. At the same time, they inflate colorful air sacs on their necks or breasts to produce loud booming sounds that can be heard for miles. The hens, meanwhile, stroll among the performers and choose a mate, then go off to nest and rear their young alone.

Lek

As an Animal Behavior term, this is used to describe a communal mating ground, used especially by many Bird species and a few Mammals, where males set up and defend small TERRITORIES packed close together in an arena. Females visit the area for mating and the sole function of the territories seems to be in female attraction. Communal display area used by certain bird species.

Lemming

Plump rodents that look like overgrown voles, lemmings are about six inches long with stubby tails and thick, silky fur. Most species are creatures of the Far North, where they live in colonies on damp meadows and open tundra and feed on tender grasses and roots. They nest in burrows, with each female producing as many as 30 young per year. Though tales of lemmings committing mass suicide are false, it is easy to see how the truth has been misinterpreted. Every few years, for unknown reasons, lemmings experience population explosions that trigger mass migrations. On occasion the processions become so frantic that great numbers of lemmings drown while trying to swim across lakes and rivers, and this has given rise to the myth of the suicide march.

Levels (Water)

The height of the surface of the water in a lake, river, sea etc. Water levels vary greatly depending on the amount of rainfall received over a given period of time, and the speed with which snow and ice melt in the spring.

Lichen

Find a crust of lichen clinging to a rock or tree trunk and you have discovered not one plant but two, for lichens are actually algae and fungi living together in intimate partnership. The alga, through photosynthesis, produces food to nourish both, while the fungus absorbs water, which keeps the alga moist, and shades its lightsensitive partner. In addition, some lichens serve the environment by secreting acids that help break rocks down into soil. Despite their amazing diversity of form, lichens can be grouped into three broad categories. The leafy types that cling to trees and rocks are foliose lichens; the granular kinds that form crusty patches on rocks are crustose lichens; and the branching tufts that are attached at the bottom or hang from trees are fruticose lichens. Though commonly green, lichens are also found in bright colors and are a source of natural dyes. One kind, called reindeer moss, is the major food of caribou and other foragers in the Far North.

Life form

Characteristic structure of a plant or animal.

Life history

A system of interrelated adaptive traits forming a set of reproductive tactics.

Life table

A summary by age of the survivorship and fecundity in a population, usually of females.

Life zone

A more or less distinct belt of vegetation occurring within, and characteristic of, a particular range of latitude or elevation.

Lightning

Beautiful but terrifying, the natural fireworks called lightning are the result of electrical discharges from clouds. As a storm cloud chums in the sky, it builds up a positive charge at the top and a negative charge at the bottom. When the voltage within the cloud becomes great enough, a powerful current of electricity passes between the negatively charged base of the cloud and the positively charged earth, creating the bright flash we see as lightning. The tremendous heat of a lightning bolt, greater than that on the surface of the sun, causes the air to expand explosively, and the resultant shock waves produce the sound we hear as thunder. Extremely dangerous, lightning kills well over 100 Americans a year, more than are killed by hurricanes or tornadoes. The worst places to be during thunderstorms are under isolated trees or on high ground; the safest places are in cars or buildings.

Lignite

Brown and crumbly, lignite can be thought of as coal in the making. Like the harder coals that are most often used for fuel, it is formed from dead plant material, or peat, that originated in ancient swampy forests. But it has not been subjected to the intense heat and pressure required to produce the harder coals. Lignite is burned for fuel in some places. Because it deteriorates during transport, however, it is used mainly by consumers located close to the mines.

Ligule

The embranous leaf sheath found in grasses.

Lily

In its broadest sense the term lily refers to a plant family that includes thousands of species, from onions and asparagus to tulips and trilliums. Most are perennial herbs that grow from bulbs, but some are woody, and a few, such as the greenbriars, are evergreens. On all, however, the floral parts-sepals, stamens, and so onoccur in multiples of three. Within the lily family, members of the genus Lilium are the so-called true lilies. These include a number of wild species, such as the wood lily and Canada lily, which brighten moist meadows and roadsides with showy trumpet-shaped blooms, and the chaparral lily, a plant of dry slopes in the West. Other well-known wild lilies range from beargrass and sego lilies to wild hyacinths and Solomon's seal.

Limestone

A common, widely distributed sedimentary rock, limestone is composed of the mineral calcium carbonate. It is usually grayish white, but iron and other impurities can stain it yellow, brown, and occasionally red. Often rich in fossils, most limestones are formed from the remains of ancient marine animals and plants. When the organisms died, their shells and skeletons rained down onto the ocean floor and were eventually compacted into thick beds of rock. Limestone can also form from the precipitation of calcium carbonate that is dissolved in seawater and hot springs.

Limiting factors

There are several limiting factors in an environment which determine whether an organism can live in a particular environment. Limiting factors on land include temperature, water, light, competition, and soil. Every organism needs certain requirements for its survival.

Most organisms can survive if the temperature is within a certain range. The freezing condition of the tundra has resulted in animals with thick fur, lots of body fat, and small ears. Animals in a desert will have large ears, like the elephant, to disperse body heat.

The amounts of sunlight and rainfall are also limiting factors for both plants and animals. Both affect plant growth. Which plants grow in a biome determines which animals inhabit that biome. For example, grey squirrels, which feed on nuts, are found in woodlands, but not in deserts where nuts aren't found.

Competition results when two different species try to fill the same niche. This usually results in one species displacing another species, or the extinction of one of the species.

Limpet

Small snails with flattened, conical shells, limpets are found along both coasts. They cling to rocks by means of a muscular, suckerlike foot and can survive the battering of even the most powerful waves. At high tide limpets creep about and scrape algae from the rocks with their rasping tongues. When the water recedes, each one returns to its home base-a slight depression hollowed into the rock-where it anchors itself until the return of high water.

Limpkin

Aramus guarauna

A denizen of freshwater wetlands in Florida and southern Georgia, the limpkin looks like a heron, flies like a crane, and acts like a rail. Named for its peculiar, halting gait, the chocolate brown, white-streaked bird wades the shallows of marshes, swamps and mud flats, capturing snails and other prey with its long, heavy, slightly down-turned bill. The bird's shrill wail, which can sound almost human as it echoes in the night, has earned the limpkin such nicknames as crying bird and mourning widow. In early spring mated pairs build shallow nests of sticks near the water, where they raise four to eight young. Limpkins teach their young to forage for shellfish at water's edge. Almost wiped out by aggressive hunters, limpkins are now protected.

Linnaeus, Carolus (b. 5/23/1707, d. 1/10/1778)

Listed species

Endangered and Threatened species term.

A species, subspecies, or distinct vertebrate population segment that has been added to the Federal lists of Endangered and Threatened Wildlife and Plants as they appear in sections 17.11 and 17.12 of Title 50 of the Code of Federal Regulations (50 CFR 17.11 and 17.12).

Endangered and Threatened species term.

The formal process through which the Service adds species to the Federal List of Endangered and Threatened Wildlife and Plants.

Listing moratorium

Endangered and Threatened species term.

Public Law 104-6 "Emergency Supplemental Appropriations and Rescissions for the Department of Defense to Preserve and Enhance Military Readiness Act of 1995" specifically prohibited ". . . making a final determination that a species is threatened or endangered or that habitat constitutes critical habitat . . . ." This measure was signed into law on April 10, 1995, and prohibits the listing of species as threatened or endangered or the designation of critical habitat.

Listing priority

Endangered and Threatened species term.

A number from 1 to 12 indicating the relative urgency for listing plants or animals as threatened or endangered. The criteria used to assign this number reflect the magnitude and immediacy of threat to the species, as well as the relative distinctiveness or isolation of the genetic material they possess. This latter criterion is applied by giving a higher priority number to species which are the only remaining species in their genus, and a lower priority number to subspecies and varieties. These listing priorities are described in detail in the Federal Register on September 21, 1983, as pages 43098-43105.

Liverwort

Primitive, prostrate relatives of mosses, liverworts are plants of moist, shady places, where they often spread in dense mats across soil, rocks, and rotting logs. Some are mere leathery, leaflike fronds; others are branched and lined with tiny rounded, overlapping leaves. Lacking true roots, they are anchored in place by threadlike rhizoids. Liverworts produce spores but also reproduce by means of tiny buds, called gemmae, that dot their surfaces.

Lizard

Closely related to snakes, lizards are reptiles and, like their legless cousins, have dry, scaly skins that protect them from dehydration. They are especially common in warm regions and can thrive in deserts and other places where moisture is scarce. Unable to regulate their internal body temperature, lizards warm up by basking in the sun and cool off by scuttling into the shade. Some species are vegetarians, but most feed on insects, rodents, and other small prey. Lizards may hiss, bite, inflate their bodies, or lash their tails in self-defense, but some have developed more unusual strategies. Homed lizards can squirt blood from the comers of their eyes. Others, including the glass lizard, rely on an even odder trick: when seized, the glass lizard's tail breaks off, and the amputated section, which continues to wriggle, distracts the enemy while the lizard escapes.

Lobelia

Filled with an acrid, milky juice, the upright stems of the lobelias are topped by lovely tubular flowers. Each has two lips, the upper divided into two lobes and the lower into three. Of our several native lobelias, the most spectacular by far is the cardinal flower, admired for its brilliant crimson blooms. Another, Indian tobacco, was once used medicinally and so earned such colorful nicknames as gagroot and asthma-weed.

Lobster

Well-known for their intimidating claws, protective shells, and tasty flesh, American lobsters are found off the Atlantic Coast from Labrador to the Carolinas. Lobsters, when taken from the ocean, are a dark greenish red. On the sea floor they rove about waving their antennae and swiveling their eye stalks as they search for food and watch for enemies. If lucky, they may live 50 years, but most caught in pots are far younger. Hiding by day in burrows or under rocks, they roam the ocean floor at night to scavenge and prey on crabs, snails, fish, and others of their own kind. Their two foreclaws are specialized: the larger one is used to crush hard-shelled prey, and the smaller one, equipped with sharp teeth, is used for tearing food apart. When confronted by enemies, lobsters flip their powerful abdomens to swim backward out of harm's way. Female lobsters produce thousands of eggs, which are carried under the abdomen until they hatch. The free-swimming larvae drift near the surface for a time, then sink to the bottom, shedding their hard shells periodically as they increase in size. Barring mishaps, lobsters may reach a length of two feet, weigh more than 20 pounds, and live for many decades. Spiny lobsters, found off the coasts of Florida and California, are named for the spines on their shells. Though they lack the large, meaty claws of the American lobster, they are often caught for the flesh in their muscular abdomens.

Local extinction

Disappearance of a population from a habitat patch or local area. Local extinctions can accumulate into regional extinctions and finally global extinction.

Locoweed

Oxytropis

Loco is Spanish for "crazy," and loco is indeed the way livestock behave after eating these lowgrowing prairie plants. Horses, cattle, and sheep become disoriented, unable to walk or see normally, and prone to violent frenzies. With no known antidote, the slow-acting poison in the plants often leads to death. Ironically, the locoweeds are an acquired taste, for animals avoid them when other food is available. Once they begin eating the plants, however, they keep coming back for more. Many species are native to dry soils in the West. Members of the pea family, all bear clusters of purple, red, or white flowers. The milk vetches also are called locoweeds and have the same deadly effects.

Locust

First appearing as huge gray clouds on the horizon, dense swarms of voracious locusts descend on western farmlands from time to time, devouring crops and grasslands, denuding shrubs and trees, and generally ravaging the countryside. The insects are actually various species of short-homed grasshoppers, whose populations explode in years when spring rains are particularly heavy. Abandoning their normally solitary ways, the locusts then gather into ravenous swarms that can number in the billions. A particularly notorious plague of locusts invaded the Great Plains in the 1870's and caused many millions of dollars' worth of damage.

Locust

Robinia

Trees of the pea family, the locusts can be recognized by their compound leaves, gracefully drooping flower clusters, and the armament of thorns on their branches. In spring the black locust, an attractive shade tree up to 80 feet tall, fills the air with the sweet perfume of its creamy flowers. In fall the blooms are followed by long, leathery pods containing hard, glossy seeds, which are eaten by squirrels and other animals. Its hard, durable wood is used for fence posts and railroad ties. The clammy locust, named for the sticky hairs on its twigs and pods, bears showy clusters of rose-colored, scentless blossoms and is also planted as an ornamental.

Loess

A sediment composed of fine rock particles created by the grinding action of Ice Age glaciers, loess was carried south by meltwater streams and later was blown eastward in what must have been enormous dust storms. Subsequent weathering of this blanket of sediment has created some of the richest soil on earth. It is thickest near the rivers, such as the high bluffs of the Mississippi not far from St. Louis.

Loggerhead

Caretta caretta

Large, lumbering sea turtles, loggerheads swim along at an average speed of one mile per hour, pausing now and then to bask at the ocean's surface. They are imposing animals that often weigh 500 pounds or more and are topped by domed shells up to four feet long. Their big heads are equipped with powerful jaws well suited for crushing the hard-shelled crabs and mollusks they sometimes eat; they also feed on sponges, fish, jellyfish, and plants. Every other year the females crawl out of the sea to lay their eggs on warm, sandy beaches, including a few sites on our South Atlantic coast. Despite the large numbers of eggs that they deposit, coastal development and overcollecting have caused their population to decline. Loggerhead females dig a deep hole in the beach, where they lay more than 100 leathery eggs the size of Ping-Pong balls. Afterward, they cover the eggs with sand and crawl back to the sea. When the eggs hatch eight weeks later, the tiny turtles immediately scramble down the beach into their ocean home.

Logistic equation

Mathematical expression for a particular sigmoid growth curve in which the percent rate of increase decreases in linear fashion as population size increases.

Longshore current

Flowing parallel to seashores and driven by prevailing winds, longshore currents occur where waves strike the shore at an angle. As they flow along the coast, longshore currents pick up sand and redeposit it farther downcurrent. Together with tides and rip currents, they are constantly reshaping the contours of sandy beaches, sandbars, and barrier islands. Trouble occurs when man interferes with this natural, dynamic process by building seawalls, jetties, and other devices meant to halt erosion. These structures trap sand on their windward side but prevent sand from being redeposited on the leeward side-thus saving one beach at the expense of others.

Longspur

Calcarius

Named for their elongated hind claws, longspurs are chunky, gregarious, sparrowlike birds. They are dull colored much of the year and can be hard to spot as they travel with flocks of homed larks and snow buntings, foraging for seeds on windswept plains. In the summer, however, the males wear brightly patterned breeding plumage. Even so, few people ever see them, for the chestnut-collared and McCown's longspurs nest only on northern plains, and the Lapland and Smith's longspurs on Arctic tundra.

Loon

Gavia

A characteristic and haunting sound of northern lakes is the loud, yodeling call of the common loon; echoing through the night air, it shatters the silence with what seems to be hysterical human laughter. Like all the loons, the common loon is a sturdy, goose-size diving bird with a stout, spear-shaped bill and webbed feet placed far back on the body for propulsion under water. During dives for fish, loons can remain submerged for five minutes or more and reach depths of 200 feet. Although the birds have difficulty walking, during the breeding season they venture ashore to incubate one to three speckled eggs in loose nests at the water's edge. Both parents share in the feeding and care of the downy chicks, which sometimes hitch rides on the backs of the adults. The four species found in North America nest on Arctic tundra or northern inland lakes but winter as far south as Florida on the Atlantic Coast, and southern California in the West.

Lordosis

An Animal Behavior term, this is used to describe the posture shown by receptive females of many Mammal species in the presence of a male. The back is curved downwards so that the hindquarters are raised, and the tail is deflected to one side making it easy for the male to mount. The equivalent posture in primates, presentation, has become a social signal used by both females and males when submissive.

Loosestrife

Lythrum

Tall, attractive wildflowers, several native loosestrifes grace moist soils from the salt marshes of New Jersey to damp meadows in southern California. Up to six feet tall, the plants have pairs of narrow lance-shaped leaves and six-petaled tubular flowers of varying hues. None of the native species, however, are as aggressive or conspicuous as the imported purple loosestrife, a showy immigrant from Europe that bears spectacular spikes of magenta blooms from June through September. It is so prolific that in many areas its impenetrable tangles of stalks and roots have crowded out native wetland plants. Providing little in the way of food or cover, the vast stands of purple loosestrife have also displaced much native wildlife.

Loss of habitat (Wildlife)

Habitat is the natural environment characteristically occupied by an organism. Loss of habitat to human development, forestry, agriculture and other activities is the primary cause of biodiversity loss around the world.

Lotus

Nelumbo lutea

Rooted in the muck of shallow lakes and streams, the American lotus flaunts its fragrant, creamy yellow flowers on stems that rise three feet above the water. The leaves are picturesque as well: olive-green discs up to two feet wide that are set like parasols atop stout stalks. The waxy blossoms, each six to eight inches across, last about five days before their petals fall, leaving behind the seedpods, which resemble the spouts of watering cans. Pitted with holes, they are embedded with shiny black seeds, which native Americans once gathered for roasting and grinding into meal. The starchy, tuberous roots were also harvested and eaten like sweet potatoes. Today the pods are sought for use in dried flower arrangements. Though lotuses are found throughout the eastern half of the country, they are becoming increasingly rare.

Louse

Tiny, flat, wingless insects that feed on humans and other animals, lice fall into two broad categories. Chewing lice attack birds and mammals, subsisting on feathers or hair. Sucking lice cling to the bodies of mammals, including humans, and feed on their blood. Associated with unsanitary living conditions, sucking lice are tenacious pests that cement their eggs, called nits, to hair and clothing. They are also unhealthy, with some kinds transmitting serious diseases.

Lousewort

Pedicularis

With finely divided, fernlike foliage and spikes of tubular two-lipped flowers, the louseworts are pretty plants whose name derives from a mistaken belief that they transmit lice to any animals grazing on them. Wood betony, with red to yellow blossoms, is a widespread example. Another, elephant heads, is a rose-red wildflower of mountain meadows and swamps; its blooms do indeed look like elephant heads, complete with ears and trunks.

Luna moth

Actias luna

Named for the ancient Romans' goddess of the moon, the green-winged luna moth is one of the loveliest creatures of the night. It is found only in eastern North America, where, in its spiny caterpillar stage, it feeds avidly on the leaves of trees. Then it spins a silken cocoon, sometimes incorporating a fallen leaf, and metamorphoses into a mature moth. The adults never eat but spend their brief lives searching for mates. The males are ever on the alert for the enticing scent given off by courting females. At one time the fluttering dance of dozens of males on the trail of female lunas was a common sight around street lights on summer evenings. Exposure to pesticides and pollutants has, however, reduced the population of these beautiful, now endangered, insects.

Lupine

Lupinus

In early summer the flower spikes of wild lupines brighten fields and roadsides throughout the East. But it is in the West that these legumes really flourish, with more than 70 species tinting mountains and plains with blues, pinks, yellows, and whites. Eastern or western, all lupines bear bonnet -shaped flowers and compound leaves with the leaflets radiating from their stems like the spokes on a wheel. As do all legumes, lupines have nitrogen-fixing nodules on their roots and so do well in poor, dry soils. Texas bluebonnet may be the best-loved lupine, but California claims the biggest: three times taller than its relatives, the yellow-blossomed tree lupine grows to an astonishing nine feet.

Lynx

Felis lynx

Solitary and seldom seen, lynxes are cats of the cold coniferous forests of Canada and the western mountains. They sleep by day in caves or hollow trees but at night are very active, some-

times traveling for miles in search of prey. Expert stalkers, they can creep to within a few feet of a prospective meal before bounding out for the capture. They also hunt by lying in ambush, waiting quietly for hours on a limb over a trail. Similar in appearance to bobcats, which live farther south, lynxes are about three feet in length, with tufted ears, long legs, and a stubby tail. Their long, silky fur is grayish with darker spots, and their large, furry feet serve as snowshoes in winter-an adaptation that allows lynxes to pursue their favorite quarry, the similarly equipped snowshoe hare, even in deep snow. Since lynxes depend on hares for most of their food, their population rises and falls in 10year cycles that match those of the hares.

Mackerel

Close relatives of the tunas, the oceangoing mackerels share their larger cousins' streamlined torpedo shape, silvery blue iridescence, and forked tails. Up to two feet in length, they are valuable food fish and are regularly netted in large quantities. Mackerels fight fiercely when hooked-sometimes leaping high into the air-and are highly regarded game fish as well.

Roving the seas in huge schools, mackerels prey on smaller fish and squid. They in tum are eaten by porpoises, whales, seabirds, and other fish. In the Pacific, mackerels range from Alaska to California, while in the Atlantic they are found from the cold northern waters off Labrador south to the Carolinas.

Madrone

Arbutus

The Texas madrone, native to central Texas, is a little tree with a crooked trunk and rarely exceeds 20 feet in height. In contrast, the Arizona madrone, found in the mountains of the Southwest, reaches 50 feet, while the Pacific madrone of coastal forests sometimes soars to 125 feet. Despite these differences in stature, however, the family resemblance is strong. All three species of madrones have a smooth, red, paper-thin bark that peels away to expose the bright new growth beneath, and their oval evergreen leaves are a dark, glossy green. They bear clusters of fragrant, white or pinkish urn-shaped flowers, and all produce mealy, red or orange fruits that are relished by band-tailed pigeons and other birds.

Magma

The molten rock found deep beneath the earth's crust is known as magma. It contains a complex mix of chemicals and gases, which eventually crystallizes into igneous rocks. Magma that wells up and flows onto the surface through volcanoes or fissures is called lava.

Magnolia

On spring evenings in the South, when the creamy white blossoms of the southern, or evergreen, magnolia are on display, filling the air with lemony perfume, it is easy to understand why many people consider it to be the most beautiful of all flowering trees. While the southern magnolia may reach a height of 100 feet or more, most others are small to medium-size trees, 30 to 50 feet tall. Magnolia leaves-deciduous on some species, evergreen on others-are oval and large. Those of the bigleaf magnolia, so glossy that they look polished, may be 32 inches long, perhaps the largest of any North American tree. The gray or brown bark is smooth and thin, releasing a spicy aroma when bruised or cut. All species bear magnificent cup-shaped white or greenish blossoms in spring, but not all have the compelling sweetness of the southern magnolia. Borne in conelike clusters, the seeds dangle for a time on threads before falling to the earth.

Magpie

Pica

Long-tailed and boldly patterned in black and white, magpies are conspicuous, noisy birds of the West. Like their relatives the crows and jays, they travel in small flocks and feed on everything from insects and fruit to carrion and birds' eggs. They often breed in loose colonies, building their domed nests of sticks in tall shrubs or thorny trees. The black-billed magpie is a widespread species, while the yellow-billed magpie is found only in parts of California.

Mallard

Anas platyrhynchos

The most widespread and numerous of all our ducks, the mallard is found in wetlands throughout the Northern Hemisphere. The males are distinguished by their glossy green heads and single white neck ring, while the females are a mottled brown. Mallards are often seen foraging in shallow water, with their tail ends sticking straight up as they dabble for food on the bottom. They also filter seeds at the surface and graze on land. Their varied diet consists of seeds, shoots, and grain, as well as insects and small aquatic animals.

Mallards nest across most of the continent and can be found even in city parks. The nest, a shallow bowl of grasses and marsh plants, is usually concealed near the water. As the eggs are laid, the female lines it with down plucked from her breast. Soon after hatching, the 7 to 10 downy yellow young waddle after their mother, who leads her brood to the water.

Mallow

In times past, the sweets known as marshmallows were made from the roots of a wetland wildflower of that name. Though today's confection contains not a trace of the plant, the mallow family supplies a number of important food, fiber, and floral crops. Cotton, which covers millions of acres in the South, is a mallow. So is okra, the plant whose mucilaginous fruits thicken Creole gumbos. Ornamental mallows include hollyhocks and hibiscus. Mallows are characterized by five-petaled symmetrical flowers with the stamens united in a cylindrical column that encloses the pistil. The leaves, covered with fine, fuzzy-tipped hairs, alternate along the stem, and the fruits are dry five-parted capsules that split lengthwise to release their seeds. Most of our mallows are herbs or shrubs, though two tree-size tropicals, the upland cotton and the sea hibiscus, have become naturalized along the Florida coast.

Mammal

Of the class Mammalia, the highest class of vertebrates. Mammals are warm-blooded animals that have mammary glands and a four-chambered heart. Most give birth to live young, and are either partially or completely covered in hair. At first glance, a mouse and a whale do not seem even remotely alike, but as different as they appear, both the tiny land dweller and the giant sea dweller are mammals. The two, in fact, have a number of traits in common, not all of which are unique to mammals. Both are air-breathing vertebrates, but so are lizards and toads. Both are warm-blooded, but so are birds. And both bear live young, but so do a number of snakes, frogs, and insects. What the mouse and the whale share with no other class of animals are two deceptively simple characteristics: hair and mammary glands. Like the mouse, most mammals are completely covered with fur.

Others, however, have only small patches of hair or very little at all. Whales and walruses, for instance, have just a few bristles, and armadillos have mere tufts of hair between their armor plates.

The main function of fur is to insulate; it keeps the body warm. This is especially important because, unlike fish, reptiles, and other cold-blooded creatures, whose body temperature fluctuates with their environment, mammals must maintain a constant temperature. For some animals, hair serves other purposes as well. The mottled brown fur of fawns and the snowy white fur of snowshoe hares provide excellent camouflage. Structures such as porcupine quills (used for defense) and cat whiskers (used as sensory devices) are specially modified hairs. Another trait unique to mammals-mammary glands- is the one that gives them their name. While the young of other animal groups often are dependent on uncertain food supplies, baby mammals always have milk, for the mother's body continues to produce it even when solid food is scarce. The richest milk of all is produced by sea dwellers such as whales and seals. Containing enormous quantities of fat, it allows the young to put on weight very quickly (baby whales can gain 200 pounds a day). The fat content also results in a layer of blubber that insulates the body from the frigid sea.

Mammals live just about anywhere North America supports some 400 species of mammals-about one-tenth of the world's total. Extremely adaptable, mammals are found in almost every conceivable habitat, from scorching deserts to the arctic tundra and from mountaintops to the watery deep. Some fly or glide through the air, while others spend their entire lives in the darker realms underground. Though several mammals are active in daylight, a surprising number prefer to sleep by day and hunt for food at night. Many mammals that live in forests are specially adapted for life in trees. Opossums, for instance, have a prehensile tail for grasping branches, and squirrels have sharp claws that enable them to scurry up and down tree trunks. Flying squirrels have folds of skin which they stretch out to glide through the air, while bats, the only true fliers among mammals, have wings made of thin membranes that extend between their elongated "fingers." Gophers, moles, and other burrowers spend much of their time underground. Equipped with strong claws and enlarged forelimbs, they move with ease through the soil. Many have short fur and lack external ears, and some that rarely come up to the surface have poor vision or are completely blind. Mammals that live on the ground have their own special adaptations. Deer and horses, for example, with their long legs and sturdy hooves, are built for running, and their teeth are shaped for cutting and grinding vegetation. Wolves and bobcats, on the other hand, live on animal prey and have highly developed canine teeth for piercing and tearing flesh.

Aquatic mammals, such as whales, porpoises, seals, and manatees, are uniquely adapted for life in the water-so much so, in fact, that some of them resemble fish. On many, the forelimbs are enlarged into paddlelike structures, the tail or combined hindlimbs look like a fish's tail, and the entire body is streamlined.

Mammals, equipped with superior brains, have relatively sophisticated social organizations and forms of communication. Wolves, which spend their lives in hierarchical groups called packs, exchange information about dominance and territory through scent, sound, and body language. Beavers and prairie dogs cooperate with others of their kind in building and excavating and by warning each other of danger. Among the most intelligent of mammals, whales and porpoises communicate with their species through a complex system of squeaks, trills, and bellows. In respect to communication, however, one mammal surpasses all others. Humans not only can communicate detailed information, but they can also store that information for the benefit of succeeding generations.

Mammoth

Mammuthus

Majestic beasts that lived during the last ice age, mammoths have been extinct for thousands of years. These relatives of modem elephants were massive creatures with domed heads, huge curved tusks, and ridged molars for grinding coarse grasses. Of the several kinds that roamed North America, the imperial mammoths, standing 13 feet high, were the largest. The slightly smaller Columbian mammoths were sometimes hunted by tribesmen on the Great Plains, while woolly mammoths, with tusks up to 16 feet long, were masters of the Far North. A shaggy outer coat of hair over dense underfur, plus a thick layer of fat, protected them from frigid weather. The frozen carcasses of woolly mammoths are occasionally unearthed in the Arctic. Often perfectly preserved, they are vivid relics that make the Ice Age seem like only yesterday.

Manatee

Trichechus manatus

Plump, placid mammals that live in warm coastal waters and river mouths in Florida, manatees have blimplike bodies up to 15 feet long and weigh as much as 1,500 pounds. Sometimes called sea cows, they move about slowly, propelled by two front flippers and a broad, flattened tail. Manatees surface every few minutes to take in air but spend most of their time underwater, grazing on aquatic plants. Their prodigious consumption-up to 100 pounds of plants per animal each day-plays a useful role in keeping channels clear of water hyacinths and other weeds. Since they often linger near the surface, many of these gentle giants have been killed or maimed by the propellers of motorboats. In winter, manatees, unhappy in chilly water, seek out warm springs and even the heated outflow from factories and power plants. Manatees are gentle, slow-moving creatures of Florida's brackish inlets and estuaries. Group members greet one another by touching muzzles, and they sometimes warn each other of danger with high-pitched chirps. Though the resemblance is far from obvious, manatees supposedly inspired the folklore about mermaids.

Mangrove

The shores of south Florida are lined for miles with dense stands of red mangroves, our only trees able to live in salt water. Topped with a canopy of leathery green leaves, the trees have roots that arch out like buttresses from the main trunks and serve as props. Columbus, when he first encountered tangled thickets of mangroves, described them in his log as being "so thick a cat couldn't get ashore." Seeming to march out across the shallows, the roots of the trees not only protect the shoreline from erosion by wind and wave but also help build land. By trapping sediment and debris, the roots create new islands and extend old shorelines seaward. Nurseries for a teeming community of marine life, they also serve as barriers that keep predators from the throngs of water birds that nest among their branches. While red mangroves prefer the seashore and the edges of brackish estuaries, two other species live in salt marshes farther inland. Black mangroves thrive in mucky areas between salt water and dry land and are surrounded by little forests of pencillike pneumatophores. Projecting from the mud, these odd structures serve as snorkels, allowing the buried roots to breathe. White mangroves are found on still-drier soils farther inland.

Manta

The giants of the skates and rays, mantas live in warm waters of both the Atlantic and Pacific oceans. Their name comes from a Spanish word for "blanket" -a reference to their wide, winglike pectoral fins. A pair of fleshy "horns" on their heads accounts for the nickname devil ray; a whiplike tail adds to their evil appearance. Some mantas are enormous, with a span of more than 20 feet from fin tip to fin tip and a weight of well over a ton. Despite their bulk, they "fly" gracefully through the water by rhythmically undulating their fins, and sometimes make spectacular leaps into the air.

Mantid

Long, slender insects with prominent eyes, mantids are formidable predators. They hold their front legs folded forward, as if in prayer, and so are commonly called praying mantises. But this pose is less pious than it appears, for mantids so positioned are in fact waiting in ambush for prey. Their grasping forelegs, which can lash out in an instant, are lined with needlesharp spines from which no victim can escape. In fall, the females, notorious for eating their mates, produce foamy masses containing up to 200 eggs, which hatch the following spring. Several species are native to North America, but the largest and best known are the introduced European and Chinese mantises.

Mantle

The tissue of a mollusk that secretes the shell.

Manufacturing (Industry)

The industry concerned with the invention or fabrication of items or products. Manufacturing is a chief economic activity, and is heavily concentrated in urban areas. Major manufactured items include motor vehicles, processed food, chemicals, and metals.

Manzanita

Arctostaphylos

Although the manzanitas range in size from creeping mats of foliage to trees some 30 feet tall, most are vigorous evergreen shrubs. Easily recognized by their tough, twisting branches and smooth, shiny reddish bark, they often form dense, virtually impenetrable thickets on arid slopes in the West. The clusters of pink or white urn-shaped flowers that droop from the twig tips in spring are later replaced by berrylike fruits that yield a tasty jelly.

Maple

Acer

Handsome and hardy, maple trees come in all shapes and sizes and are found in nearly every state. Perhaps the best known are the sugar maples of the East, which explode with brilliant color in autumn. The trees are famous both for the sugary sap that yields maple syrup and for the durable wood used for fine furniture.

Silver maples, also common in the East, are named for the silvery undersides of their leaves. Turning easily on slender stalks, the leaves seem to shimmer with the slightest breeze. The bigleaf maple of the West Coast, though shorter in stature at 40 to 60 feet, has leaves up to a foot wide. Smaller and more shrublike is the Rocky Mountain maple, which manages to survive in the poor, gravelly soils of cliffs and canyons.

All the maples have leaves that grow in opposite pairs. The flowers, though small, are often in conspicuous clusters; red maples, for instance, cast a scarlet haze over moist woods in early spring, flowering well before the leaves appear. Maple seeds come in paired keys, or samaras. Once they dry, the winged fruits whirl earthward like tiny toy helicopters.

Mapping method

See Spot-mapping method.

MAPS:

Bird Biology Avian Conservation term.

Monitoring Avian Productivity and Survivorship program, which utilizes constant-effort mist netting and banding and intensive point counts during the breeding season at a continent-wide network of stations.

Marble

Prized for its beauty, strength, and durability, marble is limestone that has been recrystallized by heat and pressure within the earth's crust. Pure marble is snow-white, but impurities give

it a range of colors, including gray, red, pink, green, yellow, and black. Marble has been used for building and sculpture since ancient times. The stately Lincoln Memorial in Washington, D.C., a contemporary example, was built of marble quarried in Alabama, Colorado, and Georgia. Large deposits of marble are also found in Vermont and Tennessee.

Mariposa lily

Calochortus

Flourishing on the dry slopes of western mountains and foothills, in hard-packed desert soils, and in the shade of coniferous forests, mariposa lilies offer a charming contrast to the austerity of their environment. Although the flowers of some kinds are globe shaped and others dangle like bells, most are open, upright, and as cheerfullooking as tulips. The blooms range in color from white to yellow, orange, scarlet, and purplish, with each of the three petals commonly marked at its base with a darker spot. The tasty bulbs of some of the mariposas were valued as food by native Americans and early settlers. One kind, the sego lily, is credited with saving Mormon pioneers from starvation and is now honored as the state flower of Utah.

Marlin

Aristocrats among sport fish, the speedy, streamlined marlins are known for their fighting ability and their spectacular leaps when hooked. Related to sailfish, they have a prominent back fin that folds down into a groove when they are swimming at full speed. (Marlins can attain bursts of 60 miles per hour.) They use their spearlike bills to stun prey as they swim through schools of smaller fish, then tum back and swallow their victims whole. Marlins are found in warm water off both coasts. Striped marlins live in the Pacific, and white marlins swim in Atlantic waters. But the most highly prized of all is the wide-ranging blue marlin; at 15 feet or more, and weighing up to 1,000 pounds, it can challenge the most dedicated fisherman.

Marmot

Marmota

These largest members of the squirrel family are stocky, ground-dwelling rodents about two feet long, with short legs and bushy tails. They live in burrows in rocky slopes and open fields. Hibernating throughout the winter, marmots emerge in spring to feed on grasses and other plants. The most widely distributed species is the feisty woodchuck, or groundhog, of Canada and the eastern United States. Others include the yellow-bellied marmot, or rockchuck, of the Rockies and Sierras, and the hoary marmot of the Pacific Northwest. Often sitting up alertly as if on guard duty, marmots respond to danger with sharp, piercing whistles-sounds that account for their nickname, whistlers.

Marsh

A marsh is a type of wetland, featuring cattails, and other herbaceous low-growing woody plants) in a context of shallow water. A marsh is different from a swamp, which is dominated by trees rather than grasses and low herbs. The water of a marsh can be fresh or brackish. Estuarine marshes often are based on soils consisting of sandy bottoms.

Marshes are critically important wildlife often serving as breeding grounds for a wide variety of life.

Marsh marigold

Caltha

Two species of marsh marigolds-both of them perennial wildflowers of wet soils-share the continent. The easterner makes its home in swamps and moist lowlands, while the western marsh marigold thrives on soggy alpine meadows and beside icy mountain streams. Both kinds are often called cowslips, though the plants are actually related to buttercups. Eastern marsh marigolds, in fact, look much like large buttercups, greeting April with a splendid show of bright yellow flowers up to two inches across. The western species, also known as elkslip, blooms later-from June until Septemberand has white flowers with knots of golden stamens at their centers.

Marsupial

A maternal pouch distinguishes most marsupials from all other mammals. Born at a very early stage of development-hardly more than embryos-marsupial young make their way into the pouch on the mother's belly, immediately begin nursing, and remain there until they are able to get about on their own. The most familiar examples are the kangaroos and koalas of Australia, and the hardy, adaptable opossum, the only marsupial native to North America.

Marten

Martes americana

A solitary, bushy-tailed member of the weasel family, the marten lives in the cool coniferous forests of the Far North and western mountains. It is a fast and agile climber, well equipped for pursuit of the red squirrels that are its favorite prey. (Indeed, as it bounds from limb to limb, it might easily be mistaken for a large, dark squirrel itself.) On the ground the marten is equally quick and curious, nosing into nooks and crannies in search of insects, small animals, nuts, and fruit. It dens in hollow trees and meets others of its kind only during the summer mating season. Trapped extensively for its soft, lustrous fur, the marten has disappeared from parts of its former range.

Martin

Progne subis

Purple martins, our largest swallows, used to nest primarily in abandoned woodpecker holes in dead trees. Some also took up residence in hollow gourds hung up for them by Indians, who enjoyed their company. Today, however, most martin colonies live in special man-made multiunit birdhouses to which they return year after year. In some regions starlings and house sparrows have crowded them out, but where competition is light, colonies sometimes number more than 200 pairs. Like other swallows, martins feed mainly on insects caught in flight. They not only help control these pests but also delight humans with their musical chirping.

Marty Stouffer

Marty Stouffer is the world's most recognizable and authoritative spokesperson for America's wildlife. His long-running TV Series "Wild America" and his highly successful home-video are seen by millions of people each and every day. For the millions of viewers worldwide who regularly watch the "Wild America" Series, Marty Stouffer opens a window on the great outdoors and introduces watchers of all ages to the wild creatures which call North America home.

Regardless of the fame and awards showered on him over the years, Marty still exudes the un-jaded, boyish sense of wonder and enthusiasm for Nature that began as a child growing up in rural Arkansas. His mother, Agnes, encouraged her daughter, Mari, and her three sons, Marty, Mark and Marshall, to relate not just to the family Dog, Goat and Donkey but to the wild creatures of the forest as well. Orphaned birds and mammals were rescued, raised and released back into the countryside near their rural Fort Smith property.

"Leona," the Owl, learned to fly in the Stouffer living room, "Foxy," the Fox, shared "Whisper" the Spaniel's food bowl and "Stanley," a baby Beaver, lived in the bathtub for months. Marty's dad, Martin, introduced his oldest son to hunting and to the art of tracking. Martin bought the family a Brownie box camera for still photographs and a Kodak 8mm movie camera which Marty and his brothers used to create "corny" (as Marty says) home movies about themselves, their adventures, and the animals around them.

But Marty yearned for adventure beyond the local woodlands. Through skills honed as an outdoorsman in the Arkansas woods, he survived his solo trip to Alaska at the age of 18. An August snowstorm buried the remote Brooks Range, and shut Marty off from the outside world.

He was able to survive for weeks by killing and eating a Dall sheep ram. When the folks back home actually paid money to see the unsophisticated movie he made about his trip, the young naturalist/filmmaker was amazed... and pleased. He immediately began planning his next big adventure.

After graduating from the University of Arkansas with a degree in English in June of 1970, Marty began producing his second film, this one for a safari company in Botswana, Africa. The professional 16mm film equipment he used on this project was a big step up from the amateur super 8mm camera he had used in Alaska. The Lion, Cape Buffalo and Elephant of Africa were magnificent, but the wholesale slaughter of great numbers of a wide variety of animals he witnessed daily - some, acceptably, for camp meat but most only for trophies - saddened him.

He was 21 years old, disillusioned, at a remote tent camp in the immense Okavango Swamp, alone and lonely in a rapidly changing Africa, when he made some choices about his life.

Marty returned to America a changed young man. He determined to somehow make a living creating films which would promote the conservation of wildlife. In the early 1970's, he started his career in earnest. While remaining a hunter at heart, he began capturing his quarry on film. For seven years after his bloody African experience, hunting with a bow or rifle would not be a part of his life. But, making a living marketing Nature films was tough. He produced and distributed films like "Bighorn" and "At the Crossroads" to schools, libraries and parks as he sold still photographs to magazines like Natural History, Audubon and Reader's Digest. While his impressive library of wildlife film footage grew, his bank account did not.

In the mid 1970's, with his brother Mark, he financed and co-produced the heart-warming Feature film, "The Man Who Loved Bears," narrated by Will Geer and the primetime NBC-TV Special "The Predators," narrated by Robert Redford. Marty and Mark also co-produced television projects with Paul Newman and several John Denver Specials for ABC-TV.

Finally, after numerous rejections of his various TV Series proposals by the major TV networks, the programming managers at PBS found his idea for a half-hour outdoor Series set in America too appealing - and too cost effective - to turn down. "Wild America" was born.

Unlike any Wildlife Series to date, "Wild America" focuses on the sometimes shocking reality of life in the wild, including, Marty says jokingly, "sex and violence." In all seriousness, before the arrival of this new Series, producers, such as Walt Disney and Marlin Perkins, had steered clear of natural behavior involving reproduction and predation.

Marty's stories, incorporating these dramatic "facts of life," and told simply in his honest home-spun style, won the hearts of a loyal audience. It also helped that the programs were magnificently filmed in slow-motion, time-lapse, telephoto and closeup cinematography. The Series became an almost-instant hit. It was one of PBS's most highly-rated regular Series, never leaving the Top Ten, and it remains the most broadcast Series which has ever aired on Public Television.

Today, Marty has expanded his horizons even farther, embarking on a booming home video business that includes over a dozen new titles like "Great Escapes," "Spectacular Showdowns," "Dangerous Encounters," and "Tender Times." More than two million videos have been sold to date.

And a theatrical Feature film, also entitled "Wild America," has been produced. This fast-paced comedy-adventure profiles Marty, Mark and Marshall Stouffer growing up wild and crazy in rural Arkansas and on the road filming. The Feature was created with "Forrest Gump" producer, Steve Tisch, Jim Robinson of Morgan Creek and Warner Bros.

Plans are also on the drawing board for direct merchandising and licensing of "Wild America" clothing, furniture, toys, luggage and camping equipment — a whole line-up of exciting new products. Three million feet of film and tens of thousands of photographs celebrating the beauty and drama of American wildlife are being readied for marketing. Even a major wildlife theme park attraction is waiting in the wings.

Today, Marty lives in the high country outside Aspen, Colorado, with his wife, Diane, their children; Hannah and Luke, and the family's Springer Spaniel, "Shadow." Their home still sees a parade of wild orphans like Fishers, Kestrels and Otters that are lovingly raised, usually filmed and always returned to the wilderness by the Stouffer family.

In addition to filming, Marty explores for historical artifacts and, along with his children, has a collection of "small white rocks." He enjoys skiing and riding deep into the Colorado wilderness on pack trips with his mules, "Dolly" and "Janey", on what he describes as "The Sacred Hunt"- a spiritual return to his roots as an ethical hunter.

A gifted and lively personality and storyteller, Marty smiles broadly as he looks back over his thirty-year career as America's premiere naturalist and reminisces about his fascinating adventures with animals and people - friendly and otherwise - down through the years. "We've had one heck of a good time," he says with a big grin.

He has succeeded, against all odds, in producing a long-running, prime-time Wildlife Series of a kind and quality found nowhere else on American television. His unique approach takes the mystery out of wildlife but still preserves the magic.

Marty's earliest exposures to wildlife filmmaking were to the lecture films of Wally Taber and the theatrical Walt Disney True-Life Adventures - his most recent mentors have been film presenter David Attenborough, poet Robert Bly and writer Pia Melody.

A look at the career of Marty Stouffer is also a fascinating exploration into the rich and varied history of the evolving Wildlife Film. In the early stages of filmmaking, adventure and travel dominated the genre in the form of travelogues. Human hunters, such as Osa & Martin Johnson and Theodore Roosevelt, documenting their expeditions to exotic places, were the main focus; with animals serving only as objects of the hunt. Next came a scientific era, with films showing animal experts in "talking head" interviews. The focus became a connection between science, education and the natural world.

What followed was a turn-around in approach, as filmmakers displayed animals in purely entertaining ways. Some, like Arne Sucksdorff, presented Nature as a thing of beauty to be appreciated like a work of art. Walt Disney's films largely dominated this phase of filmmaking - with amusing stories of lovable humanized creatures - showing an innocent and simple - if somewhat inaccurate and anthropomorphized - side of the natural world.

Finally, a growing concern for our threatened environment dictated the most recent - and current - stage: a focus on diminishing species and an acknowledgment that animals are not only beautiful, but also important as environmental barometers for the continued health of humans.

By amazing comparison, Marty Stouffer's own career also evolved to encompass four distinct stages of film development - adventure, science, entertainment and environment. The first time Marty consciously combined photography and wildlife was in making several short 8mm home movies of Duck hunting trips during his teens. These early efforts evolved into expeditions to Alaska and Africa, as he documented on film his travels and the hunts encountered there. Next, his curiosity and social conscience combined and created such early film projects as "Bighorn!"and "At the Crossroads - the Story of America's Endangered Species."

Evolving yet again, he worked on popular TV Specials with John Denver, Paul Newman and Robert Redford before settling into the "Wild America" niche and creating more than 120 exciting episodes of this popular continuing Series. Now in the editing room are programs about Polar Bear mothers, Bison fathers, Mustangs living wild and free, beautiful Wildflowers and amazing Bird Bills.

With the future bright and beckoning, there is certainly no end in sight. The country boy hit the big time, and he's loving every minute of it. As Marty says with a big grin, "Until next time, enjoy our 'Wild America'!"

Mastodon

Mammut americanum

Distant relatives of elephants and mammoths, American mastodons died out about 8,000 years ago. The imposing beasts stood 10 feet tall and wielded impressive, curved tusks up to 8 feet long. Shaggy, reddish-brown fur protected them from the cold, and their grooved teeth - the size oflarge bricks-were used for grinding up huge quantities of plant food. Fossils of these ancient behemoths- found from Alaska to Florida, but mostly in the East-are proof that mastodons were once a familiar presence on the North American landscape. Huge tusks have even been unearthed in New York City, evidence that the hairy giants once trudged through spruce forests where skyscrapers now stand. Mastodons were shorter and more heavily built than modern elephants. Hunting by humans may have played a role in their extinction.

Masturbate

Masturbate refers to Masturbation, which is sexual stimulation, particularly of one's own genitals.

Masturbation

Masturbation refers to sexual stimulation, particularly of one's own genitals. It is also accomplished manually, by other types of bodily contact (except for sexual intercourse), by use of objects or tools, or by some combination of these methods.

It can refer to stimulation either by oneself or by another.

Some people are able to achieve orgasm only through masturbation and not sexual intercourse. It has been observed in many species, both in the wild and in captivity.

Materialism

Biological Philosophy term. The affirmation that only material things exist, that there is no such thing as spirit. In the eighteenth century, materialism countered the religious belief that there was a soul to survive the death of the body, and thus, that there was an afterlife. Today materialism expresses itself in the effort to link neuro-science to conscious experience: thought is purely material behavior. Materialism is a part of the belief system of some in the Enlightenment and of many scientists and others today. It is a necessary working rule of science, without necessarily being a "belief" of all scientists, i.e., scientific investigation assumes materialism for purposes of science, whether the scientist is a materialist or not.

Mating

Mating is the pairing of opposite sexes for copulation. In some birds, for example, it includes nest-building and the rearing of offspring.

Mayapple

Podophyllum peltatum

Maylemon might be a more fitting name for the mayapple, since its fruit resembles the lemon in color, shape, and flavor. Found on rich soils in the East, the plant sends up stems one to two feet tall, topped with deeply lobed, umbrellalike leaves. A creamy cup-shaped flower emerges from a fork in the stem, followed by a yellow oblong berry one to two inches in length. The fruit is sometimes used to make jams and beverages, and the roots have a long history of use in folk medicine. Known as mandrake to early herbalists, the mayapple contributed potent treatments for everything from warts to jaundice. Even today, extracts have proved valuable in treating several kinds of cancer.

Marsh

A red-winged blackbird perched on a cattail, rudely scolding anyone who comes near, or a lazy turtle basking on a log amid a patch of fragrant waterlilies-such scenes are commonplace in freshwater marshes. In contrast to swamps, which are dominated by trees, these shallow, richly productive wetlands support a vast array of nonwoody plants. In addition to the familiar cattails and waterlilies, they are home to pickerelweed, sedges, sawgrasses, and even such unusual plants as sun dews and bladderworts, which capture and consume insects. Mosquitoes and dragonflies hum and hover in the air, while fish and frogs lurk in the water below. Marsh-loving mammals include muskrats, mink, and masked raccoons. But the most elegant denizens of all are the birds: herons, egrets, ibises, coots, rails, and especially the huge numbers of ducks and geese that depend on marshes both as permanent homes and as resting places on their long annual migrations.

Mayfield method

Bird Biology Avian Conservation term.

A method used to calculate the rate of nesting success based on the number of days that a nest was under observation (i.e., nest days of "exposure").

Mayfly

In late spring and early summer, huge clouds of fragile mayflies swarm over lakes, ponds, and streams to mate, lay their eggs, and die within a day or two. Prior to this grand finale, these gauzy-winged insects live as aquatic nymphs complete with six legs, seven pairs of gills, and three feathery "tails." After as long as two years in the water, where they molt many times, they crawl out and molt twice more, the second time developing from winged subadults into fully mature adults. Mature mayflies eat nothing; their digestive systems simply fill with air for added buoyancy. Fish eagerly devour both the nymphs and adults, and many anglers' fishing flies are designed to imitate them.

Maypop

See Passionflower.

Meadowlark

Sturn ella

Stocky, short-tailed birds that are well camouflaged on the back with streaks of brown, mead0wlarks can easily be recognized by the black V on their bright yellow breasts. Our two species, whose ranges overlap in the central states, look so much alike, however, that they are readily distinguished from each other only by their different singing styles: the eastern meadowlark's loud, clear whistles contrast dramatically with the melodious, flutelike song of the western meadowlark. Ground dwellers, the birds build dome-shaped nests in grassy fields and feed on insects and seeds. Despite their name, meadowlarks are related not to larks but to blackbirds.

Meadow rue

Thalictrum

Rarely wandering far from streams ides or moist woodlands, meadow rues are moisture-loving plants that flourish all across North America. They are erect, branching perennials that range in height from a foot or less on western mountains to almost 10 feet in eastern ditches, and are much admired for their delicate blue-green foliage. The blooms are pretty, too: from late spring to late summer the meadow rues are covered with airy clusters of dainty white, yellow, or purple petalless flowers.

Meadowsweet

Filipendula

Tall, fragrant wildflowers, the meadowsweets were named not for any preference for meadows and prairies, but because their sweet-scented blooms once were used for flavoring that old English beverage, mead. Our best-known species, called queen of the prairie, is an eight-foottall perennial with huge compound leaves and branching clusters of deep pink flowers that last all summer. In the East the closely related wild spireas also are known as meadowsweets.

Mealybug

Named for the waxy white powder that covers their bodies, mealybugs are notorious insect pests that live by sucking juice from the leaves and stems of plants. The females-soft, oval, and wingless-are often found feeding in clusters on the underside of leaves, while the slender, winged males fly from plant to plant in search of mates. Left unchecked, mealybugs can weaken or kill the plants they infest, but in most cases they are easily controlled.

Meander

As a river flows across its floodplain, it often forms the broad, looping curves known as meanders. (The word is derived from a winding Turkish river so named by the ancient Greeks.) On the outside edge of a curve, where the current is fastest, the riverbank erodes, while sediment is deposited on its inner edge, gradually changing a small twist into a large, looping curve. Ever-changing, meanders sometimes are transformed into crescent-shaped oxbow lakes.

Meaning

An Animal Behavior term, this is used to describe the information gleaned by the recipient of a signal. This can only be assessed in Animals by the way in which it responds to the signal. To an unmated female, the meaning of a male courtship display may be "approach and attempt pair formation".

Measurement bias

A systematic under- or overestimation of the true values due to a difference between the actual measurement and what one intends to measure.

Measurement endpoint

See Endpoint.

Measuring worm

The larvae of a widespread family of delicate moths, measuring worms are named for their peculiar looping gait. By arching up the middle of its body, a measuring worm pulls the rear part forward, then stretches out its head end to repeat the process. Giving the impression that they are measuring the surface as they move across it, measuring worms are also called inchworms. North America alone harbors some 1,200 species of these tiny foliage-eating acrobats, some of which damage shade trees.

Mechanistic

Biological Philosophy term. As in "mechanistic universe." The idea that everything works mechanically, like a clock. It is the idea of the universe associated with Newton who discovered the laws of gravity and planetary motion. Such a universe is a deterministic universe. According to another thinker, Laplace, if we had all the data, we would be able to predict everything that is to happen in the world, as we can predict where the hands of a clock will be three weeks from this moment. Einstein put it this way: "I shall never believe that God plays dice with the world." This notion is rejected by the quantum theory that rules contemporary physics, which shows that randomness, accident, a degree of chaos, is basic to matter.

Melanic

Showing dark pigmentation.

Menhaden

Brevoortia tyrannus

One of the most abundant and important fish of our Atlantic coastal waters, menhaden are named for an Indian word meaning "that which enriches the soil. " Their flesh is so oily that these large-headed, silvery members of the herring family are seldom eaten by humans. Native Americans, however, used menhaden as fertilizer, burying one fish in each hill of com. Today the oil is an ingredient in soaps, paints, and other products, and the fish meal and scraps are used in livestock feed and fertilizer. Up to 18 inches long, menhaden travel in enormous schools, swimming north in summer and south in winter. Bluefish, striped bass, and many others eat huge numbers of menhaden, which are also used for bait.

Merganser

Slim and swift on the wing, mergansers are unique among ducks in having slender, sawtoothed bills that they use for seizing fish and other prey in underwater dives. All three North American species nest in forested regions and migrate south to open lakes, rivers, or coastal waters for the winter. The smallest and most elegant species is the hooded merganser, which has a fan-shaped white crest bordered with black. Unlike the other mergansers, "hoodies" rarely gather in flocks and usually winter on ponds and quiet estuaries. The common merganser is large and sleek; the male has a glossy green head without a crest, while the somewhat smaller red-breasted merganser has a distinctive spiky crest. Common mergansers nest in holes in trees and winter on fresh water, whereas red-breasted mergansers nest on the ground and prefer to spend the cold months on salt water. Male red-breasted mergansers make catlike sounds when courting females. Sometimes a flock of these birds will form a long moving chain across the water's surface, driving fish into shallower areas where they can easily be plucked from the water.

Mermaid's purse

Often seen littering the seashore or attached to clumps of seaweed at low tide, mermaid's purses are the egg cases of skates and certain sharks, such as dogfish. Those of the skates are black, leathery, and pillow-shaped, with a hornlike projection at each corner. The purses of dogfish are similar in shape but are translucent and have long tendrils, which are used for anchorage. Skates lay their eggs in the sand well offshore, so the cases found on the beach are generally empty. But dogfish and other egg-laying sharks deposit their purses in seaweed beds near shore, and intact cases can frequently be found when the tide recedes. The embryos within take several months to hatch.

Mesa

Often ochre or deep red in color, mesas are steep-sided, flat-topped tablelands that rise in stark splendor from the deserts of the Southwest. They range in size from a few acres to hundreds of square miles and are isolated remnants of much larger plateaus that once stood high above the present desert floor. Mesas are capped by a resistant layer of rock that withstood the assault of wind and water while the softer layers below were worn away, forming steep slopes. One of North America's most famous table mountains, Mesa Verde, looms above its surroundings in southwestern Colorado. Twenty miles long and 15 miles wide, this massive mesa is incised with caves that were home to the cliffdwelling ancestors of the Pueblo Indians. Mesas are majestic testaments both to the power of erosion and to its limitations, since these huge flat-topped hills are capped with harder layers that could not be worn away. Aptly enough, mesa is Spanish for "table."

Mesic

Moderately moist.

Mesquite

Prosopis

The hardy and tenacious mesquites are thorny shrubs and trees that thrive in the hot, dry climate and poor soils of the Southwest. Their remarkable taproots probe downward more than 60 feet in search of groundwater, while extensive lateral roots fan out from the trunk to soak up newly fallen rain. In very dry areas mesquites may be only a few feet tall, but with adequate moisture they can grow to some 50 feet in height, with a girth of up to 3 feet. The twisted trunks are covered with thick, craggy bark, and the twigs bear sharp spines up to two inches long. Mesquite leaves, in contrast, are delicate and feathery. The dainty spikes of greenishwhite flowers that appear in spring and summer give rise later to long pods filled with pulpy seeds. Sweet and rich in protein, the seeds were once a staple in the diet of native Americans. They also are relished by deer, rabbits, peccaries, and domestic livestock. Mesquite wood makes good lumber, and it also yields an aromatic smoke used to flavor grilled meats.

Message Call

An Animal Behavior term, this is used to describe the information about the sender encoded in a signal. Thus, a male courtship display may convey the message "I am an unmated male in breeding condition".

Metamorphic rock

Rocks that have been altered by intense heat or pressure within the earth's crust are known as metamorphic rocks. They originate as sedimentary or igneous rocks, such as sandstone or granite, but are transformed into new types of rocks when their minerals recrystallize or are realigned. Metamorphism can occur when buried rocks come in contact with magma pushing its way to the surface. It can also result from major regional geologic events, such as movements of the earth's crust, which produce tremendous heat and pressure and so alter all the rocks in the area. Many metamorphic rocks, such as gneisses, are characterized by alternating light and dark bands; others, such as slate, occur in plates. The skyscrapers in New York City rest on a solid foundation of metamorphic rocks, mainly schist, gneiss, and marble.

Metamorphosis

Many kinds of animals undergo astonishing transformations as they mature. These changes, called metamorphosis, are so dramatic that creatures at various stages in their life histories sometimes appear to belong to completely different species. Wormlike beetle larvae, for example, become winged adult insects; legless, fishlike tadpoles tum into tailless frogs with powerful hind legs; and microscopic, freeswimming oyster larvae are transformed into hard-shelled, stationary adults. In the course of metamorphosis, some organs are lost while others are gained. An earthbound caterpillar develops wings, and its chewing jaws are replaced by a long, sucking snout. The tadpole trades its gills for lungs, and its tail shortens to nothing as its legs grow longer. A tiny, translucent, floating lobster larva becomes an armored giant with legs and claws.

Some insects, such as beetles, bees, and butterflies, undergo what is called complete metamorphosis. That is, they pass through four separate stages of development: egg, larva, pupa, and adult. During the inactive, nonfeeding pupal stage, their bodies are completely reorganized into winged adults. Other insects, such as grasshoppers and dragonflies, in contrast, undergo incomplete metamorphosis, a three-stage process. They do not pupate but gradually assume the adult form during a series of molts.

Metaphysical naturalism

Belief which stipulatively includes as well as spirits and souls, non-natural values, and universals as they are commonly conceived) do not exist. It is often simply referred to occasionally as philosophical naturalism.

Metapopulation

A collection or set of local populations living where discrete patches of the area are habitable and the intervening regions are not; basic demographic unit composed of a set of populations in different habitat patches linked by movement of individuals.

Metatarsal gland

Tufted, discoloured hair patches found between the hock and the hoof on the inside of each hind leg in deer. These areas are a source of scent used for communication. Also Tarsal gland.

Meteorite

Stony or metallic objects that drop to earth from outer space are called meteorites. While most are quite small, the largest measure several feet in diameter and weigh thousands of pounds. Meteorites offer scientists clues about the composition of the planets and other extraterrestrial bodies. Relatively rare (most bum up as they hurtle through our atmosphere, where they are visible as "shooting stars"), some 500 meteorites are estimated to hit the earth each year, though very few are ever recovered. In 1982, however, a six-pound meteorite crashed through the roof of a house in Connecticut-just a mile from another home that had been hit 11 years earlier.

Mica

Occurring in thin, flexible, shiny sheets, layers of the familiar mineral known as mica can sometimes be peeled apart with the fingernail, almost like the pages of a book. Composed mainly of aluminum, oxygen, and silicon, mica has a crystal structure with perfect cleavage, the property that allows it to be split into sheets. Depending on the type, it may be black, brown, violet, or transparent, and in fragmented form it appears as the shiny flecks in blocks of granite. The most common kind, called muscovite, was so named because the Russians once used large sheets of mica as window glass. Mica still is used in the manufacture of electronic components, ceramics, plastics, and paints.

Microhabitat

The particular parts of a habitat that an individual encounters in the course of its activities.

Midge

At dusk, midges often swarm in such dense clouds near bodies of water that they produce an audible hum. Tiny but prolific, these fragilelooking flies closely resemble mosquitoes, but they do not bite. The females lay their eggs in ponds or streams, where the wormlike larvae scavenge for bits of food in the bottom sediments. The larvae of some, called bloodworms, are used as bait by anglers. Eaten by trout and many larger animals, the larvae are important links in freshwater food webs.

Migrant

Animal that spends the summer and winter in different areas.

Migration

Regular, periodic movements of animals in large numbers, usually away from and back to a place of origin. Many birds undertake seasonal migrations-typically in the spring and fall-to find more favorable conditions of temperature, food, or water. Such migrations may involve a change of latitude, altitude, or both, and are intended to provide a suitable breeding area. Twice every year, as the spring thaw begins and again as summer wanes, many birds, mammals, and other animals migrate between their seasonal homes. In the course of these periodic, roundtrip movements between summer and winter habitats, the migrants often battle tremendous obstacles and cover vast distances. Arctic terns, for instance, fly thousands of miles, trading one polar locale for another; eels undertake arduous journeys from inland lakes and rivers to spawning grounds in the Atlantic Ocean; and salmon hurl themselves against the current as they swim from the sea back to the freshwater streams where they were hatched.

These large-scale movements, involving thousands of individuals or even entire populations, enable animals to find food during times of scarcity or to congregate for mating. Most migrations are triggered by changes in day length, the onset of cold weather, or the phases of the moon. But migration is a complex phenomenon, with animals responding to both environmental and physiological cues.

Birds are the most familiar and spectacular migrants, with about 90 percent of our North American species moving south in the fall and north again in spring. Some, such as the lesser golden-plover, fly thousands of miles from the Arctic tundra to winter in the southern hemisphere. Others, such as robins and goldfinches, travel a few hundred miles to their wintering grounds, while the mountain quail of the West migrates just a few miles, walking from alpine nesting areas to valleys below the snow line.

Many birds travel along well-defined routes called flyways. Songbirds and some waterfowl often fly by night, using the stars and moon as a guide, and pause to rest and refuel during the day. Raptors, cranes, and others migrate by day, relying on the sun for orientation. Still others seem to depend on such clues as the earth's

magnetic field and even barometric pressure to guide their flight.

Migrating birds generally fly at altitudes of 5,000 feet or less, but in clear weather they may soar to more than 20,000 feet. Their speed varies with the weather, and birds tend to travel faster in spring than in the fall. The current speed record is held by a lesser yellowlegs. Banded on Cape Cod, it was found six days later in the West Indies, some 1,888 miles away, and so averaged more than 300 miles a day.

Mammals also are accomplished migrants. Each year as winter approaches, caribou trek more than 600 miles south from the arctic tundra to the shelter of the far northern forest, where food is easier to find. Come spring, the massive herds once again head north toward their breeding grounds. Not all treks are so extensive, however. Wapiti, mountain goats, and mountain sheep move downslope at summer's end to feed in sheltered valleys, journeys that seldom amount to more than 10 miles.

Many bats, especially the red and hoary bats, summer in the northern United States and winter in the southern states. Those that hibernate may well travel hundreds of miles to reach the caves where they spend the winter.

Among the migrating marine mammals, northern fur seals shuttle between Alaska and California, a trip of up to 1,700 miles. Some of the whales also make astonishing seasonal journeys, leaving frigid polar regions to bear their young in tropical seas thousands of miles away.

Several snakes, including rattlers, travel many miles to gather in winter dens. But of all the reptiles, the sea turtles are the ones that undertake the most extensive migrations; they often swim hundreds or even thousands of miles between feeding grounds in the open ocean and the beaches where they lay their eggs.

The most celebrated migratory fish are the salmon, which leave the rivers where they were hatched, and swim to sea; then after a journey of as much as 3,000 miles and four years, they return to the same river to mate and die. Migrant marine fish include striped bass and bluefin tuna.

Even insects migrate. Each fall, millions of monarch butterflies travel as much as 1,800 miles from their northern summer range to a few wintering sites in central Mexico and California. The return trip is made in stages, as females stop to lay eggs and die. Their offspring complete the flight back to where their forebears lived the previous summer.

The routes of most migratory animals are well known, but the question of how they navigate on their journeys is still debated. Birds use topographic features, the sun and stars, wind direction, and even the earth's magnetic field to find their way. Whales, caribou, and wapiti follow ancient routes that older individuals remember. And salmon recognize the distinctive "odors" of the rivers where they were spawned.

No one is sure what triggers the urge to migrate, but as the time approaches, birds, for instance, fatten up, often increasing their body weight by as much as 50 percent. The study of these age-old journeys is far from complete, with many mysteries remaining about navigation and the mechanisms that compel migration.

Migration

Regular, extensive, seasonal movements of animals between their breeding regions and their "wintering" areas.

Migration, Bird

Bird Biology Avian Conservation term.

Altitudinal migration--a vertical pattern of migration in which populations that breed in the alpine or subalpine zones in summer move to lower levels in winter. Inverted altitudinal migration refers to organisms that move to higher levels in winter.

Leap-frog migration--a pattern of migration taken when subspecies of the same species occupy two or more breeding areas (and also wintering areas) in the axis of migratory flight. Subspecies that breed progressively closer to one end of the axis winter progressively closer to the other end. An example is the Fox Sparrow, of which six subspecies inhabit the Pacific coast of North America. On its migration south, each subspecies flies over winter areas already occupied by the subspecies that breeds south of it.

Long-distance migration--a pattern of latitudinal migration used by a species that moves from arctic or temperate regions where it breeds to tropical or subtropical regions for the winter.

Loop migration--a circular pattern of migration such that the migration pathway in the fall differs from the migration pathway in the spring.

Short-distance migration--a pattern of latitudinal migration used by species that move within, rather than between, temperate or tropical zones.

Minimum viable population:

a threshold number of individuals that will ensure (with some probability level) that a population will persist in a viable state for a given interval of time.

Migration

An Animal Behavior term, this is used to describe the long-distance movements of Animals and especially the regular seasonal movements between breeding and wintering grounds or different feeding places shown by many Birds and Fish as well as some Mammals and Insects.

Migratory

The act of moving from one place to another in search of food, better climate, or other environmental features.

Milksnake

See Kingsnake.

Milkvetch

See Locoweed.

Milkweed

Asclepias

The fragrant blossoms and spindle-shaped seedpods of the milkweeds are familiar sights along roadsides and in meadows and forest clearings across North America. Sturdy plants with stout stems and large oval leaves, most are filled with poisonous, milky sap. In summer the milkweeds bear clusters of colorful five-petaled flowers that are ingeniously constructed to aid cross pollination. The nectar-filled blossoms contain wishbone-shaped structures with a waxy mass of pollen hanging from each end. Catching on the legs of foraging insects, the pollen masses are carried away like saddlebags and dislodged on the next milkweed the insect visits. The blooms are followed by warty pods that burst open to scatter their seeds on the wind.

Milkweed beetle

Tetraopes

For their entire lives milkweed beetles are irrevocably linked to milkweeds. They lay their eggs on the plants, the larvae feast on milkweed tissue as they tunnel through roots and stems, and the adults feed on the leaves. The acrid, milky sap of the milkweeds makes the beetles themselves distasteful to predators-and their bold red and black coloring advertises this fact. Finicky feeders, each of the several species found in North America relies on just one or two kinds of milkweed. One of the most common, the red milkweed beetle, produces squeaking sounds by rubbing together rough areas on its body.

Milkwort

Poly gala

Named for an old belief that nursing mothers gave more milk after eating these wildflowers, milkworts of many species thrive all across the continent and are found everywhere from dry, open fields to moist meadows and swamps. Most are low, branching plants crowned with clusters of tiny flowers in a rainbow of hues. Variously shaped, the flower heads of some, such as orange milkwort and the purplish field milkwort, resemble the flower clusters of clover. In contrast, Seneca snakeroot, so named because Indians used its leaves to treat snakebite, bears its pale flowers in long spikes; and fringed polygala, or gaywings, has much larger flowers that look like fanciful magenta birds in flight.

Millipede

Slinking along on dozens of tiny legs, a millipede looks like a cross between an earthworm and a caterpillar. (While some species have fewer than 30 legs and others have several hundred, none have anywhere near the thousand suggested by their name.) Denizens of dark, damp places, millipedes wriggle through soil and un-

der stones and logs, where they feed on rootlets and decaying vegetation. Unlike their relatives the centipedes, which are equipped with poison fangs, millipedes do not bite. When provoked by would-be predators, they coil up tightly to protect their tender undersides, and as a last resort, they can release a foul-smelling toxin.

Mimicry

An Animal Behavior term, this is used to describe the resemblance between two Animals in behavior or physical features such that the two are confused to the advAntage of one or both of them. In Batesian mimicry, an edible mimic resembles a distasteful model making predators less likely to eat it. In Mullerian mimicry, features are shared by two or more noxious species so predators learn to avoid all of them more easily. In Aggressive mimicry, a predator resembles a harmless or attractive species enabling it to approach prey more closely. The term mimicry may also be applied to the Imitation of behavior as in Birds which learn the songs of other species.

Mimicry

Plants and animals sometimes bear a striking resemblance to entirely different plants, animals, or nonliving things. Use of these built-in disguises, called mimicry, plays an important role in survival. A bird in search of insects, for example, is likely to avoid what appears to be an inedible leaf, unaware that it is passing up an entirely edible katydid. The boldly colored viceroy butterfly, though perfectly palatable to birds, likewise is avoided because it looks almost exactly like the foul-tasting monarch. Similarly, the harmless scarlet kingsnake mimics the bright colors of the venomous coral snake. In aggressive mimicry it is the predator who wears a disguise-much like the proverbial wolf in sheep's clothing. Alligator snapping turtles, for instance, lure fish by wiggling their wormlike tongues, while trumpet fish imitate the colors of harmless species in order to sneak up on their prey. Plants also practice mimicry. Certain kinds of trilliums, for example, smell like carrion and so attract the flies and beetles that pollinate their blooms. The aptly named stinking Benjamin is the rankest of these floral mimics.

Mineral

The building blocks of rocks, ores, and gems, minerals are as ordinary as table salt or as rare as rubies. Geologists define a mineral as any naturally occurring solid that was never part of a living organism, has a fixed chemical composition, and has its atoms arranged in a regular crystal pattern. Some 3,000 minerals have been identified, but only about 100 are common. With their varied colors, textures, and wide range of uses, minerals have long intrigued mankind. Some, such as sulfur and fluorite, have important industrial uses; others, such as amethysts, have been imbued with mystical properties; and still others-sapphires, for example-are prized as gems.

Mink

Mustela vison

Valued for their glossy, luxurious fur, minks are bushy-tailed weasels that live in marshes and in thickets near lakes and streams. Though found in nearly every area except the Southwest, minks are rarely seen because they spend the day hidden in burrows or abandoned beaver lodges. At night they hunt for frogs, fish, crayfish, and other aquatic creatures, as well as larger fare, such as muskrats and rabbits. When threatened by foxes, owls, or other enemies, minks put up a terrific fuss, spitting, hissing, and emitting a foul, skunklike odor. They even fight with each other and prefer to spend their lives alone except during the mating season. The young can feed themselves in a few months and mate when one year old. Once widely sought for their fur, wild minks are rarely trapped nowadays. Instead, the animals are raised in captivity. Brown-furred in the wild, ranch-reared minks have been bred to yield coats of various colors, including blond and black.

Minnow

Though the word minnow is commonly used to mean any small fish, it actually refers to members of the largest family of freshwater fish-a family that in North America alone embraces some 280 species. Some of them are indeed small; shiners, goldfish, dace, and chubs, seldom more than a few inches long, all belong to the minnow family and serve as food for larger fish. Others, such as carp and western squawfish, in contrast, grow up to four feet in length and are themselves sought as game fish. In spring and summer many spawning minnows take on showy colors and sprout warty tubercles on their heads-the trappings of courtship. Fallfish protect their fertilized eggs with a layer of stones that they carry to the nest in their mouths. The most unusual breeding behavior, however, belongs to the bitterlings: the female develops a tubelike ovipositor and uses it to inject her eggs into the gill cavity of a freshwater mussel. After being showered with the male's sperm, the eggs develop and hatch within the protective mantle of the mussel, which is unharmed by its nursery duty.

Mint

Peppermint and spearmint are the celebrities of the mint family, lending their freshness to candies, liqueurs, toothpastes, and of course juleps. But botanically, a host of other plants also qualify as mints. These include rosemary, oregano, thyme, sage, and basil-in fact, the mints account for 25 percent of our culinary spices. Bee balm, wild bergamot, and catnip are among the many wild species found in fields and along

roadsides all across North America. Whatever the species, all the mints are characterized by square stems; oval, tooth-edged leaves borne in opposite pairs; and two-lipped tubular flowers of pale purple, pink, or white. The tiny blossoms are massed in whorls or spikes, usually reaching their peak display in midsummer. Volatile oils stored in resinous dots on the stems and leaves give mints their fragrance. In some species, such as peppermint and thyme, the oils are reported to have medicinal properties as well.

Miracle

Biological Philosophy term. An event that contravenes the laws of nature. Such events were not thought of as freaks but as signs of the action of God. Thus, the miracle stories of the New Testament were used to "prove" the existence of God, the divinity of Jesus, the legitimacy of the church, etc. They were at one time much more important to the argument between science and religion than they are today.

Mirage

Often appearing in the distance as shimmering ponds in the middle of roads on hot summer days, mirages result from the bending of light rays by layers of air of different temperatures. The "ponds,» in fact, are simply images of the sky, produced when light rays are bent by the hot air just above the pavement. Under certain conditions objects such as trees or even ships at sea may appear magnified, upside down, or high above their actual locations.

Mistletoe

Phoradendron f1avescens

Though today it is an enduring symbol of the holiday season, in the past mistletoe represented supernatural powers. Awed by the way this parasite sprouts from tree limbs and prospers without sustenance from the soil, primitive man hung it over his doorways to ward off witches. American mistletoe flourishes from New Jersey to Florida, and across the South to California. Clinging to tree branches, its ball of fleshy green leaves and stems may measure several feet across. The flowers are inconspicuous, but the shiny white winter berries attract flocks of birds. The seeds, which are sticky, adhere to the birds' beaks and so are carried from tree to tree to sprout into new clusters of mistletoe.

Mite

Tiny cousins of spiders and scorpions, mites are eight-legged animals that live in soil or water as well as on plants and animals. Of the thousands of species found in North America, some are large enough to be seen, while others are microscopic. Many feed on important crops as well as on stored grain and other products, causing enormous damage. Best known, however, are the parasitic mites, which burrow into the skin of humans and domestic animals. The minuscule larvae of harvest mites, called chiggers, often torment campers in the woods. These pests virtually strip-mine the skin, releasing irritating chemicals that make for endless itching. Various mites also live in nasal passages and other body cavities.

Mixed forest

Between our eastern deciduous forest and the northern coniferous forest of Canada lies an intermediate zone of mixed forest. Stretching from the Great Lakes to Nova Scotia, this broad belt of mixed woodland is characterized by warm summers, cold winters, moderate rainfall, and rich soil. Its trees include a mingling of southerly broad-leaved species, such as maple, beech, basswood, ash, and oak, and northerly conifers, such as white pine, hemlock, balsam fir, and tamarack. Local conditions determine which trees grow where. The cool, shaded north side of a hill in New England, for example, might be all "north woods," with hemlock and fir. Its sunny south slope, in contrast, might support sugar maple, oak, and hickory.

Mobbing

An Animal Behavior term, this is used to describe the response shown by some Animals, especially small Birds, to potential predators, such as Owls, whereby they approach the predator and fly around it calling noisily. Several possible functions have Been suggested for this: for example, it may drive off the predator or draw the attention of others to the danger.

Moccasin

See Cottonmouth.

Mockingbird

Mimus polyglottos

Though mockingbirds have a sweet, melodious song of their own, they are best known for their imitations of the songs of dozens of other birds. So versatile are these mimics, in fact, that their repertoire also includes the sounds of crickets, frogs, and even dogs. Tireless balladeers, they sing for hours at a time, both day and night.

Neatly attired in gray and white, mockingbirds are often seen in gardens, thickets, and low trees, where they aggressively defend their nests against all intruders. In spring and summer they consume huge quantities of insects. In fall and winter, however, their diet turns to fruit, and in parts of the South they sometimes damage orchard crops. Popular nonetheless, these cheerful mimics are the state bird of Arkansas, Texas, Mississippi, Florida, and Tennessee. These birds are renowned for reciting the songs of other birds, from the melancholy coos of mourning doves to the fatuous clucking of chickens. They will typically repeat a phrase over and over again before going on to another.

Modal action pattern

An Animal Behavior term, see Fixed action pattern.

Mojarra

Silvery, heavily scaled fish with forked tails, mojarras commonly cruise the bottoms of warm, shallow coastal seas in extensive schools. Equipped with mouths that can be stretched out to form long, downward-pointing tubes, they root through the bottom sediments, sucking in small shrimps, crabs, and worms. Mojarras often enter the brackish water of bays and estuaries. Some species, such as the spotfin mojarra and the silver jenny of the East and Gulf coasts, even venture into fresh water.

Mole

Built for burrowing, moles have pointed noses, tapered heads, and thick, glossy fur. Shovellike forelegs push soil aside, while powerful hindlegs propel the creatures forward. Though moles are blind or nearly so, their hearing is acute. The eastern mole tunnels near the surface when searching for worms and insects, often leaving unsightly ridges on lawns. Deeper burrows are used for raising young and escaping winter's cold. The star-nosed mole lives near water, diving for snails and aquatic insects. It is named for the fleshy sensory projections on its nose. Our largest species, the seven-inch Townsend's mole, and our smallest, the three-inch shrew mole, both live in the Far West.

Mollusk

Clams, oysters, snails, slugs, squids, and octopuses-all are mollusks, members of the group of animals second only to insects in number and diversity. Mollusks are characterized by contrasts. Some, such as certain clams and oysters, live deep in the ocean, while others, including some kinds of snails, live high on mountain slopes. Though the vast majority have hard shells, others, such as slugs and octopuses, have no shells at all. And while most are smaller than a human hand, the giant squid may grow to a length of 60 feet. All share several bodily traits, however, though they take different forms in different species. All mollusks are soft-bodied invertebrates with a layer of tissue, called the mantle, that surrounds the gills, intestines, and other organs and secretes the substance that hardens into shell. Many feed by means of a rasplike structure called the radula, covered with tiny teeth. Most also have a muscular foot, used both for locomotion and for digging.

A few mollusks are destructive. Shipworms, for example, bore into wood pilings and boats, causing enormous damage. For the most part, however, mollusks are beneficial. Their shells and pearls provide beautiful jewelry, and the flesh of oysters, clams, scallops, mussels, snails, and even squids is a valuable source of food.

Molt

The process of shedding old feathers, hair, or skin is known as molting. In amphibians and reptiles this is a dramatic event, with the whole outer layer of skin being sloughed off at once. When it is time to molt, a snake rubs its snout against a rock or tree until the skin tears, then wriggles out, leaving the old covering behind.

Temperate-zone mammals typically molt twice a year. The fall molt produces a heavy winter coat, which is shed the following spring. The situation is more complicated among birds. Most species, including the familiar songbirds, lose their feathers gradually-a few at a time-over the course of one to three months, and the birds can fly throughout. Ducks and some of the other water birds, in contrast, molt all their flight feathers at once and remain grounded until the new growth is complete.

Monadnock

When erosion wears away a broad plateau, leaving an isolated peak surrounded by lowlands, the resulting landform is called a monadnock. The archetype for these geological features is Mount Monadnock in southwestern New Hampshire; composed of sturdy metamorphic rock, it rises to a height of 3,165 feet. Another famous example, Stone Mountain in Georgia, is a great granite monolith that towers some 825 feet above the surrounding plains. Monadnocks generally survive because they are formed of rock that is highly resistant to erosion.

Monarch

Danaus plexippus

Boldly patterned orange and black butterflies, monarchs are among the greatest migrators of the insect world. At summer's end monarchs from eastern and central North America head south, flying thousands of miles to congregate by the millions in winter havens in the mountains of Mexico. In one colony 20 acres of trees were found to be carpeted by the resting butterflies. Western monarchs gather at wintering sites along the California coast, roosting in groves of Monterey pines and eucalyptus trees. In spring they leave their refuge and start the long trip north; stopping en route, they lay eggs and die. Once mature, the offspring continue the journey northward. Monarchs are milkweed butterflies; the caterpillars feed on the plant's leaves, ingesting its poisonous sap with impunity. The noxious juice protects the fat caterpillars, and later the mature butterflies, from being eaten by birds and other predators: after one taste, they learn not to meddle with monarchs.

Monitoring

Measuring population trends using any of various counting methods.

Monkey flower

Mimulus

Few wildflowers put on as colorful a display as the monkey flowers. Related to snapdragons, they bear a profusion of tubular two-lipped blossoms that, to many observers, look very much like grinning monkey faces. The charming blooms-in yellow, orange, red, purple, blue, or white- brighten streamsides and other damp locations in the East. In the West, where the monkey flowers are most numerous, some kinds also thrive in dry, gravelly soils and on high mountain slopes.

Monkshood

Aconitum

Named for their hood-shaped blossoms, which resemble monks' cowls, these wildflowers prefer the rich soils of mountain meadows and ravines. The blooms-purple, blue, or white-are borne in spiky clusters. A powerful poison called aconitine is contained in the roots of all monkshoods. Used in ancient times to execute criminals, it was once thought to cause the death of wolves as they foraged for roots in winter-hence its alternate name, wolfsbane.

Moon

The Moon has no formal name other than "the Moon", although it is occasionally called Earth's moon, to distinguish it from the generic term "moon" (referring to any of the various natural satellites of other planets). The related adjective for the Moon is lunar (again from the Latin root), but this is not found in combination with the forms seleno-/-selene (again from the Greek). The average distance from the Earth to the Moon is 238,854 mi, which is about 30 times the diameter of the Earth. At this distance, it takes sunlight reflected from the lunar surface approximately 1.3 seconds to reach Earth. The Moon's diameter is 2,159 mi, which is about 3.7 times smaller than the Earth. The Moon keeps nearly the same face turned toward Earth at all times.

About 59% of the lunar surface isvisible from Earth. The side of the Moon that faces Earth is called the near side and the opposite side is called the far side. The far side should not be confused with the dark side, as the unilluminated hemisphere only corresponds to the far side during full moon. Spacecraft are cut off from direct radio communication with Earth when behind the Moon since electromagnetic waves propogate in straight lines.

The Moon makes a complete orbit about the Earth with respect to the fixed stars approximately once every 27.3 days. However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show its sameside to Earth, which is about 29.5 days.

The Earth and Moon have many physical effects upon one another, including the tides. Most of the tidal effects seen on the Earth are caused by the Moon's gravitational pull. Tidal effects result in an increase of the mean Earth-Moon distance of about 4 meters per century, or 4 centimetres per year. The Moon is one-fourth the diameter of Earth and 1/81 the mass.

Mooneye

Hiodon

Mooneyes and their smaller cousins, the goldeyes, are aptly named fish that live in lakes and rivers throughout central North America. Equipped with teeth on the tongue and on the roof of the mouth, they catch and devour minnows, aquatic insects, and small shellfish. The mooneyes' resemblance to other, better-known fish has earned them the alternate name "toothed herring." Up to 18 inches long, they are sometimes sold as smoked fish.

Moon snail

Housed in the whorls of large, rounded shells, moon snails are able predators that plow across the sandy sea floor, leaving a telltale trail. When the snail encounters a clam, it uses its finely toothed tongue, or radula, to drill a hole through the victim's shell, then feasts on the soft flesh within. Females glue their eggs to sand grains, forming curious ring-shaped structures, called sand collars, that are sometimes found washed up on sandy shores.

Moorhen

Gallinula chloropus

Chickenlike birds formerly known as common gallinules, common moorhens live in marshes and weedy ponds, where they feed on insects, snails, and seeds. These waterbirds are agile swimmers, but they also have long toes that enable them to run about on lily pads and other floating plants. Though they sometimes fly to safety when they sense danger, they are weak and clumsy on the wing and are more likely to dash into the vegetation for cover. Moorhens build cuplike nests on platforms of reeds or in shrubs at the water's edge, raising two, and occasionally three, broods a year. The downy chicks follow their parents, catching insects on their own as they roam through the dense vegetation.

Moose

Alces alces

Inhabiting dense forests throughout Canada, Maine, Alaska, and the northern Rockies, moose are the giants of the deer family. They may lack the grace of other deer, but they are nevertheless among America's most magnificent mammals. A bull moose crashing through the underbrush in a northern bog is a sight not soon forgotten. Alaska boasts the largest males: they weigh some 1,800 pounds, stand more than seven feet tall at the shoulder, and have antlers with a spread of over six feet. In addition to a massive body and a big, overhanging muzzle, the moose is characterized by a fold of skin on the throat called the bell. Though long and spindly-looking, its legs are well suited for moving swiftly across snow, wading in water, and swimming.

During the fall rutting season, when their low, mooing calls echo through the forest, bulls battle over cows in savage antler-to-antler confrontations. By December the contests end and the bulls shed their hefty headgear.

In summer, moose wade into ponds and streams to eat aquatic plants, and in winter they browse on twigs and bark. Once exterminated in parts of their range-they were used as food by native Americans and early settlers, and their antlers have always been prized as trophiesmoose have recently made a comeback.

Moraine

The accumulations of boulders, rocks, sand, and other material carried along by glaciers and deposited when the ice melts are called moraines. Lateral moraines form along the sides of valley glaciers and consist of debris that falls down from adjoining slopes. Medial moraines result when two glaciers merge and two lateral moraines unite as a stripe of rubble down the center of the compound glacier. Terminal moraines form along the leading edges of glaciers, where the melting ice drops its cargo of rocks and sediment in a line across the valley. A ground moraine is a layer of debris deposited beneath a glacier. Many moraines in northern regions were left by the great continental ice sheets.

Moray

Thick-bodied eels that swim with serpentine undulations, morays are among the meanestlooking characters in the sea. Though intimidating and large-some are more than six feet long - these denizens of rock and coral reefs are basically shy. Their unnerving habit of keeping their toothy jaws agape is simply the morays' means of breathing. By day, morays seek the solitude and shelter of caves in rock and coral formations, but aided by an extraordinary sense of smell, they can strike out fiercely when a smaller fish swims by-or when a foolhardy diver's hand intrudes on their privacy. After dark, morays leave their lairs to stalk fish and other creatures of the reef.

Morning glory

Ipomoea

Truly a glory of the early hours, morning glories unfurl their colorful trumpet-shaped flowers shortly after dawn, then close them again just a few hours later. The twining vines, which may climb to 10 or 20 feet, are widely planted to decorate fences and trellises. Wild morning glories, however, can also be serious pests, causing damage to crops such as com and cotton. Yet one species-the familiar sweet potato-is an important crop in its own right. Less well known is the wild potato vine, or man of the earth; its giant edible root, growing several feet long and weighing up to 30 pounds, served as an important source of food for both native Americans and early settlers.

Morph

A specific form, shape, or structure.

Mortality

Ratio of the number of deaths of individuals to the population, often described as a function of age; death rate.

Mosquito

Found all across North America, mosquitoes are notorious insect pests. Females lay clutches of 150 to 300 eggs almost anywhere that they can find water, whether in marshes or in discarded tin cans. After hatching, the hyperactive larvae, called wrigglers, eat prodigiously, using bristly brushes on either side of the head to sweep food particles into their mouths. The larvae pupate within a week, and a few days later the longlegged, fragile-looking adults emerge. Males live on a diet of plant juices, but the females of most species need a meal of blood to nourish their developing eggs. They pierce their victims' skin with stilettolike mouthparts, then sip their bloody feast. This strategy is not merely annoying; it can result in the transmission of such serious diseases as malaria and yellow fever. Fortunately, in North America these ailments have been largely eliminated through stringent control efforts.

Mosquito fish

Gambusia affinis

Only 21/2 inches long, the stout-bodied little mosquito fish earned its name from its voracious appetite for mosquito larvae. A native of the Southeast, where it thrives in ponds, ditches, slow-moving streams, and even brackish water, it has been transplanted to other areas of the world to help control the insect pests.

Mosquito fish are live bearers, with the females annually giving birth to three or four broods of some 200 or more fully formed miniature fish. Though inconspicuous themselves, mosquito fish have a number of colorful relatives, including guppies and mollies, that are popular with aquarium hobbyists.

Moss

Among the most primitive of land plants, mosses lack true roots, stems, leaves, or even an internal system of tubes for transporting water and nutrients. In addition, they are incapable of flowering or setting seed and reproduce instead by means of tiny, single-celled spores produced in special capsules. Seldom more than a few inches tall, mosses grow in dense mats. Primitive though they are, mosses are hardy, thriving even on Arctic tundra. Their ability to live on bare and burned-over areas gives them an important role in soil formation. By colonizing bare rock, mats of moss prepare a toehold for higher plants. By absorbing large amounts of water, they help prevent erosion. The most extraordinary of our North i\fierican species is luminous moss. Glittering like gold, this cave-dweller produces its own tiny lenses that concentrate the feeble light of its gloomy environment and so allow it to carry on photosynthesis. The most valuable mosses are the sphagnums, the mosses that form peat. Gradually filling bogs, they convert wet land to dry. The decomposed peat is also mined and used to improve poor soils.

Moth

Generally thought of as lackluster cousins of the beautiful butterflies, moths are indeed usually the stouter and less colorful of the two. Like butterflies, they have patterned wings covered with scales, and most have hollow, coiled tongues for sipping nectar. Moths are best distinguished from their showier relatives by their antennae, which may be feathery or threadlike but never have the clubby tips found on butter fly antennae. Most moths, moreover, are nocturnal, while butterflies are active by day; on many summer evenings the dusky forms of moths are seen fluttering about porch lights. Cecropia moths, found from the Atlantic coast to the Rockies, may have a wingspan of more than five inches. Males locate females with their large feathery antennae, which can sense the odor of a prospective mate more than a mile away. Of the more than 11,000 species of moths and butterflies in North America, the vast majority are moths. Their life cycle, like that of butterflies, includes four stages-egg, larva (caterpillar), pupa (usually a silken cocoon), and adult. Moths generally deposit their eggs on the plants that their larvae eat, although some kinds feed on such fare as fungi, fabrics, and even beeswax. The caterpillars, some of which are quite colorful, feed almost constantly; many, in fact, are destructive agricultural pests. Hawk moths, tiger moths, and tussock moths are some common North American varieties.

Moth mullein

Verbascum blattaria

Found in fields and roadsides throughout North America, the moth mullein sends up three-foot spikes of pretty five-petaled flowers from June through October. Some say the plant was named for the fancied resemblance of its fuzzy stamens to a moth's antennae. Others claim it received its name because its white or yellow blooms attract those night-flying insects. Whatever the origin, country folk used to pack its leaves among their woolens in the belief that they would ward off clothes moths.

Motivation

An Animal Behavior term, this is used to describe the internal changes responsible for making an Animal behave differently at different times. Confronted with food, Animals do not always eat, nor do they attempt to mate whenever a potential partner appears. The study of motivation is aimed at discovering the processes responsible for such changes.

Mountain

Ascend any mountain, whether along the rugged trails of the Colorado Rockies or the gentler slopes of the ancient Appalachians, and you will witness astonishing changes. From their forested foothills to their craggy, snowcapped summits, mountains are layered with. a series of life zones, each characterized by its own distinct community of plants and wildlife.

The towering peaks of the West best dramatize the broad range of conditions encountered from foothills to mountaintop. Douglas firs form dense, fragrant stands on the lower slopes; elk and mule deer graze in flower-filled mountain meadows; farther up, at the timberline, gnarled bristlecone pines and other stnted conifers weather the fierce winds, and delicate forget-me-nots, moss campions, and gentians carpet the alpine tundra with a vivid patchwork of color. Beyone are the perpetually snow-capped summits, virtually devoid of life. Running from Alabama to Newfoundland, the lush, rounded ridges of the East, remnants of peaks once as lofty as those in the West, also exhibit a range of habitats on their slopes.

Moult

A process seen in birds during which old feathers are lost and replaced by new ones.

Mountain ash

Sorbus

The slow-growing, relatively short-lived mountain ashes are pretty little trees that tolerate cold, marginal conditions. As their name suggests, they are most common at higher elevations, on rocky hillsides or along stream banks. Though the European mountain ash, widely planted as an ornamental, grows to heights of 60 feet or more, the native American species seldom exceed 30 feet. With straight trunks and rounded crowns of feathery foliage, the trees wear broad, showy clusters of white flowers in late spring and shiny red fruits in the fall. The fruits persist long after the leaves have fallen, providing a winter feast for many birds. In northern regions moose browse extensively on the twigs.

Mountain beaver

Aplodontia rufa

Neither mountain dwellers nor beavers, these stocky, burrowing rodents live in damp, forested regions of California and the Pacific Northwest. Also called sewellels, mountain beavers are about a foot long, with coarse, grayishbrown fur, rounded ears, and a tiny stub of a tail. Mainly nocturnal, they emerge after dark to forage for small plants. Their burrows, which are often dug into stream banks, usually include special chambers for storing food.

Mountain goat

Oreamnos americanus

Surefooted despite a weight of up to 300 pounds, mountain goats are native to the northern Rockies and spend most of their time high above the timberline. Sharp-edged, skid-resistant hooves enable them to maneuver along narrow ledges and clamber up steep, icy slopes as they search for grasses, lichens, and other food. A dense coat of thick white fur keeps them well insulated in this cold and windy world. Both males and females have backward-curving black horns and bearded chins. Mountain goats migrate up and down the slopes with the seasons, descending from the tundra to the tree line when winter snows threaten their food supply. The kids are born in early spring - usually in single births, but sometimes as twins. They can stand up and walk within minutes of birth, and in just a few days they are able to follow their mothers across incredibly rugged terrain.
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Mountain laurel

Kalmia latifolia

In Appalachian woodlands the spring flowering of mountain laurel provides one of nature's loveliest displays. Often growing in dense thickets, this shrub or small tree, which may reach 30 feet in height, is covered with glossy evergreen leaves, two to four inches long-a handsome foil for the large, showy flower clusters. Each pale pink, cup-shaped bloom resembles a tiny, colorful skirt, giving mountain laurel the alternative name calico bush. Favoring acid soils, mountain laurel is native to open woods and abandoned pastures from Maine to Florida and west as far as central Tennessee. No relation to the old-world laurel used by the ancients for victory wreaths, mountain laurel is poisonous to livestock, though whitetailed deer browse on its foliage with no ill effect.

Mountain lion

Felis concolor

As elusive as they are powerful, mountain lions are large cats that live in more areas than one might imagine- from the swamps of Florida to the deserts and mountains of the West. Known by different names in different places, mountain lions are variously called cougars, pumas, panthers, painters, and catamounts.

Up to five feet long, with gray to tawny fur and a black-tipped tail, mountain lions are solitary creatures that hunt by night, primarily for deer and elk. These furtive predators generally stalk their prey, then rush in for the kill, but they sometimes pounce from overhanging trees or cliffs. Despite the fears of ranchers and campers, mountain lions rarely attack livestock and tend to avoid humans completely. Their bloodcurdling mating call-a scream that sounds like a terrified woman-is sometimes heard in remote areas. Litters of as many as five playful, spotted cubs are usually born in summer, and the young cats remain with their mother for a year or more before setting out on their own.

Mountain sheep

Ovis canadensis

Thanks to their massive, spiraling headgear, mountain sheep are also known as bighorns. Though heavily built, these mountain dwellers are amazingly nimble. Equipped with an excellent sense of balance and cushioned hooves that provide good traction, they are extraordinary climbers and jumpers-well adapted to the rugged, rocky terrain of western mountains from Canada to Mexico. During the rutting season in late fall, the rams compete for females in impressive jousting matches. Charging each other head on, they butt their enormous horns with explosive crashes as the smaller-homed ewes look on. Though the strongest rams usually win these contests, they use up so much energy that they seldom live as long as the losers.

Mounting

An Animal Behavior term, this is used to describe the posture, on the back of the female, adopted by the male during mating in most Birds and Mammals.

Mourning cloak

Nymphalis antiopa

Flashy in flight, the mourning cloak butterfly displays a row of electric blue spots along its shiny gold wing margins. Common from coast to coast, the insect shows its colors not just in summer but in the winter months as well. Hibernating as an adult, it sometimes emerges from the crevices where it winters, and can be seen fluttering about on warm days, even while snow is still on the ground. The caterpillarsblack and bristly with a row of red spots-feed on the leaves of willows, poplars, and elms.

Mouse

Originally used for the old-world house mouse, which was introduced to North America as early as the 1500's, the word mouse now refers to a number of small rodents with soft gray or brown fur, large rounded ears, and a long thin tail. Among the many native North American mice are the tiny harvest mice, which prefer open grassy areas; pocket mice, with pouches on their cheeks for carrying food; jumping and kangaroo mice, noted for their remarkable hopping ability; and the ubiquitous white-footed mice. Since most mice are easy prey for hawks and other birds, as well as four-footed predators, they tend to be nocturnal and remain in hiding during the daylight hours. Abundant throughout North America, mice generally feed on seeds or vegetation, but one, the grasshopper mouse, is itself an aggressive predator.

Mouthbrooding

An Animal Behavior term, this is used to describe a mode of parental care shown by some Fish in which the female protects the eggs within her mouth until they hatch; the young may also return to the mouth thereafter when danger threatens.

Mucus

Slimy, viscous fluid secretion.

Mudminnow

Though not minnows at all (they are more closely related to pikes), the mudminnows are in fact very much associated with mud. They live in weed-choked ponds, sloughs, and slowmoving streams, where they frequently bury themselves tail-first in the bottom mud. Remarkably hardy little fish, they can thrive in water with a very low oxygen content. Our biggest mudminnow, the Alaska blackfish, grows up to eight inches in length. It used to be caught in large numbers in the fall, then frozen for use as winter food for sled dogs.

Mudpuppy

Necturus

Oversized salamanders up to 17 inches long, mudpuppies live in lakes and streams. They are slimy and dull colored with darker spots, and have three pairs of bushy red gills on each side of the neck. Hiding on the bottom by day, mudpuppies go on the prowl at dusk, hunting for fish eggs, crayfish, insects, and other small aquatic prey. In spring, after mating, the females lay several dozen eggs, depositing them one by one beneath sticks, stones, and other underwater objects. The larvae hatch several weeks later and are mature when about eight years old.

Mulberry

Morus

Only two species of mulberries are native to North America: the red mulberry, a good-sized tree up to 70 feet tall, which is widely distributed in the East, and the much smaller Texas mulberry, which occurs in the Southwest. Others have been introduced from Eurasia, including the black mulberry, which was brought over in colonial times. Another, the white mulberry, has been cultivated in the Orient for centuries, since its foliage is the main food of the silkworm. Widely planted in the Southeast in a failed attempt at domestic silkworm culture, it has long since escaped to the wild and now grows throughout the East. A cold-tolerant variety of white mulberry, called Russian mulbeny, has been widely planted in windbreaks in the West. The sweet, knobby multiple fruits of all the mulberries are shaped like blackberries but range in color from white to red to black. Though all are edible, most are consumed by songbirds and other wildlife.

Mule ears

Wyethia

Natives of our western mountain states, mule ears paint hillsides, meadows, and open woods with their cheerful yellow blossoms from spring until midsummer. Reaching a height of two feet, they do not come anywhere near the stature of their stately relatives the sunflowers. Mule ears owe their common name to the shape of the long leaves that grow from their base. Their botanical designation reflects the name of the Pioneer of the Pioneers in the Pacific Northwest, the 19th-century fur trader and explorer Capt. Nathaniel]. Wyeth.

Mullein

Verbascum

The common mullein is easily identified by its spirelike form and woolly gray-green leaves, which have inspired such names as velvet plant and old man's flannel. (People used to line their shoes with the leaves for warmth.) A biennial found in pastures and waste places across America, this Eurasian native produces a broad, ground-hugging rosette of large, felty leaves in its first year. In its second season it sends up a ramrod-straight stalk six to eight feet tall, covered with cheerful yellow flowers.

Mullet

Several species of these fish are found in North America's coastal seas and estuaries. The most abundant are the striped mullet, which sometimes reaches a length of three feet and a weight of 15 pounds, and the very similar but unstriped white mullet. Preferring warm and temperate waters, mullets range from Cape Cod to the Gulf of Mexico; the striped mullet is also found in the Pacific from California south. Mullets feed on algae and small animals that they filter from the bottom mud, grinding them in their gizzardlike stomachs and digesting them in exceptionally long intestines. They travel in large schools and are often seen leaping into the air with a silvery flash, then flopping back into the water with a splash. Although they are mainly saltwater fish, mullets sometimes swim for long distances up coastal rivers.

Multi-brooded

Bird Biology Avian Conservation term.

Producing more than one clutch or brood per season, usually in reference to a life history trait of a species. Natal dispersal: movement from birth (natal) site to first breeding or potential breeding site.

Murre

Uria

Among the most numerous of all seabirds, murres are handsome members of the auk family. Both the common murre and the slightly larger thick-billed murre can be recognized by their prim black-and-white plumage, their long, pointed beaks, and their upright, penguinesque stance. Although their wings are stubby, murres are rapid fliers. They also use their wings to "fly" under the water, diving more than 200 feet in pursuit of small fish and other prey. Murres winter at sea but in summer congregate in huge nesting colonies on far northern coasts and islands. Each pair tends a single egg, laid directly on the bare rock. Strongly tapered at one end, the egg tends to roll in a circle when disturbed, rather than falling off the cliff. At three weeks old, the chicks jump into the sea and are fed there by the adults until they can fly.

Mushroom

Intriguing and diverse, mushrooms come in a wide variety of sizes, shapes, and colors. Most of these fascinating fungi have the familiar umbrella form, with stalk and cap, but on some the tops are conical, and a few even flare out like trumpets. From red and purple to yellow and white, mushrooms are adorned with a rainbow of hues. And while some are deadly poisonous, others are prized by gourmets. Often seeming to spring from the ground overnight, mushrooms sometimes grow in circles, called fairy rings, which were once believed to be footprints left by dancing sprites. The parts we see, however, are only the spore-producing reproductive bodies of the fungus, most of which is hidden underground in the form of a mass of cottony threads called the mycelium. On the underside of their caps, many mushrooms have thin gills radiating like the spokes of a wheel; the undersides of others are perforated with minute pores. These structures produce spores by the millions, to be scattered by the winds. If the spores land on moist soil or rotting wood, new mycelia develop and can live underground for years before sending up mushrooms.

Muskeg

Dotting the vast northern coniferous forests of Canada and Alaska are countless sphagnum bogs known as muskegs. Drainage is poor in these lands of low relief, and glacier-carved depressions are numerous. The result is a patchwork of bogs where ponds have gradually filled in with soggy sphagnum. Slow to decay in these cold climes, the moss eventually accumulated into thick deposits of peat, permitting black spruces and other conifers to take root where there once was open water.

Musk ox

Ovibos moschatus

Beyond the tree line on the wind-whipped tundra of the Far North and on nearby Arctic islands lives the stocky, long-haired musk ox. Both sexes wear broad horns that are plastered against the skull like helmets and curve up at the tips. Feeding on grasses, willows, and other tundra vegetation, musk oxen live in small herds consisting of a single bull and several cows. During the fall mating season, bulls engage in savage battles to establish dominance; in early spring each cow gives birth to a single calf. When threatened, musk oxen form a circle around their calves and face outward, presenting their foes with a daunting array of horns. This defensive ploy works well against wolves but not against humans, who have exterminated the musk ox in much of its former range.

Muskrat

Ondatra zibethicus

Well-adapted for life in ponds, marshes, and slow-moving rivers, muskrats are stocky rodents that can swim for long distances underwater and remain submerged for minutes at a time. They reach a length of two feet and have partially webbed hind feet, a long scaly tail that is flattened from side to side, and lustrous fur that ranges in color from pale brown to almost black. Muskrats build two kinds of shelter: burrows in the banks of streams, and dome-shaped lodges of grasses and reeds in the shallows of marshes; both have underwater entrances. During the summer muskrats can often be seen carrying mouthfuls of cattails or bulrushes to their dens; they also feed on crayfish, clams, and fish.

Musk turtle

Sternotherus

Close relatives of mud turtles, musk turtles live in bayous, ponds, and other quiet waters, which they seldom leave except to nest and bask in the sun. They forage on the bottom for insects, carrion, and other morsels- including the bait on fishhooks. They are not at all appreciated by the anglers who catch them, however: these pugnacious little reptiles not only bite when handled, but also emit a foul-smelling musky fluid. Of our several species of musk turtles, only the aptly named stinkpot extends its range beyond the Deep South.

Mussel

Found both in fresh water and in the sea, mussels are bivalve mollusks that resemble clams. The saltwater kinds live mostly in shallow waters and in the intertidal zone, where they are found partially buried in the bottom or attached to rocks, pilings, and other supports. Often living in clusters or even huge colonies, mussels anchor themselves in place with tough threads secreted by a special gland. The widespread blue mussel is edible and highly esteemed as food. American Indians also ate large quantities of freshwater mussels, whose shells were at one time used for making mother-of-pearl buttons as well. Unlike saltwater mussels, whose larvae float with the plankton, the larvae of many freshwater species are parasitic. Looking much like miniature clams, the larvae are expelled by the adult mussels and clamp shut on the fins and gills of fish. There they are enclosed in fleshy cysts and feed on fish tissue until they mature and drop off into the water.

Mustard

Of all the members of this large plant family, black mustard is the most familiar. Its yellow flowers tum whole fields golden in spring; its young leaves are cooked and eaten as greens; and its dark brown seeds flavor the popular condiment that bears its name. Food plants such as cabbage, kale, broccoli, turnips, and radishes, as well as many garden flowers, also are family members. Wild mustards, many of them back-

yard weeds, include the desert candle, prince's plume, winter cress, and shepherd's purse. All have four-petaled yellow, purple-red, pink, or white flowers. The petals form a cross that gives the family its scientific name, Cruciferae, or crossbearers.

Mutualism

The close association of individuals of two different species for the benefit of both is called mutualism. A cow, for example, provides both living space and food for the bacteria that live in its digestive tract; the bacteria, in tum, help break down cellulose in the cow's food, rendering it digestible. The yucca plant and the yucca moth likewise have a mutually beneficial relationship. The plant relies on the moth for pollination, while the moth's larva depends on the plant for seeds, its sole source of food. In the case of lichens-plants composed of an alga and a fungus living together-the alga manufactures food for both, while the fungus absorbs water and helps shade the alga.

Mutualism

An Animal Behavior term, this is used to describe association between different species to their mutual advAntage (see also Symbiosis).

Native

A naturally occurring species.

Natural bridge

Arches formed of solid rock, natural bridges are elegant erosional remnants. Some are created when most of the roof of a limestone cave collapses, leaving a small section as a natural span. A famous example of this type is Natural Bridge in Virginia. Ninety feet long and rising almost 200 feet above Cedar Creek, it was once owned by Thomas Jefferson and now has a highway running across its top. Other natural bridges occur when meandering streams or percolating groundwater undercut walls of rock, gradually enlarging an opening to form a graceful arch. The world's largest natural bridge is Rainbow Bridge in Utah. Spanning 275 feet and towering to a height of almost 300 feet, it is, according to Indian legend, a rainbow turned into stone.

Natural gas

An important energy resource, natural gas is a mixture of methane and other flammable gases. Like coal and oil, it was formed from long-buried organic matter and is usually found with or near petroleum deposits. (Natural gas provides the pressure for oil gushers.) Nonpolluting and easy to transport, it is used for cooking, heating, and many industrial purposes. The major natural gas fields in North America are found in Louisiana, Oklahoma, Texas, and Alberta, Canada.

Natural History

Biological Philosophy term. An obsolescent term: the non-systematic study, description, and classification of animals, plants, minerals, and other natural objects: zoology, botany, mineralogy; with emphasis on study in the field rather than the lab. It is not usually applied to astronomy, physics, and chemistry.

Natural history

Natural history is a broad term for what are now usually viewed as several distinct sciences.

. Most definitions include the study of living things; other definitions extend the topic to include all of nature. A person interested in natural history is known as a naturalist.

The roots of natural history go back to ancient philosophers who analyzed the diversity of the natural world. From the ancient Greeks until the work of 18th century naturalists, the central concept tying together the various domains of natural history was the scala naturae, which arranged minerals, vegetables, animals, and higher beings on a linear scale of increasing "perfection." Natural history was basically static through the Middle Ages, when the work of Aristotle was adapted into Christian philosophy. After a time, scholars (herbalists and humanists, particularly) returned to direct observation of plants and animals for natural history, and many began to accumulate large collections of exotic specimens and unusual creatures. The rapid increase in the number of known organisms prompted many attempts at classifying and organizing species into families, culminating in the system of Linnaeus. Natural history as a term was frequently used to refer to all descriptive aspects of the study of nature, as opposed to political or ecclesiastical history; it was the counterpart to the analytical study of nature. Natural history, formerly the main subject taught by college science professors, was increasingly relegated to an amateur activity, rather than a part of science proper. Particularly in Britain and America, this grew into specialist hobbies. Amateur collectors and natural history entrepreneurs played an important role in building the large natural history collections of the 19th and early-20th centuries.

Natural history museums

The term "natural history" forms the descriptive part of institution names, such as Smithsonian's National Museum of Natural History in Washington D.C.

Natural history museums played an important role in the emergence of professional biological disciplines and research programs. Particularly in the 19th century, scientists began to use their natural history collections as teaching tools for advanced students and the basis for their own research efforts.

Natural history societies

The term "natural history" alone, or sometimes together with archaeology, forms the name of many national, regional and local natural history societies that maintain records.

Naturalism

Philosophy Term

Methodological naturalism. Naturalism is any of several philosophical stances, (including strange entities like non-natural values, and universals as they are commonly conceived)

. Naturalism does not necessarily claim that phenomena or hypotheses commonly labeled as supernatural do not exist or are wrong, but insists that all phenomena and hypotheses can be studied by the same methods and therefore anything considered supernatural is either nonexistent, unknowable, or not inherently different from natural phenomena or hypotheses.

Any method of inquiry or investigation or any procedure for gaining knowledge that limits itself to natural, physical, and material approaches and explanations can be described as naturalistic.

Many modern philosophers of science use the terms methodological naturalism or scientific naturalism to refer to the long standing convention which makes the assumption that events in nature are explained only by natural causes, without assuming the existence or non-existence of the supernatural, and so considers supernatural explanations for such events to be outside science. They contrast this with the approach known as ontological naturalism.

This distinction between approaches to the philosophy of naturalism is made by philosophers supporting science and to counter the tendency of some proponents to refer to methodological naturalism as scientific materialism or as methodological materialism and conflate it with metaphysical naturalism to support their claim that modern science is flawed. They contrast this with their preferred approach of a revived connection which welcomes supernatural explanations for natural phenomena and supports "theistic science" or Natural Law

Biological Philosophy term. The idea that not only is nature governed by laws, but that nature has written in the hearts of human beings the laws by which they should govern their lives. In other words, we can know without the help of the Bible the difference between right and wrong. Natural law is conceived to be the foundation on which positive law, the specific laws of individual groups, tribes, nations, is built. It is considered a universal law and is still an operative concept, though the term itself may not be used. The notion of natural law is almost universally rejected by modern social science. Nevertheless, the Nurenburg war-crimes trials after World War II, for instance, had no foundation in written laws, and were based on the assumption of natural laws binding all human beings; the present insistence on human rights also implies the affirmation of a kind of natural law.

Natural Philosophy

Biological Philosophy term. Jefferson: "To describe the phenomena of nature, to explain their causes...and to inquire into the whole constitution of the universe.... But natural philosophy is subservient to purposes of a higher kind, and is chiefly to be valued as it lays a sure foundation for natural religion and moral philosophy; by leading us, in a satisfactory manner, to the knowledge of the Author and Governor of the universe". In the eighteenth and preceding centuries natural philosophy was the general term for most of the studies we group under the term natural science today.

Natural Religion

Biological Philosophy term. A Renaissance idea that survived in the Enlightenment. According to the Renaissance idea, God had revealed certain religious truths to Adam and Eve, and these had been passed down to all peoples, so that the residue of this revelation could be found in all cultures of the world: There is one God; we must worship him; we know right from wrong as exemplified in the Ten Commandments of Moses; we know there will be reward and punishment after death. This is the idea that the Jesuits had when they went to China; they thought they found this in Confucius. In the Enlightenment the notion of a primitive revelation was dropped, but some of the basic ideas survived: observation of the natural world taught the notions of one God, the need for worship, natural knowledge of right and wrong, perhaps even reward and punishment.

Naturalist

Someone who studies Natural History, probably in the field rather than the lab.

Natural selection

The process by which individuals sufficiently adapted to their environment to survive and breed successfully have their characteristics passed on to following generations. Those that aren't sufficiently adapted either do not themselves survive to breed, or their offspring do not survive.

Nature

Biological Philosophy term. The tell-tale word of the Enlightenment, the one that slips into every argument without challenge, and so the one with the most slippery meaning. Nature is best understood according to what it is opposed to:

To Supernature or the action of God in the world, e.g., divine grace or help in living a good life, divine revelation, or God's telling human beings the truth about Himself and the world in the Bible, divine intervention in history to select a chosen people or redeem humanity. Nature is what is left when you exclude all these influences. The idea of the supernatural is denied by the Enlightenment, which raises the question: if there is a God, as many Enlightenment thinkers believed there was, is he natural, a part of nature, or is he, as the creator of nature, beyond nature, i.e., supernatural? Perhaps the way to address this question is this: God is "natural" in that he created the world according to certain laws and lets it operate by those laws. He is not arbitrary. A "supernatural" God would be a God who arbitrarily manipulates creation, who violates its laws at will to bring about events that he happens to be interested in. This is the kind of God the Enlightenment didn't want to have to deal with because what worried the Enlightenment was Miracles, events that violated the laws of nature and presumably came about through the work of God or, perhaps, the devil. These were considered important to the arguments for and against Christianity. To the Enlightenment, miracles were superstition.

To Technology or art:

Nature is what is not made by human hands, what is not the product of human technology.

To Nurture or Culture or History:

Nature is those aspects of human life which are attributable to heredity, to biological configurations and not to the influences of culture.

To Europe and the Authority of Tradition:

(An extension of the opposition above). Jefferson: "Nature was America for Jefferson. His interest in nature and his use of the word was therefore a form of nationalism. In Europe national sentiment was expressed through a common history, a royal family, a culture, or a literature. In America and for Jefferson it was expressed through, and as, nature.

To The Church or Feudalism:

Before the Enlightenment, and to large corporate enterprise and the state after the Enlightenment. "Nature was a valley between two ranges of social control”.

To Consciousness:

Emerson: Nature is anything that is not me; by implication, all that is not part of my personal consciousness, including other people and my own body as an object of consciousness.

Nature

Nature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe. "Nature" refers to the unspoiled areas of the world, and also to life in general. The term generally does not include manufactured objects and human interaction unless qualified in ways such as, e.g., "human nature" or "the whole of nature". Nature is also generally distinguished from the manmade world. The word "nature" derives from the Latin word natura, or "the course of things, natural character." Natura was a Latin translation of the Greek word which originally related to the innate way in which plants and animals grow of their own accord, and to the Greek word for plants generally. The concept of nature as a whole, the physical

world, is a more recent development that gained increasingly wide use with the advent of modern society in the last several centuries.

Within the various uses of the word today, "nature" may refer to the general realm of various types of living plants and animals, and in some cases to the processes associated with inanimate objects; the way that particular types of things exist and change of their own accord, such as the Earth,and matter, of which all these things are composed. It is often taken to mean the wild animals, rocks, forest, beaches, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention. This more traditional concept of natural things which can still be found today implies a distinction between the natural and the manmade worlds, with the latter being understood as that which has been brought into being by a creation of humans.

Nature documentary

A nature documentary is a wildlife film or nature documentary is a presentation about animals or other non-human living creatures, usually concentrating on film taken in their natural habitat. Such programmes are most frequently made for television, particularly for public television and science channels, but some are also made for the commercial television networks. Wildlife and natural history films have boomed in popularity and have become one of modern society's most important sources of information about the natural world. Yet they have been largely ignored by film and television critics and scholars. Most programs or series focus on a particular species or family of animals. Although most take a scientific and educational approach, some present animals purely for the viewer's pleasure. Although almost all have a human host or presenter, the role varies widely, ranging from explanatory observer to extensive interaction or even confrontation with animals. Well-known nature documentary makers and presenters include Marty Stouffer and Marlin Perkins. Most documentaries are for television and are usually of 25 or 50 minutes duration, but some are made as full-length cinematic presentations.

In recent years most traditional style 'blue chip' programming has become prohibitively expensive and are funded by a set of co-producers, usually a broadcaster from one or several countries, a production company and sometimes a distributor which then has the rights to sell the show into more territories than the original broadcaster. Alternatively, programs are simply done as cheaply as possible, now being shot on Video in a day and a half, rather than on film in a year and a half.

Nature essay

Biological Philosophy term. A literary form. It is hardly necessary to define essay; it is more important to define literary writing in terms of scientific writing. Here are a couple of sentences from John Burroughs: "Details are indispensable to the specialist, but a knowledge of relations and of wholes satisfies me more.... All the facts of natural science that throw light upon the methods and the spirit of nature are doubly welcome... The ground underfoot becomes a history, the stars overhead a revelation, the play of the invisible and unsuspected forces about me and through me a new kind of gospel....".

Navigation

An Animal Behavior term, this is used to describe the ability of Animals to find their way to a goal regardless of the lcation from which they start (see also Homing). To do this requires more than just Orientation using a "compass," but also information equivalent to possessing a map, as the compass direction of the goal depends on knowing the position of the starting point.

Needle

Narrow leaves found in conifers.

Needlefish

Sleek and flashy speedsters of coastal seas, needlefish are streamlined creatures with elongated bodies that taper to long, pointed beaks. Armed with sharp teeth, they prey by night on smaller fish, overtaking their quarry with bulletlike runs and spectacular out-of-the-water leaps that are worthy of their relatives the flying fish. Edible despite the unappetizing greenish hue of their flesh, needlefish have a strange history of turning the table on fishermen. Dazzled by nighttime lights on boats and propelled by vibrating tails, they sometimes hurl themselves headlong out of the spray and smash into unsuspecting boatmen. The five-foot houndfish, the largest of the needlefish, can become a truly lethal weapon: hurtling through the air, it can strike with enough force to seriously injure anyone who happens to be in its path.

Neighborhood effect

Increased impact of landscape features located in the immediate neighborhood of a focal patch compared with features farther from the local patch.

Nematode

Ranging in size from microscopic to many feet in length, nematodes are incredibly abundant roundworms that live virtually everywhere. The many free-living species abound in soil and water-and even in such hostile environments as hot springs and cider vinegar. Others live as parasites on plants and animals. Numerous kinds are food or crop pests, and some nematodessuch as hookworms, lungworms, and trichinae-cause serious illnesses in humans as well as in dogs, sheep, horses, and other animals.

Neophobia

An Animal Behavior term, this is used to describe the dislike of novelty, especially where Animals reject food which is novel or presented to them in a different place (see also Bait shyness.)

Neotropical migrant

Bird Biology Avian Conservation term.

A migratory bird in the Neotropical faunal region. The Neotropical Migratory Bird Conservation Program focuses primarily on species that nest in the Nearctic faunal region and winter in the Neotropical region.

Nest

A structure built by Birds and other Animals in which to raise their young. While some creatures spend their lives in the open, exposed to the elements and to enemies, others build nests-safe havens that serve as warm beds, cozy homes, protected nurseries, hibernation chambers, or even, in some cases, small cities. Nests may be used year-round or only during the breeding season, and they may be built of found materials or of substances produced by the nest builder itself. Since birds and mammals are warm-blooded animals whose bodies must be kept at a constant high temperature, most of them build nests to help keep their offspring warm. Though they sometimes serve to shelter the adults as well, their primary purpose is to provide a safe, warm place for the developing young. Birds' nests, which are usually cup shaped, saucer shaped, or domed, are placed in bushes, trees, buildings, or even on the ground. Most are one-family structures built of grass, sticks, mud, or other material. Woodpeckers, in contrast, dig holes in trees, while kingfishers and some seabirds and swallows nest in burrows. Others, including cormorants, herons, gulls, and terns, seek safety in numbers and take advantage of limited space by nesting in colonies. Though birds are the best-known nest builders, some kinds don't make nests at all. A number of seabirds and a few land birds simply lay their eggs on ledges or on the ground; goatsuckers, for example, incubate their eggs on bare soil or forest litter. Nor do all mammals build nests. Bats retreat to caves, tree holes, or buildings, while large, fast-moving animals such as deer, bison, and whales give birth to well-developed young and so have no need for nests.

A great many mammals do build nests, however, often in the form of burrows lined with grass or fur. A few carnivores, such as foxes and weasels, use burrows to protect their young, and many rodents-pocket mice and chipmunks, for instance-use them not only as nurseries but for food storage and as permanent homes.

The nests of other mammals come in a variety of forms. Jumping mice construct domes of grass, while squirrels build both leafy platforms and domed nests high in trees. Wood rats assemble large piles of sticks, bones, and other debris, which they place in trees, shrubs, or among rocks. Beavers, perhaps the most ingenious engineers of all, build sizable lodges complete with underwater entrances.

Amphibians, rather than building nests, lay eggs that are protected in jellylike strings or masses. Few reptiles build nests, either, preferring to bury their eggs in the ground and leave them to hatch unattended. Alligators and crocodiles, however, lay their eggs in large mounds of vegetation, and the female stands guard until the hatchlings can fend for themselves.

Among the few fish that build nests are the sunfish, which lay their eggs in sandy depressions that are swept clean of debris. Much more complex are the nests of male sticklebacks; constructed of grass and other plant material, they are used to attract females and shelter the eggs.

While most nests are thought of as beds, nurseries, or single-family dwellings, the nests of social insects such as ants, bees, and wasps are more like small cities. They include nurseries, food storage areas, the queen's chambers, and other specialized zones, all connected by intricate networks of passageways. Hundreds of

sterile workers are constantly busy collecting food, defending and cleaning the nest, making repairs, and tending the young.

A few other invertebrates build nests. Tarantulas, for instance, live in burrows, while trapdoor spiders reside in web-lined tunnels fitted with hinged doors at the top. And webworms and tent caterpillars spin webs that shelter large numbers of larvae.

A nest that has been built and abandoned by one animal is likely to be used again by others. Woodpecker holes, for example, are commonly taken over by other cavity-nesting birds and even by bats and squirrels. When a catbird leaves its nest, a cup-shaped structure placed in a low shrub, a white-footed mouse may roof it over and use it to raise its own young; and once the mouse has left, a bumblebee queen might move in and start a colony. The chambers and tunnels excavated by prairie dogs likewise may later be adopted by burrowing owls.

In some cases nests are occupied by intruders long before their builders move out. Ants' nests almost always contain a variety of other insects; some prey on the ant larvae, while others are simply harmless freeloaders. And a few species of wasps, bees, and ants never build nests of their own but take over those of other insects, often by force.

The nests of birds and mammals are not immune to intruders, either. They often contain fleas, mites, and other irritating parasites. But perhaps the most flagrant interlopers of all are cowbirds; they regularly shirk their parental responsibilities by laying eggs in the nests of other birds, leaving their offspring to be raised by unwitting foster parents.

Nest parasitism

Bird Biology Avian Conservation term.

Expression used by some authors for brood parasitism; the taking over of nests of other species.

Nest success

Bird Biology Avian Conservation term.

Survival of eggs or nestlings (usually excluding those of brood parasites)(see Hatching success).

Net reproductive rate

The number of offspring that females are expected to bear on average during their lifetimes.

Nettle

Urtica

Best-known for the itchy, burning rash they cause on contact with the skin, nettles are natural practitioners of chemical warfare. The bristly hairs that cover the leaves and stems are actually hollow tubes filled with an irritating fluid. When a person brushes against the plant, the hairs inject their noxious contents, causing a rash that can last for hours. Thriving in rich, moist soil, nettles grow as weeds across much of North America. Though universally cursed by gardeners with ungloved hands and by walkers with bare legs, the plants were once regarded as valuable. Rich in vitamin C, the young shoots, boiled to remove the irritants, make a tasty soup or vegetable. Nettles also yield a strong fiber and have been cultivated for textiles, paper, and rope.

Newt

Like other salamanders, some of our newts are strongly aquatic, others primarily terrestrial. But still others, including the wide-ranging eastern newt, manage to be both by turns. The newt's gilled aquatic larva hatches in the spring and spends its first summer in the natal pond. The gills then disappear, and the larva transforms into a brightly colored land-dwelling creature known as a red eft. Foraging for insects and worms, the diminutive predator roams the forest floor for the next two or three years. Then, at sexual maturity, the eft returns to water and changes once again-this time into a larger, dull greenish adult newt-and spends the rest of its life as an aquatic hunter.

Newtonian Universe

Biological Philosophy term. The idea that the universe works mechanically, like a clock. It is called Newtonian, because it arose from the Newtonian discovery of the laws of gravity and planetary motion. The Newtonian Universe is a deterministic universe. See Mechanistic.

Niche

The role a species or individual plays in relation to all the other kinds of plants and animals in its habitat is known as its ecological niche. In a coniferous forest, for example, some of the animals are insect eaters, others are large carnivores, and still others feed on seeds; each kind occupies a separate niche. The hawks and owls that live there, in tum, are both large birds of prey that eat smaller birds and mammals. But since the hawks operate by day and the owls by night, they occupy different niches.

Niche

Multidimensional utilization distribution, giving a population's use of resources ordered along resource axes.

Niche

An Animal Behavior term, this is used to describe the position in the ecological community occupied by a particular species defined by the HABITAT it occupies, what it eats and what it is eaten by.

Nighthawk

Chordeiles

Not hawks at all, the nighthawks are close relatives of the whippoorwill. And like their cousin, they are active by night, especially at dawn and dusk, snatching up insects in flight in their large gaping mouths. Birds of open places rather than the forests preferred by whippoorwills, nighthawks nest on burned-over areas, fields, and deserts. The common nighthawk has also taken to nesting on the flat gravel roofs of buildings in cities. The display flight of the male is a familiar sight at dusk: hovering high above the building where its mate is guarding her two eggs, the bird dives suddenly downward, with its wings making a loud booming sound. In early fall the nighthawks begin drifting south toward their wintering grounds in the tropics, traveling by day in large, silent flocks.

Night heron

Stocky birds with shorter necks and legs than other herons and egrets, the night herons are nonconformists in their habits as well. Whereas most of their kin feed by day and gather to roost at night, the night herons set out at dusk to begin their search for food. While it is true that they occasionally hunt during the day, especially when skies are overcast, for the most part they spend the daylight hours hidden in trees and wait until dark to prowl in shallow streams, marshes, and lagoons. The wide-ranging black-crowned night heron, which breeds on every continent except Australia and Antarctica, is found across most of the United States. It feeds primarily on fish but also takes frogs, mice, and even the young of other birds. The yellow-crowned night heron, which is most common in the Southeast, has a stouter bill than its cousin and preys mainly on hard-shelled crayfish and crabs. Although night herons usually nest in colonies in trees, shrubs, or dense cattails, returning year after year to the same nests, the less gregarious yellow-crown sometimes nests alone. Both parents incubate their clutch of three to five blue-green eggs and share in feeding the young. Immature birds are streaked and spotted with brown and do not acquire full adult plumage until they are three years old.

Nightshade

A large and varied group of plants, the nightshade family is notorious for its many poisonous species. Yet it also includes some of our most important crop plants, among them tomatoes, potatoes, sweet and hot peppers, eggplants, and tobacco. Like other, more dangerous species, however, even potatoes and tomatoes have slightly toxic leaves and stems, and some of the hot peppers contain compounds so irritating that they can easily cause blisters. Among the wild species are bittersweet nightshade, a rampant weed, and black nightshade, named for its dark fruit. Though poisonous as it develops, the fruit makes delicious jams and pies when ripe. Buffalo bur and horse nettle also contain poisons but are so thorny that they are avoided by both humans and livestock. The edible ground cherries and toxic thornapples are nightshades, too- members of a family so diverse that it also includes the innocent petunia.

No jeopardy biological opinion

Endangered and Threatened species term.

A Service Section 7 biological opinion that determines that a Federal action is not likely to jeopardize the existence of a listed species or result in the destruction or adverse modification of critical habitat.

Noble Savage

Biological Philosophy term. The idea, connected with Jean-Jacques Rousseau, that the source of human evil is civilization, and that human beings untouched by civilization are naturally noble, moral, good. See Savage.

Nocturnal

Active after dark.

Nocturnal animal

During the night, when daytime creatures such as human beings are fast asleep, a host of nocturnal animals are wide awake and on the move -whether searching for food, escaping from enemies, or courting the opposite sex. Wellsuited to darkness, these creatures depend less on eyesight than on smell and hearing--senses that are quickened by the cool, calm, damp night air, through which sounds and odors carry especially well. Unlike their human cousins, most mammals are nocturnal. The timid, wide-eyed woodland rodents, which nibble on plants and seeds under cover of darkness, are in turn consumed by such predators as foxes, bobcats, and weasels. Three familiar omnivores- raccoons, skunks, and opossums-take advantage of the smorgasbord available in loose-lidded garbage cans. And high overhead, flying squirrels emerge from their dens to chatter among themselves and glide from tree to tree, while sonar-guided bats flutter through the air in pursuit of insects. Among the birds that work the night shift, the best known are the owls, which, guided by moonlight as well as by sound, swoop down on unwary mice and voles. Night herons also set out at dusk to search in shallow water for fish and crayfish. Whippoorwills and nighthawks are up and flying as well, sweeping the air for moths and other night-flying insects.

In spring and fall hordes of migrants add to the action. While many of the larger birds migrate by day, the smaller, more vulnerable songbirds travel under the stars. This enables them both to avoid diurnal birds of prey and to spend the hotter daylight hours resting and feeding. At ground level, nightcrawlers inch from their tunnels in the earth, while centipedes scurry among fallen leaves in search of food. All kinds of beetles and moths collect on our window screens, while garden spiders busily spin their webs and throngs of crickets and katydids fill the night air with their serenades.

In the deserts of the Southwest, the majority of animals are active by night, since few can survive the searing heat of day. During the sunlit hours only a few birds and butterflies make themselves known, while the cool of evening brings out a parade of sidewinders, scorpions, kangaroo rats, owls, and coyotes. Even some of the plants are more "active" by night. Yuccas and cereus cacti, for example, bloom after dark and so accommodate the night-flying moths that are their pollinators.

Nighttime seashores are less noisy but no less populated than during the day. Beach fleas and sandhoppers by the thousands emerge from their burrows and are joined by multitudes of sideways-scuttling ghost crabs-all gleaning tiny morsels of plant and animal matter that have been left by the beach's day visitors or dumped by the tide. Loggerheads and other sea turtles lumber from the surf to scoop out sandy nests and deposit caches ofleathery eggs that resemble PingPong balls and hatch some eight weeks later. The California grunion also lays its eggs at night. Hosts of these silvery fish flop ashore on the highest tides in spring. There the females work their tails into the wet sand to deposit their eggs, while the squirming males fertilize them. Their task accomplished, the grunions then ride the next wave back into the sea. Within the oceans themselves, darkness moves vertically, retreating far below the surface under the penetrating light of day, then returning to the surface after sunset. Following this daily fall and rise of darkness are millions of copepods and other tiny crustaceans that sink as the light advances, then slowly make their way upward at dusk to feed on microscopic plants. These animals attract night-feeding fish, shrimp, and squids, which are in turn consumed by larger fish, such as sharks, whose voracious feeding frenzies often roil the silvery moonlit surface.

Life carries on even in the darkest ocean depths. Sponges, clams, sea cucumbers, fish, and other animals live far below the blue-green twilight zone, where they survive by preying on each other and by scavenging the table scraps that filter down from meals consumed by their neighbors above. These creatures of the murky deep are remarkably adapted-like the blind and colorless salamanders of deep caves-to a life of eternal night.

Node

Part of stem at which leaves arise.

Norway rat

Rattus norvegicus

Native of the Old World, the Norway rat did not reach our shores until the late 18th century. Before long, however, it became the dominant rat of both city and countryside. Slightly larger than its cousin the black rat, another old-world immigrant, this gray-brown rodent grows up to 10 inches long, excluding its scaly tail, and often weighs over a pound. Omnivorous and extremely destructive, Norway rats eat almost anything from garbage to grain, often gnawing their way into stored supplies and contaminating the food. They live practically everywhere-burrowing into trash heaps, invading the spaces between walls, digging tunnels in fields-and form well-organized colonies. Extremely prolific, females can breed at three months, and produce an average of five litters a year. Norway rats have been known to attack humans, and like the black rat, they carry a number of serious diseases.

Nudibranch

A marine snail without a shell; also called a sea slug.

Numerical response

Change in the population size of a predatory species as a result of a change in the density of its prey.

Nut

Dry and often hard fruit containing a single seed. See Fruit.

Nutcracker

Nucifraga columbiana

Bold and lively members of the crow family, Clark's nutcrackers live in the chilly coniferous forests of the Rocky Mountains and the Sierra Nevada, where they specialize in prying the seeds from pinecones. They are particularly fond of the large, nutritious nuts of pinyon pines. In late summer and fall the birds eat some of the seeds on the spot, but they also begin storing them for a winter food supply. Tucking them into a pouch under the tongue, they fly to less-snowy lower slopes, where they poke holes in the ground with their pointed bills and bury several seeds in each. A single nutcracker making many such trips can cache over 30,000 seeds in a year. Remarkably, by remembering the positions of nearby landmarks, nutcrackers find and retrieve their hordes months later--even when the ground is covered with snow.

Nuthatch

Sitta

Unique in their ability to climb headfirst down tree trunks, nuthatches busily probe the bark for insects and spiders; they also eat acorns and nuts, which they wedge into crevices. Their name derives from the term nut-hack, referring to the way in which they use their beaks to hack open these wedged bits of food.

Common winter visitors to suet- and seedfilled bird feeders, nuthatches range from Canada south into Mexico. Our best-known species is the white-breasted nuthatch, nattily patterned in blue-gray, black, and white. Others include the red-breasted, brown-headed, and pygmy nuthatches. Forest dwellers that nest in tree cavities, they are especially partial to abandoned woodpecker holes. These appealing little creatures, quite fearless around humans, have endeared themselves to bird lovers far and wide.

Nutria

Myocastor coypus

An immigrant to our shores from South America, the nutria, also known as the coypu, is a whiskered, muskratlike aquatic rodent some two feet long, excluding its long naked tail. Introduced years ago in the southern states to stock fur farms, some escaped and their descendants have since made themselves at home in scattered locations all across the continent. Nutrias excavate snug burrows in muddy waterside banks and feed by night on the varied water plants growing at their doorsteps. Like raccoons, they grasp their food with their dexterous paws and deftly feed themselves by hand. Able swimmers, even baby nutrias can paddle about in swamps and ponds within a day of their birth. The unusually high position of the mother's mammaries along her sides enables the precocious young to cling to her back and suckle even as she swims.

Nymph

Pre-adult stage in certain insects, notably bugs, which has some characters in common with the adult stage.

Oak

Quercus

The most widely distributed of all our trees and shrubs, oaks are, in the main, slow-growing woodland monarchs favoring well-drained soil. But of our 68 native species, some prefer swamps, others grow on prairies, and shrubby evergreen oaks thrive in the arid Southwest. The toughness of their wood has made oaks symbols of stout endurance. Some species, in fact, yield the densest of all American timberswood so hard and resistant to decay that in the days before steel, it was the material of choice for shipbuilding. Oaks also supplied bam timbers, axles, mine props, and even the wedges that frontiersmen used to split other woods. As an aid to identification, the oaks are divided into two broad groups: red oaks and white oaks. The leaves of the whites have rounded lobes, and their sweet acorns take six months to mature. The red oaks, in contrast, have tiny bristles at the tips of their leaves or pointed lobes, and bitter acorns that take two years to mature.

Ocean

A large expanse of sea. The oceans surrounding Canada are the Pacific, Atlantic and Arctic. One great, continuous body of salt water that encircles the globe, the ocean covers some 70 percent of the earth's surface. This vast circulatory system provides moisture for the rain that sustains life on land; it buffers our climate; and it teems with an astonishing variety of life, from microscopic plankton to gargantuan whales. The water is rich with dissolved minerals that were washed in from the land, especially sodium chloride-ordinary table salt-which accounts for its characteristic taste and smell.

Winds keep the seas in constant motion and help produce the currents that circulate in welldefined patterns. One of the best-known currents is the Gulf Stream. Flowing northward in the Atlantic Ocean, its relatively balmy waters warm coastal regions all along the eastern seaboard. In the Pacific Ocean the California Current chills the coastal strip in summer but makes its winters mild. Meanwhile, the sea level rises and falls with the tides, which roll in and out on a regular schedule in response to the gravitational pull of the moon and sun.

The relentless movement of the sea, driven by winds, currents, and tides, generates waves that batter the coast, constantly altering the profile of the land. The continents themselves do not end at the shoreline; instead, they slope off gently into the ocean, creating underwater plains known as continental shelves. Along our east coast the shelf is quite wide, in some areas extending dozens of miles out to sea before plunging steeply to the ocean floor. On the Pacific coast the shelf is much narrower-barely present at all off parts of California. Penetrated by sunlight and loaded with nutrients, the continental shelves host a wealth of marine life and, in places, hold huge reservoirs of petroleum.

Ocotillo

Fouquieria splendens

One of the strangest, most colorful shrubs of our southwestern deserts, the ocotillo through most of the year resembles nothing so much as a loose bundle of long, spiny coachwhips. The arrival of winter rains, however, prompts the shrub to sprout small, rounded leaves along the length of each branch; though the ocotillo sheds this foliage as soon as the soil dries again, the leaf stalks persist and harden into spines. The rains also bring an explosion of color as the ocotillo bursts into bloom, with 6- to 1O-inch clusters of scarlet flowers at the ends of the whips. Because of these displays, the ocotillo has been adopted as an ornamental in its native range. Desertdwelling Indians also planted it in hedgerows to make coyote-proof chicken runs, and cut its branches to weave walls for their huts.

Octopus

Bizarre creatures of the deep, octopuses are named for the eight sucker-lined tentacles that radiate from their sac-shaped bodies. The several species that live in North American waters range in size from the giant Pacific octopus, with a diameter (including tentacles) of up to 30 feet, to a tiny 2- to 3-inch species found in deep water north of Cape Cod. Living on the sea floor, octopuses use their tentacles to crawl about and to ensnare their prey. Tough, parrotlike beaks enable these soft-bodied creatures to crush and eat such hard-shelled fare as lobsters, crabs, and snails. When threatened by morays or other enemies, octopuses eject a murky cloud of ink and then, by forcing water from their bodies, jet off to the nearest crevice for cover.

Omnivore

Unlike herbivores, which eat only plants, and carnivores, which eat only animals, omnivores are creatures that feed on the full range of available food. Snapping turtles, for example, consume everything from aquatic plants to fish, frogs, and even small mammals. Opossums and raccoons also enjoy a whole smorgasboard of

plant and animal matter, from berries and mushrooms to bird's eggs and insects. Rats and other rodent pests have eclectic tastes as well, which often lead them to food discarded by humans, the most omnivorous omnivores of all.

Omnivorous

An Animal that eats both meat and plant food.

Omnivore

An Animal Behavior term, this is used to describe an Animal which eats a varied diet including both Animal and vegetable matter.

Onion

Allium

Odor is the identifying characteristic of the wild onions-when bruised, their leaves and bulbs are just as pungent as their cultivated relatives. The wild sorts are edible, too, and were eagerly gathered by Native Americans. Though found in every state, wild onions are most plentiful on western mountains and plains. Growing from underground bulbs, the leaves of the wild onions are flat green straps or hollow quills, depending upon the species, and the sunbursts of blossoms that appear by midsummer range from white or greenish to purple and pink.

Ontogeny

An Animal Behavior term, this is used to describe the development of an individual organism. The study of ontogeny examines the way in which genetic and environmental factors mold behavior during the lifetime of the individual Animal.

Open field

An Animal Behavior term, this is used to describe an arena, usually divided into squares, used to study the activity and exploRation of Animals.

Operant

An Animal Behavior term, used by Skinnerian psychologists to denote a behavior pattern that could be modified in some way by its consequences. For example, lever pressing is an operAnt because its frequency rises if it is followed by delivery of food to a hungry Animal.

Operculum

A plate found in some mollusks and used to seal off the entrance to the shell.

Opossum

Didelphis virginiana

A marsupial about the size of a cat, the Virginia opossum is the only North American mammal that carries its offspring kangaroo-style, in a pouch. A dozen or so larvalike babies are born at a time, each one so tiny-smaller than a honeybee- that an entire litter can fit in the palm of a hand. Blind and hairless, they make their way through their mother's coarse fur to the warm pouch, where they immediately begin to nurse. After two months the young, recognizable at last as miniature opossums, go topside to ride on their mother's back until they are old enough to fend for themselves. Roaming by night, these adaptable omnivores are well known as raiders of garbage cans. By day they hole up in second-hand burrows, tree cavities, or abandoned squirrel nests. At home in treetops, opossums use their long, naked tails as extra hands as they clamber through the branches. When threatened by predators, they occasionally feign death by lapsing into a comatose state-the classic and sometimes life-saving ruse called playing possum.

Optimal foraging

An Animal Behavior term, this is the theory that Animals searching for food should behave in the most efficient way. This is most often taken to imply that they should behave so as to maximize their net Rate of energy intake, that is, the energy they gain less the energy they expend in each unit of time spent foraging. Experiments suggest that many Animals come remarkably close to achieving this.

Optomotor response

An Animal Behavior term, this is used to describe the response whereby Animals attempt to keep themselves static in relation to their visual world. Thus, a wide variety of Animals placed in a striped drum that rotates slOwly will move their head and eyes to follow the stripes and keep the image still.

Orb-weaving spider

The classic spider web, with a silken spiral spun over radiating threads, is the handiwork of orb weavers. Marvels of geometric design, the delicate orb webs are also death traps for flying insects; once ensnared on the sticky threads, they rarely escape. Alerted by the slightest movement in the web's network, the resident spider quickly pounces on its flailing victim, devouring it on the spot or wrapping it in silk for later consumption. Orb weavers often eat their web at the end of the day and, working in darkness, construct a new one in about an hour. Baby spiders spin miniature versions of the orb web.

Orchid

Often called the royal family of flowering plants, the orchids, with some 35,000 species worldwide, outnumber every other family of flowers. And to those who think of them only as exotic hothouse blooms, it often comes as a surprise to learn that some 200 species of native wild orchids grow often literally-in America's backyards. Supremely adaptable, orchids have wandered north beyond the Arctic circle to thrive in climates too harsh for any tree. In less frigid climes, they have colonized habitats ranging from the hammocks of subtropical Florida to the dry woodlands of the West and wet northern bogs. Florida boasts the most native orchidsover 100 species. The Northeast also has a rich assortment, with more than 60 kinds flourishing in meadows, bogs, and woodlands, while in the Southwest they are found mainly in canyons and high valleys, where mountain streams supply a constant source of water. Many of our native orchids, with lilting names like rose pogonia and twayblade, calypso and grass pink, have smaller blooms than their tropical relatives, but they are every bit as fascinating. Like their hothouse kin, their blossoms flaunt three petals and three petallike sepals, with the pollen-producing stamens and pollen-receptive stigmas fused into a central structure called the column. One of the petals, "the lip," is generally distended and serves as a landing platform for pollinators, which include moths, bees, flies, bats, birds, butterflies, and even mosquitoes. Specific orchids often depend on a single type of pollinator, and many have developed ingenious strategies for attracting that one visitor. Vivid colors, scents, and nectar draw bees and butterflies to some orchids, while those that rely on flies smell like rotting meat. Still others attract male insects by posing as potential mates; the flowers not only mimic female insects in appearance but also release similar perfumes. When the males try to mate, they cover themselves with pollen and then carry it to the next flower they visit. Some orchids appeal to insects' aggressive instincts. The tropical, multibranched oncidiums, found as far north as the Florida Everglades, mimic swarms of bees and so provoke attacks from nearby hives.

As remarkable as the flowers are, the orchids' dustlike seeds-so tiny that a single pod may contain millions-also are one of nature's wonders. Light enough to blow for hundreds of miles on the wind, they have economized on their weight by eliminating the stores of food customary in other seeds. As a result, they can germinate only with the aid of special fungi that provide nutriments. Often this partnership continues throughout the life of the plant-the orchid deriving its nourishment from the fungus, which lives in association with the plant's roots. Depending on the species, orchids are either epiphytic or terrestrial. Living without contact with the soil, epiphytes attach themselves to tree branches. They draw nutrients from airborne dust and decayed matter that washes in among their roots, and absorb moisture from rain showers. Typical of tropical habitats, North American epiphytic orchids are limited to the extreme Southeast. A notable example is the vinelike vanilla orchid of Florida, whose seedpods are the source of natural vanilla flavoring.

More-northern regions are home to the terrestrial orchids, which take root in the soil. Because they live as perennials, dying back to the ground in autumn and sprouting anew from the roots in spring, they are far less vulnerable to winter frosts. Some survive for years in this fashion. Lady's slippers, for example, may be 15 years old before bearing their first flowers; those dainty, moccasin-shaped pink, white, or yellow blossoms are unforgettable, however, and have made lady's slippers among the most beloved of woodland flowers.

The downy rattlesnake plantain, in contrast, bears only tiny blossoms; its appeal lies instead in its rosette of green and white checkered leaves. Pioneers thought the leaves resembled snakeskins, and so believed them to be an antidote for snakebite. Indeed, given the many unusual fearures of our native orchids, it is not surprising that they have inspired a vast array of superstitions. Besides their supposed value as antitoxins, orchids were once taken as remedies for ills ranging from gout to insomnia, while lady's slippers, when boiled in milk, were held to be an aphrodisiac. In addition to rousing passion, these innocent blooms were said to mark the sites of crimes and tragedies. Though no longer much sought for herbal medicines, orchids are, unfortunately, victims of their own surpassing beauty. Everywhere they are increasingly rare, for wildflower enthusiasts, ignorant of the plants' dependence on soil fungi, yearly transplant thousands to gardens, where the orchids almost invariably starve and die.

Oregon grape Mahonia

Oregon grapes produce bright, fragrant yellow flowers, followed by edible blue berries. These features, combined with their shiny, hollylike leaves, make them popular ornamentals. Evergreen members of the barberry family, the Oregon grapes are also known as holly grapes. Like the hollies, they sport shiny, spiny leaves, and like grapes, in autumn they are arrayed with clusters of dark blue berries that can be made into jams, jellies, and even wines. They are valued also for the clusters of fragrant, small, cupped yellow blossoms borne at the tips of the twigs in spring, and one of the showier species has been adopted as the state flower of Oregon. This 3- to l0 -foot shrub is a native of the Pacific Northwest, where it forms thickets in open woodlands. Enthusiastic gardeners, however, have transplanted it to temperate regions all across the country. Another common species, the creeping holly grape, thrives in shady canyons and on rocky slopes from the foothills of the Coastal Ranges of California to the Rockies.

Organic

Biological Philosophy term. The opposite of mechanistic. The basic metaphor, if you look at the world this way, is living things: the universe is like a living thing. How? A living thing is not a bunch of separate things, like the wheels and cogs of a clock, but a single, thing. It grows from a seed which contains all that is necessary to organize its growth, though it is affected and changed by outside influences. The Romantic movement adopted this view of things in opposition to the mechanistic, Newtonian view of things. There is a suggestion of large-scale "animism" in this view, that the universe is inhabited and given shape by an inherent spiritual principle, God or what Emerson called the "oversoul." Which moves us towards Pantheism.

Oriole

Icterus

Their striking colors-orange and black or yellow and black-make orioles the most flamboyant members of the blackbird family. Shy birds whose musical whistles resound from the treetops, they weave distinctive, pouch-shaped hanging nests of grass, string, hair, and various plant fibers. The more modestly colored females build the nests, while the males provide insects and fruit to feed the family. Most orioles, such as Scott's oriole of the Southwest and the spot-breasted oriole of Florida, prefer warm climates. Two species, however, manage to thrive in the northern states. The orchard oriole, a rust-breasted bird, nests in eastern fruit trees. The other, the northern oriole, includes two races: the famed Baltimore oriole of the East and the very similar Bullock's oriole of the West. Altamira orioles, formerly known as Lichtenstein's orioles, are found at the southern tip of Texas, where their nests hang from the branches of tall trees.

Orientation

An Animal Behavior term, this is used to describe the movement of Animals in relation to their environment. For example, Animals may orient in relation to landmarks or some goal that they can perceive. At a more complex level, some Animals are known to use the sun, stars or the earth's magnetic field to orient in a particular compass direction (see also Navigation).

Orpine

See Stonecrop

Osage orange

Madura pomifera

The osage orange's fruits are not at all like true oranges; they contain a bitter, milky sap and are inedible. A tree native to the south-central states, the osage orange is distinguished by the odd round fruits it bears in autumn. Up to five inches across and sometimes weighing several pounds, they look like unripe oranges and exude a milky sap when bruised. The tree's common name also refers to the Osage Indians, who used the hard, resilient wood for bows and clubs. Up to 30 feet tall with zigzagging, thorny branches, osage oranges grow rapidly and are resistant to heat and drought. Pruned to form hedges, they were, until the introduction of wire fencing, the standard enclosures for prairie farms, serving both as animal-proof barriers and as sturdy windbreaks.

Osprey

Pandion haliaetus

Brown and white, with wingspans of nearly six feet, ospreys are formidable birds of prey that feed exclusively on fish. Also known as fish hawks, they hover over rivers, lakes, and seacoasts as they search for prey. Once they spot a tantalizing flash, ospreys plunge feet-first into the water, often with a great splash, and seize their slippery catch in sharp talons. On the flight home they usually hold the fish facing forward and so reduce wind resistance. Osprey nests, made of sticks, driftwood, and odd debris that has washed up on shore, are usually built in places that command panoramic views, including treetops, telephone poles, chimneys, and man-made nesting platforms. When the chicks hatch, the father delivers about six pounds of fish per day to the nest, where the mother feeds shredded morsels to the young.

A few decades ago, osprey populations were severely reduced because the birds ate fish from water polluted with DDT. The poison, which affected reproduction, caused the birds to lay eggs with thin, easily broken shells. Thanks to conservation efforts, however, the noble fish hawks in recent years have made a dramatic and welcome comeback.

Otter

See River otter, Sea otter.

Outcrop

Ranging in size from the small patches of bare rock found in fields to rugged, towering cliffs on mountainsides, outcrops are sections of bedrock that are not covered by soil or loose boulders. Bedrock can be exposed in a number of ways. Soil may slump down a hillside, for example; glaciers may bulldoze the land; or erosion by wind and water may scour away all the surface debris. Outcrops are "windows" to the crust below, often giving evidence of valuable ores.

Ovate

Roughly oval in outline.

Ovipositor

The egg-laying structure found at the tail-end of some female insects.

Ovoid

Egg-shaped.

Owl

Well-known for their solemn, studious appearance and their haunting nighttime calls, owls are birds of prey that are most active at dusk and after dark. While some also hunt by day, many are entirely nocturnal. In addition to rodents and other mammals, their prey includes insects, frogs, toads, and small birds. Owls are characterized by short, stout bodies, strong, hooked beaks, and sharp talons for seizing prey. Many also have feathery tufts, called ears or horns, on their heads. The birds range in size from the tiny elf owl, no bigger than a sparrow, to the great gray owl, which reaches nearly three feet from head to tail.

In his play Love's Labour's Lost, William Shakespeare wrote "then nightly sings the staring owl"-words that certainly apply to any of these big-eyed, big-headed birds, for owls do indeed stare. And in that staring face we can see some of the owl's adaptations for life in the dark. Unlike the eyes of other birds, an owl's eyes face straight ahead, like our own, giving the bird binocular vision. Unlike human eyes, however, they do not move in their sockets, so the bird must swivel its head to follow moving objects.

Although owls see well in dim light, most depend on superkeen hearing when searching for prey. Many, in fact, can locate prey in total darkness, relying on sound alone. The owl's large ear openings are hidden under the ruff of feathers framing the face-its facial disk-an arrangement that helps funnel sound into the ears. On some species, moreover, the ears are placed, asymmetrically resulting in a stereo effect that allows the bird to home in on the source of a sound with amazing accuracy. Once an owl hears an animal rustling in leaves or grass, it drops from its perch and swoops silently toward the noise. At the last instant, the bird swings its feet forward and, with its sharp talons outspread, strikes the ground at exactly the right spot to seize its victim.

Swift on the wing, owls are also noiseless in flight. Their soft, fluffy feathers muffle the sound of their broad wings, enabling them to swoop toward prey in absolute silence.

Owls are divided into two families: the barn owl, whose single species is distinguished by its heart-shaped face, and typical owls, of which there are 18 species in North America. Most of the latter are forest dwellers that spend the day roosting in trees or in other sheltered places. Their colors, mainly browns and grays, and their patterns of streaks and bars help them blend into their surroundings, making them difficult to spot even in broad daylight. The snowy owl, which hunts by day on the arctic tundra, is also camouflaged. Its plumage-white with a few black bars-blends almost perfectly with a background of snow or ice.

Our largest species, the great gray owl, lives in the vast coniferous forests of Canada and preys mainly on rodents. Its hearing is so acute that it can plunge into snow and capture voles as they scurry about hidden in their tunnels. Nearly as large is the great horned owl, an aggressive predator with large ear tufts. Found in forests, deserts, swamps, and even city parks, it is big enough to attack skunks, porcupines, and other

large prey. Its deep five-noted hooting is one of the most familiar of all owl calls.

At the other extreme is the diminutive elf owl, a resident of deserts and dry woodlands along streams near the Mexican border. It feeds on insects and, at times, lizards. Other small species include the screech owls-plump, robin-size birds with short ear rufts, best known for their whistled calls-and the northern saw-whet owl. Slightly smaller than a screech owl and lacking ear tufts, the saw-whet nests in a variety of wooded habitats but is usually found roosting by day in small, dense conifers.

Most owls nest in cavities in trees or giant saguaro cacti, or in the abandoned nests of crows or hawks. Snowy and short-eared owls, however, build crude nests on the ground, while burrowing owls lay their eggs in prailie dog dens or in burrows they dig themselves. Incubation begins with the first egg, so that the young

hatch consecutively. Both parents tend to the nest and defend it vigorously. In years of food scarcity, some species, among them the snowy owl, do not breed at all.

In view of their humanlike faces, nocturnal habits, and loud, often ominous-sounding calls, it is not surprising that owls figure prominently in tradition and folklore. Symbols of the Greek goddess Athena, the deity of wisdom, owls have long been considered the epitome of wise old birds. Their calls are said to portend significant events. Three hoots, for example, indicate a marliage, while five hoots foretell a journey.

Oddly enough, however, owls are considered harbingers of ill as well. In parts of the South, an owl perching on the roof of a house is said to be a sure sign of death. But this misfortune can be averted by turning shoes upside down.

Owl clover

Orthocarpus

Despite their name, the owl clovers are not clovers at all. Common wildflowers of western plains and open woods, they are more closely related to Indian paintbrushes. Their clustered blooms are set, like the paintbrushes' flowers, among showy bracts that in some cases are more colorful than the flowers themselves; on some species the bracts completely hide the blossoms. The plants, up to 16 inches tall, have narrow threadlike leaves. Spots on the flowers of some species make them look a bit like peering owls.

Oxbow lake

Named for the U-shaped bows on old-time ox yokes, oxbow lakes are formed from the loops of meandering rivers. Eroding their banks, the rivers eventually cut across the necks of the curves, leaving the old channels as backwaters. Sediment then fills in the ends of the loops until they become isolated lakes. As more sediment accumulates, the lakes turn into marshes and then into dry land. Though best-known in the lower Mississippi Valley, oxbow lakes are found on floodplains all across North America.

Oyster

Like mussels and clams, oysters are bivalve mollusks; their soft bodies are protected in hinged pairs of shells. They live in shallow coastal seas, where, cemented to rocks or pilings, they feed on tiny organisms filtered from the water. Beginning their lives as microscopic eggs, oysters soon hatch into free-swimming larvae. Most are gulped down by fish, but those that survive sink to the bottom after two weeks or so and attach themselves to rocks and other hard surfaces. Oysters grow about an inch a year, starting out as males and later developing into females that lay eggs by the millions. Oysters are preyed upon by all sorts of creatures. Oyster-dlill snails bore holes into the shells, starfish pull them open, and birds called oystercatchers pry the shells apart to get at their flesh. Humans relish oysters too, of course, and most of those sold commercially are raised on undersea "farms." Oysters are harvested from shallow waters along our coasts. Oystermen sometimes use giant tongs to pluck their catch from the bottom. All of our oysters are used for food; the ones that produce pearls are found in tropical seas.

Oystercatcher

Haematopus

Large, chunky shorebirds with long orange-red bills and pinkish legs, oystercatchers feed on small maline animals found by the seaside. They use their flattened, bladelike bills to pry open the shells of oysters, mussels, and clams; to probe in the sand for worms and crustaceans; and to dislodge barnacles from rocks.

Oystercatchers nest in shallow depressions in the sand or in rock crevices. The two or three spotted eggs yield precocious, downy gray young that, shortly after hatching, are able to follow their parents on foraging expeditions. Our eastern species, the American oystercatcher, has black-and-white plumage and lives on beaches from Virginia to the Gulf Coast. The black oystercatcher, outfitted in brownish black, prefers rocky western shores from California north all the way to Alaska.

Oyster plant

See Goatsbeard.

Ozone

Ozone is a naturally occurring gas, formed from normal oxygen, that protects the earth by filtering out ultraviolet radiation from the sun. Most of the world's ozone is concentrated in the stratosphere, 10-50 kilometres above the earth's surface. A form of oxygen with three oxygen atoms per molecule instead of two, ozone is a gas present in very small amounts in the atmosphere. At low altitudes it is considered an air pollutant and is an irJitating component of smog. High in the atmosphere, in contrast, ozone plays a role vital to the survival of life on earth. Ultraviolet sunlight colliding with oxygen in the upper atmosphere produces an ozone layer that shields the earth from radiation harmful to many forms of life-including humans, in whom it can cause skin cancer. Recently, gases called fluorocarbons have been shown to deplete the ozone layer, and so efforts are being made to reduce the levels of these pollutants in our atmosphere.

Pack rat

See Wood rat.

Paddlefish

Polyodon spathula

A long, broad, flattened snout distinguishes paddlefish from all other fish. Fully one-third of the length of their bodies, the spoon-shaped structures may be sensory organs used for locating the plankton and other small animals on which the fish feed. Hatchlings are born with no sign of the snout but start to grow one when they are just two to three weeks old. Also known as spoonbills and shovelnose cats, paddlefish, which grow up to six feet long, inhabit lakes and livers in the Mississippi River basin. Primitive, scaleless creatures with skeletons made of cartilage, they have only one close relative, a large, similarly snouted species that lives in the Yangtze River in China.

Painted turtle

Chrysemys picta

North Amelica's most wide-ranging turtle, the painted turtle is aptly named: its smooth oliveto-black shell is edged with red; its underside is yellow; and its head, neck, and legs are marked with red and yellow. Found in weedy freshwater marshes, quiet ponds, and slow streams, it feeds on almost anything it can find, whether plant or animal. In fairweather, groups of painted turtles bask on rocks or logs. In winter those that live in cold climates hibernate.

Pair bond

An Animal Behavior term, this is used to describe the attachment between members of a mated pair causing them to stay together. In some species, such bonds may persist throughout life but, in others, they last only for one breeding season or mating period (see Consort Relationship). In Polygamous species, one individual may have pair bonds with several others at the same time.

Palm

Elegant and graceful, most palms are trees with a single, slender, unbranched trunk topped by a featherduster crown of fan- or feather-shaped leaves. Although they are most common in the tropics, several kinds are native to warmer parts of North America, including the ';tately royal palms of southern Flolida, the palmettos that grow from the Carolinas to the Gulf Coast, and the Washington palms of the Southwest.

Both native and exotic palms are commonly planted as ornamentals in the Sun Belt. In the past, however, Amelican Indians built huts with palm trunks and used the leaves to thatch them. Leaves were sometimes woven into hats, mats, and baskets. Indians also relished the trees' edible fruits and the honey that bees harvested from the huge, drooping clusters of fragrant white or yellow flowers. Today imported coconut palms are grown in Florida, and date palms from overseas are an important crop in California and the Southwest.

Palmate

In plants, a leaf divided into lobes which fancifully resembles a hand. The flattened shape of the antlers of some members in the Deer family, such as in the Moose.

Paloverde

Cercidium

Through most of the year these small trees of the southwestern deserts remain leafless, smoothbranched skeletons. But with the first warm rains of spring, the paloverdes burst into leaf and bloom, coveling their branches with a mantle of tiny, featherlike leaves and clusters of yellow blossoms. Bees eagerly seek the nectar-rich flowers. The pods that appear later on contain seeds that native Americans traditionally collected to cook as vegetables and to glind into meal. Some 20 or 30 feet in height, the paloverdes are an important food for jackrabbits, mountain sheep, and deer. Domestic livestock, on the other hand, are deterred by the short, sharply pointed spines on the twigs and seek the thorny paloverdes only as a last resort.

Palps

Sensory appendages found around the mouth in insects and crustaceans.

Pantheism

Biological Philosophy term. That all things are suffused by divinity, are, in fact, God.

Parasite

An organism that lives on or in another organism, relying on it entirely for its nutrition. Ticks and fleas, as well as many kinds of worms, fungi, protozoans, and even certain plants, are all considered parasites-organisms that sustain themselves at the expense of other living things, called hosts. In some cases the parasites have parasites of their own. The fleas that pester our pets, for instance, are themselves hosts to much tinier mites. In ordinary concentrations most parasites do little or no harm to their hosts. A few flatworms in the digestive tract do not cause their animal host much of a problem; nor is a beech tree bothered by a scattering of beechdrops, modest plants of the forest floor that, lacking chlorophyll, tap into the tree's roots for nourishment. Other parasites, however, cause serious damage. The protozoans that cause malaria and amoebic dysentery, for example, can drastically weaken their hosts, and parasitic fungi are responsible for many plant diseases, such as wheat rust and potato blight.

Parameter

A statistical parameter is a numerical characteristic about the population of interest; A model parameter is a numerical quantity that mediates the relationships between variables in a model.

Parasitism

An Animal Behavior term, this is used to describe the system in which one species gains a living at the expense of another, usually either within it or feeding from its surface or blood. In social parasitism, one species is dependent on the societies of another, living in them and gaining food from them (sec also Brood Parasitism).

Parental investment

An Animal Behavior term, this is used to describe any investment by a parent in an individual offspring which increases the offspring's chances of surviving at a cost to the parent's ability to invest in other offspring. On the basis of this theory, parents should not invest too much time and effort in one offspring but should alloCate their investment to maximize the number of their young that survive to breed.

Parrotfish

With dazzling colors and imposing size-some species are four feet long - parrotfish are among the favorites of snorkelers and scuba divers who visit tropical reefs. The fish are named not for their rainbow of hues but for the birdlike beaks, formed of fused teeth, with which they scrape algae and bits of coral from the reef. Parrotfish also have large grinding teeth in the throat, used for crushing their food. Active by day, some parrotfish retire to crevices at night. Others, however, rest in the open on the ocean floor and protect themselves in a remarkable way. They secrete a jellylike cocoon-a kind of self-made sleeping bag-that apparently serves as a defense against nocturnal predators while they sleep.

Parsley

From parsnips to pennyworts, the parsley, or carrot, family is made up of thousands of species of plants. What all have in common are umbels-flat-topped or umbrella-shaped clusters of tiny flowers. But various members of the family have their differences as well. Some, such as Queen Anne's lace, yellow pimpernel, and golden alexanders, are dismissed as lowly weeds, while others, including sea holly and blue lace flower, are esteemed as ornamentals. Culinary parsleys include carrots, celery, and parsnips, as well as such herbs as anise, dill, fennel, cumin, coriander, and caraway. Fool's parsley and water hemlock, in contrast, both are highly toxic and can kill if consumed. The family's namesake-the small biennial herb known simply as parsley-is a Mediterranean plant that has been cultivated since ancient times both as a garnish for food and for its reputed medicinal properties.

Participation plan

Endangered and Threatened species term.

A plan describing the means to carry out one or more tasks outlined in the Implementation Schedule of a species recovery plan, minimizing the socioeconomic impacts of that action.

Partners in Flight

Bird Biology Avian Conservation term.

A Western Hemisphere program designed to conserve neotropical migratory birds and officially endorsed by numerous federal and state agencies and nongovernment organizations. Also known as Neotropical Migratory Bird Conservation Program.

Partridgeberry

Though it thrives in woodlands throughout the East, the delicate partridgeberry is easily overlooked through most of the year. In winter, however, its scarlet berlies (edible but flavorless) show up vividly against the plant's groundhugging mat of lustrous evergreen leaves. It is worth searching out in early summer, too, when pairs of tiny, fragrant flowers adorn the tips of its trailing stems. Pink in bud, they open into fuzzy, white to purplish tubular blooms.

Parturition

An Animal Behavior term, this is used to describe the act of giving birth.

Palmate

A shovel-horn type of antler characterized by broad up-reaching parallel palms, e.g., Moose antler.

Passionflower

Passiflora

Seventeenth-century Spanish priests named the passionflower, seeing in its intricate blooms symbols of the crucifixion of Christ. The three stigmas at the center, they said, represented the nails that held Him on the cross; the five stamens, His wounds; and the petals and sepals, the 10 disciples who remained faithful throughout His suffeling. The halo of threads encircling the flower they likened to the crown of thorns.

Attractive perennial vines, passionflowers are most common in the South. The yellow passionflower, however, clambers through moist thickets as far north as Pennsylvania and west to Kansas. Reaching a height of 10 feet, it bears small blossoms that are followed by purple berries. The maypop, a lavender species, ranges north to Maryland and Oklahoma and produces tasty yellow fruits the size of hen's eggs.

Passage migrant

A bird species seen mostly on migration and which does not necessarily breed in the region.

Pastoral

Biological Philosophy term. Nature as harmonious and continuous with human life; nature tamed into farm lands and hedge rows and orchards, but not so overwhelmed by human presence as to be damaged, rather "improved." A Frenchman, Buffon, famous for his contention that all animals degenerated in Western lands, insisted that America was an inferior continent, and the human beings who lived there were naturally inferior. He represents the underlying notion of pastoral: that human beings are necessary to the beauty of nature. Nature without human beings is ugly wilderness. Human beings establish order, harmony, cultivation. They must drain marshes, transform stagnant waters into canals and brooks, set fire to old forests, destroy with iron what cannot be destroyed by fire. Human beings are in this way necessary to the divine order of nature.

Pastoral Ideal

Biological Philosophy term. Living one's life in complete harmony with nature, growing one's own food, making one's own clothes, being born, living, dying, without depending on those divisions of labor that characterize civilized life.

Pastoral Design

Biological Philosophy term. A literary technique: Imagining oneself living outside civilization and according to the Pastoral Ideal, as a shepherd (ancient Greece and traditional European), a farmer, a cowboy; the purpose of placing oneself in this pastoral dreamland is to reflect on civilization. This depends on the sense that living the pastoral life purifies one's vision, makes one better able to judge.

Patch dynamics

The change in the distribution of habitat patches in a landscape generated by patterns of disturbance and subsequent patterns of vegetative succession.

Pathetic fallacy

Biological Philosophy term. Seeing animals and inanimate objects as having human emotions. See Anthropomorphism.

Pattern

A statement about relationships among several observations of nature. It connotes a particular configuration of properties of the system under investigation.

Pawpaw

Asimina triloba

Thriving in rich, moist soil from the lower Mississippi Valley to southern Michigan, these small trees with large leaves and purplish flowers are relatives of the mostly tropical custard apples. The stubby, cylindrical fruits that appear on the pawpaw's branches in late summer account for its alternate name, false banana. Yellowish-green at first, the fruits begin to darken in the fall and finally turn nearly black--a sign that the sweet, custardy flesh is ready for eating. Early settlers made jelly from pawpaws and extracted a yellow dye from the pulp. Ripe fruits can be hard to find, however, since many animals seek them as eagerly as do humans.

Pea

See Legume.

Pearly everlasting

Anaphalis margaritacea

A favolite wildflower for dlied bouquets, the well-named pearly everlasting keeps its shape and color indefinitely. Its woolly stems, one to three feet tall, are topped with wide clusters of pearly white flowers with yellow centers. The leaves, narrow and straplike, are sage green on top and whitened underneath with woolly hairs. Our only native everlasting, this cheerful wildflower is found in fields and along roadsides from coast to coast.

Pecan

See Hickory.

Peccary

Tayassu tajacu

Bristly, piglike mammals up to three feet long, collared peccalies trot through the cactus and mesquite country of the Southwest in bands of five to a dozen or more. They use their long, sensitive snouts to sniff out roots and herbs, as well as other morsels such as worms, insect larvae, birds' eggs, and lizards. Long-legged compared to true pigs, peccalies flee nimbly from coyotes and other predators. If cornered, however, they can put up a ferocious fuss, attacking enemies with their formidable tusks. Secretions from musk glands help define a herd's terlitory, and individuals occasionally sound an alarm by chattering their teeth or making barking sounds.

Pecking order

An Animal Behavior term, this is used to describe an alternative term for a Dominance hierarchy, usually only applied to Birds. This phenomenon was first described in flocks of Chickens.

Pectoral fins

A pair of fins behind and often below the head of a fish.

Peeper

See Spring peeper.

Pelagic

Meaning living in the open ocean.

Pelican

Pelecanus

Known to readers of light verse as the bird whose bill holds "more than his belican," a pelican-with a roomy pouch suspended from its long, broad beak-cannot be mistaken for any other bird. Stocky and short-legged, pelicans may be clumsy on land, but they are amazingly graceful in the air. The brown pelican, one of the two species found in North Amelica, is a seabird that lives along the south Atlantic, Gulf, and Pacific coasts. Flying above the water until it spots the silvery flash of a fish near the surface, it plunges into a headlong dive-often from as high as 50 feet-that culminates in a great splash. Returning to the surface with a fish, the pelican then pauses for a moment to let the water drain from its pouch before swallowing its prey.

The Amelican white pelican, a larger bird that nests on inland lakes in the West, is less acrobatic. Rather than diving, it fishes from the surface, dipping head and bill underwater to seize its prey. White pelicans often fish in teams, swimming abreast in a line or semicircle to herd fish into shallow water. The birds coordinate their movements in the sky as well. With the precision of a chorus line, the members of a flock sometimes flap their wings in unison as they fly.

Pelvic fins

A pair of fins to the rear but before the anal fin of a fish.

Peppertree

Schinus molle

Producing neither the familiar table spice nor the garden peppers used in salads and cooking, the peppertree is named instead for the pungent flavor of its ruddy, berrylike fruits. Native to Peru and a member of the cashew family, this handsome ornamental has become such a common sight along streets on the West Coast that it is often called California peppertree. It grows up to 40 feet tall and has branches that droop like a weeping willow's, with evergreen compound leaves filled with milky, aromatic sap. Many songbirds relish the tree's red fruits.

Perch

Fish of clear lakes and streams, perches range in size from the hefty walleye to the diminutive darters. The walleye-sometimes called the pike perch-weighs up to 25 pounds and is named for its large, glossy eyes, which, in the beam of a flashlight, shine with an eerie orange glow. The walleye is a favorite with anglers, as is its smaller relative, the yellow perch, easily recognized by its yellowish color and dark vertical stlipes. Both the yellow perch and our other medium-size perch, the sauger, weigh up to three or four pounds. The smallest members of the family are the dozens of species of brilliantly colored darters, named for their abrupt movements on the bottoms of streams. Among them are the widespread Johnny darter and the endangered snail darter.

Perching bird

Also known as passelines, perching birds are so named because of the form of their feet: all have four flexible toes-three facing forward and one facing backward-an arrangement that enables them to grasp twigs, wires, and other perches. Approximately 60 percent of all the world's bird species are perching birds, including such common and widespread groups as wrens, thrushes, titmice, finches, warblers, and jays. They range in size from tiny kinglets and sparrows to the common raven, a bird that is two feet long and has a four-foot wingspan. While all can perch, a few ground-based passerines, such as larks and pipits, have feet that are slightly modified for walking and running. Often brightly colored, many of the perching birds are well known for their ability as songbirds.

Perennial

Referring to an organism that lives for more than one year.

Perennial

Botany term. A plant that lives for more than two year. See Annual.

Perfection of nature

Biological Philosophy term. The idea that nature is not only complete, with all possible species in their place, but that nature is perfectly ordered and perfectly stable, and, when disturbed, will return to its original stability.

Periostracum

The tough external covering of many mollusks' shells.

Periwinkle

Dainty little snails with spiral shells, periwinkles live where land meets sea-on rocky shores, on wharf pilings, in salt marshes, and in mangrove swamps. Like other snails, they leave trails of mucus as they creep along, using their rasping tongues to scrape algae and other edibles from rocks and similar surfaces. The common European periwinkle, introduced to Nova Scotia in the mid-1800's, now ranges south as far as Maryland. Growing up to 1 V2 inches long, it is one of the largest species and is considered a delicacy by some. A smaller relative, the northern rough peliwinkle, lives high on rocks along both the north Atlantic and Pacific coasts and, like other periwinkles, is relished by ducks. Marsh periwinkles, about one inch long, are found in estuaries and salt marshes from the middle Atlantic states to Florida. Clinging to reeds and tall grasses, they use their long rasping tongues to feed on tiny scraps of plant food. Like other periwinkles, they are a favorite food of ducks, gulls, and various shorebirds.

Permafrost

On the frigid tundra-the treeless expanses of the Far North-and on some very high mountains above the timberline, the land is underlain by permafrost, a nearly impenetrable layer of permanently frozen soil and rock. In some places the permafrost extends downward for thousands of feet, but in the American arctic it averages about 1,000 feet in thickness. Covering and insulating the permafrost is a thin mantle of soil, known as the active zone, that thaws in summer, then freezes again in winter. Because drainage is so poor, the land in summer is dotted with countless ponds and marshes, and the surface soil becomes so spongy and waterlogged that it is difficult to walk upon. In places, seasonal freezing and thawing of the active zone sorts rocks into neat circles and polygons, creating so-called patterned ground. Pingos, another characteristic landform, are hills with cores of solid ice. And on slopes in summertime, great lobes of thawed surface soil at times ooze slowly downhill in this strange, otherworldly landscape.

Permits (Law)

Documents granting legal permission to perform an activity. Special permits must be obtained to carry out certain activities that have an impact on the environment, in order to ensure that these activities are limited.

Persimmon

Diospyros

Country folk call persimmons "possum apples" because of the animal's enthusiasm for the plumlike orange fruits that persimmon trees bear in autumn. Though soft and sweet when fully mature, the unlipe fruits are so full of tannic acid that they will pucker a person's lips. Persimmon trees are normally only 30 to 50 feet tall but grow to heights of 70 feet on Mississippi bottomlands. They are most common in the Southeast, where farmers use the fruit to fatten hogs, but range north to Connecticut and west to Texas. Sheathed in scaly grayish-brown bark that resembles alligator hide, persimmons have glossy green oval leaves and are covered with bell-shaped white flowers in May and June. The only North American members of the ebony family, persimmons produce a hard, heavy wood sometimes used for golf clubs. Persimmons figured strongly in the diet of southeastern Indians, who baked bread with a meal made from the dried fruits.

Petal

The often colorful inner row of structures surrounding reproductive part of a flower.

(Listing)

Endangered and Threatened species term.

A formal request, with the support of adequate biological data, suggesting that a species, with the support of adequate biological data, be listed, reclassified, or delisted, or that critical habitat be revised for a listed species. See also

Petrel

Pterodroma

Gull-size seabirds of the shearwater family, the petrels include several species that, collectively, are known as gadfly petrels. They nest on tropical islands and, during the nonbreeding season, roam the open sea, feeding on small squid and fish snatched from the water's surface. Most frequently seen are the black-capped petrel of the Atlantic and the mottled petrel, a rare winter visitor off the Pacific coast. The smaller birds called storm petrels belong to a different family.

Petrified wood

Petrified wood is the fossil remains of ancient trees whose tissues were replaced by the mineral silica. Examples have been found in many parts of North America, including the world's largest collection of multicolored logs, which is contained in Petrified Forest National Park in Arizona. Once the trunks of coniferous trees, the logs were buried in sediments and transformed to rock when mineral-saturated groundwater seeped into them, replacing the original wood cell by cell. Petrified trees often are so well preserved that the annual growth lings and other internal structures are visible. Such details provide fascinating insights into the kinds of trees found in North Amelica millions of years ago.

Petroleum

A vital natural resource, petroleum is used for fuel and lublicants, and in the manufacture of plastics and a host of other synthetic products. Crude oil, as it is also called, is a mixture of various hydrocarbons (compounds of hydrogen and carbon), along with traces of sulfur and other impurities. The exact composition of petroleum valies from site to site; so the oil pumped from one field may be thick, black, and tarlike, while that from another field is as light and fluid as motor oil. Petroleum is thought to be derived from the remains of tiny plants and animals that flourished in ancient seas. When these organisms died, they drifted to the ocean floor, where they mixed with and were buried under thick layers of sand and mud. Over millions of years, the layers compacted into sedimentary rock, such as sandstone and shale. The heat of compaction combined with decomposition of the organic debris, converted the ancient plants and animals into enormous deposits of crude oil and narural gas. In North America the greatest reservoirs of petroleum are found in Louisiana, Texas, Oklahoma, and Alaska.

Peyote

Lophophora williamsii

Also known as mescal button, peyote is a small, knobby, bluish-green cacrus found in limestone soils in southern Texas and northern Mexico. Stubby and spineless, it contains a number of alkaloids, including mescaline, and is best known for the hallucinogenic effects it can induce. Southwestern Indians have long used it as part of their religious rituals, chewing pieces cut from the cactus. Tapering from a mushroomlike top to a thick taproot, the mature plant averages only two inches high and some three inches across. In summer a white to pinkish flower opens on the peyote's upper surface and later gives rise to a stubby red fruit that ripens the following year.

Phacelia

Ranging in height from a few inches to four feet, phacelias bear clusters of colorful flowers on stalks that are coiled like scorpions' tails but straighten out as the blossoms open. The majority of our many species inhabit dry areas in the West. One of the best-known, the California bluebell, is a two-foot-tall annual that floulishes in dry soils throughout southern California. The East claims several phacelias, too, including Miami mist, with delicately fringed blue blossoms.

Phainopepla

Phainopepla nitens

With a prominent crest, blue-black plumage, and gemlike red eyes, the phainopepla has an air of jaunty elegance. Its name, derived from the Greek for "shining robe," was inspired by the male's blight, glossy feathers. Phainopeplas live in the arid Southwest, where they zigzag through the air and, flycatcher-style, nab insects on the wing. But their main foods are berries, especially those of the parasitic mistletoe. Growing on the mesquites in which the birds nest, the plants are valiantly defended against incursions of other fruit-eating birds. In some areas phainopeplas have developed the unusual habit of breeding in two different places in the same year. After raising a brood in southern California deserts in early spring, the birds sometimes travel to moister chaparral country, where they breed again in summer.

Phalarope

Phalaropus

Sandpiperlike shorebirds with longish legs, necks, and bills, phalaropes are nonconformists when it comes to courtship. Practicing a most unusual role reversal, the females-larger and more blightly colored than the males-aggressively seek out mates and fend off competitors. And it is the drably plumaged males that build the nests, incubate the eggs, and care for the young. Phalaropes are unconventional in their feeding habits as well; they spin around like tops on the water's surface, dabbling with their bills for crustaceans and tiny fish.

Two of the phalaropes-the red and the rednecked-nest on the tundra of the Far North and spend their winters at sea in the southern hemisphere. Before setting off for the south, the birds gather offshore by the thousands in such well-known meeting places as the Bay of Fundy in Canada. The only other species, the Wilson's phalarope (named for American ornithologist Alexander Wilson) prefers freshwater habitats; it nests on ponds and marshes on the Great Plains and winters in South Amelica.

Pheasant

Phasianus colchicus

The ring-necked pheasant was introduced so successfully in the northern plains that it was designated South Dakota's state bird. Brought to America from Asia in the 1800's, the ring-necked pheasant now floulishes across the northern states and southern Canada, where it is at home on croplands, pastures, fields, and brushy areas; it even nests on the outskirts of cities. The male is especially dramatic looking, with his long, tapering tail, and his colorfully iridescent head set off by a distinctive white collar. While this flashy plumage helps the cock attract mates, the delicate brown feathers of the hen serve as camouflage when she sits on her ground nest. If disturbed, she often feigns injury to lure intruders away from her brood of as many as 15 chicks. A startled male, on the other hand, heads almost straight up in a burst of flight, or he may dash away on foot to seek cover in a nearby patch of underbrush.

Phenotype

The way in which the genetic message of an individual is expressed in its morphology, physiology, and behavior.

Pheromone

An Animal Behavior term, this is used to describe a chemical substance which passes through the environment from one Animal to another, either as a signal which elicits a behavioral reaction in a recipient or as a messenger leading the recipient to show a physiological change. Most examples of the latter concern reproductive effects, such as faster matuRation brought about by the smell of the opposite sex.

Phlox

Numbering some 60 species, the phloxes all are North Amelican natives, though one species is also found in Siberia. Because their flowers blaze with a Iich valiety of hues, especially reds, whites, pinks, purples, and blues, the plants were named for the Greek word for "flame." Early colonists, however, often called them sawpit flowers, an allusion to the fondness of the tall eastern summer phlox and blue phlox for the moist, organic soil of lumberyards. Actually, the plants flourish in a wide range of soils and habitats, especially in the West. In California and the Great Basin, for example, the two-foot-tall showy phlox, with lancelike leaves and bright pink flowers, thlives both in forests and on sagebrush flats, while the Rocky Mountain phlox prefers dry mountain ridges, dotting them from May to August with symmetrical, ground- hugging cushions of snowy white blooms. Another low-growing species, the creeping moss pink, is an easterner found on sandy soils and rocky ledges from Maine to North Carolina. Blue phlox-also called wild sweet Williamwas used by native Americans as an herbal remedy for digestive problems, and its roots were cooked to make eyewash.

Phoebe

Sayornis

Medium-size flycatchers with little fear of humans, phoebes often build their moss and mud nests beneath bridges or under the eaves of buildings. The best known of the three North American species, the eastern phoebe, ranges from the Gulf Coast to southern Canada and west to the Rockies. It is among the earliest spling migrants, and perching males are often seen busily pumping their tails as they repeat their characteristic feebee call. The eastern phoebe is less colorful than its cousins, Say's phoebe of the West and the black phoebe of the Southwest. All three hunt actively for insects, often snatching them in midflight.

Photosynthesis

One of the miracles of the natural world is photosynthesis, the process by which green plants manufacture their own food. The two basic ingredients are water and carbon dioxide, which plants-with the aid of sunlight-are able to transform into sugar and oxygen. Water is taken up through the roots of higher plants, and carbon dioxide enters the leaves through special pores called stomates. Meanwhile, chlorophyll, the green pigment in plants, absorbs energy from sunlight and serves as a catalyst in the chemical reactions that break down the water and carbon dioxide. The water is split into oxygen, which is released into the atmosphere, and hydrogen, which combines with the carbon dioxide to produce simple sugars. These sugars are crucial building blocks that can be converted into more complex sugars and into starches, fats, and proteins.

Plants are not the only benefactors of photosynthesis, for all animal life depends, directly or indirectly, upon the process. The grains and vegetables we eat, as well as the meats and other animal products, could not exist without it. Equally essential to life is the oxygen released by photosynthesis, for without it we could not breathe. Our breathing, in rurn, plays a reciprocal role, for the carbon dioxide we exhale is one of the essential ingredients of photosynthesis.

Phylogenetic species concept

The idea that a species is the smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent.

Physiognomy

The topography and other physical characteristics of a landform and its vegetation.

Pickerelweed

Pontederia cordata

Growing in profusion across eastern North America, pickerelweed is a perennial aquatic plant that flourishes in freshwater marshes, ponds, and streams. It takes root in shallow water (the same habitat preferred by the fish known as pickerels) and sends up large shiny long-stemmed leaves and attractive spikes of purplish-blue flowers. Bees visit the blossoms for nectar, muskrats relish the foliage, and ducks feed on the nutritious nutlike seeds.

Picturesque

Biological Philosophy term. A way of describing nature which emphasizes its prettiness and its charm, as opposed to the Sublime, which emphasizes its force and overwhelming power. More literally it inverts the idea that a picture imitates nature, by looking at nature as though it were a picture. This was taken to an extreme by the French and English gentry of the eighteenth century who "framed" a natural scene by looking at it through a "Claude glass," a yellow piece of glass which gave it both a border and a yellow tint like the tint varnish gave to the colors of painted landscapes. Claude was Claude Lorraine, a French landscape painter.

Pigeon

The stout, small-headed birds known as pigeons could just as easily be considered large doves since, except for their names, no clear-cut distinctions separate the two kinds of birds. Pigeons and doves are much alike in behavior as well. When courting, for example, the male makes gentle cooing sounds, bows to the female, and feeds her seeds. The young hatch in flimsy nests of twigs, where they are fed a cheesy white substance, called pigeon's milk, that is produced in the throats of the adults. The familiar pigeons that we see in cities are well adapted for urban life. Also knowrl as rock doves, they are attracted by the high ledges of city buildings, which resemble the cliffs their old-world ancestors used as nest sites. Our only other common species, the band-tailed. pigeon, lives in western forests and feeds on seeds, nuts, and berries. The passenger pigeon, now extinct, was once our most abundant bird. Traveling in huge flocks, it probably died out as a result of overhunting and the destruction of forests.

Pika

Ochotona

Pikas harvest green plants and dry them in the summer sun for use during the winter. Related to rabbits and hares, pikas do look a bit like short-eared rabbits as they scamper among mountain rocks. Nicknames such as rock rabbit, whistling hare, and little chief hare are further testimony to the family resemblance. Found year-round above the timberline on high mountains in the West, pikas live in colonies among loose boulders. When danger threatens, usually in the form of eagles or other predators, pikas warn each other with loud, squeaky barks. Cautious about their food supply as well, the provident little creatures harvest leaves and grasses, stack them in the sun to dry, then store them in their rocky dens for the long cold winter.

Pike

Esox

From the lO-inch, I-pound grass pickerel to the 7-foot, 75-pound muskellunge, all five North American species of pikes are such aggressive predators that they have earned the nickname waterwolves. All are freshwater fish with long, slim, muscular bodies and powerful, jutting jaws armed with sharp teeth. The pikes satisfy their voracious appetites by lurking in weedy shallows and darting out to seize their victims. Although they feed mainly on other fish and frogs, even waterfowl and young muskrats do not escape the larger species. Strong fighters, the pikes are popular game fish and, once caught, make a tasty meal.

Pileated woodpecker

Dryocopus pileatus

Striking black-and-white birds with rakish red crests, pileated woodpeckers are-except for the probably extinct ivory-billed-our largest woodpeckers. Though nearly as big as crows, they are rarely seen. The best signs of their presence in the mature woodlands they prefer are the large rectangular holes they hack into tree trunks in search of carpenter ants, their favorite food. Listen, too, for their loud, ringing calls and the rhythmic hammering as they bore new holes. In spring the males also drum on dead stubs to attract mates and proclaim territory. Mated pairs chisel tidy nest holes in tree trunks, where they raise broods of three to five young.

Pillow lava

Formed when lava solidifies underwater, pillow lava consists of heaps of rocks that look like piles of sandbags. when molten lava erupts under the sea, its surface quickly chills and develops a brittle skin. Tongues of hot liquid then break through the surface and harden into the charactelistic pillow shapes. Examples can be seen in California, New Jersey, and other places where ancient sea floors are exposed on land.

Pine

Pinus

The pines are trees that invite superlatives: oldest, tallest, most useful, and more. Bristlecone pines, for example, claim the prize for longevity among trees, with some of them reaching ages of 5,000 years or more. The giants of the group are sugar pines, which can top out at 200 feet and produce cones to match - up to 2 feet long. Still other species, valued as timber, supply countless board feet oflumber for myliad uses, among them home construction, railroad ties, and even matchsticks.

All the pines have evergreen, needle-shaped leaves that are usually borne in clusters of two to five. And they all produce seeds in cones formed of overlapping woody scales. While young trees are usually conical in form, with whorls of horizontal branches radiating from the trunks, older trees sometimes assume more spreading, irregu1ar shapes.

Except for parts of the Midwest and Far North, pines range throughout North America. Though some grow on soggy soils, most species prefer dry, sunny uplands. Since they can prosper on soils too thin and rocky for agriculture, pines are extensively planted in the reforestation projects that are so vital to the enhancement of the environment.

Pinnate

A leaf divided into more than three leaflets, these being arranged in pairs on either side of the leaf stem.

Pipit

Anthus

Small, slender birds with streaked or mottled brown plumage and white outer tail feathers, pipits characteristically bob their tails as they walk along catching insecltS on the ground. Though generally inconspicuous, courting males are noted for their impressive displays: they fly straight up, then flutter back down, their songs descending in pitch as the birds float down from the sky. The American pipit, our commonest species, nests on arctic and alpine rundra and winters in open country in the South. The less common Sprague's pipit is a bird of short-grass prailies.

Pipsissewa

Chimaphila umbellata

Producing clusters of fragrant, pinkish-white starshaped flowers above whorls of shiny evergreen leaves, pipsissewa blightens dry midsummer woodlands all across temperate America. Its name, from a Cree Indian word meaning "it breaks into small pieces," refers to the Crees' belief that an extract from the leaves could break up kidney stones. Pipsissewa acrually remained a popular home remedy until the early 1900's, and it is still used for flavoling candy and soft drinks.

Pitcher plant

Among the carnivores of the plant world, pitcher plants are distinguished by their urn-shaped leaves. Within the leaves' rims, the plants serve up drops of nectar to lure insects. An unwary exploring insect will occasionally fall into the urn, or pitcher, where a band of downward-pointing hairs prevents the victim from crawling back up. Below the bristles, the intelior wall of the leaf is sleek and waxy-a further impediment to climbing out. Trapped, the insect drowns in the rainwater accumulated in the pitcher. Enzymes secreted by the plant hasten the digestion of the insect's body, which is absorbed for nourishment. While the best-known pitcher plants are colorful bog-loving curiosities of the East and Midwest, other species prosper in various habitats in the South and West. Thliving primarily in places where little nitrogen is available to their roots, pitcher plants compensate for the shortage by extracting this important nutrient from the insects they trap.

Pit viper

The cottonmouth and copperhead, as well as our various rattlesnakes, are all pit vipers-a group of poisonous snakes named for the distinctive sensory organs they have in common. Located on either side of the head between the eye and nostril, these sensory pits are extremely responsive to heat and are used to determine the whereabouts of warm-blooded prey. Pit vipers are nocturnal, and by moving their heads from side to side, they are able -with these special sensors-to gauge the exact location of birds and mammals in the dark. Once they have homed in on their targets, they strike rapidly and accurately, injecting venom with their long, hollow fangs.

Planarian

An unsegmented flatworm.

Plankton

Delived from a Greek word meaning "wander," the term plankton refers to the huge numbers of plants and animals that drift with currents in the ocean and other bodies of water. The plants, known as phytoplankton, live in the well-lit surface waters, where they carry on photosynthesis. Consisting mainly of microscopic algae, they are the basic source of food in the ocean.

Zooplankton, the floating animals, range from minute protozoans to tentacled jellyfish several feet in diameter. The larvae of many kinds of fish and shellfish also dlift as plankton before matuling into adults. Many of these animals graze on the phytoplankton. They are in turn eaten by larger drifters, which are themselves food for other creatures, including the massive blue whale, which subsists on plankton strained from seawater.

Planning (Environmental emergencies)

Determining the potential impacts of environmental emergencies on communities and natural resources is essential to minimizing the impacts of such emergencies when they occur. Of particular importance is the development of a network of appropriate responders with clearly delineated responsilities.

Plant

Close to 2.5 billion years ago, the earth's surface and atmosphere were stable enough to support primitive life. Single-cell organisms began to develop in the seas that covered the planet. A simple organism known as blue-green algae appeared and spread across the seas. Blue-green algae used sunlight and water to make food, and in the process, created oxygen. As the blue-green algae grew in the earth's seas, they began to fill the atmosphere with oxygen. The oxygen that blue-green algae produced made it possible for other types of organisms to develop.

Plants play the most important part in the cycle of nature. Without plants, there could be no life on Earth. They are the primary producers that sustain all other life forms. This is so because plants are the only organisms that can make their own food. Animals, incapable of making their own food, depend directly or indirectly on plants for their supply of food. All animals and the foods they eat can be traced back to plants.

The oxygen we breathe comes from plants. Through photosynthesis, plants take energy from the sun, carbon dioxide from the air, and water and minerals from the soil. They then give off water and oxygen. Animals and other non-producers take part in this cycle through respiration. Respiration is the process where oxygen is used by organisms to release energy from food, and carbon dioxide is given off. The cycles of photosynthesis and respiration help maintain the earth's natural balance of oxygen, carbon dioxide, and water.

Leaves are the main food-making part of most plants. They capture energy from sunlight, and turn water and carbon dioxide into sugar and starch. This sugar and starch becomes the food that provides plants with energy to grow, to produce flowers and seeds, and carry on their other life processes.

Plant Sizes

Scientists believe there are over 260,000 species of plants. Some plants are so small they can barely be seen. Others are taller than people or animals. One of the largest living plants on the earth are the sequoia trees of California. Some stand over 290 feet (88 meters) high and measure over 30 feet (9 meters) wide.

Certain characteristics of plants set them apart from other living things. Both plants and animals are complex organisms that are made up of many types of cells, but plant cells have thick, rigid walls that consist of a material called cellulose. Animal cells do not have this material. The cellulose enables plants to stand upright without the aid of an internal or external skeleton.

Plant Photosythesis

Plants require a reasonable level of heat to grow. The most favorable temperature at which photosynthesis takes place ranges from near freezing to 70 to 80° F. The rates of photosynthesis and respiration increase with rising temperatures. Any temperatures above or below these levels limit plant growth. The climate of a region determines what types of plants can survive in that region.

A plant's environment is made up of many factors. One of the most important is the weather--sunlight, temperature, and precipitation (rain, melted snow, and other moisture). Soil and other plants and animals that live in the same area are also included in the environment of a plant. All these factors form what is called a natural community.

No two natural communities are exactly alike, but many resemble one another more than they differ. Botanists divide the world into biomes--natural communities of plants, animals, and other organisms.

Plant Medicine

Plants provide many useful drugs. Some of these plants have been used as medicines for hundreds of years. The bark of the cinchona tree was used 400 years ago to reduce fever. It is still used to make quinine, a drug used to treat malaria and other diseases. Another drug, called digitalis, is used in treating heart disease. It is made from the dried leaves of the purple foxglove plant. The roots of the Mexican yam are used in producing cortisone, a drug useful in treating arthritis and a number of other diseases.

Plantain

Plantago

Unrelated to the tropical bananalike plants of the same name, the various plantains are all too familiar to gardeners and lawn keepers, who despise them as persistent, troublesome weeds. The leaves, Iibbed and broadly oval on many species, are arranged in ground-hugging basal rosettes from which rise tall, slender stalks topped with spikes of inconspicuous greenish flowers. Both wild and caged birds, as well as a number of rodents, are fond of the tiny seeds, and rabbits nibble on the foliage. Richer than spinach in several vitamins, the tender young leaves used to be served as a potherb at family dinner tables. The two most widespread species, the oval-leaved common plantain and the aptly named narrow-leaved plantain, are both oldworld natives that thrive from coast to coast.

Plateau

Broad, flat expanses of terrain that rise high above their surroundings are called plateaus. They range in height from a few hundred to many thousands of feet and may encompass vast areas. The Colorado Plateau, for instance, covers about 150,000 square miles and in most places stands about one mile above sea level.

Deeply incised with canyons, including the Grand Canyon, the Colorado Plateau was uplifted by titanic movements within the earth's crust. Other plateaus were built up as successive lava flows bulied preexisting landscapes under thick layers of basalt. Measuling about 75,000 square miles, the Columbia Plateau in the Pacific Northwest is made up of basaltic lava that poured from enormous fissures in the earth.

Play

An Animal Behavior term, this is used to describe perhaps the most difficult Category of behavior to define, because it involves many types of behavior shown in other contexts, such as fighting and prey capture. Play often lacks the organization, completeness and "earnestness" of the same behavior in other contexts. Sometimes split into Object play and Social play. It is almost entirely restricted to Mammals and most common in young ones. Its functions have Been the subject of heated and unresolved debate.

Playa

Named for the Spanish word for "beach" or "shore," a playa is a flat, dry lakebed on a sunparched desert floor. The lake may be filled after heavy downpours, but it dries out again within a few days or weeks. After the water evaporates, the playa is often left encrusted with a layer of salts, and continued flooding and drying can produce thick accumulations of halite, gypsum, and other economically important minerals. Playas are common in Death Valley, California, where they were at one time mined for borax. The Bonneville Salt Flats in Utah are another large-and spectacular-example of a playa.

Plover

Stocky, large-headed shorebirds with big eyes and short bills, plovers are generally found on beaches and mudflats. Unlike their relatives the sandpipers, they rarely probe under the mud for food. Instead, they stand still for several minutes to scan the ground in front of them and snatch up small prey, then run a few paces and pause to watch again. Our best-known plover, the raucous killdeer, is a bird not of beaches but of open fielcls. It is named for its persistent ringing kill-dee call. Another widespread species is the semipalmated

plover, whose name refers to its half-webbed toes. Despite its bold markings, this handsome little bird in fact blends perfectly with the mudflats where it forages. Far less common are the snowy and piping plovers. Both are denizens of sandy beaches, where their pale plumage provides camouflage as they scurry (llong the shore.

The strikingly patterned lesser golden plover is famous as a champion migrant, sometimes making round-trip journeys of 16,000 miles. After nesting on the Arctic tundra, flocks of these birds fly to Labrador, then set off on a nonstop trip over the Atlantic to the plains of southern South America.

Poacher

Bottom dwellers that inhabit cold ocean waters, poachers are slim-bodied fish that range from 2 to 10 inches in length. Clad in bony plates and blistling with spikes and spines, they include such aptly named characters as the spinycheek starsnout, the northern spearnose, the pricklebreast, the sawback, and the warty poacher. One species, the kelp poacher, uses its fins to scale craggy rocks and is often festooned with camouflaging seaweed and sponges that make it look like a bit of red and brown jetsam. Though often abundant, especially in the North Pacific, poachers are of no commercial value.

Pocket gopher

Pouches on the outside of their cheeks•-noticeable only when they are bulging with roots, tubers, and other vegetation-are the pockets that give pocket gophers their name. Stocky little rodents, they have strong feet and sharp teeth that are used for digging their extensive burrows. Though rarely seen above ground, they are easily located by the fan-shaped mounds of earth that they push out of their tunnels.

Most of our 15 or so species are found in western mountains (one lives in the Southeast). Their burrows aerate the soil, but the animals at times destroy root crops and pull forage plants into their tunnels-destructive habits that have led to efforts at extermination. Since pocket gophers reproduce at a prodigious rate, however, such campaigns have had limited success.

Pocket mouse

Some 20 species of pocket mice inhabit deserts and dry prailies west of the Mississippi River. Expert burrowers, they use their tunnels for nesting, food storage, and as daytime retreats. At night the tiny rodents emerge from their burrows to forage for seeds on the surface. Like their distant cousins the pocket gophers, they have fur-lined, external cheek pouches, which they stuff with seeds that they carry back to their underground larders.

Point count method

Bird Biology Avian Conservation term.

Count of contacts recorded by an observer from a fixed observation point and over a specified time interval: fixed distance (radius) point count is limited to individuals within a single fixed distance; variable distance (radius) point count is limited to individuals within distances varying according to species-characteristic detection distances (syn. variable circular plot); and unlimited distance point count includes all individuals without limits, that is, all detections recorded regardless of distance.

Point transect

Bird Biology Avian Conservation term.

A transect along which the point count method is used. No recordings are made between stations (as opposed to strip transects with continuous recordings).

Poison

See Poisonous Plant, Poisonous Snake, Shrew

Poisonous Plant

Some 700 species of plants native to North America are classed as poisonous. The toxins they contain present an array of complicated compounds, including alkaloids, glycosides, and resins, each of which affects victims in different ways. Some attack the nervous system, producing weakness or paralysis; others interfere with the heart and circulatory system; and many irritate the skin and the digestive tract.

Some poisons are fast acting, producing symptoms almost immediately. The acrid juice of buttercups, for instance, inflames the mouth and stomach within seconds. The toxins of the deadly amanita mushrooms, in contrast, may take up to 24 hours to show their full effect.

A number of poisonous plants can heal as well as harm, for a plant that is toxic in large quantities may have medicinal value in smaller amounts. Indeed, many medicines are essentially exlracts of poisonous plants administered in controlled doses. The common foxglove, for example, is the source of digitalis, a drug used to strengthen the heartbeats of cardiac patients. In large doses, however, digitalis can cause heart failure.

Further complicating this situation is the fact that a plant may be poisonous at one stage of its life cycle and not at another. Pokeweed, for instance, is relatively harmless when young, and in many areas country people gather the shoots in spring to boil as a potherb. But as the plant

matures, it accumulates such high concentrations of toxins in all its tissues, that consumption of any of its parts can be lethal.

While many poisonous plants are toxic when ingested, others inflict their misery simply by being touched, producing a skin rash called contact dermatitis. The rash is commonly caused by close encounters with a notorious plant: poison ivy (also known as poison oak). It contains an oil, urushiol, that blisters the skin of allergic individuals. The poisonwood, a small tree with purple leaves that is found in the Southeast, also causes severe dermatitis, while in the West snow-on-the-mountain, prized for its showy white blossoms, yields a milky sap so caustic it has been used to brand cattle.

In recent years the incidence of plant poisonings has been increased by the renewed populality of foraging for wild foods. Many toxic plants resemble common food plants and so fool inexperienced harvesters. Someone seeking the edible roots of the wild carrot, for instance, might accidentally pick those of its similar-looking relative, poison hemlock; and the fleshy tubers of the water hemlock are frequently mistaken for wild parsnips-with fatal effect, since one or two bites can deliver a lethal dose.

Mushrooms suffer from the most sinister reputation of all the wild edibles. This is somewhat unfair, for of the 5,000 or more kinds found in the United States, only about 100 are poisonous. But positive identification can be tricky, and some of the deadliest kinds closely resemble benign species.

Despite the great number and variety of poisonous plants, human deaths remain relatively rare. Young children are most at risk, since their natural curiosity prompts them to taste every new thing they discover. Because of their low body weight, moreover, children are susceptible to far smaller doses of toxins.

Parents often unwittingly compound the problem by putting poisonous plants about the house and yard, right in harm's way. Dumbcane and philodendron, both popular house plants, contain needlelike crystals of calcium oxalate in their stems and leaves. When eaten, the C1ystals embed in the tissues of the mouth and tongue and cause an intense burning sensation. Far more dangerous are the juicy red fruits of the yew. Though their flesh is edible, the seeds (and needles) contain taxine, a poison that can cause respiratory failure in as little as one half hour. Mountain laurel, a common wild shrub and a popular ornamental, is poisonous in all its parts, including the honey made from its nectar. Another dangerous domestic is the oleander, a common landscaping shrub in the Southeast. Every part is toxic: people have even died after using oleander twigs as barbecue skewers. Poisonous plants also take a toll on livestock, particularly in the arid West, where hungry animals may have difficulty finding other fodder. The white snakeroot, an upright weed with candelabras of fuzzy white blossoms, is often eaten by cattle, causing nausea and trembling, as well as poisoning their milk.

Among the most dangerous plants of western prailies are the locoweeds. They contain a slowacting toxin that causes disolientation, frenzied behavior, and sometimes death. Fortunately, locoweeds and most other poisonous species are so foul-tasting that one bite is usually enough to convince livestock to graze elsewhere.

Poisonous snake

Though widely feared, poisonous snakes pose relatively little danger to humans. The fact is that in North Amelica, only a dozen or so deaths per year are attributed to snakebites. And most of the victims are people who regularly handle venomous snakes. All of our poisonous snakes fall into one of two categories. The more numerous pit vipers-including the copperhead, cottonmouth, and all the rattlesnakes-have a deep, heat-sensitive pit, used to detect warm-blooded prey, in front of each eye. Pit vipers strike quickly; the venom, which they inject through long, hollow fangs, attacks the victim's blood vessels and red blood cells.

Coral snakes, brightly banded with yellow, red, and black, live only in warm areas. Instead of striking quickly, they gnaw on their victims, releasing a venom that impairs the nervous system and can sometimes paralyze such vital organs as the lungs and heart.

Pokeweed

Phytolacca americana

Up to 10 feet tall with branching stems and footlong leaves, pokeweed flourishes in fields and along roadsides throughout the East. Its spikes of tiny greenish-white flowers are followed by purple berlies borne on scarlet stems. Its root, which resembles that of a horseradish, is known for its medicinal uses. And in spring, especially in the South, the plant's young shoots are boiled and consumed as a vegetable. Despite its array of benefits, however, pokeweed must be approached with caution. It is so poisonous that if it is not properly prepared, the food and medicines it offers can be lethalhence the pokeweed's other epithet: the Jekyll and Hyde of the plant world. Pokeweed's purple berries contain a dark juice that was once used for ink, inspiring one of the plant's nicknames, inkweed.

Pollen

Minute grains produced by anthers and containing male sex cells. Consisting of tiny grains that playa vital role in the reproduction of seed-bearing plants, pollen looks to the naked eye like a yellOwish dust. Under an electron microscope, however, the grains are revealed in their astonishing valiety. With surfaces that are smooth, grooved, spiked, pitted, or ridged, pollen grains are shaped like everything from flying saucers to cantaloupes.

Pollen is produced by the stamens, or male strucrures, of floweling plants and by the male cones of conifers. In the process of pollination, pollen is transferred to the plant's female structures, where fertilization takes place and seeds then develop. Typically, much more pollen is produced than is ever used. And the pollen of some plants, such as ragweed, is, of course, a major nemesis of hay fever sufferers.

Pollination

Wind and water, as well as bees, butterflies, birds, bats, and other animals, all playa part in pollination-the process by which pollen is transferred from the male parts of plants to the female parts. Plants that depend on wind or water produce huge amounts of pollen to ensure that at least some of it arrives at its destination. Others have showy petals or enticing odors that attract pollinators such as honey bees, hummingbirds, or other creatures. The pollinators, searching for nectar or pollen to use as food, are dusted with pollen as they alight on a flower, and then unwittingly transport it to others.

Once the pollen has reached its female counterpart, fertilization takes place. In conifers, whose ovules are exposed on cones, the process is simple. In flowering plants, however, a pollen grain that lands on top of the female pistil must first germinate, sending a pollen tube down into the pistil until it reaches an ovule. There it releases a sperm nucleus that unites with an egg cell to develop into a seed.

Pollution

An unpleasant by-product of human activities such as industry, mining, and even agliculture, pollution is the contamination of our air, water, and land. Sludge-clogged livers, soup-thick smog, and roadways littered with bottles and other deblis-these are just a few of the pollution problems facing all of North America. Detergents, fertilizers, pesticides, and industrial pollutants have sullied streams and contaminated water supplies, while heaps of nonbiodegradable trash choke our waste disposal sites.

Other less visible enemies also imperil our planet. Acid rain, caused by industlial and auto

emissions, has killed fish, corroded buildings, and devastated forests. The burning of fossil fuels adds carbon dioxide to the air, which could produce the greenhouse effect: a warming of the atmosphere that would disrupt climates around the world. And burgeoning stores of nuclear wastes pose an ominous threat.

Human health is directly endangered by some pollutants. Many industrial chemicals are known carcinogens; smog can cause severe respiratory problems; and in some communities, tainted water supplies have resulted in an increased incidence of leukemia and other diseases.

The first step toward healing a sick environment is to eliminate as many pollutants as possible. The use of certain aerosol propellants, for instance, has been prohibited in an effort to save the ozone layer. Strict compliance with pollution regulations, waste treatment, recycling, and the use of biodegradable products are ways in which communities and corporations can take active roles in cleaning up the planet.

Pollution (Industry)

Any substance that is present in or has been introduced into the environment and has harmful or unpleasant effects. Pollution comes in many forms, and may be present in air, land, water, or organisms. Although some pollution is from natural sources, most is produced by human activities.

Pollution (Ocean)

Any substance introduced into the ocean that has unpleasant or harmful effects. Although ocean pollution often comes from direct sources, such as sewage or industrial liquid waste emitted by sewage treatment plants, industries, septic tanks, or waste dumped by oceangoing vessels, it may also fall out of the atmosphere or seep in from surrounding land.

Pollution (Water)

Any substance introduced into water or a body of water that has unpleasant or harmful effects. Although water pollution often comes from direct sources, such as effluent emitted into lakes and rivers by industries, it may also fall out of the atmosphere or seep in from surrounding land.

Pollution prevention

Pollution prevention refers to the use of processes, practices, materials, products or energy that avoid or minimize the creation of pollutants and waste, and reduce the overall risk to human health or the environment.

Polyandry

An Animal Behavior term, this is used to describe a mating arrangement in which one female has several males.

Polygamy

An Animal Behavior term, this is used to describe the mating system in which one individual has two or more mates, either simultaneously or successively (the latter is also known as Serial monogamy). In Polygyny, one male has several females. In Polyandry, one female has several males. The latter is rare because the reproductive success of females is usually limited by the number of eggs they can produce, Rather than by the number of mates they can have.

Polygyny

An Animal Behavior term, this is used to describe a mating arrangement in which one male has several females.

Polymorphism

Occurrence of more than one distinct form of individuals in a population.

Polyphemus moth

Antheraea polyphemus One of our native silkworm moths, the polyphemus moth was named for the one-eyed giant of Greek mythology, an allusion to the eyespot on each of its brownish wings. As a fat, leaf-green caterpillar, the polyphemus feeds on the foliage of hardwood trees, then overwinters in a silken cocoon. When the adults emerge, ready to mate, the males' antennae are especially featherythe better to detect pheromones, the alluring female scents that waft on the evening breeze.

Pond

A placid, mirror-like surface dotted with lily pads, where dragonflies shimmer in the sunlight and chorusing bullfrogs can be heard at dusk, this is the scene that comes to mind when we think of a typical pond. Though hard to define precisely, a pond is generally considered to be a small body of standing fresh water, often of uniform temperature, that is shallow enough for sunlight to penetrate to the bottom, allowing rooted plants to grow even in the deepest parts. Here pond weed and other plants live completely submerged, while duckweed floats on the surface, its tiny roots dangling below. Water lilies require shallower water, and even closer to shore are cattails, arrowheads, and arums. Beavers' expertly built dams actually create ponds, in the midst of which these busy engineers construct the lodges where they rest by day and raise their young.

For its rich variety of animal life, from microscopic plankton to visiting moose, the pond serves as food factory, nursery, and battleground. Here all manner of insects, fish, amphibians, birds, and mammals compete for food, shelter, and breeding space. As a pond ages, however, its cast of characters changes, for built up sediment and encroaching vegetation eventually turn it into a marsh and then dry land.

Pond lily

Nuphar

Though pretty, the sunny yellow flowers of pond lilies, or spatterdocks, are not so large and lovely as those of the lotuses and water lilies. The plants, in fact, are sometimes scorned as weeds because they grow so vigorously that they crowd out other plants. They do, however, provide a feast for wildlife. Ducks eat the seeds, moose graze on the floating leaves, and muskrats and beavers store the sweet roots, which were also eaten by Indians and early settlers.

Pondweed

Potamogeton

Bottom-rooted aquatics, pondweeds flourish in lakes, ponds, and streams. Some species are entirely submerged, while others have narrow underwater leaves and larger leaves that float on the surface. Their tiny green flowers are borne on spikes that project from the water. Though far from showy, pondweeds are of vital importance to wildlife. Fish and other animals find cover in thickets of pondweed, and waterfowl eat the nutlets as well as the plants themselves.

Poppy

A large and attractive family of flowers, the poppies are prized for their colorful but short-lived blossoms. Most have milky or colored sap and many have deeply cut foliage. Each flower stalk ends in a single bud that opens to reveal four to six broad petals surrounding a knot of stamens. The blooms are followed by fruit capsules that open to release their seeds through pores. One of the best known is the California poppy, whose golden blossoms blanket grassy hills and arid slopes from California to Utah. Up to eight feet tall, the shrublike Matilija poppy has giant white flowers with yellow centers.

Population

A group of coexisting (conspecific) individuals that interbreed if they are sexually reproductive.

Population viability analysis (PVA)

Analysis that estimates minimum viable populations.

Porcupine

Erethizon dorsatum

Easily recognized by the long, sharp quills that cover its stocky, short-legged body and stubby tail, the porcupine is the only rodent of its kind in North America. The quills-approximately 30,000 on each animal-are modified hairs that come loose when they are touched. Any predator that attacks a porcupine retreats with its face and paws covered with the barbed spines, which work their way deep into the flesh, causing infection and, sometimes, death. A forest dweller in the West, the Northeast, and Canada, the porcupine spend its days sleeping. At night it forages in trees, feeding on bark, twigs, and buds and often causing extensive damage. In spring the female leaves the trees and moves into a den to give birth to a single young. The newborn's quills are soft but harden within minutes. And within hours the youngster is able to climb trees with its mother.

Porcupinefish

When pursued or perturbed, porcupinefish balloon from bite-size to basketball-size by gulping air or water. The sharp spines that give the fish their name bristle from the taut skin and act as a further deterrent to would-be predators. Unlike those of their cousins the burrfish (whose spines are always erect) the "quills" of the porcupinefish lie flat against their bodies when they deflate. Their beaklike teeth-one big tooth in the upper jaw, and another in the lower jaw-enable them to crush mollusks and other hardshelled prey. Found off the Atlantic and Pacific coasts, the whimsical-looking creatures are sometimes inflated, dried, and sold as souvenirs.

Porgy

Abundant on the Atlantic and Gulf coasts in habitats that range from rocks and reefs to pilings and seagrass beds, porgies are popular food and game fish. Most members of the family eat shellfish and weigh less than one pound. Exceptions include the 30-pound sheepshead and the lO-pound jolthead porgy, which is named for its habit of dislodging mollusks with its head. One of the most familiar species, found from Cape Cod to the Carolinas, is called the scup in New England, the northern porgy in New York, and the fair maid in the South.

Porpoise

Small relatives of whales, porpoises resemble their cousins the dolphins but are chunkier, with snouts that are short and blunt rather than beaked. Streamlined sea mammals with a torpedo shape designed for efficient swimming, they travel in pairs or in larger groups, moving through the water at speeds of up to 14 miles per hour. like whales and dolphins, they breathe through a blowhole on the top of the head and must surface regularly for air. When swimming rapidly, they sometimes leap out of the water to take a breath.

Porpoises are intelligent creatures that communicate by means of high-pitched whistles and squeals. They also emit ultrasonic clicks in order to find their prey-primarily fish and squid - by means of echolocation. They breed in summer, and each female gives birth to a single calf about one year later. like dolphins, porpoises are sometimes inadvertently caught and drowned in the nets of commercial fishing vessels.

Harbor porpoises, which live off both the Atlantic and Pacific coasts, often venture into bays and the mouths of large rivers, where groups sometimes cooperate in rounding up schools of fish. More playful and gregarious are Dall's porpoises. Patterned in black and white like miniature killer whales, they live in the North Pacific, where they are frequently seen swimming near the bows of moving ships.

Portuguese man-of-war

Physalia physalis

Looking like a large jellyfish as it drifts on the surface of warm seas, the Portuguese man-ofwar is actually a colony of organisms, called polyps, that work in concert to capture and devour prey. Buoyed by a balloonlike float, the beautiful but dangerous man-of-war hides its arsenal underwater: dangling from the float are long, trailing tentacles armed with deadly stinging cells. When touched by fish or other prey, the tentacles paralyze the victim and pull it toward specialized polyps that digest the food for the entire colony. Although encounters with this notorious creature can be painful, some animals fear it not at all. Certain fish live unharmed among its tentacles, and loggerhead turtles eat the man-ofwar with impunity.

Postfledging mortality

Bird Biology Avian Conservation term.

The death rate of young after fledging, calculated from the following: the fates of young birds after fledging (or hatching in the case of precocial young), when these fates can be observed directly; changes in the ratio between juvenile and adult birds in populations; and the number of surviving young needed to replace adult losses, when adult mortality rates and the production of fledglings are known.

Pothole

Deep circular depressions in the bedrock floor of rivers, potholes are a testament to the erosive power of running water. As turbulent water forms eddies in the stream, stones and pebbles often get caught in the swirl. Churning around and around in the same spot, the stones gradually scour deep holes in the underlying rock of the riverbed. The abrasive tools-pebbles, stones, and even grains of sand-can often be found at the bottom of the hole.

Prairie

See Grassland.

Prairie chicken

Tympanuchus

Grouse of the grasslands, prairie chickens are best known for their remarkable springtime courtship displays. Gathering at dawn on traditional mating grounds, groups of males begin to leap, stomp, and strut about, their tails fanned and their neck feathers erect. At the same time, inflated pouches on their throats resonate with booming calls that can be heard two miles away. Females view the entertainment, then mate and go off to nest and raise their young alone. The greater prairie chicken-at 18 inches in length, the larger of our two species-is found from Michigan westward across the Great Plains, while the lesser prairie chicken lives farther south. Because farmland has gradually usurped their habitat, all prairie chickens have declined in number over the years. One subspecies, the Attwater's prairie chicken, found along the Texas coast, is seriously endangered; and another, the heath hen of the East, is extinct.

Prairie dog

Cynomys

The playful and sociable prairie dogs are squirrellike, burrowing rodents that live in colonies, or towns, on the Great Plains. They are named for their high-pitched staccato barks, signals that warn each other to hide from approaching badgers, hawks, or coyotes. Prairie dogs also communicate by nuzzling, kissing, and grooming, which reinforce the bonds within each coterie, or extended family, in the larger colony. Each coterie may have up to 100 burrows, elaborately interconnected and sometimes a dozen feet deep. Until early in this century, vast numbers of prairie dogs were found on the Great Plains. A single colony in western Texas, for example, covered thousands of square miles and was populated by some 400 million prairie dogs. Today the great towns have disappeared. Poisoned and shot by ranchers because they were thought to compete with livestock for food, prairie dogs now survive only in small, isolated towns in parks and wildlife refuges. One form, the Utah prairie dog, has so declined in numbers in the past several decades that it is now endangered.

Prairie pothole

Across the plains of western Minnesota, the Dakotas, and south-central Canada, the land is dotted with glacial "thumbprints" created over 10,000 years ago. Water-filled depressions called prairie potholes, they cover some 300,000 square miles and are the breeding grounds for more than half of the continent's ducks. These miniature marshes range in size from more than 100 acres to fewer than 10 and are home to an array of plants and animals, including the ubiquitous cattails and muskrats. Despite the fact that many of our prairie wetlands have been lost to drainage and development, the potholes continue to provide vital nesting places and rest stops along North America's waterfowl flyways.

Praying mantis

See Mantid

Precipitation

Any form of water, such as rain, snow, sleet, or hail, that falls to the earth's surface. Rain and snow, as well as drizzle, sleet, and hail, are all forms of precipitation-moisture that falls from clouds to the earth. Clouds are formed when water vapor rises in the air, becomes chilled, and condenses into droplets or flakes. If the clouds become dense enough, droplets adhere to each other, increasing in size until they become heavy enough to fall as rain. When the clouds are low and the air is relatively still, moisture often descends as a fine mist, called drizzle.

Freezing temperatures produce precipitation in the form of sleet, hail, and snow. Sleet, which consists of moisture that has frozen into small pellets of ice, falls only in winter. In warmer weather the pellets, though frozen in the upper atmosphere, melt before they reach the ground, and fall as rain. Hail is formed when frozen pellets are tossed around in the air by updrafts, adding numerous layers of ice until they become so large and heavy that they fall to earth. (Hailstones can be dangerous; they have been known to injure livestock and break tlle windshields of cars.) Unlike sleet and hail, which begin as frozen rain, snow is made up of delicate crystals formed directly from supercooled water vapor. Though every snowflake has a six-sided shape, the design of each one is unique.

Whatever form it takes, precipitation provides the water that feeds rivers, lakes, and streams. Eventually it flows off the land into the sea, where it evaporates, beginning the cycle of precipitation all over again.

Precision

A quality, associated with a class of measurements, that refers to the way in which repeated observations conform to themselves.

Predator

When we think of predators, we tend to think of animals with fangs and claws, or hooked beaks and talons. Indeed, wolves, bobcats, owls, and hawks are all predators, but strictly speaking, so is any animal that kills and feeds on other animals. A robin pulling a worm out of the ground, for example, has much in common with an eagle swooping down on a prairie dog, and an insect-eating dragonfly is a predator, too.

In fact, few animals are exclusively predatory or vegetarian. Foxes, for example, occasionally feed on berries and grapes, while other creatures that we think of as vegetarians sometimes prey on other animals. Chipmunks, for instance, feed mainly on seeds and nuts, but when the opportunity arises, they also capture and consume insects and young birds.

Predator

An Animal that hunts other Animals for food.

Predators

Biological Philosophy term. They take on importance in "balance-of-nature" approaches to the environment: The ancients had to explain the presence of these fierce beasts on a "good" earth, and they did so by saying they were necessary (1) to keep populations in control, that is, to preserve the balance of nature, and (2) to furnish the natural world some protection from human beings.

Precocial

An Animal Behavior term, this is used in describing those species in which offspring are able to move about and feed themselves at an early age. Unlike Altricial species, these young are well developed at birth, with fur or feathers and open eyes, and they start to walk soon afterwards. The term Precocial is the opposite of the term Altricial. Some birds and animals are born semi-independent. Deer and elk can walk almost immediately and can leave the calving area. Many birds, including ducks, shorebirds and grouse are also precocial and leave the nest within a few hours of being born.

Preparedness (Environmental emergencies)

Readiness to respond to an environmental emergency is crucial to minimizing the harmful effects it could have on the environment.

Presentation

An Animal Behavior term, see Lordosis.

Prevention (Environmental emergencies)

A variety of method to help prevent environmental emergencies from occurring, whenever possible. These include education, regulations and other legal instruments governing the handling of hazardous materials.

Prickly ash

Zanthoxylum americanum

A shrub or small tree of rocky woodlands and riverbanks, the common prickly ash is one of the few nontropical members of the citrus family. It bears clusters of small greenish-yellow flowers in early spring before the feathery leaves emerge. like its relative Hercules' club, the ash's branches are armed with stout thoms-a superfluous defense, since the whole plant is infused with a bitter, lemony oil that wildlife avoids. Early settlers, however, chewed the aromatic bark to numb toothache pain, dubbing prickly ash the toothache tree.

Prickly pear

Opuntia

Close relatives of the cholla cacti, prickly pears can be recognized by their jointed stems, which are formed of broad, flattened pads that resemble spiny green beaver tails. Found throughout the Southwest and as far north as the prairie provinces of Canada, prickly pears of various species may grow as tall as 15 feet or spread in thickets 30 feet across. New pads sprout small, fleshy leaves, but they soon drop off, leaving behind needle-sharp spines and clusters of tiny, irritating barbed bristles. In spring prickly pears produce flowers up to four inches across in brilliant shades of yellow, orange, and red; these are followed by juicy, reddish-purple, figlike fruits. In the Southwest the fruits are made into syrup and jelly, while the pads are peeled and eaten as a vegetable.

Primaries

Flight feathers located on the outer half of a bird's wing.

Primary succession

The sequence of communities developing in a newly exposed site devoid of life.

Primitive

Biological Philosophy term. As opposed to civilized. The notion of "culture" has freed us somewhat of the rigidity of the opposition between the primitive and the civilized. Conventionally, hunter-gatherer cultures are primitive; agriculture would mark the beginning of civilization.

Primitive Organisms

Primrose

Primula

Partial to cool moist places, our many species of primroses grow along stream banks, in meadows, and on damp mountain slopes. Since their name derives from the Latin word for "first," it is not surprising that many of them bloom in early spring. A single stalk shoots up from a rosette of leaves and is topped by a cluster of five-petaled flowers. Though the blooms come in a rainbow of colors, they usually have yellow centers that lead pollinating insects to the flowers' hidden troves of nectar. The bird's-eye primrose, for instance, is pink with a yellow center, and the rosy mountain primrose also has a yellow "eye."

Prince's plume

Stanleya

These royally named plants, which flourish on deserts and plains throughout much of the West, are members of the mustard family. Conspicuous in bloom, they produce tall showy plumes of four-petaled flowers that on most species are bright lemon-yellow. Desert plume, the commonest species, flaunts its flowers on stalks up to five feet tall. But because, like all the other prince's plumes, it thrives on soils rich in the poisonous element selenium, desert plume is toxic and poses a threat to grazing animals.

Process

The operation of some factor or factors that produce a particular relationship among observations.

Productivity

The number of young produced per pair of animals, or the reproductive performance of the population, estimated as the proportion of young in the total population just after the breeding season.

Promethea moth

Callosamia promethea

Attractively patterned members of the silkworm moth family, these insects are found throughout the East, as far north as southern Canada, and west to the Great Plains. In the larval stage promethea moths are easy to identify: the caterpillars are green with five conspicuous tubercles on the back-four bright red ones at the head end and a yellow one at the rear. They feed on the foliage of the spicebush and on sassafras, cherry, and other trees. Overwintering as pupae, they hang from the twigs of their food trees in two-inch-long, leaf-wrapped silk cocoons and emerge as adults in the spring.

Pronghorn

Antilocapra americana

North America's swiftest mammal-the graceful and agile pronghorn-can leap 20 feet in a bound and is able to sprint over prairies and sagebrush flats at speeds of 60 miles per hour. Sometimes called the American antelope, the pronghorn is unique; it has no close relatives and is virtually unchanged from ancestors that roamed the earth some 2 million years ago.

Mainly brown, with two white stripes across the chest, a large white rump patch with hairs that are raised in warning when danger looms, and two-pronged horns, the creature is easily recognized. Males are strongly territorial and compete with each other for harems during the autumn rut. The fawns, often twins, are born the following spring. True to their heritage, they can run faster than humans within days of their birth. Pronghorns feed in the morning and evening, grazing on grasses and weeds and occasionally browsing on shrubs.

Pronotum

The hardened dorsal plate covering the thorax of an insect.

Propose

Endangered and Threatened species term.

The formal process of publishing a proposed Federal regulation in the Federal Register and establishing a comment period for public input into the decision-making process. Plants and animals must be proposed for listing as threatened or endangered species, and the resulting public comments must be analyzed, before the Service can make a final decision.

Proposed species

Endangered and Threatened species term.

Any species of fish, wildlife, or plant that is proposed in the Federal Register to be listed under Section 4 of the Endangered Species Act.

Protected Areas (Wildlife)

A terrestrial or marine area that is legally designated to protect plants, animals or ecosystems. They range from closed reserves, with a ban on the removal of any resource, to multiple-use areas managed to meet a variety of objectives, including conservation.

Protozoan

Amoebas, paramecia, and thousands of other kinds of protozoans flourish worldwide in fresh and salt water and in damp soil. Though they consist of but a single cell and most are microscopic in size, protozoans lead remarkably complex and varied lives. Many can reproduce sexually, but others simply divide in two or sprout buds that develop into new individuals. Some move about, propelled by whiplike flagella or tiny, hairlike cilia. While many kinds require oxygen, others survive in such airless environments as septic tanks

and the intestines oflarger animals. Some are parasitic, including those that cause malaria and dysentery. And a few protozoans, like plants, can manufacture food through photosynthesis.

Proximate factors

Aspects of the environment that organisms use as cues for behavior; for example, daylength.

Ptarmigan

Lagopus

Small, stocky grouse that live on chilly arctic tundra and on treeless mountaintops in the West, ptarmigans are masters of camouflage. In summer their mottled black and brown plumage blends with the scrubby tundra vegetation, and in winter their feathers are as white as the surrounding snow. like all grouse, they have feathered legs, but in winter their feet and toes are also feathered, conserving heat and acting in effect as snowshoes. Ptarmigans feed on insects, berries, and tender leaves during the warm months and tum to buds, twigs, and seeds in winter. During the spring mating season the males are adorned with prominent red combs over their eyes and display by strutting, cackling, and making short, fluttering flights. The females build the nests and incubate the eggs alone, but the males stand guard and sometimes help to tend the young.

Of the two species that live in the Arctic, the willow ptarmigan inhabits birch and willow thickets, while the rock ptarmigan prefers higher, more barren ground. The white-tailed ptarmigan is found on alpine meadows high in the Rocky Mountains from Alaska to New Mexico.

Puffball

Like mushrooms, puffballs are the spore-producing fruiting bodies of underground fungi. Forsaking the umbrella shape of their mushroom kin, most are spherical, but others are shaped like clubs, pears, or toy tops. Their surfaces may be warty, spiny, pitted, or smooth. When they are young, the flesh of most is white and spongy; but as they age, it darkens, and if poked or kicked, the mature fungus emits a dusty cloud of tiny spores. While most puffballs are just an inch or two across, some grow as big as basketballs. Many species are edible when young and fleshy, but since a few are poisonous, puffballs should be sampled only with expert guidance.

Puffer

Aptly named, the puffers-also known as blowfish or swellfish-discourage predators by gulping air or water until they are inflated to twice their normal size. Turning belly up, they bob at the surface of the sea until the danger passes, then deflate with a great belch and go on their merry way, searching for crabs and clams, which they crush with their tough beaks.

Puffin

Fratercula

These squat little seabirds may look comically awkward on land and rather heavy in the air, but once in their element, the water, they become able predators. "Flying" through the sea on stubby wings, they dive-bomb shoals of herring, sand eels, sardines, and other small fish, as well as squid. Though they dispatch their victims one by one, they can carry as many as 20 small fish crosswise in their brightly colored beaks.

Atlantic puffins ply the cold waters off Canada and New England. Their western cousins, the homed and the tufted puffins-named for their eye ornaments and head plumes-are at home in the North Pacific. All remain at sea in winter, returning to land only during the breeding season. Puffins often nest in well-populated colonies usually on remote, rugged islands free from eggand chick-eating land predators. They deposit a single egg deep within a burrow excavated in soft earth, or in a feather- or grass-lined lair in a rocky cleft. After fattening up their hatchling on fish, the parents return to the sea. The young puffins, still unable to fly, eventually scramble to the shore by night and plunge into the water.

Pulp and Paper (Industry)

The pulp and paper industry refers to the use of ground wood or other vegetable fibres to manufacture different types of paper, including cardboards.

Pseudopregnancy

An Animal Behavior term, this is used to describe the reproductive state which occurs in many female Mammals, such as Rats and Mice, after mating. Their cycles cease for a few days and only resume again if they are not pregnAnt.

Pupa

The stage in an insect's life-cycle between the larva and adult; also called the chrysalis.

Pupation

An Animal Behavior term, this is used to describe the inactive state adopted during metamorphosis by those Insects in which larva and adult are quite different. For example, Maggots pupate and later emerge as Flies.

Pyrite

Commonly known as fool's gold, pyrite is a shiny yellow metal that has tricked many a prospector. In fact, its impressive striated crystals sometimes do occur in gold-laden veins. An important source of sulfur, pyrite is found in Utah, Colorado, and many other locations.

Quack grass

Agropyron repens

A native of Europe, quack grass-also known as quick grass and couch grass-is an immigrant that thrives in fields and waste places all across the continent. Three to four feet tall with narrow leaves and erect flower spikes, it spreads rapidly by means of underground stems. Since quack grass is difficult to eradicate, most farmers consider it an aggressive weed. It can, however, be harvested as hay, and it helps anchor the soil against erosion.

Quadrat

Bird Biology Avian Conservation term.

A small sample plot, usually square or rectangular.

Quahog

Mercenaria mercenaria

Hard-shelled clams, or quahogs, are among the most popular shellfish with seafood fanciers along the East Coast. Small ones are savored as littlenecks, slightly bigger ones are called cherrystones, and the largest are diced for clam chowder. Their strong, hinged shells-gray and conspicuously ridged on the outside, but smooth and white or purplish within-were fashioned into wampum and used as currency by American Indians. These bivalves live buried in the sand or mud, with a pair of tubelike siphons exposed. They feed by drawing water into one siphon, filtering out edible morsels, then expelling the water.

Quail

Small chickenlike creatures less than 12 inches long, these relatives of grouse and pheasants are among our most beautiful birds. The males wear bold, attractive patterns, while the females, though more subdued, look enough like their mates to be easily recognized. Quail form pairs in spring, when the male's loud calls advertise his territory. In some species only the female builds the nest and incubates the clutch of 10 or more eggs, but the male always assists in rearing the chicks. The family remains together, often joining other families to form large coveys in winter. The only eastern quail is the northern bobwhite, named for its whistled call. Since quails are not migratory, severe winters in northern states can destroy whole bobwhite populations. The most familiar western species is the California quail, which sports a jaunty black head plume. Gambel's quail, at home on southwestern deserts, has a similar topknot. Another southwesterner, the secretive Montezuma quail, hugs the ground and slips away when danger threatens. Sometimes, however, it just freezes on the spot, a habit that has earned it the nickname fool quail.

Quartz

Hard and durable, quartz is one of the most common rock-forming minerals. Composed of silica, it is also the basic component of beach sand. Pure quartz is clear and colorless, but impurities yield a whole range of colors. Among the many kinds of quartz are prized gem-quality crystals such as amethyst and citrine; agate, which has wavy bands of color; and chalcedony, a translucent, waxy variety. Of great economic importance, quartz sand is used in glassmaking; sandstone and other rocks formed of quartz are valuable building stones; and quartz crystals are used in watches and electronic equipment.

Queen Anne's lace

Oaucus carota

Recognized by its familiar flowers that brighten fields and roadsides with splashes of white, Queen Anne's lace is also called wild carrot. In fact, this biennial, a member of the parsley family, is the ancestor of the garden carrot. The flower head that appears atop each stem is actually composed of many tiny blooms-one three-inch flower head may contain thousands of florets. A single red-purple bloom often appears at the center of the white florets. According to legend, it symbolizes the blood of Queen Anne of Great Britain, who pricked her finger while making lace. It is a tale that not only gives the summertime bloom its name but at the same time recalls the plant's old-world origins.

Quicksand

Folklore, films, and fiction are filled with tales of hapless travelers who step into quicksand and are slowly sucked down into a soupy grave. But while quicksand is quite real and can cause death, the stories about its dangers are somewhat exaggerated. Simply a mixture of sand and water, quicksand is found in places where groundwater flows up through loose sand. Objects heavier than water sink in it, but it does not suck them down. It is possible to escape quicksand either by being pulled to safety or by discarding heavy objects such as backpacks, lying on the back with arms and legs spread out to distribute body weight, and slowly rolling to solid ground.

Rabbit

Sylvilagus

Furry mammals with long ears, short, fluffy tails, and long hind legs for hopping, rabbits flourish all across the continent. In contrast to the larger, longer-eared hares, rabbits bear young that are naked and blind, while lhose of jackrabbits and other hares are fully furred and have their eyes wide open at birth.

Rabbits live in a broad range of habitats, from forests and swamps to dry brush country and suburban areas. The most widespread species, the eastern cottontail, is found virtually everywhere east of the Rockies. Like other rabbits, it is active from dusk to dawn, feeding on green plants in summer and on bark and twigs in winter. The lO-inch pygmy rabbit, which lives among the sagebrush in the Great Basin, is the only species with gray instead of white on the underside of its tail.

The pygmy rabbit digs tunnels for nesting, but most others nest in shallow, fur-lined depressions among grass, shrubs, or leaves. Females give birth to as many as four litters a year, with up to seven young in each. Able to leave the nest within two weeks, the young can reproduce when they are less than six months old.

Rabbitbrush

Chrysothamnus

Abundant in the West, the rabbitbrushes are hardy shrubs found on deserts, plains, and mountain slopes. Though some species grow 12 feet tall, most are compact bushes 1 to 3 feet in height. In late summer the plants are covered with dense clusters of small flowers that tint the land with a golden haze. The narrow, pointed leaves, though often pungently aromatic, are nevertheless eaten by rabbits, deer, and other wildlife. Because of their tolerance for salty and disturbed soil, rabbitbrushes are useful for erosion control, and one species shows promise as a native source of rubber.

Raccoon

Procyon lotor

Easily recognized by their bushy, ringed tails and the black masks across the eyes, raccoons are familiar mammals across most of the United States and southern Canada. Stocky yet agile, they are good climbers and swimmers that den in hollow trees and spend the night foraging. Raccoons are adept at catching fish, frogs, and crayfish by groping in the shallows of swamps and streams with their remarkably dexterous forepaws. (The tendency of captive individuals to wash their food is probably not an act of cleanliness but a reflection of the fact that wild raccoons find so much of their food in water.) Adaptable omnivores, raccoons also relish birds, mice, insects, earthworms, fruits, nuts, and just about anything else that is edible.

Because of their eclectic appetites, raccoons sometimes earn a reputation as pests. Gardeners and farmers regret their taste for com, and conservationists deplore their fondness for loon eggs. And when the masked marauders move from the wilds into the suburbs, they soon become skilled at raiding garbage cans.

Though not true hibernators, raccoons sleep through much of the winter. By February, however, the mating urge sends the males out regardless of the weather. Nine weeks later each female bears three to six kits. Educated by their mothers in the warm months, they enter their first winter well trained for life on their own.

Racer

Coluber constrictor

A swift, slender snake up to six feet long, the racer glides through its grassy or wooded haunts with its head held high off the ground. If chased, it often climbs into bushes or small trees, and when cornered, it strikes repeatedly while vibrating its tail. If it is in dried vegetation, the resulting sound is easily mistaken for a rattlesnake's rattle. Nonpoisonous, the racer seizes mice and other small prey, which it swallows whole. Although only one species is found in North America, its color and markings differ dramatically from region to region.

Racism

Biological Philosophy term. This managed to express itself in both pre- and post-Darwinian understandings. In the pre-Darwinian scheme of things, based on the idea of the Great Chain of Being the question was this: do the various races occupy different levels on the chain, some higher, some lower, or are they all basically human? In the post-Darwinian scheme of things, based on evolution, the question was: are some of the races more primitive than others?

Radio (Weather)

The use of radio frequencies to transmit up-to-the-minute weather forecasts and reports continuously over VHF-FM radio, 24 hours a day, seven days a week.

Radon

Colorless, odorless, tasteless-and radioactive-radon is a gas produced by the gradual decay of uranium, which is present in small quantities in rocks and soil. Outdoors it occurs in low concentrations that are harmless. But the gas sometimes seeps into housing, where it can build up to levels that are hazardous to human health. While some areas, such as eastern Pennsylvania, are radon hot spots, zones of contamination have been found in every state.

Radula

The tongue of a snail, which has teeth to bore holes in shells or prey.

Ragweed

Ambrosia

Though numbingly ordinary in appearance, the ragweeds are an extraordinary menace to hay fever sufferers. Their spikes of inconspicuous greenish-yellow flowers produce billions of pollen grains, which in late summer are carried by the wind not only to other ragweeds, where they enable the plants to set seed, but to the noses and throats of millions of allergic humans. Viewed through an electron microscope, the pollen, covered with nasty hooks and spines, looks just as troublesome as it actually is. Of our several native ragweeds, which flourish in vacant lots and neglected fields all across the country, two are most abundant. Common ragweed, with finely cut, fernlike leaves, reaches a modest height of one to four feet. Giant ragweed, with leaves divided into three to five broad lobes, grows up to 15 feet tall.

Rail

More often heard than seen, rails are secretive marsh birds that prefer to stay hidden among reeds and grasses. When pursued, they are more likely to run than fly, taking advantage of their slender shape, long legs, and large feet to slip away through dense vegetation. Rails build bulky nests on the ground or among reeds over water, usually concealing them under a canopy of surrounding plants. The downy black chicks follow their parents through the marsh in search of insects, snails, and seeds.

Of our several species, the Virginia rail and the sora-both robin-size birds of freshwater marshes-are the most common and widespread. The Virginia rail has a long, thin bill and a grating call, while the sora's bill is stubby and yellow and its calls include a medley of whinnying and piping notes. The king rail of freshwater marshes and the clapper rail of salt marshes resemble the Virginia rail but are twice its size.

Rain (Weather)

Moisture condensed from atmospheric vapor that falls to earth in drops.

Rain shadow

Just as mountains cast shadows by blocking sunlight, they can also create so-called rain shadows by preventing moisture in the air from reaching their leeward side. When moist air blows against a mountain range, it is forced upward. The air cools as it rises, and the moisture condenses and falls as rain or snow on the windward slopes. Once the air has crossed the mountains, it descends and wamlS up. By now it not only is too dry to produce rainfall, it also evaporates moisture from the leeward land, creating very arid conditions. In the state of Washington, for example, the coastal fringe receives over 100 inches of rain per year, while the area east of the lofty Cascade Mountains gets barely 10 inches. Since rain shadows create such dry conditions, they playa major role in the formation of deserts, such as our huge Great Basin desert.

Rainbow

Whether seen nearby in the spray of a garden hose or miles away on the clouds of a distant rainstorm, the multicolored arcs we call rainbows are produced in the same way. Mydads of water droplets act as tiny prisms that bend sunlight into its spectrum of colors. The backs of the droplets then reflect the colored light back to our eyes. Since the light is bent at a slightly different angle for each color, we see bands of red, orange, yellow, green, blue, and violet.

Rainforest

Although the term rain forest usually conjures up images of lush tropical jungles, North America also boasts a unique temperate rain forest-a ribbon of incredibly luxuriant vegetation along the coast from northern California to the Alaska panhandle. Where moist winds from the Pacific Ocean meet the coast ranges, rain and snow fall in abundance. A continual dousing of up to 200 inches of precipitation each year results in a phenomenal growth of trees and shrubs. Conifers such as Sitka spruces, western hemlocks, and western red cedars tower to heights of 200 feet or more and often have trunks over 10 feet in diameter. Beneath this canopy flourishes a rich mix of bigleaf maples, alders, and other hardwood trees; shrubs such as blueberries and elderberries; and in places, a lush carpet of ferns, mosses, and club mosses. A wealth of wildlife, from bald eagles to deer and elk, also finds a haven in this magnificent forest.

Rainforest biome

The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches of rain falls yearly.

Rain forests belong to the tropical wet climate group. The temperature in a rain forest rarely gets higher than 93 °F or drops below 68 °F ; average humidity is between 77 and 88%; rainfall is often more than 100 inches a year. There is usually a brief season of less rain. In monsoonal areas, there is a real dry season. Almost all rain forests lie near the equator.

Rainforests now cover less than 6% of Earth's land surface. Scientists estimate that more than half of all the world's plant and animal species live in tropical rain forests. Tropical rainforests produce 40% of Earth's oxygen.

A tropical rain forest has more kinds of trees than any other area in the world. Scientists have counted about 100 to 300 species in one 2 1/2-acre (1-hectare) area in South America. Seventy percent of the plants in the rainforest are trees.

About 1/4 of all the medicines we use come from rainforest plants. All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don't branch out for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect the them from water loss and freezing temperatures. It also makes it difficult for plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers.

Despite these differences, each of the three largest rainforests--the American, the African, and the Asian--has a different group of animal and plant species. Each rain forest has many species of monkeys, all of which differ from the species of the other two rain forests. In addition, different areas of the same rain forest may have different species. Many kinds of trees that grow in the mountains of the Amazon rain forest do not grow in the lowlands of that same forest.

Rainforest Animal Life

Many species of animal life can be found in the rain forest. Common characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to a life in the trees, such as the

tails of New World monkeys. Other characteristics are bright colors and sharp patterns, loud vocalizations, and diets heavy on fruits.

Insects make up the largest single group of animals that live in tropical forests. They include brightly colored butterflies, mosquitoes, camouflaged stick insects, and huge colonies of ants.

The Amazon river basin rainforest contains a wider variety of plant and animal life than any other biome in the world. The second largest population of plant and animal life can be found in scattered locations and islands of Southeast Asia. The lowest variety can be found in Africa. There may be 40 to 100 different species in 2.5 acres (1 hectare) of a tropical rain forest.

Rainforest Layers

There are four very distinct layers of trees in a tropical rain forest. These layers have been identified as the emergent, upper canopy, understory, and forest floor.

trees are spaced wide apart, and are 100 to 240 feet tall with umbrella-shaped canopies that grow above the forest. Because emergent trees are exposed to drying winds, they tend to have small, pointed leaves. Some species lose their leaves during the brief dry season in monsoon rainforests. These giant trees have straight, smooth trunks with few branches. Their root system is very shallow, and to support their size they grow buttresses that can spread out to a distance of 30 feet.

The upper canopy of 60 to 130 foot trees allows light to be easily available at the top of this layer, but greatly reduced any light below it. Most of the rainforest's animals live in the upper canopy. There is so much food available at this level that some animals never go down to the forest floor. The leaves have "drip spouts" that allows rain to run off. This keeps them dry and prevents mold and mildew from forming in the humid environment.

The understory, or lower canopy, consists of 60 foot trees. This layer is made up of the trunks of canopy trees, shrubs, plants and small trees. There is little air movement. As a result the humidity is constantly high. This level is in constant shade.

The forest floor is usually completely shaded, except where a canopy tree has fallen and created an opening. Most areas of the forest floor receive so little light that few bushes or herbs can grow there. As a result, a person can easily walk through most parts of a tropical rain forest. Less than 1 % of the light that strikes the top of the forest penetrates to the forest floor. The top soil is very thin and of poor quality. A lot of litter falls to the ground where it is quickly broken down by decomposers like termites, earthworms and fungi. The heat and humidity further help to break down the litter. This organic matter is then just as quickly absorbed by the trees' shallow roots.

Rainforest Plant Life

Besides these four layers, a shrub/sapling layer receives about 3 % of the light that filters in through the canopies. These stunted trees are capable of a sudden growth surge when a gap in the canopy opens above them.

The air beneath the lower canopy is almost always humid. The trees themselves give off water through the pores (stomata) of their leaves. This process, called transpiration, can account for as much as half of the precipitation in the rain forest.

Rainforest plants have made many adaptations to their environment. With over 80 inches of rain per year, plants have made adaptations that helps them shed water off their leaves quickly so the branches don't get weighed down and break. Many plants have drip tips and grooved leaves, and some leaves have oily coatings to shed water. To absorb as much sunlight as possible on the dark understory, leaves are very large. Some trees have leaf stalks that turn with the movement of the sun so they always absorb the maximum amount of light. Leaves in the upper canopy are dark green, small and leathery to reduce water loss in the strong sunlight. Some trees will grow large leaves at the lower canopy level and small leaves in the upper canopy. Other plants grow in the upper canopy on larger trees to get sunlight. These are the epiphytes such as orchids and bromeliads. Many trees have buttress and stilt roots for extra support in the shallow, wet soil of the rainforests.

Over 2,500 species of vines grow in the rainforest. Lianas start off as small shrubs that grow on the forest floor. To reach the sunlight in the upper canopy it sends out tendrils to grab sapling trees. The liana and the tree grow towards the canopy together. The vines grow from one tree to another and make up 40% of the canopy leaves. The rattan vine has spikes on the underside of its leaves that point backwards to grab onto sapling trees. Other "strangler" vines will use trees as support and grow thicker and thicker as they reach the canopy, strangling its host tree. They look like trees whose centers have been hollowed out.

Dominant species do not exist in tropical rainforests. Lowland dipterocarp forest can consist of many different species of Dipterocarpaceae, but not all of the same species. Trees of the same species are very seldom found growing close together. This bio diversity and separation of the species prevents mass contamination and die-off from disease or insect infestation. Bio diversity also insures that there will be enough pollinators to take care of each species' needs. Animals depend on the staggered blooming and fruiting of rainforest plants to supply them with a year-round source of food.

Rainforest Soil

When early explorers first discovered the rainforests of Africa, Southeast Asia and South America, they were amazed by the dense growth, trees with giant buttresses, vines and epiphytes . The tropical vegetation grew so dense that it was difficult to cut one's way through it. It was thought at the time that the soil of a rainforest must be very fertile, filled with nutrients, enabling it to support the immense trees and other vegetation they found.

Today we know that the soil of the tropical rainforests is shallow, very poor in nutrients and almost without soluble minerals. Thousands of years of heavy rains have washed away the nutrients in the soil obtained from weathered rocks. The rainforest has a very short

. Nutrients generally stay in an ecosystem by being recycled and in a rainforest are mainly found in the living plants and the layers of decomposing leaf litter. Various species of decomposers like insects, bacteria, and fungi make quick work of turning dead plant and animal matter into nutrients. Plants take up these nutrients the moment they are released.

A study in the Amazon rainforest found that 99% of nutrients are held in root mats. When a rainforest is burned or cut down the nutrients are removed from the ecosystem. The soil can only be used for a very short time before it becomes completely depleted of all nutrients.

Range

The geographic area a species is known or believed to occupy.

Rapids

Rapids-areas where water flows quickly over a rocky, uneven streambed-can be formed where large chunks of debris block a watercourse or where rivers flow down steep slopes or across ledges of erosion-resistant rock. Because they are navigational hazards, these stretches of shallow, turbulent water often must be circumvented by man-made waterways; the Soo Canals, for instance, bypass the rapids between Lake Superior and Lake Huron. Whether the rapids occur in mighty rivers or modest streams, their well-aerated water is home to a surprising variety of life, from microscopic plants to insect larvae, equipped with all manner of hooks and suckers for clinging to the rocks. Rapids provide sheer beauty, too, a fact confirmed by just one view of the rushing Colorado River in the Grand Canyon.

Raspberry

Rubus

From woodlands and waste places in the East to canyons and moist slopes in the West, the delectable, thimble-shaped fruits of wild raspberries provide welcome snacks for hikers and are also harvested for jams and other treats. Many kinds of wildlife relish the fruits as well and find cover among the thickets of prickly, arching canes. The plants' five-petaled blossoms are similar to wild roses, which is hardly surprising, since the raspberries, like their kin the dewberries and blackberries, are members of the rose family.

Rat

Looking much like overgrown mice, rats are furry rodents with pointed snouts and long tails. The most familiar are the Norway rat and the black rat, introduced from the Old World. Aggressive, adaptable, and prolific, these rats have plagued mankind for centuries, infesting barns and dwellings and causing substantial damage. A number of our native rodents are also called rats. More closely related to mice and voles than to the old-world rats, they include cotton rats, rice rats, and wood rats, among others. They thrive in all sorts of habitats, from sun-parched deserts to temperate rain forests, feeding on everything from grain to bird eggs. They also vary dramatically in their habits. The kangaroo rat, for instance, hops about kangaroo-style on its hind legs, while the muskrat is a large, aquatic member of the vole family.

Rat snake

Elaphe

Agile, powerful predators that kill by constriction, rat snakes have an appetite for rats that has earned them the gratitude of farmers from southern Canada to Mexico. The various species also eat mice, frogs, and lizards and are at home in woodlands, swamps, and farmlands. While rat snakes usually forage on the ground, they are experts at climbing trees in search of birds and their eggs. When threatened, they rear up, vibrate their tails, and hiss menacingly. Up to eight feet long, some species are quite colorful.

Rate of increase

A measurement of the change in numbers of a population.

Rattlesnake

Rattlesnakes are venomous pit vipers well known for their trademark warning device: hollow, horny segments at the tip of the tail that are loosely connected and produce a buzzing sound when vibrated. A new rattle is added each time the snake sheds its skin, but they are easily broken off and so, contrary to folklore, offer no clue to the snake's age. Rattlesnakes range in length from a mere 18 inches (the diminutive pygmy rattlesnake) to a record 8 feet (the eastern diamondback).

Most rattlesnakes live west of the Mississippi River, especially in arid areas, and feed on small mammals, birds, and lizards. Timber rattlers, one of the few species found in the East, often hibernate in large groups in caves and rocky crevices. Like other rattlesnakes, they bear live young in broods of a dozen or more. Other common species include the large and colorful western diamondback and the sidewinder, noted for its unusual looping locomotion.

Raven

Corvus

Large, glossy black birds with thick bills, ravens make deep croaking sounds rather than the familiar caws of their smaller cousins the crows. Ravens also prefer wilder places than crows and are most likely to be seen near rocky hills, seaside cliffs, and remote areas of the Far North. Ravens are primarily scavengers but also feed on insects, clams, worms, and even young birds. Like crows, they are extremely intelligent.

The more widespread of our two species, the common raven, is found all across northern North America and much of the West. (Some isolated populations also manage to thrive in the Appalachians.) The Chihuahuan raven, formerly known as the white-necked raven, is smaller and more sociable; it lives in the arid Southwest.

Ray

Like sharks, rays are primitive fish with skeletons of cartilage rather than bone. They are distinguished by their broad, flattened bodies, which are extended by enlarged, winglike pectoral fins. The biggest ray, the manta, has "wings" that are more than 20 feet across. Occurring in both the Atlantic and Pacific oceans, rays live for the most part on the seafloor, where they feed on shellfish and crustaceans. Although most species are harmless, the electric ray produces powerful shocks both to stun prey and to defend itself, while the stingray can deliver painful blows with its venomous tail spine. Most rays give birth to live young, but skates lay eggs in horny capsules known as mermaid's purses.

Ray florets

Small flowers found on the outer fringe of the inflorescence in flowers of the daisy family.

Razor clam

Mollusks found in shallows along the seashores of both coasts, razor clams, also known as jackknife clams, are easily recognized by their distinctive shells. Long, narrow, and blunt on both ends, they look much like old-fashioned straight razors. Most species dig into the sand and mud on the ocean floor and, like other clams, feed by filtering protozoans and organic particles from the water. Members of the family vary considerably in size; the West Coast's rosy razor clam is 1 to 3 inches in length, while the common razor clam of the Atlantic grows up to 10 inches long.

Reason

Biological Philosophy term. "Jefferson held that reason is implanted in both physical nature and human nature. The reason of physical nature is its order. The reason of human nature is our ability to understand a fair portion of that order." This is an idea typical of the Enlightenment. The idea of reason inherent in nature goes back to Plato's notion of a universe of "divine" ideas of which the natural objects of our universe are imitations. There is a certain ambiguous allegiance, still, to this idea among scientists. The modern world no longer looks to the rational structure of the universe to discover the grounds for its moral ideals, but when Einstein protests that "God does not play dice with the universe," he is expressing a sense of an inherent rationality in the natural world.

Reauthorization

Endangered and Threatened species term.

A term referring to periodic action taken by Congress to reauthorize the Endangered Species Act. By reauthorizing an act, Congress extends it and may also amend it.

Reclassify Endangered and Threatened species term.

The process of changing a species' official threatened or endangered classification.

Endangered and Threatened species term.

The process by which the decline of an endangered or threatened species is arrested or reversed, or threats to its survival neutralized so that its long-term survival in nature can be ensured.

Recovery outline

Endangered and Threatened species term.

The first Service recovery document provided for a listed species. While very brief, the document serves to direct recovery efforts pending the completion of the species' recovery plan.

Recovery permit

Endangered and Threatened species term.

Permits issued under Section 10(a)(1)(A) of the Federal Endangered Species Act for scientific research and other activities benefitting the recovery of Federally listed species.

Endangered and Threatened species term.

A document drafted by the Service or other knowledgeable individual or group, that serves as a guide for activities to be undertaken by Federal, State, or private entities in helping to recover and conserve endangered or threatened species.

Recovery plan

A plan that details actions or conditions necessary to promote species recovery, that is, improvement in the status of species listed under the Endangered Species Act to the point at which listing is no longer appropriate. Plans are required for virtually all listed species.

Recovery priority

Endangered and Threatened species term.

A number, ranging from a high of 1C to a low of 18, whereby priorities to listed species and recovery tasks are assigned. The criteria on which the recovery priority number is based are degree of threat, recovery potential, taxonomic distinctiveness, and presence of an actual or imminent conflict between the species and development activities.

Recovery team

A group, established by the U.S. Fish and Wildlife Service (USFWS) or National Marine Fisheries Service (NMFS) (the agencies that share authority for listing species as endangered or threatened under the Endangered Species Act), that prepares a recovery plan for a species listed under the Endangered Species Act. The team usually consists of representatives from agencies that are charged with implementing the plan, scientists with expertise about the species involved, representatives from industries that may be affected by the plan, and USFWS/NMFS personnel.

Recreation

An activity or pastime pursued for pleasure or interest. Our natural environment is the setting for a variety of outdoor recreational activities.

Recruitment

The addition of new individuals to a population by reproduction, commonly measured as the proportion of young in the population just before the breeding season.

Recurved

Turned backwards in a curve.

Redbud

Cercis

Small, elegant, and valued as ornamentals, redbuds are among the first flowering trees to bloom in spring, when they are covered with purplish pink blossoms even before their leaves unfurl. The flowers-delicate and reminiscent of sweetpeas-grow in clusters all along the older branches and even sprout from the trunk. The fruits that follow are flat, beanlike pods containing shiny brown seeds.

Two species are native to North America. The eastern redbud, found in moist soils and along stream banks in the eastern half of the country, has large heart-shaped leaves and seldom exceeds 25 feet in height. The smaller, shrubbier California redbud, which grows on dry hillsides and along mountain streams in the Far West, has leaves that are more rounded.

Redirected activity

An Animal Behavior term, this is used to describe a behavior shown to an inappropriate stimulus when the appropriate one is not available. Denied food, a hungry Pigeon may peck at pebbles.

Redpoll

Carduelis

These robust little finches with red caps and black chins breed in the Far North, but in winter twittering flocks of redpolls venture south as far as Missouri and Virginia. They feed on seeds, especially those of birches and alders, knocking them from the catkins and picking them off the ground. When dusk approaches or severe weather threatens, redpolls store seeds in tiny throat pouches, an adaptation that allows them to take cover and eat at their leisure. During incubation, the females, which lay five to seven eggs, are fed by their rosy-breasted mates.

Redundancy

An Animal Behavior term, this is used to describe the inclusion in a message of more detail than is absolutely necessary for its recognition under ideal conditions. Redundancy in Animal signals, such as their repetition several times, may make sure that the message conveyed by them is receivcd and understood.

Redwood

Sequoia sempervirens

Redwoods are nature's skyscrapers, the tallest trees of all. Splendid 275-foot giants are not uncommon, and the loftiest living specimen, at 368 feet, is the tallest known tree in the world. Redwoods take four or five centuries to mature, and survive easily twice that long. As they age, the lower branches fall away, leaving stately trunks that are 15 feet or more in diameter and sheathed in bark up to 1 foot thick. The foliage of these titans is surprisingly delicate; the flattened needles lying in two rows along the twigs are only half an inch long. The seed-laden cones are also small-about one inch long.

Redwoods thrive only along the Pacific Coast from central California to southern Oregon, flourishing in the areas where summer fog rolls in regularly from the ocean. The reddish, straight-grained wood is light, splits and cuts easily, and resists insects and decay better than almost any other timber, making redwoods highly desirable for home building, outdoor furniture, wine vats, water tanks, and railroad ties.

Reed grass

Phragmites communis

Growing in dense patches and attaining heights of up to 15 feet, reed grass is a common sight in marshes, in brackish estuaries, and along damp roadsides. The upright stems of the giant grass, topped with brown to purplish plumes of tiny flowers and long, silky hairs, are a pretty sight swaying in the breeze. But the flowers rarely produce seed; instead, reed grass spreads by means of creeping underground stems that are sometimes more than 30 feet long.

Reflex

An Animal Behavior term, this is used to describe an automatic and involuntary response which is the simplest form of reaction to an external stimulus. Reflexes may involve as few as two or three nerve cells. Examples are a Dog scratching when its side is irritated and the constriction of the pupil of the eye when light shines into it.

Refugium

An area that remains unchanged while areas surrounding it change markedly; hence the area serves as a refuge for species requiring specific habitats.

Regeneration

A crayfish that loses a claw and grows a new one is demonstrating regeneration-the ability to replace lost body parts. Commonest among invertebrates, regeneration can be quite dramatic in certain worms and sponges: when they are cut into pieces, each one grows into a new individual. While salamanders can grow new limbs and lizards new tails, regeneration is limited in vertebrates. Humans, for example, can replace skin, hair, nails, and liver tissue, but little else.

Region 3

Endangered and Threatened species term.

The geographic unit of the Service that is composed of Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin.

Regurgitation

An Animal Behavior term, this is used to describe the method of feeding of another individual with food brought up from an Animal's own stomach. Common in social Insects, which share food in this way; and some Birds, such as Gulls, which feed their young by regurgitation.

Reinforcement

An Animal Behavior term used by those who study learning for events which raise or lower the probability of a response. Thus, a Rat may press a bar to obtain food (positive reinforcement) or to avoid electric shock (negative reinforcement). In both cases, the Animal is being rewarded.

Relative abundance

A percent measure or index of abundances of individuals of all species in a community.

Relative frequency

see Frequency.

Releaser

An Animal Behavior term, this is used to describe any of the physical and behavioral attributes of an Animal which have Been molded by natural selection to elicit a response from other individuals. Most sounds and scents that Animals make, as well as visual displays involving movements and bright colors, are examples of releasers (see also Sign Stimulus).

Remora

These oceangoing hitchhikers, also known as sharksuckers, get their nickname from the suction disks on the tops of their flat heads. The fish use the disks to cling to sharks, barracudas, turtles, whales, and other hosts and so travel effortlessly through tropical and temperate seas. Some species prefer specific hosts, while others are less choosy about their transportation. Up to three feet long, remoras eat scraps dropped by their hosts but can also forage on their own: detaching themselves with a sliding motion, the fish join other remoras in pursuit of prey.

Remote sensing

The imaging of earth features from suborbital and orbital altitudes, using various wavelengths of the visible and invisible spectrum.

Reporting (Law)

To assess regulatory compliance at the national level it is necessary to gather, compile, synthesize and interpret a variety of data and information. Government agency enforcement and program staff report on inspection and other data collected in the performance of their regular verification duties-including inspections and investigations.

Reproduction

Biological reproduction is the physical act by which new individual organisms are produced. Reproduction is a fundamental feature of all known organisms and each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: Asexual and Sexual. In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a cell into two daughter cells is an example of asexual reproduction. Sexual reproduction requires the involvement of two individuals, typically one of each gender. Normal human reproduction is a common example of sexual reproduction. In general, more-complex organisms reproduce sexually while simpler, usually unicellular, organisms reproduce asexually.

Reptile

Snakes, lizards, turtles, and crocodilians all belong to the class of animals known as reptiles. Of the 275 or so species found in North America, there are about US kinds each of snakes and lizards, nearly 50 turtles, and just 2 crocodilians (the American alligator and the American crocodile). No single trait distinguishes reptiles from all other creatures, as do the feathers of birds or the hair of mammals. But all are cold-blooded vertebrates that breathe with lungs rather than gills and have dry, scaly skins. Lizards and snakes are covered with scales that overlap like the shingles on a roof, while turtles and crocodilians wear a covering of larger adjoining plates. Both scales and plates conserve moisture and serve as suits of armor that protect against predators.

Unlike birds and mammals, which have their own built-in thermostats, reptiles cannot regulate their body temperature internally. Since excessive cold makes them sluggish, many must bask in the morning sun before they begin moving about. Those that live in deserts, however, often have to take refuge in the shade or in burrows to escape the scorching midday sun.

In contrast to amphibians, which depend on water to reproduce, all reptiles breed on land. Though most species lay eggs, some give birth to live young. Unlike salamanders and frogs, which go through a larval stage, young reptiles look like miniature versions of the adults.

Research (Science and technology)

A systematic investigation to establish facts. Much of government's work involves conducting research on a wide range of environmental topics.

Resident

Inhabiting a given locality throughout the year; see also Sedentary.

Resource

A substance or object required by an organism for normal maintenance, growth, and reproduction.

Resource holding potential

An Animal Behavior term, this is used to describe the ability of an individual or group to monopolize resources, such as food or mates, and so deny others access to them.

Restoration ecology

The re-creation of a natural or self-sustaining community or ecosystem.

Rhizome

An underground stem.

Rhododendron

Natives of cool, moist regions, rhododendrons form dense thickets on rocky hillsides and along stream banks in the Northeast and Pacific Northwest. On high mountain slopes they also range south into Georgia and Alabama. Some of the 20 or so wild rhododendron species are in bloom from April into July, bearing showy clusters of five-lobed, bell-shaped blossoms of white, pink, or purple touched with spots of green, yellow, or brown. The shrubs range in size from the 16-inch-tall Lapland rosebay, found in Alaska and on Northeastern peaks, to the treelike rosebay rhododendron of the Appalachians, which can grow to a height of 40 feet.

Rhododendrons typically have oval leathery leaves that are dark green and glossy on the upper surface. Up to 10 inches long, the leaves persist through the winter, curling into cylinders in cold weather to prevent loss of moisture.

Rhyolite

An igneous rock with the same composition as granite, rhyolite is formed from viscous lavas that erupted from volcanoes or squeezed through fissures in older rock. Light-colored and fine-grained, rhyolite contains quartz and feldspar, with flecks of mica and other minerals. Frothy, gas-filled flows of rhyolite form the spongy rock known as pumice. The shiny black volcanic glass called obsidian results when lava of the same chemical composition cools too rapidly for individual crystals to form.

Rice, wild

Zizania aquatica

Though both wild rice and true rice, like most cultivated grains, are members of the grass family, the two are only distantly related. The wild species is a tall, reedlike aquatic plant that once flourished in still, shallow waters from the Great Lakes south to Texas but now is confined mainly to the lake country of northern Minnesota and Wisconsin. The plants, up to 10 feet tall, are anchored in the bottom mud in water up to 6 feet deep. Long, narrow leaves are scattered along the stems, which in summer are topped with foot-long plumes of tiny green or purplish flowers. The seeds-thin, black, protein-rich kernels that ripen in the fall-have for generations been a mainstay of northern Indian tribes, such as the Ojibwa and Chippewa. Indians still harvest the crop each year by shaking the ripe grains into their canoes. Today, however, most wild rice comes from cultivated paddies.

Rice rat

Oryzomys palustris

Small rodents of wet places in the Southeast, marsh rice rats got their name from their fondness for the shoots and seeds of rice. Able swimmers and divers, they also feed on crayfish, clams, and other aquatic vegetation. Several litters are born each year, with the young leaving the nest in seven weeks. Since females are by then able to breed, their numbers increase quickly where food is plentiful and predators, such as hawks, are scarce.

Ringtail

Bassariscus astutus

A long, bushy tail banded in black and white and a sharply pointed snout make this shy relative of the raccoon easy to identify-if you manage to spot one. Active mainly at night, the ringtail is an agile climber that often sleeps the day away in trees. It also likes rough, rocky places, where it moves easily along the most pre cipitous ledges. Wherever it settles down, preferably near water, the ringtail feeds on small mammals, birds, insects, and fruits. Born in late spring, the young are tended by both parents. Ringtails, smaller and more agile than raccoons, are usually found in wooded, rocky parts of the Southwest. During the day, a long, bushy tail dangling from a high branch may betray the presence of a dozing ringtail. The ringtail's alternate name, cacomistle, is derived from Indian words for "half" and "mountain lion." Its nickname, miner's cat, can be traced to the fact that it was once kept in mines to control rodent populations.

Rip current

A real danger to swimmers and surfers, rip currents are fast-moving, narrow streams of water that flow to sea from land. They form along seacoasts where waves strike the shore at an angle; there water from successive waves builds up until it escapes by rushing seaward in a sudden surge. Since rip currents are narrow, experts recommend that swimmers not fight them but swim parallel to the shore until safely beyond their pull.

Riparian

Along the bank of a river or lake.

Risk assessment

A risk assessment is an estimate of the chance that environmental or health problems will result from a particular activity. Risk assessments play an important role in determining controls for the manufacture, use and transportation of toxic chemicals.

Ritualization

An Animal Behavior term, this is used to describe a process which occurs during the evolution of Animal signals so that they become more stereotyped and striking, and hence clearly distinguished from the actions, such as Displacement Activities and Intention Movements from which they originated, as well as clear and unambiguous in the message they convey.

River

With stretches of roaring white water as well as placid, slow-moving sections that meander across plains to terminate in brackish estuaries, rivers change in character as they make their way from their upland sources to the sea. Their inhabitants change too, for the plants and animals that thrive in swift currents are quite different from those that prefer to live in lazier waters.

The clear, fast-moving rivers that rush down hills and mountains are home to creatures adapted for survival in strong currents. Crayfish hide under rocks; salamanders attach their sticky eggs to fallen logs; insect larvae anchor themselves with hooks, claws, suckers, or cement; and trout and salmon, their bodies streamlined, manage to hold their own against the current and even swim upstream.

In quieter waters the wildlife is more like that of marshes, lakes, and ponds. Water lilies, pondweeds, and numerous other plants thrive in the relatively warm, slow-moving water, and a variety of birds and mammals come to feed on the river's abundant supply of insects, reptiles, fish, amphibians, and crustaceans.

River otter

Lutra canadensis

River otters are gregarious, fun-loving animals that seem to spend as much time romping and playing as they do hunting and fishing. Not even a deep covering of snow will deter them from sliding down riverbanks and plunging into the icy water. With dense, sleek fur, webbed feet, and a layer of insulating fat under the skin, these playful, appealing members of the weasel family are well suited for aquatic life. Streamlined swimmers with powerful tails that help propel them through the water, otters can travel as far as a quarter of a mile before surfacing to breathe. They live in lakes, rivers, and marshes, where they eat fish, frogs, crayfish, and other prey. Born in burrows or in abandoned muskrat or beaver lodges, otter pups are helpless and blind at first; but when they are several months old, their mothers teach them how to swim, dive, and hunt. The fathers begin to assist in the pups' schooling in about the sixth month. The sociable family group is often joined by others to toboggan in the snow, slide down muddy riverbanks, or frolic in the water, occasionally "talking" to each other with a varied repertoire of growls, chirps, and squeals.

Roadrunner

Geococcyx californianus

Roadrunners running swiftly on long, sturdy legs, with necks outstretched chase lizards and other prey. Desert dwellers, they build cup-shaped nests of sticks in low trees or among clumps of cacti. The four to six eggs are incubated mainly by the males. Comical in both appearance and behavior, the greater roadrunner, our only species, is an entertaining bird to watch. An inhabitant of dry country in the Southwest, the two-foot-Iong ground-dwelling cuckoo is a bit disheveled looking, with a shaggy crest, wings that seem too short, and a bill and tail that seem too long. The bird can coo like a dove or crow like a cock, and it would rather run than fly. It moves along furtively, pausing to peer about, until it spots a lizard. Then the roadrunner gives chase, sprinting forward at up to 15 miles an hour until it nabs its prey. Holding the lizard in its bill, the bird whacks it against a rock and then swallows it whole. Other meals consist of snakes, scorpions, crickets, mice, and even small birds snatched from the air as they fly by. Honored as the state bird of New Mexico, the roadrunner is also known by such names as snake killer and chaparral cock.

Robber fly

Also known as assassin flies, robber flies are formidable predators that ambush other insects on the wing. They perch watchfully until a prospective meal flies by, then give chase. Capturing their prey with their long, spiny legs, they suck the bodies dry. Big-eyed and bristle-faced, some robber flies are long and slender, while others are as stout as bumblebees. Each species has a characteristic hunting ground-some, for example, the grass; others, the beach.

Robin

Turdus migratorius

Easily recognized by its reddish-orange breast, the American robin has adapted handily to life in suburban gardens and city parks and is now more abundant in settled areas than in its ancestral woodland habitat. Each spring it builds a grass-lined, cup-shaped nest cemented together with mud. Although trees are the favored site for nests, they also appear on windowsills and other ledges on buildings. When the robin's delicate blue eggs hatch, both parents tend the nestlings. As the chicks grow older, the female begins laying a second clutch of eggs, and the male takes over nursery duty, feeding the young a diet of earthworms, insects, and fruit.

Despite their reputation as harbingers of spring, robins do not always live up to their image. While many do migrate early in the season, others remain in the North throughout the winter, living on berries in sheltered places.

Rock

Rocks, composed of one or more minerals, are the solid materials that make up the earth's crust. They are an ingredient of soil and provide us with building materials, valuable ores, and a great deal more. They also hold important clues to the history of the planet.

Rocks are divided into three major groupsigneous, sedimentary, and metamorphic-depending on the way in which they were formed. Igneous rocks solidified from molten magma. Coarse-grained varieties, such as granite, cooled slowly deep within the crust. Denser types, such as basalt, are volcanic and cooled quickly at or near the earth's surface.

Sedimentary rocks consist of material deposited by natural processes, such as windblown sand, decaying plant or animal matter, and chemicals precipitated from water. Over long periods of time, the material accumulated in layers and was compacted into rock. Examples include sandstone, composed of eroded sediments cemented into dense beds; and limestone, layers of calcium carbonate, often containing fossils.

Metamorphic rocks form when sedimentary or igneous rocks are altered by heat or pressure. Marble, a popular building stone, forms from limestone; and slate, a roofing tile, from shale.

Rocky Mountains

The Rocky Mountains are located in western North America. They are known for their beautiful scenery with mountains, trees and big game. People visit the Rockies for many recreational activities like hiking, hunting, camping, skiing and lots of other sports.

The Rocky Mountains have unpredictable weather which can change rapidly. As with other highland climates, the climate changes with increasing altitude. In general, the Rockies have mild summers, cold winters and a lot of precipitation.

The Rockies have very different seasons. In the winter there is deep snow, high winds, and sudden blizzards are common. At night it can get to -35 F or below! In the spring there is unpredictable weather. It could be wet or dry, cold or warm. In the summer there are sunny mornings, afternoon thunderstorms and clear nights. In the fall there are cool, crisp days, wind and decreasing precipitation.

There is lots of vegetation. The forests are full of pine trees, firs and spruces.Plants are very sturdy, most clinging to rock or hard soil.

Some adaptions that animals have made to the climate is that the hoofed species are very surefooted for the mountainous terrain they live on. Many animals migrate to lower and warmer elevations during the winter months. Some animals shed their brown fur to replace it with white so that they blend in with the snow. Some hibernate and some even have big feet so that they can walk on snow.

The average precipitation per year is 14 inches. The average for winter is 1.4 inches. The average precipitation for the season of spring is 4.2 inches. For summer it is 5.9 inches and for fall it is 2.6 inches. In the winter there are some snowstorms and blizzards. It snows later in the fall and there is decreasing precipitation. There is a lot of thunder and lighting in the summer. It rains and snows in the spring. The Rocky Mountains are rich in environmental treasures. Conservation and protection is important to make sure the Rockies are just as wonderful as they are today for many generations.

Rocky shore

Dramatic, jagged cliffs rising straight out of the sea; colorful, kelp-draped rocks; and clouds of salty mist sprayed from seething waves, these are all features of the rocky shore. Here seabirds nest among rugged crags; sea otters dive and frolic in the waves; and tufts of seaweed soften the contours of wave-cut rocks.

As the tide recedes, a series of lifezones is revealed. Blue-green algae and lichens grow in the uppermost zone, where Snails called periwinkles cling to cliffs that are moistened only by the splashing of the waves. Rubbery strands (of branching, ribbon-like rockweeds cushion the barnacle-encrusted rocks of the intertidal zone, which is alternately washed by the waves and exposed to the air. In the lowest zone, laid bare only by the lowest tides, sea urchins and starfish live in jungles of leathery kelp and other seaweeds. When the waves recede, tide pools are left behind among the rocks. They are often filled with a surprising array of life, from sea anemones to sponges. On the Pacific Coast, sculpted cliffs shelter nesting seabirds, while sea lions bask on the rocks below. The rocky coast of the Northeast, shaped by glaciers as well as the steady assault of the sea, is dotted by islands and incised with deep bays and quiet coves.

Rodent

Rodents are the most numerous mammals in the world. In North America they comprise some 200 species-about half of all our mammals-and range in size from the pygmy mouse, which is four inches long, including its tail, to the beaver, which reaches a length of four feet and can weigh 60 pounds. Among the most familiar rodents are chipmunks, squirrels, mice, voles, rats, lemmings, gophers, and porcupines.

Some rodent populations are huge. (As many as 400 voles, for example, may inhabit a single acre.) In part this is because many rodents breed year-round. Moreover, seeds, their principal food, are plentiful in most habitats. Another secret of their success is their distinctive, chisellike incisors. These teeth, one pair on each jaw, keep growing throughout the rodent's life. As the animal gnaws, its incisors are constantly renewed and sharpened, making them ideally suited for opening nuts and tough seed coats. The success of rodents is a mixed blessing. Some carry diseases, and many cause considerable damage to crops and property. But rodents are also the mainstay in the diets of a host of other animals. Rodents, the world's most abundant mammals, are well adapted for a variety of tasks and habitats. Some, such as least chipmunks, have dexterous, handlike forepaws: marmots post sentries at their grazing grounds to stand guard while the others feed. Porcupines fend off aggressors with a bristling armor of barbed quills.

Rose

Rosa

Though virtually all of our garden roses are descended from European or Asian ancestors, North America is richly endowed with native wild roses-some 170 species by one count. They include the arctic rose, a three-foot-tall prickly shrub of the Far North with deep pink flowers; the widespread pasture rose, with delicate, rosy-red blooms; and the prairie rose, a four- to six-foot shrub with arching canes and pale to dark pink blossoms. Wild roses typically have hooked thorns or needlelike prickles; compound leaves with 3 to 11 toothed leaflets; and fragrant, five-petaled flowers. After their season of bloom, usually in late spring, roses produce hips, fleshy orange fruits filled with seeds. Rich in vitamin C, wild rose hips are harvested for making jam and tea. Wild roses often form dense thickets in fields and fencerows, providing cover for a variety of wildlife. Long the symbols of luxury and love, roses also have practical value: their nutritious hips, rich in vitamin C, are widely used in dietary supplements.

Rosette

Radiating arrangement of leaves.

Rosinweed

Silphium

Resembling sunflowers in appearance, the rosinweeds are coarse, vigorous wildflowers that grow up to 10 feet tall and are most common on the Great Plains. Their yellow flower heads, two to five inches across, are borne atop stems filled with the resinous sap for which the plants were named. The paired leaves of one species, the cup plant, join at the stem to form cups, while those at the base of the aptly named compass plant almost always point north and south.

Ruminant

An Animal that has a four-chambered stomach. Their method of eating is called rumination; this is a process that permits an Animal to forage and ingest food rapidly, then complete the chewing at a later time. When they forage and eat they chew their food and it enters one chamber of the stomach. Later while they are resting, they regurgitate their food, chew it a second time then swallow it again.

Rumination

An Animal Behavior term, this is used to describe the system of digestion used by certain Animals with cloven hooves, such as Deer and Cattle (ruminAnts). Newly eaten food is stored in a special stomach compartment. called the rumen, from which it is passed back to the mouth for chewing after eating is completed.

Runner

Creeping stem that occurs above ground and may root at nodes or tip.

Rush

Juncus

Found in marshes and wet meadows, rushes are grasslike plants that have long cylindrical stems with clusters of tiny flowers near the top. People used to fashion the stems into rope, baskets, mats, and chair seats. When stripped of their skin and dipped in fat, the stems' pithy cores also served as wicks for crude candles called rushlights. Though a few other plants, such as bulrushes, scouring rushes, and spikerushes, borrowed the name, they are not true rushes.

Rutting

An Animal Behavior term, this is used to describe the behavior of male Deer during the mating season when they herd females to form Harems and call to and fight with intruding males. This period is often referred to as the rutting season.

Saber-toothed cat

Smilodon

Also known as saber-toothed tigers, these longextinct carnivores were giant members of the cat family. Larger than lions, with powerful neck and shoulder muscles and two enormous fangs, saber-toothed cats must have been terrifying creatures to behold. They probably used their eight-inch-Iong, daggerlike teeth to rip open the bellies or slash the throats of mammoths, giant ground sloths, and other prey. Once widespread in North America, the saber-tooths died out over 10,000 years ago. The remains of hundreds have been discovered in the La Brea tar pits in California; the beasts most likely were lured there by struggling animals that were about to perish in the tar. Saber-toothed cats roamed North America thousands of years ago hunting large planteating animals, especially mastodons. But just as those elephantlike creatures became extinct, so too did the sabertooths, perhaps falling victim to a profound climatic change.

Sage

Salvia

Relatives of the familiar culinary herb, the wild sages range from low-growing annuals to substantial shrubs. They all bear two-lipped tubular flowers, usually in clusters along the stems, which, like the stems of others in the mint family, are square in cross-section. Various wild sages bloom throughout the summer, tinting

fields and roadsides with shades of violet, blue, red, and pink. Chia, a blue-flowered western species, yields small, nutritious seeds that American Indians ground into flour. Other kinds have been used medicinally for everything from flesh wounds to digestive problems.

Sagebrush

Artemisia

Plants of contrasts, the sagebrushes have a spicy odor that belies their bitter taste. Cattle shun the shrubs, and so they spread over western plains and foothills wherever overgrazing has damaged the land. Big sagebrush, the most common species, ranges from 3 to over 12 feet in height, depending on growing conditions. It has small, wedge-shaped leaves that end in three rounded teeth, and bears clusters of tiny yellow flowers on the twig tips. Sagebrush withstands drought by sending roots deep into the soil and by shielding its leaves with a down of silvery, reflective hairs. Though despised by ranchers, sagebrush was used as fuel by pioneers, and Indians wove moccasins from the strips of gray bark that peel naturally from older branches. Deer and antelope depend upon sagebrush for fall and winter forage, and sage grouse feed on its buds and leaves. Sagebrush, found in arid parts of the West, is easily ignited, and in earlier times settlers and American Indians used the plant for fuel. Today the fragrant wood finds favor in backyard barbecues.

Saguaro

Carnegiea giganteus

King of the cacti, the majestic saguaros of southern Arizona and nearby California tower to heights of 50 feet. Their tall columnar trunks and upright branches consist mainly of spongy, water-storing tissue wrapped in a pleated, accordionlike skin. Saguaros are in decline in much of their range, partly due to poachers, who steal the magnificent cacti for sale to landscapers. Living storage tanks, saguaros can swell to twice their normal size during the rainy season, absorbing up to a ton of water through a vast network of shallow roots. The cacti, which live for up to 200 years, are the ultimate late bloomers, passing an entire human lifetime before developing their first buds. White-winged doves visit the creamy white blooms by day, and bats seek them out at night, pollinating the flowers in their search for nectar. The juicy red fruits, eagerly consumed by desert wildlife, are also gathered by Papago Indians, who eat them raw or use them to make cakes and syrup.

St. Elmo's fire

An eerie glow that was first observed on the masts of ships during stormy weather, St. EI-'" mo's fire is caused by electrical discharges between turbulent air and high, pointed objects. The phenomenon, which also occurs on the propellers and wingtips of airplanes and at the tops of steeples, can be thought of as a gentle, harmless form of static electricity. Seen by such voyagers as Columbus and Magellan, St. Elmo's fire was named for the patron saint of sailors.

St. Johnswort

Hypericum

Herbs and small shrubs that are most common in dry, rocky waste places, the St. Johnsworts typically have five-petaled yellow flowers with a tuft of yellow stamens at the center. The oblong opposite leaves of most species are dotted with tiny, translucent glands. The plants, named for St. John the Baptist, were once thought to ward off evil spirits. Recently, a substance from one species has shown promise in fighting viruses.

Salal

Gaultheria shallon

Flourishing on the Pacific Coast from California to Alaska, this handsome shrub reaches a height of eight feet in redwood forests, though it generally is much shorter. Like its close relative, wintergreen, salal is adorned with waxy white or pink urn-shaped flowers in spring and early summer. Its blue-black berries are used for jam and are eaten by wildlife, and its aromatic, evergreen foliage is a popular holiday decoration.

Salamander

Long-tailed and short-legged, salamanders look like lizards but have skin that is thin and moist instead of scaled. In North America, which has more of these amphibians than any other continent, they are found primarily in the East (especially in the Appalachians) and along the West Coast. These harmless creatures prefer wet habitats, but most salamanders live in damp burrows or under logs or rocks, visiting ponds and streams only to lay their eggs. Except for the feathery gills on their necks, the tadpoles resemble those of frogs and toads. Some species lay their eggs on land, producing hatchlings that bypass the tadpole stage and look like the adults. Many salamanders breathe with lungs, but others absorb oxygen directly through the skin. A few species spend their entire lives in water and breathe with gills even as adults. Among these aquatic salamanders are the pale, blind species that live in caves or underground streams.

Salmon

Although these cold-water fish are prized for their commercial and sport value, their astonishing migrations are the salmon's most famous characteristic. Born in clear lakes and streams, the young fish swim out to sea, and then, years later, they return. Driven by a remarkable instinct, they undertake a grueling odyssey back up the swift rivers, battling currents and leaping waterfalls, to the very same lakes and streams where they hatched. On the way their silvery scales take on new hues, and the snouts of males become beaklike. Pacific salmon arrive with just enough energy left to spawn before they die. One kind, the chinook, routinely swims hundreds of miles at sea, then travels 2,000 miles more up the Yukon River to spawn. Atlantic salmon also make arduous spawning trips- but survive to return another year.

Salt

See Halite.

Salt lake

Unlike other lakes, salt lakes have inlets but no outlets: the water they contain is trapped in enclosed drainage basins. Seasonal rains keep them supplied with water, but since it escapes only by evaporation, mineral salts are left behind and become more concentrated year after year. Often much saltier than the sea, salt lakes occur mainly in deserts. Many, for instance, are located in the Great Basin, where the renowned Great Salt Lake is found.

Saltmarsh

Flat expanses of coastal land that are washed by tidewater and that support salt-tolerant grasses and other plants, salt marshes are among the world's most productive habitats. They serve as vital nurseries for commercially important fish and shellfish. As dead plant matter decays, it forms the basis of a rich and complex food web. When the tide is out, sandpipers probe the mud for worms and crustaceans, and fiddler crabs scuttle about in search of edible debris left by the receding water. Legions of migrating ducks and geese find food and shelter in the marshes. Rails slip secretively through the grass; herons and egrets wade in the shallows; and airborne ospreys, gulls, and terns scout for meals. Mammals such as minks and raccoons also hunt for prey here. But perhaps those most at home in salt marshes are muskrats. They build domed lodges with underwater entrances, where they can hide from predators and raise their young.

Saltwort

Salsola kali

Also known as Russian thistle, saltwort is a prickly herb that flourishes on beaches. Its tolerance for dry, sandy soils has enabled this oldworld immigrant to spread across the western plains as well, where it is one of many ubiquitous tumbleweeds. Bushy and up to three feet tall, saltwort has spine-tipped leaves and tiny green flowers. Once the fruits have matured, the plant dries out, breaks free from its roots, and tumbles across the windswept land.

Sand

Most abundant on beaches and in deserts, sand consists of rock particles that are larger than silt and smaller than gravel. The tiny grains are formed by the decomposition of solid rock by such agents as wind, rain, frost, and glacial ice. Made up mostly of quartz, sand may also contain feldspar, gypsum, basalt, and other substances, and the sand on beaches often includes fragments of shell and coral. Huge amounts of sand are carried by rivers to the sea, whose currents sculpt it into sandbars and barrier islands. It is easily blown by the wind as well, forming the graceful dunes found on beaches and in deserts. A valuable resource, sand is used to make abrasives, glass, and other materials.

Sandbur

Cenchrus

Wherever the soil is sandy-on beaches, along roadsides, and in abandoned fields-sandburs are likely to make an appearance. In spring they look like just another coarse, sprawling grass. But in summer the sandburs produce tiny flowers enclosed in annoying burs, whose barbed spines are sharp enough to pierce the skin. Once the seeds inside mature, the burs break easily from the plant, clinging to passing humans and grazing animals.

Sand dollar

Marked with a five-petaled motif on the upper surface, sand dollars are flat, round marine animals related to sea urchins and sea stars. They grow to about three inches in diameter and are covered with minute, movable spines that give them a fuzzy feel. Burrowing in the sand, they feed on bits of organic material that they find among the grains. Empty skeletons, bleached white, are often found washed up on beaches on both the Atlantic and Pacific coasts.

Sandpiper

The most diverse family of shorebirds, our sandpipers include some 40 small to medium-size wading birds found mainly near fresh water and along seashores. In addition to those known as sandpipers, other waders such as sanderlings, dowitchers, snipe, and godwits also belong to the family. Sandpipers range in size from the sparrow-size least sandpiper to the chicken-size long-billed curlew, and most are inconspicuously patterned in browns, grays, and white. The varied shapes of their bills enable different species to specialize in different prey, including mollusks, insects, and crustaceans. Sanderlings, for instance, are a familiar sight on beaches, where they scurry after the receding waves, seeking food by pecking in the sand with their short, pointed bills. Woodcocks, in contrast, use their long, slender bills to probe deep in the mud for earthworms. Gregarious birds, sandpipers are often seen in large flocks as they migrate between their northern breeding grounds, usually in the Arctic, to wintering areas that may be as far away as South America.

Sandstone

A common sedimentary rock that is sometimes beautifully tinted by iron and other minerals, sandstone is the basis of such awesome scenery as the towering cliffs of Mesa Verde in Colorado, the wind-sculpted spans that astonish visitors at Arches National Park, Utah, and the startling towers and monoliths of the Southwest's Monument Valley. Sandstone forms when grains of sand, deposited in thick beds by wind and water, are subjected to immense pressure and cemented together by lime, silica, iron oxide, or other minerals. A rich repository of fossils, sandstone can also reveal the ripple marks of longvanished seas and the bedding of dunes in bygone deserts.

Sand verbena

Abronia

Charming wildflowers that sprawl over dry, sun-drenched ground, sand verbenas thrive on beaches, deserts, and other dry areas in the West. The stems of many species are sticky, and the leaves of most are thick and juicy. Although the sand verbenas' rounded heads of trumpetshaped flowers resemble those of true verbenas, the two plants are not related. Fragrant and colorful, sand verbenas are frequently planted in rock gardens and seaside gardens.

Sandwort

Arenaria

Growing in low creeping mats or tall open tufts, sandworts are attractive wildflowers of rocky ledges and sandy soils. The pointed, needlelike leaves are arranged in pairs or clusters along the plants' wiry stems, which are topped with fivepetaled white flowers that glisten like tiny stars. Among the many species that thrive in rocky crags on high alpine slopes are mountain sandwort of the Appalachians and Fendler's sandwort, a Rocky Mountain species. The lovers of dry, sandy soils include Nuttall's sandwort of the Pacific states and the pine-barren sandwort, found on the East Coast.

Sandy shore

Gulls-their scolding cries resounding above the swash of foaming surf-are often the. most obvious signs of life on sandy seashores. But many other, less conspicuous creatures also inhabit the ribbons of beach where land meets sea. Countless clams, mole crabs, lugworms, and other animals lie hidden in the sand, filtering plankton and bits of organic debris from the water of each breaking wave. Also feasting at the water's edge are throngs of shorebirds, such as sanderlings, sandpipers, and plovers. Higher on the beach, ghost crabs and sand fleas stay safely buried in the sand by day but emerge in droves after dark to feed on plants and animals that have washed ashore. A variety of visitors, among them horseshoe crabs and sea turtles, use beaches as breeding grounds, gathering each year at customary places to perpetuate their kind. Farther back from the shore, beyond the reach of the relentless surf, is the domain of plants that not only thrive in sand but can tolerate the salty air and blazing sun as well. Sea oats, wild roses, silverweed, and other sturdy survivors serve both to anchor the otherwise shifting dunes and to provide shelter for colonies of nesting gulls and terns.

Saprophyte

A plant that lacks chlorophyll and which gains its nutrition from decaying organic matter, such as fallen leaves.

Sapsucker

Sphyrapicus

The appropriately named sapsuckers are highly specialized woodpeckers that use their sharp beaks to drill neat rows of small holes in the bark of trees. Then, with brush-tipped tongues, they lap up the sap that oozes out and also eat the insects it attracts. They sometimes snatch insects in midair, as well, and occasionally feed on wild fruit. In typical woodpecker fashion, sapsuckers excavate nest holes in trees, often dead ones. Females incubate the eggs during the day, and males take over at night. Both parents share in feeding the young. Unlike other woodpeckers, the sapsuckers are strongly migratory. Yellow-bellied sapsuckers, for instance, travel thousands of miles when the seasons change.

Sassafras

Sassafras albidum

An eastern tree that sometimes reaches a height of 65 feet, the sassafras is instantly recognized by its foliage, for its leaves come in three distinct shapes-oval, mittenlike, and trilobed. The tree is particulary lovely in autumn, when its foliage takes on fiery hues that contrast dramatically with red-stemmed, dark blue fruits.

Indians used sassafras to treat complaints ranging from rheumatism to malaria, and colonists prized sassafras tea as a tonic. For many years oil from the root bark flavored root beer, chewing gum, and toothpaste and was even used as a dental antiseptic. The oil has now been declared unsafe, however, because its chief ingredient, safrole, may be carcinogenic.

Santa Ana wind

During the winter in southern California, the wind blows westward across the Santa Ana Mountains. As it ascends the windward slopes, the air loses most of its moisture in the form of rain or snow. Then as it rolls down the leeward slopes, it is compressed and warmed, producing a strong, hot, dry wind known as the Santa Ana. Sucking moisture out of the chaparral as it blows toward the coast, the wind greatly increases the risk of raging brushfires.

Saprophyte

Organisms that get nourishment from dead and decaying plants and animals are called saprophytes. Chief among them are many bacteria, as well as fungi such as mushrooms, molds, and even the mildew on an old leather shoe. All these saprophytes secrete enzymes into the nonliving host and break it down into substances that can be digested. While some cause food spoilage and other damage, saprophytes perform an essential service in recycling vital nutrients.

Sapsucker

Sphyrapicus

Sassafras

Sassafras albidum

Sasquatch

Sasquatch, also called Bigfoot, is supposedly a humanlike creature said to live in the Pacific Northwest. Bigfoot has been reported most often in the mountains of California, Oregon, and Washington, and of British Columbia in Canada. Canadians call it Sasquatch. Bigfoot stories resemble those about the Abdominal Snowman, a hairy beast said to live in the Himalaya. Hundreds of people have reported seeing the Bigfoot or its footprints. They describe the creature as standing from 7 to 10 feet tall and weighing more than 500 pounds. Like an ape, it has thick fur, long arms, powerful shoulders, and a short neck. It supposedly walks like a human being and leaves footprints that measure about 16 inches long and about 6 inches wide. Evidence of the Bigfoot’s existence has not been sufficient to convince most scientists. Many scientists believe that some of the evidence, which includes footprints and photographs, has been faked. Bigfoot is apparently similar to the Abominable Snowman, which is also called Yeti. The Snowman is also an obviously mythical creature said to live on Mount Everest and other mountains of the Himalaya range of Asia. Reports of such a creature have also come from remote parts of China and the Soviet Union. According to legend, the Abominable Snowman is a hairy beast with a large, apelike body and a face that resembles that of a human being. It supposedly has long arms that reach to its knees, and it is reported to walk erect on its thick legs. Legend says that the Snowman sometimes attacks villagers. There is no direct evidence that the Yeti exists, even though individuals have photographed “Snowman” tracks in the snows near Everest. See Abominable Snowman.

Satellite male

An Animal Behavior term, this is used to describe a male that associates with another male that is attractive to females: the satellite male attempts to intercept the females and mate with them as they approach. Satellite males attend territory owners on the Leks of Grouse, for example, and also occur close to calling males among some Frogs.

Savage

Biological Philosophy term. A human being who does not feel the restraints of civilization. Savages are at the stage of cultural "childhood" according to such nineteenth-century thinkers as the anthropologist Lewis Henry Morgan. See Noble Savage and Primitive.

Sawfish

Pristis

Large rays that look and swim much like sharks, sawfish are named for their long, flat snouts, which are edged on both sides with razor-sharp teeth. When they spot a school of fish, sawfish slash through the shoal with this double-edged tool, then eat the dead and injured prey. They also use their snouts to probe the bottom for shellfish and other morsels. Sawfish live in warm, shallow waters off the Atlantic and Gulf coasts but also enter the lower reaches of rivers, where they give birth to live young.

Sawfly

A saw-toothed egg-laying apparatus gives the sawflies their name. Using this organ, the female sawfly cuts slits into stems or leaves and inserts her eggs, which hatch into caterpillarlike larvae. The voracious larvae feed on the young leaves of roses, currant bushes, and other plants, sometimes burrowing into the tissue to form galls. Other highly destructive species attack conifers and can quickly denude a tree. Sawflies are closely related to ants and wasps but lack the narrow "waists" typical of their kin.

Saw palmetto

Serenoa repens

Unlike most other palms, the saw palmetto is a low, sprawling shrub that often forms dense thickets extending for miles. Common on dunes and in sandy pine barrens, the saw palmetto ranges from South Carolina to the Florida Keys and west to the Mississippi Delta. Its fan-shaped leaves, up to three feet in diameter, vary in color from yellowish green to silvery white, and the leafstalks are armed with small, curved spines that resemble the teeth of a saw. The tiny, creamy white flowers that bloom among the saw palmetto's graceful leaves are followed by black, olivelike fruits. Fleshy and juicy when ripe, the fruits are an important winter food for Florida's white-tailed deer.

Saxifrage

Saxifraga

Often springing up in crevices on cliffs-as if their roots had split the rock-saxifrages are hardy wildflowers whose name means "rock breaker." The name also may be traced to the plants' early use in a remedy for breaking up kidney stones. Saxifrages produce stems up to three feet tall and bear clusters of five-petaled, usually white blooms. A species common in the East is early saxifrage, which has a rosette of hairy leaves at its base and bears clusters of white flowers atop a hairy stem in early spring. Another, the low-growing purple saxifrage, found on mountain ledges from Newfoundland to Washington and Oregon, is notable for its rich reddish-lavender flowers. A number of other saxifrages are cultivated in rock gardens.

Scale insect

A bane of gardeners and fruit growers, scale insects are named for the waxy, usually oval shells that cover their bodies. Huge numbers of these pests sometimes infest fruit trees and other plants, which they weaken or even kill by sucking sap. The males do not eat, living only long enough to mate with the legless, wingless females. Among the more destructive species are the San]ose scale, the oyster shell scale, and the cottony cushion scale.

Scallop

Fan-shaped mollusks with earlike projections at the hinges of their fluted shells, scallops are found off all our coasts. While some species live permanently attached to rocks or pilings, most propel themselves through the water by vigorously clapping their shells together. (The large muscle that closes the shells is the part we eat.) The shells are lined with a fleshy mantle fringed with sensory tentacles and a row of tiny blue eyes. Although the eyes can distinguish only light and dark, they enable scallops to detect approaching predators in time to jet away. Two common species are the three-inch bay scallop, found in shallow water along the East Coast, and the deep-sea scallop, which can grow to eight inches.

Scatter hoarding

An Animal Behavior term, see Hoarding.

Scavenger

An Animal Behavior term, this is used to describe an Animal that eats organic debris and other decaying matter.

Scavenger

Animals that feed primarily on carrion are known as scavengers. By eating these unwanted remains, they serve as nature's cleanup crew, ridding the landscape of decaying carcasses. Vultures, which soar in sweeping circles as they search for carrion, are among the few animals that live primarily as scavengers. Others scavenge only when the opportunity arises. Arctic foxes, for instance, often tag along after polar bears, picking up their scraps.

Scent marking

An Animal Behavior term, this is used to describe the labeling of objects or individuals with scent, either from special glands or in the urine or feces. Scent marks function as signals and may transmit several types of information although their exact role in social communication is poorly understood.

Schist

The coarse-grained metamorphic rock called schist is composed of wavy bands of minerals that tend to split into layers. Mica schist, named for the thin, flaky sheets of mica that run through the rock, is the most prevalent type. Common in the Appalachian Mountains from New England to Georgia, it is often silvery and is strongly banded. Talc schist, also named for its dominant mineral and found in the Appalachians, is grayish green and has a greasy feel.

Schooling

An Animal Behavior term, this is used to describe the formation of Fish into tight shoals, found especially in species subject to predation. Predators are confused and have difficulty in focusing on a single prey within a school.

Science and technology

Science is a branch of knowledge conducted on objective principles involving the systematized observation of and experiments with phenomena-particularly those concerned with the material and functions of the physical universe. Science is the foundation of government policies, programs and regulations. Technology is the application of scientific knowledge to practical uses.

Science assessment

A science assessment is an objective appraisal of existing scientific knowledge on an issue or subject, for the purpose of transferring relevant information to policy makers, the general public, science audiences and others.

Scientific name

Endangered and Threatened species term.

A formal, Latinized name applied to a taxonomic group of animals or plants. A species' scientific name is a two-part combination consisting of the name of the genus, followed by a species name. For example, the scientific name of gray bat is Myotis grisescens. If a species has been further divided into subspecies, a third part is added to the scientific name. The Ozark big-eared bat is Plecotus townsendii ingens. "Ingens" distinguishes the Ozark subspecies from other subspecies of the big-eared bat.

Scientific names

Scientific take permit

Endangered and Threatened species term.

A type of recovery permit authorized under Section 10 allowing for research pertaining to species recovery such as taking blood samples from a peregrine falcon for genetic analysis, or conducting surveys of freshwater mussel beds to determine species status and distribution.

Scorpion

Four pairs of legs mark the scorpions as arachnids, relatives of spiders, ticks, and mites. Solitary nocturnal predators found in the South and West, the creatures emerge from crevices and other hiding places at dusk and use their pincerlike foreclaws to grasp and tear apart prey. In addition to insects, they feed on spiders and various small animals. The scorpion's most notorious characteristic, curved ominously over its back, is its segmented tail, tipped with a venomous stinger. Used to subdue larger prey and for self-defense, the scorpion's sting usually causes only local pain and swelling in humans, though the neurotoxic venom of a few species is potentially fatal.

Scorpionfish

Carnivorous bottom dwellers with a tendency to lurk among reefs and other rocky places, scorpionfish are also known as rockfish. They live in temperate or tropical seas, with some species favoring shallow water and others living at depths as great as 1,000 feet. Up to three feet long, many scorpionfish are brightly colored (deepwater species are usually bright red), and their heads are frequently ornamented with fleshy flaps and spines. Scorpionfish also have strong, sharp spines on their back fins. In a few species the spines are venomous, but even without the poison they can deliver painful woundshence the name scorpionfish. Among the commercially important species are the redfish, or ocean perch, of the Atlantic, and the bocaccio, common off the Pacific Coast.

Scorpion fly

Slender insects with long, thin, many-veined wings, threadlike antennae, and elongated, downturned "snouts," scorpion flies are harmless scavengers. They are named for the males' upturned, bulb-tipped abdomens, which resemble scorpion tails. The many species found across North America live mainly in moist deciduous woods and other cool, damp places. They feed primarily on dead insects but also eat some plant material. Females lay their eggs in the soil; and the larvae, which resemble caterpillars, emerge a week or so later and immediately begin scavenging on their own.

Scoter

Melanitta

Excellent swimmers and deep-sea divers, our three species of these sea ducks nest in the Far North - the surf scoter in boggy woodlands, the black scoter and the white-winged scoter on open tundra. Females lay six to eight eggs, which they incubate for about a month. Almost as soon as the downy ducklings hatch, they are able to walk, swim, and find their own food. On their breeding grounds the scoters' varied diet includes freshwater mollusks, fish, and vegetation. But when at sea (they winter along both coasts), the dark, stocky ducks become specialists. Gathering in huge flocks over mussel beds, they dive to depths of up to 40 feet and use their powerful bills to wrench mussels and other mollusks from underwater rocks.

Screw

A screw is a shaft with a thread along its surface.

Sculpin

Homely creatures with broad heads and short tapering bodies, sculpins are scaleless fish that live on the bottom in both fresh and salt water. Though most are more bone than flesh, the 30inch cabezon of the Pacific is sometimes eaten. The slightly smaller sea raven of the North Atlantic, bizarrely ornamented with prickles and spines, can inflate its body when annoyed. Their freshwater cousin, the four-inch muddler, or miller's thumb, lives in lakes and streams.

Sea anemone

Looking very much like flowers, sea anemones are brightly colored marine animals that add a patchwork of hues to tide pools, rocky coastal areas, and the sea floor. Their bodies are cylindrical, attached at the bottom to rocks or other objects and topped by waving, petallike tentacles that surround a central mouth. Some species feed on plankton, but others have stinging cells on the tentacles that paralyze fish and other small prey, which is then swept into the mouth to be digested. When alarmed and when tides are particularly low, sea anemones retract their tentacles and cover their mouth openings, protecting themselves from injury and dessication. They reproduce both by sprouting new individuals at the bases of their bodies and by shedding eggs and sperm into the water.

Sea bass

This varied family of nearly 400 species encompasses many commercial and sport fish, some of which are delectable while others are deadly. Among the sea basses are kelp bass, sand bass, coneys, hinds, and groupers. All have full bodies and big, broad mouths, and most live on the bottom in warm seas. In size, however, variety prevails, with lengths ranging from two inches to six feet or more. The giant of the family is a grouper, the jewfish, which can exceed 600 pounds. The sex life of sea bass is also varied. Most are hermaphrodites, with both male and female reproductive organs. Groupers, on the other hand, begin life as one sex and, as they mature, are transformed into the opposite sex.

Seabird

The term seabird is often loosely applied to any bird that spends time on the ocean, including sea ducks, gulls, loons, and many others. Strictly speaking, however, a seabird is one that obtains its food entirely at sea and comes ashore only to nest. Under this narrower definition the true seabirds are albatrosses, shearwaters, and storm-petrels (collectively known as tubenoses), as well as auks, gannets, kittiwakes, some of the cormorants, and a few terns.

Sea chub

Because of their habit of following ships in large schools, the sea chubs have earned the nickname rudderfish. Typically dark in color, these ocean dwellers have deep, oval bodies and small heads and mouths. They feed on seaweeds and other underwater plants, as well as the small animals that live on the vegetation. In the Atlantic Ocean, the Bermuda chub ranges from Cape Cod to the Caribbean. The halfmoon, a Pacific relative, is most often found in shallow water near rocky coasts.

Sea cow

See Manatee.

Sea cucumber

Like their namesakes, sea cucumbers are long, cylindrical, and warty. But they are animals, not plants, and are related to sea urchins and sea stars. Seldom more than a foot long, sea cucumbers have a circular mouth ringed by branched tentacles at one end of the body. They are creatures of the ocean floor, where they find food in the mud. When threatened, some species eject a tangle of sticky filaments into the face of the enemy, creating enough confusion to deter the would-be attacker.

Sea fan

Gorgonia

Despite the fact that they look much like lacy trees swaying with the current, the gracefully branched sea fans are really a type of coral. They consist of colonies of individual animals, called polyps, that grow together in the fanlike patterns for which these underwater beauties are named. Anchored at the base to rocks, sea fans have flexible internal skeletons covered by a thin layer of brightly colored living tissue. The polyps extend their tentacles through this tissue to gather the plankton on which they feed. Growing to a height of two feet or so, these exoticlooking creatures are especially abundant in the reefs and shallow waters off the coast of Florida and in the Caribbean.

Sea hare

Mollusks with much-reduced shells or no shells at all, sea hares are so named because of their prominent tentacles, which resemble rabbit ears. Grazing on seaweed along both coasts of North America, the creatures creep about on a large, muscular foot, much as snails do, but they can also swim by flapping fleshy lobes on both sides of their bodies. Though harmless, sea hares can startle anyone who disturbs them by emitting a cloud of inky purple-red fluid.

Seahorse

Hippocampus

With horselike head and bony armor, a seahorse seems an unlikely fish. But the several species, from 2 to 12 inches long, that live in warm, shallow seas along our coasts are, in fact, true fish. Weak swimmers, seahorses resist strong currents by grasping seaweed with their prehensile tails. Securely tethered, they use their tubular snouts to suck in animals that pass by. Seahorses reproduce in a most unusual way. In mating, the pair produces musical sounds as the female deposits eggs in a pouch on the male's belly. There they are fertilized, and several weeks later the male contorts his body and expels as many as 200 tiny young, one at a time.

Seal

Marine mammals that seem half dog and half dolphin, the seals and sea lions are well adapted to life in the sea. Descended from land-dwelling carnivores, they have the canine muzzles and teeth-and in some cases, even the voices-of their terrestrial ancestors. But their streamlined bodies and flippers allow them to swim as gracefully as fish. Equipped with ears and nostrils that close up tightly when they dive, seals can descend hundreds of feet below the surface and can hold their breath for more than half an hour. Because they are protected by dense fur and a thick layer of blubber under the skin, seals are comfortable even in the iciest water. Most feed mainly on fish, but some also eat squid, octopus, crabs, and clams. Seals are divided into two families: the earless, or true, seals, which lack external ears and have small hind flippers that cannot be turned forward; and the eared seals, also known as sea lions and fur seals, which have visible external ears and large hind flippers that do turn forward. Some sea lions have a leonine mane on the neck. California sea lions, which are very playful, are the "trained seals" seen in circuses. While most earless seals are monogamous, others have multiple mates. Fur seals and sea lions, for example, assemble each year at traditional breeding grounds called rookeriesstretches of beach where the males compete for territories and for harems of 3 to 30 or more females. The females almost always give birth to a single pup, born on land or on an ice floe. Aside from sharks, killer whales, and polar bears, the seals' worst enemies are human hunters, who in the past have decimated a number of species for their fur. Thanks to enlightened legislation, however, seal numbers have rebounded in recent years. Seals are of two families: earless seals, with small, inconspicuous ear openings; and eared seals, with visible

But more noticeable is the fact less seals have small hind cannot turn forward, so that the Animals must drag themselves along. The eared seals, in contrast, have large hind f1ippers that can turn forward, enabling them to walk on land. Within the two groups, a species can be recognized by such clues as size, color, and where it lives.

Sea lion

See Seal.

Sea oats

Uniola paniculata

Growing up to six feet tall, the grass called sea oats is found on sandy seashores from Virginia and southern California southward. Long, narrow leaves grow along the stems, which by the end of summer are topped with graceful, plumelike clusters of golden yellow fruits. Unlike most plants, sea oats easily tolerate the strong winds, salt spray, and blowing sands of the seashore. Their fast-growing roots, which penetrate deep into the sand in search of moisture, enable them to survive drought, one of the principal hazards of life on the exposed, sunny dunes. And their networks of shoots that spread just beneath the surface make them very effective for anchoring the dunes against erosion.

Sea otter

Enhydra lutris

A resident of the great offshore kelp forests along the Pacific coast, our smallest marine mammal, the sea otter, is best known for its tool-using talents. Diving to depths of as much as 180 feet and able to stay underwater for four minutes at a time, it snatches sea urchins, abalones, mussels, and clams from the bottom, then returns to the surface, often bringing along a flat stone. Floating on its back with the stone on its belly, the sea otter hammers its prey on this improvised anvil until the shell cracks open, and so gets at the flesh inside. Sea otters not only eat on their backs but also rest-and even sleep-floating along belly-up. When a pup is born-just one to a litter-the mother carries it, too, on her stomach until the youngster starts diving on its own, at about two months. Inveterate mariners, sea otters spend virtually their entire lives at sea, heading for shore only during severe storms. Once hunted nearly to extinction for their glossy pelts, sea otters are now protected and have made a dramatic comeback. Today they flourish along the West Coast from central California to Alaska, with as many as 100,000 cavorting in the kelp offshore.

Search image

An Animal Behavior term, this is used to describe the phenomenon in which, although Animals may have initial difficulty spotting cryptic prey, having found one item, they often quickly find others. They appear to have learned to sec the prey and are said to have formed a Search image for it.

Sea robin

Bottom-dwelling fish that are found mainly in shallow coastal waters, sea robins typically have big, broad heads covered with bony plates; slender, tapered bodies; and enormous winglike pectoral fins. The first few rays of the pectoral fins are separate, resembling fingers, and are used for walking across the sea floor and feeling for crabs and other food. Notable for their noisy repertoires, especially during the spawning season, sea robins make a variety of grunts, groans, and drumming sounds by vibrating their oversized swim bladders.

Sea shell

See Mollusk.

Sea slug

These mollusks without shells are among the sea's most spectacular inhabitants. Some are as smooth as ribbons, others bristle with elaborate fingerlike projections, and nearly all are painted with dazzling hues. Predators should not be deceived by their beauty, however, for many sea slugs defend themselves by exuding acids and poisons. While some are content to graze on algae and plankton, most are carnivores. Those that feed on creatures such as sea anemones and jellyfish are immune to those animals' stings; swallowed whole, the stinging cells are shunted to projections on the sea slug's back, ready to be fired if the slug is harassed.

Sea squirt

Touch the saclike body of a sea squirt, and it will live up to its name by squirting out a jet of water. These leathery, bottle-shaped creatures live attached to rocks and other objects (either singly or in colonies) and filter food from water pumped through the body. They begin life as free-swimming, tadpolelike larvae with primitive, flexible backbones, but they soon settle to the bottom and mature into sedentary adults.

Sea stack

Shaped by the steady hammering of waves, sea stacks are isolated, often picturesque columns of rock that rise from the sea off rocky shores. They form as waves attack coastal cliffs, wearing away the weaker rocks and leaving headlands composed of the more resistant. Over time, these promontories are narrowed as water cuts through the rock, producing natural arches. Eventually these, too, give way to the assault of the sea: the tops of the arches collapse, leaving behind the pillarlike sea stacks. Because the stacks provide a safe haven from shoreside predators, they are often colonized by seabirds for use as rookeries.

Sea star

Also known as starfish, sea stars are spinyskinned marine animals that usually have 5 arms but can have as many as 40, arranged symmetrically around a central disc. If they lose an arm to a predator or an accident, a new one grows in its place. The undersides of the arms are lined with hundreds of tiny, rubbery tube feet, each one tipped with a suction cup. Operated by a combination of muscular contraction and hydraulic pressure, the tube feet enable sea stars to crawl across the sea floor. The animals also use them to slowly but steadily open the shells of clams and mussels, their principal prey. Once the valves have been pulled apart, the sea star slips its stomach, turned inside out, between the shells and digests the soft parts. Sea stars are commonly seen along rocky coasts, especially at low tide when they are often stranded in tide pools. Most reproduce by releasing sperm and eggs into the water, where the fertilized eggs develop into free-swimming larvae, which later settle to the bottom to mature.

Sea turtle

Rovers in the open ocean, sea turtles are so completely adapted to marine life that they rarely come ashore except to lay their eggs. Their streamlined shells are thinner and lighter in weight than those of land turtles, and their paddlelike limbs, though clumsy on shore, enable the huge reptiles to swim through the water at speeds of up to 20 miles per hour. Every two or three years, sea turtles migrate hundreds or even thousands of miles to nest on sandy beaches. After mating in shallow water, the female heaves herself up on the shore at night, digs a deep hole with her hind flippers, and lays dozens of eggs in it. Then she covers the clutch with sand and returns to sea. About eight weeks later, the young turtles hatch and rush toward the water, dodging gulls and other hungry predators. When they mature, the turtles return to nest on the very same beaches where they were born. The sea turtles include leatherbacks (at up to 1,200 pounds, the giants of the clan), loggerheads, green turtles, ridleys, and hawksbills. Once abundant in North American waters, all the sea turtles have been drastically reduced in numbers as a result of coastal development, nest plundering, and overhunting.

Sea urchin

Common both in rocky tide pools and in offshore waters, sea urchins are globular relatives of sea stars and sand dollars. Their hard outer skeletons bristle with green or purple movable spines, which, in a few species, are poisonous. They are also equipped with tiny, sucker-tipped tube feet arranged in long rows; working in concert with the spines, the feet allow them to creep over rocks and through beds of kelp. Sea urchins feed mainly on algae, though some are also scavengers. They rasp the food off rocks and other surfaces using five sharp teeth that are located on the underside of the body. When sea urchins die, their spines break off, and the empty limestone skeletons, called tests, frequently wash up on shore, where they are collected by beachcombers. Sea urchins are a favorite food of sea otters, and many gourmets consider the eggs of some species a delicacy.

Seasons

The Earth rotates about its axis, which is tilted at 23.5 degrees. This tilt and the sun's radiation result in the Earth's seasons. The sun emits rays that hit the earth's surface at different angles. These rays transmit the highest level of energy when they strike the earth at a right angle (90 °). Temperatures in these areas tend to be the hottest places on earth. Other locations, where the sun's rays hit at lesser angles, tend to be cooler.

As the Earth rotates on it's tilted axis around the sun, different parts of the Earth receive higher and lower levels of radiant energy. This creates the seasons.

Seaweed

Such names as sea palm, sea staghorn, and feather boa attest to the varied forms of the marine algae commonly called seaweeds. Most are anchored to rocks and other surfaces by rootlike structures called holdfasts, and some, such as the rockweeds, are studded with little air bladders that serve as flotation devices. Although the branching fronds of many species resemble stems and leaves, seaweeds lack the internal plumbing systems of higher plants and instead take in nutrients directly from the water. Seaweeds are classified into three groups on the basis of color. The brown algae, including gulfweeds and kelps, are the largest, with the giant kelp of the Pacific growing to lengths of more than 200 feet. Red algae, such as laver, dulse, and Irish moss, tend to be smaller and more delicate and are associated with relatively warm waters. Sea lettuce and other green algae are less common than the red and brown kinds. Sometimes used for food, seaweeds have many other commercial uses. Some supply thickeners for ice creams and pharmaceuticals, as well as the agar used in laboratories. Others, such as kelp, are harvested for use in the production of everything from paint to beer.

Secondaries

Flight feathers located on the inner half of the wing of birds.

Secondary succession

Progression of communities in habitats where the climax community has been disturbed or removed entirely.

Endangered and Threatened species term.

The section of the Endangered Species Act that deals with listing and recovery of species, and designation of critical habitat.

Section 4(d) rule

Endangered and Threatened species term.

A special regulation developed by the Service under authority of Section 4(d) modifying the normal protective regulations for a particular threatened species when it is determined that such a rule is necessary and advisable to provide for the conservation of that species.

Endangered and Threatened species term.

The section of the Endangered Species Act that authorizes the Service to provide financial assistance to States through cooperative agreements supporting the conservation of endangered and threatened species.

Endangered and Threatened species term.

The section of the Endangered Species Act that requires all Federal agencies, in "consultation" with the Service, to insure that their actions are not likely to jeopardize the continued existence of listed species or result in destruction or adverse modification of critical habitat.

Endangered and Threatened species term.

The section of the Endangered Species Act that deals with prohibited actions, including the import and export, take, possession of illegally taken species, transport, or sale of endangered or threatened species.

Endangered and Threatened species term.

The section of the Endangered Species Act that lays out the guidelines under which a permit may be issued to authorize activities prohibited by Section 9, such as take of endangered or threatened species.

Sedentary

Not migratory; see also Resident.

Sedge

Though often mistaken for grasses, the various sedges-usually found in marshes and other moist places-belong to an entirely separate plant family. A glance at the stems, however, is enough to tell them apart: grasses have round, hollow stems, while those of most sedges are triangular and solid. Even so, the confusion persists and is reflected in the names of many species. The saw-toothed sedge that covers much of the Florida Everglades, for example, is called sawgrass. Another widespread sedge is called yellow nutgrass; regarded as a weed by northern farmers, it is cultivated in parts of the South for its edible tubers, known as earth almonds.

Sedimentary rock

The terra-cotta walls of the Grand Canyon and the colorful pinnacles looming over Bryce Canyon are both made up of sedimentary rock. They formed from natural debris that built up, layer upon layer, over millions of years and was finally compacted into rock. Some sedimentary rocks, such as sandstone and shale, formed from particles eroded from preexisting rocks. Others, like limestone and dolomite, are composed of the skeletons of ancient sea creatures or of minerals that were dissolved in water. Still othersgypsum and halite, for instance-are products of evaporation. Many sedimentary rocks have a bedded structure, and some are loaded with fossils that provide clues about ancient life.

Sedimentation (Water)

Sedimentation is an increase in the amount of solid particles suspended in water, caused primarily by soil erosion. The main human causes of sedimentation are forestry, farming, and construction. When sediment settles, it can smother the feeding and spawning grounds of fish and kill aquatic organisms.

Seed

Serving as links between generations, seeds are the self-contained reproductive structures produced by flowering plants, conifers, and a few others. Each seed contains a miniature plant, or embryo, and a supply of food, both of which are enclosed in a protective coat. This durable package can remain viable for a long time-the record is held by arctic lupine seeds that were able to germinate after more than 10,000 years.

Self-heal

Prunella vulgaris

Also known as heal-all and hookheal, self-heal has a long history of medicinal uses. The plant was used to cure ailments of the mouth and throat, and the bruised leaves, when applied to cuts and scrapes, were supposed to promote healing. Self-heal, because of the yawning shape of its blooms, was once believed to cure ailments of the mouth and throat, The plant does in fact make a most convenient bandage, since it flourishes throughout the continent. Sometimes erect and sometimes forming dense, ground-hugging mats, this ubiquitous member of the mint family has square stems and spikes of two-lipped, usually purple flowers.

Senna

Cassia

Esteemed for centuries for their medicinal properties, senna leaves still serve as the basis for a number of modern laxatives. Our several native species thrive in a variety of habitats, from dry grasslands to moist woods. Perennial members of the pea family, with feathery compound leaves, they bear clusters of bright yellow, fivepetaled flowers, which are followed in autumn by flattened, beanlike seed pods.

Sensitive period

An Animal Behavior term, this is used to describe a a period of time during development when Animals are most likely to respond to particular stimuli. Many behavioral and physiological processes tend to occur at a specific stage because of this. The classic example is the Imprinting of young Birds on their Mothers which occurs most readily during the first few days of life.

Sensory adaptation

An Animal Behavior term, this is used to describe the loss of sensitivity which occurs when sense organs are exposed for a long time to a strong stimulus. Sensory adaptation is one reason why Animals may cease to respond to stimuli (see also Habituation).

Sepal

The outer row of structures surrounding the reproductive part of a flower.

Sequoia

See Giant sequoia.

Sere

A series of stages of community change in a particular area leading toward a stable state.

Serpentinite

A greenish-black metamorphic rock with a greasy feel, serpentinite forms when rocks rich in olivine and other magnesium minerals are altered by moderate amounts of heat and pressure. It frequently contains veins of the fibrous mineral chrysotile, which is the chief source of asbestos. Because of its color and its resemblance to marble, serpentinite is often used as a decorative stone. It is common in mountainous regions of California, Montana, and Maine.

Serviceberry

Amelanchier

One of the first trees to bloom in spring, serviceberries are covered with clouds of dainty white five-petaled flowers just as the shad are running upriver to spawn. It was for this reason that colonists called them shadbushes- just one of many common names. Extremely hardy, several species grow across North America; some are small trees, but many are shrubs no more than 15 feet tall. Their purple fruits, which resemble blueberries, ripen in June and are quickly devoured by birds and other woodland creatures. Colonists used the fruits for jams and pies, and American Indians mixed them with venison or buffalo meat to make pemmican.

Severe weather

Includes conditions such as: high wind, heavy rain, hail, heavy snowfall, blizzard, severe thunderstorm and tornado.

Sewage (Water)

Waste matter, usually in the form of human excrement.

Sex

Sex refers to the process in biological reproduction that dates back 4+ billion years. DNA links back in an unbroken series of sexual reproduction taking forward information to present day. The category of sex reflects the biological reproductive function rather than sexuality or other behaviors. In some animals, sex may be assigned to specific structures rather than the entire organism.

Sexual intercourse

Sexual intercourse, also called coitus, or simply, to have sex is the human form of reproduction. In humans this is performed relatively frequently, and primarily for sexual pleasure rather than in response to a seasonal stimulus. To engage in sexual intercourse, the erect penis is inserted into the vagina and one or both of the partners move their hips to move the penis backward and forward inside the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasms are achieved. Penetration by the hardened erect penis is also known as intromission, or by the Latin name immissio penis.

Shad

Alosa

Members of the herring family, shad live in the ocean but, like salmon, swim up coastal rivers to spawn. Our commonest species, the American shad, is about two feet long and weighs from two to five pounds. An important food and game fish in the East, it has been introduced in Pacific waters as well.

Signaled by the warming of coastal rivers in spring, shad swim upstream to lay their eggs. The young hatch within a week or two and grow about five inches long over the summer, then head for the sea, where they mature in three to five years on a diet of plankton. In the past, shad were heavily netted during spring spawning runs. But overfishing, dam building, and pollution have depleted the numbers of these once-plentiful fish, which are prized for both their flesh and their roe.

Shadbush

See Serviceberry.

Shaggymane

Coprinus comatus

Like other inky-cap mushrooms, the shaggymane goes through a strange transformation as it ages: its white, shaggy, torpedo-shaped cap and gills gradually turn black and disintegrate into an inky liquid. Once used as a substitute for ink, the fluid contains the spores that propagate the fungus. The shaggymane, which grows in grassy places from coast to coast, is delightfully edible when young, but once it begins to change color, it should be left alone.

Shale

Shale, the most common sedimentary rock, is formed of thinly bedded layers of clay, mud, or silt that were deposited in ancient lakes or shallow seas. As the debris accumulated, it was gradually compacted into relatively soft rock that can easily be split into thin layers. Some shales, called oil shales-often found sandwiched between beds of sandstone or limestone-are rich in organic matter. In the process of compaction, the trapped organic debris was converted to hydrocarbons that can be distilled to produce oil. While extraction is expensive and difficult, the oil is usable as fuel. Colorado, Wyoming, and Utah have large deposits of oil shale.

Shark

Though universally feared, the speedy, torpedoshaped fish known as sharks are also widely misunderstood. Of the more than 250 species, for example, only a few behave aggressively toward humans, and shark attacks in fact are extremely rare. Ironically, the largest sharks- the whale sharks, which grow up to 45 feet long and are the biggest of all fish-are among the most harmless, feeding only on microscopic plankton. Others have been known to swallow such inedible objects as cans, bottles, and rubber tires, but more typical fare consists of everything from fish and crabs to dolphins and seals, as well as other sharks.

Equipped with unusually keen senses, sharks detect prey not only by sight, sound, and smell but also by sensing faint electrical fields in the water. They are on the move continuously, though not because they are always hunting, as is commonly believed (some go for days without eating); lacking the air-filled swim bladders that make other fish buoyant, sharks would sink if they remained still. They also differ from most other fish in having skeletons composed of cartilage rather than bone and in possessing several rows of teeth, which are constantly replaced as they wear out. The sharp scales that cover the skin are toothlike as well; tough and abrasive, dried shark skin was once used as sandpaper.

Shearwater

Gliding between ocean waves with their narrow wings outstretched, shearwaters adeptly snatch fish, squid, and other food from just beneath the water's surface. The birds-one to two feet long, with tubed nostrils atop their hooked beaks-are related to fulmars and petrels. They spend most of their lives at sea, coming ashore only to nest in island burrows. Tireless travelers, most shearwaters seen off our coasts could easily have nested on islands of such distant lands as Chile or New Zealand.

Shell

See Mollusk.

Shepherd's purse

Capsella bursa-pastoris

Heart-shaped capsules filled with tiny reddish seeds give the shepherd's purse its name, for they resemble the leather pouches that shepherds used to wear on their belts. An old-world weed that has become established in croplands, gardens, lawns, and waste places practically everywhere, shepherd's purse first produces a low rosette of sharply toothed leaves that look much like dandelions, then later sends up a branching stem as much as 20 inches tall. The plant flowers practically year-round, its stem tips bearing clusters of tiny white blossoms, which mature into the "purses." Herbalists have traditionally recommended this member of the mustard familyas a remedy for internal bleeding. Today its tender young leaves are sometimes gathered and eaten as salad greens.

Shiner

Notropis

The midgets of the minnow family, shiners are little freshwater fish that live in streams, ponds, and lakes all across North America. Averaging two to four inches in length, they feed mainly on tiny insects but also eat algae-and are in turn eaten by larger fish. In fact, anglers commonly use shiners as live bait. Though generally silvery, the males of some species, such as the common shiner and the bleeding shiner, take on brilliant colors during the spawning season.

Shipworm

Teredo

Despite their name, shipworms are not worms but marine mollusks-relatives of clams-that bore into wood and often do serious damage to piers and other structures. Unlike the shells of most mollusks, those of shipworms have developed into filelike drilling instruments. Located at one end of the creature's long, worm-shaped body, the shells are used to tunnel deep into wood, some of which is eaten. The other end of the animal remains attached to the burrow's entrance, taking in food and oxygen from the sea.

Shooting star

Dodecatheon

With stamens joined in a downward-pointing cone and petals swept back like trailing flames, these charming wildflowers do indeed resemble shooting stars. According to legend, they spring up wherever a real star has fallen to earth. In fact, shooting stars are versatile plants that are found in many places; they grow both in sundrenched grasslands and in shaded woods, especially in mountains in the West. In early spring a ground-hugging rosette of oval or spatulashaped leaves appears. Then at blossom time a single leafless stalk up to 20 inches tall arises from its center, with a constellation of as many as 25 fragrant red, purple, pink, or white flowers dangling gracefully from the top.

Shorebird

The birds known collectively as shorebirds are a varied assemblage that includes a number of closely related families--the plovers, the oystercatchers, the stilts and avocets, and the many sandpipers. Most are long legged and use their bills to probe for food along the shores of fresh and salt water. Many are familiar sights on ocean beaches, often pausing on their migrations. But a few, such as the killdeer (a plover) and the common snipe (a sandpiper), live far from the sea.

Shrew

Found all across North America, shrews live in habitats as diverse as deserts (the desert shrew), moist forests (the smoky shrew), tundra (the arctic shrew), and mountain streams (the water shrew). They also vary in size; the pygmy shrew is our smallest mammal, but even the largest, the short-tailed shrew, is only four inches long. Shrews are bundles of nervous, energy, active at any hour (though mostly at night) searching out invertebrates and carrion to support their geared-up metabolism. The short-tailed shrew, our only poisonous mammal, even tackles frogs and mice much larger than itself. The shrews' frenetic lives burn out quickly, however, with few of them ever reaching a second birthday.

Shrike

Lanius

Equipped with strong, slightly hooked beaks, shrikes are songbirds that hunt for a living. They survey their surroundings from exposed perches, then chase down insects and small birds, rodents, and reptiles. Since they often hang their prey on thorns or barbed wire fences, shrikes have been nicknamed butcherbirds.

Two species are native to North America: the northern shrike of boreal Canada and Alaska, which wanders south in winters when food is scarce, and the more southerly loggerhead shrike, a widespread but increasingly scarce bird of fields and fencerows. Both build bulky cupshaped nests in trees or shrubs and raise families of four to six young.

Shrimp

Semitransparent, delicate-bodied relatives of lobsters and crabs, shrimp are common marine and freshwater crustaceans. Many are commercially harvested and represent the shellfish industry's most valuable catch.

Ranging in size from less than half an inch to about eight inches long (the larger ones are often called prawns), shrimp have flexible bodies, long antennae, and numerous pairs of jointed appendages. Those nearest the head are used for handling food. Behind them are five pairs of walking legs and, along the abdomen, five pairs of appendages known as swimmerets, which are used for sculling through the water. By sweeping their fanlike tails downward, shrimp can also move rapidly in reverse. Many shrimp live on ocean bottoms, where they scavenge for plant and animal matter; others prey on krill and shellfish larvae; and still others, known as cleaner shrimp, eat parasites off the bodies of fish. Some shrimp simply lay their eggs and abandon them. But the females of most species carry them attached to the swimmerets until the eggs hatch into larvae, which gradually metamorphose into adults.

Shrub

The term shrub applies to any woody plant less than 10 feet tall with several stems branching from the ground. Unlike trees, shrubs have no single stem that dominates as a trunk. Branching in various patterns, shrubs can be low and spreading, broad and round, or tall and narrow. Under favorable conditions, shrubs such as honeysuckles sometimes form small trees, while certain trees-willows and sumacs, for instance-grow as shrubs in harsh environments.

Sidewinder

See Rattlesnake.

Sign stimulus

An Animal Behavior term, this is used to describe an external stimulus to which an Animal responds in a specific way, such as the key features of a Prey Animal that elicit stalking or the swollen belly of a female Fish that leads a male to court. Those sign stimuli evolved to function as signals are known as Releasers.

Silver

Treasured since ancient times, silver is among the most lustrous and malleable of the precious metals. Though it is sometimes mined in pure form, most silver is obtained as a by-product in the refining of other metals. In the 1800's, prospectors were lured by discoveries of silver in the Rocky Mountains, and much of our silver is still mined there. Most familiar as jewelry, flatware, and coins, silver also has important uses in photography, electronics, and dentistry.

Silverfish

A bane of tidy housekeepers, silverfish are small, primitive, wingless insects with long antennae and three spearlike tail filaments. They lurk in warm, dark cupboards and behind partitions but venture out at night to feed on such starchy delicacies as wallpaper, book-binding glues, and even starched fabrics. Silverfish lay their eggs in household nooks and crannies; the young, which look like miniature adults, require two years or more to mature.

Sink habitat

A habitat in which reproduction is insufficient to balance local mortality. The population can persist in the habitat only by being a net importer of individuals.

Sink population

A population that occupies habitat types in which reproductive output is inadequate to maintain local population levels. The population may be replenished by emigrants from source populations.

Sinkhole

Sinkholes are deep round holes, sometimes filled with water, that form in areas where the bedrock is limestone and rainfall is moderate to heavy. Some are produced when the roof of an underground cavern collapses. Others are created as acidic rainwater percolates through limestone, gradually dissolving the rock until the overlying soil suddenly subsides. Sinkholes vary in size and depth, but some are large enough to cause considerable damage, swallowing up cars, trucks, and even houses. Parts of Kentucky, Alabama, Indiana, and Missouri are dotted with sinkholes, and they formed many of Florida's lakes.

Siphon

The tube through which water enters and leaves a mollusk.

Siren

Odd, eellike salamanders with bushy external gills and no hind legs, sirens never mature into land-dwelling adults. Instead, they remain in water throughout their lives, which may be as long as 25 years. They hide by day in weedy ponds and on the muddy bottoms of swamps and lakes, foraging at night for worms, snails, insects, and small fish. Found mainly in the Southeast, our three species range in size from the six-inch-long dwarf siren to the greater siren, which reaches nearly three feet.

Skate

Flat-bodied relatives of sharks, with broad, winglike pectoral fins, skates belong to a family of rays that lay eggs in leathery cases instead of giving birth to live young. The cases, called mermaids' purses, often wash up on beaches.

Skates are harmless, unobtrusive creatures that spend the day half-buried in sand on the ocean floor, moving about at night to hunt for shellfish, which they crush with their powerful, flat teeth. Like big, exotic birds, they propel themselves along the sea bottom by gracefully undulating their huge fins. The largest North American species is the eight-footlong big skate of the Pacific Ocean. Smaller kinds, including the little skate and the barndoor skate, are found in the Atlantic.

Skimmer

Rynchops niger

Black skimmers, also known as cutwaters and scissorbills, fly low over the sea, slicing the surface with their knifelike bills. When the lower mandible-up to an inch longer than the upper one-strikes a small fish or shrimp, the bill instantly snaps shut. The bird then angles its head back, swallows its prey, and continues its inflight fishing without missing a beat. About the size of crows, but with a slender build, skimmers are black above and white below, with red feet and black-tipped red bills. Their eyes have vertical pupils, like those of cats, that can be narrowed to thin slits to reduce the glare from sand and sea. Nesting on beaches and islands along the Atlantic and Gulf coasts, skimmers lay their speckled eggs in depressions in the sand. The chicks sometimes hide by scooping out shallow holes and then kicking sand into the air; falling onto their tawny backs, the sand serves as camouflage.

Skink

So shiny that their scales seem polished, skinks are small, secretive lizards that feed by day on insects, spiders, and worms. Our largest species, at 13 inches long, is the Great Plains skink of the central and southwestern states. An aggressive creature, it will bite if handled. The five-lined skink-about eight inches long, with five pale stripes down its dark back-lives in eastern woodlands. The females, like those of some other skinks, stand guard over their eggs until they hatch. The young, with yellow stripes and bright blue tails, look very different from the adults. The five-inch ground skink, another easterner, employs a typical skink defensive ruse: when seized by a predator, its tail breaks off, distracting the would-be attacker. Fleeing to safety, the skink later grows a new tail.

Skipper

Named for their abrupt, darting flight, skippers seem always to be in a hurry as they flit from flower to flower. Neither true butterflies nor moths, they exhibit characteristics of both. Like butterflies, skippers have clubbed antennae and are active by day. But their stout, hairy bodies, relatively small wings, and generally drab appearance are typical of moths. When at rest, many of the skippers show their dual allegiance by holding their forewings up, as butterflies do, and their hindwings down, like moths. Some 300 species of skippers are found throughout North America.

Skua

Catharacta skua

Pirates of the high seas, great skuas are large, predatory seabirds that steal food from gulls and gannets. These close relatives of jaegers are dark, hawk-beaked marauders that watch patiently while other birds go after fish, then harass them in midair until they disgorge their catch. Great skuas (sometimes called bonxies or seahawks) also follow ships for scraps, kill and eat ducks, and prey on the eggs and young of neighbors that share their North Atlantic nesting grounds. Another species, the south polar skua, breeds in the Antarctic and is a rare summer visitor to both our East and West coasts.

Skullcap

Scutellaria

Woods, meadows, and thickets in temperate parts of North America are home to nearly 100 species of skullcaps, which are named for the hoodlike upper lip on their flowers. Most are tall perennials with blue or violet blooms, branching stems, and oval, toothed leaves that grow in opposite pairs. One common species, mad-dog skullcap, was once touted as a cure for rabies; others, including downy skullcap, were believed to cure nervous disorders. While the rabies claim has been discredited, research has shown that the plants may have sedative effects.

Skunk

Our several skunks are short-legged, bushytailed members of the weasel family that are notorious for their foul-smelling defensive spray. Their conspicuous black-and-white patterns serve to scare off most potential foes. When necessary, however, a skunk will also stamp its feet and raise its tail. If all these warnings are ignored, the skunk then fires a jet of acrid fluid from its anal glands. The spray can cause temporary blindness, and the odor lingers for days. Skunks spend the day in burrows, rock piles, or abandoned buildings and come out at night to feed on insects, rodents, birds' eggs, dead animals, grain, and fruit. Our most common species, the striped skunk, is found across most of North America. Spotted skunks live in the South and West, while hooded and hog-nosed skunks prefer the arid Southwest. Striped skunks, our most common species, forage after dark for a variety of foods. They are frequently seen sniffing around lawns and gardens, where many a family pet has been doused with foulsmelling spray after ignoring the warnings of a startled skunk. A jet of skunk spray can accurately hit targets up to 12 feet away.

Skunk cabbage

Harbingers of spring in damp eastern woodlands, skunk cabbages often send up their hoodlike floral sheaths (or spathes) before the last snow has melted. The sheath, which encloses a knoblike structure (the spadix) studded with tiny flowers, has a foul odor and a brown to purple color that imitate rotting flesh. The fetid guise serves the plant well, however, for it attracts the flies that pollinate the blooms. Once the skunk cabbage has flowered, it unfurls bright green leaves up to two feet tall.

A similar species, called western or yellow skunk cabbage, has a skunky odor as well, but its floral sheath is yellow. It grows in the Far West from California to Alaska.

Slate

A metamorphic rock that can be split into durable sheets, slate is used for roofing, flagstones, and blackboards. Most slate originated as shale that was later altered in composition and structure by heat and pressure. Mica, quartz, and chlorite are the chief ingredients of slate, which is usually gray to black but can also be red or green if other minerals are present. In North America slate is quarried primarily in Pennsylvania and Vermont.

Slider

Chrysemys scripta

A freshwater turtle that prefers the shallow, weedy areas of ponds and lakes, the slider gets its name from a reputation for slipping instantly into the water at the first sign of danger. Its shell is dark, with yellowish stripes, and behind the eyes is a red, orange, or yellow mark. One of the so-called basking turtles, sliders are exceptionally fond of sunbathing: they are often seen stacked two or three deep on logs as they laze in the sunshine.

Slug

Slimy, soft-bodied mollusks, slugs are simply snails without the protective spiral shells. Like other snails, they have two pairs of tentacles on the head, with eyes on the ends of the longer pair, and they glide along on a ribbon of mucus secreted by their own bodies. Slugs keep from drying out by hiding in crevices during the heat of the day; they venture out only at night and on damp or rainy days. Most are vegetarian and can cause considerable damage in gardens, but a few are carnivorous, preying on earthworms and other snails. Among the better-known species is the five-inch-long great slug, a European immigrant that has become a widespread garden pest throughout much of North America. Banana slugs, wiener-size pests, are a bane of gardeners in the Pacific Northwest.

Smelt

Small relatives of salmon, most smelts are saltwater fish that spawn in freshwater lakes and streams. Pond smelts, however, live only in fresh water, and populations of several marine species have become permanent lake dwellers as well. Rainbow smelts, for example, native to the Atlantic, were introduced to the Great Lakes and Lake Champlain and now thrive in great numbers in their inland homes. Like salmon, smelts are highly esteemed as food fish. Some are netted on spawning runs, while others are caught in lakes, especially by ice fishermen in winter. Eulachons, or candlefish, a Pacific species, once served as more than food; they are so oily at spawning time that Indians dried them, added wicks, and burned the fish as candles.

Smog

Ground-level ozone. Smog is formed in the Earth's lower atmosphere, near ground level, when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight. Ninety per cent of all smog found in urban areas is made up of ground-level ozone-the same chemical found in the stratosphere. In large enough quantities, ground-level ozone can cause respiratory problems in humans and other animals, and damage to plants and building materials. As the name suggests, smog often is a mixture of smoke and fog. In industrial areas it is the hazy polluted air that results when smoke from burning fuels reacts with water droplets to producc sulfur compounds. Another kind of smog is formed when automobile exhaust fumes react with sunlight to produce ozone and other irritants. Both types of smog damage lungs, plant life, and even buildings. The ill effects are at their worst during temperature inversions, when a layer of warm air lies over cooler, polluted air and prevents the smog from dispersing.

Smokethorn

Psorothamnus spinosus

These short, spiny trees of the arid Southwest usually grow in dry streambeds, or washes, where the occasional £lash flood does not harm them. In fact, they benefit from the torrents: their seeds cannot germinate until their tough skins have been broken by tumbling along the stream bottom. The trees sprout a few leaves after it rains, but the foliage soon drops away, leaving grayish twigs that look as insubstantial as puffs of smoke. In early June, however, smokethorns make a bolder show, covering themselves with purple flowers.

Smut

Serious agricultural pests, smuts are parasitic fungi that attack a variety of plants, especially corn, wheat, and other grains. When smuts infect plants, they sap the vitality of the host and produce a number of symptoms. Pustules form on the flowers, seeds, leaves, stems, or bulbs and become filled with dark, powdery spores. When the blisters rupture, the spores disperse, infecting nearby plants, or lie dormant in the soil, awaiting the next generation of hosts.

Snail

Soft-bodied mollusks that live coiled inside spiral shells, snails are found almost everywhere. The vast majority live in the ocean, but many others thrive in fresh water and on land. Snails move about by rhythmically contracting a strong, muscular foot that extends outside the shell. At the front of the foot is the head, which has paired tentacles and eyes and, in the mouth, a special "tongue" lined with tiny, rasping teeth that are used for scraping off bits of food. While most snails are vegetarians or scavengers, a few are predators. One kind, the oyster drill, for instance, is a serious pest in oyster beds. It bores holes right through oyster shells to get at the animals inside. Snails live both on land and in water. Aquatic species, such as the apple snail, which lays its eggs on low branches or stems near the water, usually have gills, but land snails all have lungs.

Snake

Long, slender, legless reptiles that slither about on their bellies, snakes have always fascinated humans, inspiring both curiosity and fear. While many people think of them as slimy, their skin (which is shed several times a year) is in fact dry and scaly. Living both in water and on the land, they are equally adept at swimming, gliding through grass or across rocks, and even climbing trees. Since snakes, like other reptiles, are cold-blooded, they regulate their body temperature by moving back and forth between sun and shade. All snakes are predators, feeding on everything from insects and amphibians to birds and mammals. Poisonous kinds kill their prey with injections of venom, but constrictors suffocate their victims, and many others swallow live animals whole. Some snakes, such as the familiar garter snakes, bear live young, but most lay eggs. Our North American species range in size from the 9-inch Florida crowned snake to the indigo snake, which is nearly 10 feet long.

Snake bird

See Anhinga.

Snapper

Most abundant along the Florida and Gulf coasts, the snappers are a family of colorful fish prized by both anglers and lovers of seafood. They are large, sharp-toothed carnivores that average two to three feet in length and travel in dense schools, feeding on crabs, shrimp, and smaller fish. The red snapper, named for its uniformly rosy hue, is the most popular and delectable of the family. It dwells in far deeper waters than the schoolmaster and yellowtail snappers, found among coral reefs, and the gray, or mangrove, snapper, which lives amid the tangled roots of mangrove thickets. While most species are edible, the dog snapper, named for its formidable fangs, is sometimes poisonous.

Snapping turtle

Quick to lunge at prey or passersby, snapping turtles are big, aggressive reptiles that use their strong jaws for defense. Much of the time, however, they lie quietly in the ooze of rivers, lakes, and ponds, where they feed on aquatic plants and small prey. They also relish an occasional duckling snatched from below. In early summer females leave the water to bury clutches of eggs on land. At home from Canada to the Gulf Coast, the common snapper grows up to 20 inches long and may weigh over 30 pounds. The 200-pound alligator snapper of the South and Midwest-the largest freshwater turtle in North America - has a pink wormlike growth on its tongue that it wiggles to lure fish into its gaping maw.

Snipe

Gallinago gallinago

A long-billed shorebird found in marshes and wet meadows, the common snipe is a secretive creature that wears a concealing pattern of stripes and bars. It spends its time probing the damp soil with its bill, in search of earthworms, insects, and other prey. It is seldom seen until it suddenly takes to the air and zigzags off to safety.

On its breeding grounds in the northern states and Canada, the male snipe performs a striking display flight that includes deep power dives, during which air rushing through the tail feathers produces a weird whinnying sound. Four speckled eggs are incubated by the female, but both adults tend the downy young, which leave the nest soon after hatching and begin finding their own food when only a few days old.

Snook

Centropomus

Fine food and game fish with long, silvery bodies and protruding lower jaws, our four species of snooks live mainly where land meets sea and salt water mingles with fresh. They are found in shallow coastal seas and warm bays and lagoons along the south Atlantic and Gulf coasts, but they also venture well inland in fresh water. Feeding mostly by night on fish and crustaceans, snooks, sometimes more than four feet long, put up a ferocious fight when hooked by anglers.

Snow

Atmospheric vapor frozen into ice crystals that falls to earth in light white flakes. A snowstorm is a heavy fall of snow, especially with a high wind. A severe snowstorm is called a blizzard. When temperatures in a cloud are below freezing, its moisture condenses directly into crystals of ice that grow into snowflakes. While all are six sided, the crystals are endlessly varied in detail. These snowflakes are in many patterns, since many look like stars, but others form columns, needles, or plates. Snow is far less dense than rain-when melted, 10 inches of snow equal 1 inch of rain - but in many areas snow is a major source of water. It also insulates plants and hibernating animals from winter's cold.

Snow, when it melts, is an important water source for streams and reservoirs in many regions.

Snow plant

Sarcodes sanguinea

Appearing in spring just after the snow melts, the fleshy red stems and blood-red flowers of snow plants are a startling sight on the barren forest floor. Because they lack chlorophyll, snow plants cannot manufacture their own food and instead draw nutrients from decaying organic matter in the soil. Seldom exceeding 12 inches in height, these wildflowers flourish only at elevations between 4,000 and 9,000 feet on the mountains of California and Oregon.

Soapwort

Saponaria officinalis

An attractive wildflower that is common along roadsides and railroad tracks, soapwort is named for the lather-producing substances in its sap. Weavers and textile mills once used the plant to clean and whiten cloth, but it was popular in the laundry and bath as well. Also known as bouncing bet, soapwort has straight, thickjointed stems up to three feet tall and bears clusters of pink or white flowers from late spring through early autumn. The five-petaled blooms exude a spicy fragrance that is especially noticeable toward nightfall.

Social Darwinism

Biological Philosophy term. An extension of the idea of biological evolution to human culture. An extreme laissez-faire notion that the poor are poor because they lack certain genetic characteristics that would fit them for economic survival. As the argument goes, society has no obligation to its poor since to help them would be to allow inferior types to survive, and thus interfere with evolution and weaken society. The theory is based on ignorance of the great variety and relativity of social and economic systems, ignorance of the possibility that certain people who seem inferior in one sort of society might be heroically successful in another sort of society, e.g., Indians with great hunting skills found it hard to survive in an agrarian culture.

Social facilitation

An Animal Behavior term, this is used to describe the effect whereby the performance of a behavior pattern by one Animal leads others to start behaving in the same way or to show more of it. Unlike Imitation, it does not involve the acquisition of new behavior but is simply a way in which Synchrony between Animals in their activities is achieved.

Sociobiology

Biological Philosophy term. The study of social animals, insects, bees, etc., who are genetically programmed to create certain social structures. This suggests that there may be genetic grounds for certain aspects of human behavior, that human society may not all be the result of "learned" behavior. This idea, propounded most importantly by E. O. Wilson, has been opposed by Stephen Jay Gould.

Sociobiology

An Animal Behavior term, this is used to describe that branch of behavior study concerned with the social behavior of Animals, its ecology and its evolution.

Softshell turtle

Trionyx

Nicknamed "flapjacks" because of their flat, rounded form, softshell turtles have a leathery skin rather than horny plates on their carapaces. Three species-the spiny, smooth, and Florida softshells-inhabit lakes and rivers across much of North America. They often rest half-buried in mud in the shallows, where they can stretch their long necks toward the surface. Softshells also enjoy sunbathing on rocks and floating logs. Fast-moving both in water and on land, softshells can strike with stunning speed to capture insects, fish, and other prey. They also have a well-deserved reputation for pugnacity: anyone who handles them is likely to come away quite badly scratched and bitten. Softshell turtles are distinguished by their long, tubelike snouts, which they often use as snorkels when they are underwater, buried in mud. The spiny softshell is named for the spines or warts at the front of its dot-marked, leathery shell.

Soil

Most of the earth's land surface is covered by a mantle of soil, which varies from less than an inch to many feet in thickness. This complex substance consists mostly of weathered and eroded rock fragments (mainly clay, along with sand and silt), but these particles do not become soil until they are enriched with organic matter-the decomposed remains of plants and animals. Both the water that clings to the particles and the air in the spaces between them are also essential components of living soil. Depending on its composition, the color, texture, and other characteristics of soil vary from place to place and over time. Because soil is the substance in which most land plants grow, it is essential to life on earth. Plants not only are anchored in soil but also rely on it for water and mineral nutrients. And the plants in turn serve directly or indirectly as food for all land animals. Slow to form but easily destroyed, soil is a vital natural resource that must be treated with utmost care.

Sole

See Flatfish.

Sole

The underside of the foot in mollusks.

Soliciting

An Animal Behavior term, this is used to describe the posture adopted by a female which functions as an invitation to a male to mate. For example, Lordosis in Mammals and a horizontal posture with tail fluttered up and down in many Birds.

Solomon's seal

Polygonatum

Some say the Solomon's seals are named for the scars on their rootstocks, which resemble the seals affixed to official documents; others claim that King Solomon used the roots to heal, or "seal," wounds. Whatever the case, Solomon's seals are most graceful plants, forming clumps of arching stems that rise in parallel curves up to six feet tall. Common in the East and parts of the Southwest, the plants are adorned in May and June with rows of white or yellowish flowers that dangle like little bells from their stems.

Song

An Animal Behavior term, this is used to describe any lengthy sound signal produced by Animals. Song may be simple, as in many Insects, or elaborate, as in Birds and Whaless. Most songs probably function in rival repulsion and mate attraction.

Sonograph

An Animal Behavior term, this is used to describe a machine for analyzing sounds which produces a plot of frequency against time known as a sonogram.

Soul

Biological Philosophy term. The spiritual component of the human being. According to Plato, the soul is a spiritual principle of thought that should govern human choice and action. According to Aristotle, each living thing is composed of "matter and form," the soul is the human "form," the organizing principle that shapes the chaos of matter into a human creature rather than some other kind. Christian elaboration of these two philosophical ideas make the soul the seat of intelligence and free will, the "purely spiritual" activity of humans. The immortality of the soul is based on the notion that it has a purely spiritual activity, and must itself be purely spiritual and able to survive the loss of the body. The contemporary question is this: is human intelligence reducible to the firings of neurons studied by neurology, or is there something more, a soul, for which the neurons are merely the supporting organ.

Sound spectrograph

An Animal Behavior term, see Sonograph.

Source habitat

A habitat that is a net exporter of individuals.

Source population

A population that occupies habitat suitable for reproduction, in which the output of offspring results in a population that exceeds the carrying capacity of the local habitat, promoting dispersal.

Sourwood

Oxydendrum arboreum

Though the sourwood's sap is sour, its nectar is sweet; in midsummer, when its branches are arrayed with drooping clusters of creamy-white bell-shaped flowers, bees swarm to the tree and produce a honey that is prized by gourmets. Occasionally reaching a height of 60 feet, sourwood is attractive in autumn as well, for its long oval leaves then take on a spectacular scarlet hue. Sourwood ranges from Pennsylvania to Florida and is also planted as an ornamental.

Southern pine forest

Stretching along the coastal plain of Texas to central Florida and north to Virginia, the Southern pine forest is a wide belt of sandy soil dominated by longleaf, loblolly, and slash pines, often with an understory of young oaks and other saplings in their shade, but frequent fires (many of them deliberately set by woodsmen) serve to keep the broadleaf interlopers from taking over and, at the same time, restore the vigor of the commercially valuable pines. The southern pine forests are home to a variety of creatures adapted for survival in this unique habitat. The sandy soil, easily excavated, is well suited to burrowers such as spadefoot toads, gopher tortoises, and pocket gophers. Ground level is occupied by animals as diverse as shrews and white-tailed deer. In the trees above, woodpeckers, warblers, and other birds probe the bark for insects and fill the forest with staccato drumming and melodious song.

Spadefish

Chaetodipterus

Found near rocks, reefs, and pilings along the East Coast and off southern California, spadefish put up a respectable fight when hooked, and their tasty flesh is worth the struggle. Their bodies, usually one to two feet in length, are deep and flattened from side to side. On young fish the silvery sides are striped with dark vertical bars, but they tend to fade as the fish mature. Small mouths and teeth limit spadefish to a diet of plants, barnacles, and tiny crustaceans.

Spadefoot toad

Scaphiopus

Equipped with a horny tubercle on each hind foot (their "spades"), spadefoot toads can burrow quickly, rear end first, into sandy or other loose soils. And there the secretive, seldom seen amphibians remain by day, emerging only after dark to feed and breed. The toads rely on temporary pools for reproduction and so must gather quickly after spring rains to mate and lay their eggs. Hatching almost at once, the tadpoles can become toads in less than two weeks, a record time for any North American frog or toad.

Spadix

The upright spike of florets, found in arums.

Spanish moss

Tillandsia usneoides

A symbol of the South, Spanish moss hangs in graceful swags from trees, shrubs, and even fences and utility wires from southern Virginia to eastern Texas. The branching, gray-green strands, as long as 15 feet or more, do not harm the trees, for Spanish moss is an epiphyte, drawing its nutrients and moisture from air and rainwater. Producing inconspicuous flowers, it spreads by means of downy, windblown seeds.

Sparrow

Some 30 species of sparrows-small, streaked brown birds with stout, conical beaks-are native to North America. Many of them live in grasslands, but sparrows are found almost everywhere-from the tundra and spruce forests of the Far North to deserts and southern dunes. Although most sparrows are seed eaters, they also feed on insects, and a few supplement their diets with snails and berries. They build tidy cup-shaped nests of grasses and twigs, usually hiding them on the ground or in shrubs. Both parents tend the nestlings, feeding them insects until they leave the nest at about 10 days old.

Among the most familiar species are the song sparrows, birds of gardens and thickets that are noted for their cheerful singing; the chipping sparrows, which have rusty caps and white eyebrows; and the field sparrows, whose sweet, whistled notes announce the courting season.

Spathe

The large bract surrounding the spadix in arums.

Spatial learning

An Animal Behavior term, this is used to describe learning the positions of objects in space. Spatial learning is very importAnt for most Animals so that they can become familiar with their Home Range and the location within it of essentials such as food and shelter.

Spawning

An Animal Behavior term, this is used to describe the production of eggs and sperm in those Animals, such as most Fish species, where fertilization is external and eggs and sperm are just released into the water.

Specialist

A species with narrow food preferences, habitat preferences, or both (see Generalist).

Species

A species is a class of living organisms that have similar characteristics and are capable of exchanging genes or interbreeding. A group of individuals that can interbreed and beget fertile offspring. A group of actually or potentially interbreeding populations that are reproductively isolated from all other kinds of organisms. Unit of classification defining animals or plants that are able to breed with one another and produce viable offspring.

Species-area relationship

A plot (often log-log) of the numbers of species of a particular taxon against area, such as islands or other biogeographic regions.

Species diversity

See Diversity.

Species richness

The number of species in a given area.

Species

Endangered and Threatened species term.

From Section 3(15) of the Federal Endangered Species Act: "The term 'species' includes any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature." A population of individuals that are more or less alike, and that are able to breed and produce fertile offspring under natural conditions.

Species-area relationship

A plot (often log-log) of the numbers of species of a particular taxon against area, such as islands or other biogeographic regions.

Species at Risk

See Endangered species.

Species conservation

A species is a class of living organisms that have similar characteristics and are capable of exchanging genes or interbreeding. Conserving species diversity means ensuring that healthy populations are maintained in their native areas, and that suitable habitat is preserved.

Species diversity

See Diversity.

Endangered and Threatened species term.

"Species of concern" is an informal term that refers to those species which Region 3 believes might be in need of concentrated conservation actions. Such conservation actions vary depending on the health of the populations and degree and types of threats. At one extreme, there may only need to be periodic monitoring of populations and threats to the species and its habitat. At the other extreme, a species may need to be listed as a Federal threatened or endangered species. Species of concern receive no legal protection and the use of the term does not necessarily mean that the species will eventually be proposed for listing as a threatened or endangered species.

Species richness

The number of species in a given area.

Specific hunger

An Animal Behavior term, this is used to describe the occurrence of an appetite for particular nutrients. Animals needing salt will travel long distances to salt licks and, similarly, laying Birds develop a taste for the calcium they need to make egg shells.

Speculum

On many ducks, the trailing portion of the wing, called the speculum, often has a distinctive colour pattern that can aid in identification. Visually, it is that portion of the rear wing between the elbow and the body.

Speedwell

Veronica

No one knows just how the speedwells got their name. Some say that the bright flowers, which adorn roadsides well into summer, seem to cheer travelers on their way. Others trace the name to the speed with which the weedy kinds can spread. In fact, this adaptable clan flourishes in swamps, woodlands, mountain ravines, and lawns across most of North America. Whether upright or sprawling, all have pretty white, blue, or purplish four-petaled flowers. Some, such as water speedwell, bear the blooms in spikes; on other species they grow singly on slender stalks. Some speedwells are American natives; others were introduced from the Old World.

Sphagnum

Also known as peat moss, the sphagnums are aquatic mosses that are notable for their role in converting open water to dry land. The plants, up to a foot long and covered with tiny leaves just one cell thick, are most commonly found in bogs, where they form floating mats that, over time, can completely fill these wetlands. Because they secrete acids that retard decay, the mosses eventually accumulate in great spongy deposits that are gradually compacted into peat. Able to absorb up to 20 times their weight in water, sphagnums are often used as additives to garden soils and as packing material for shipping live plants. In Europe peat is also harvested and dried for use as fuel. Sphagnum mosses vary in color, spanning the spectrum from pale green to deep red.

Sphinx moth

With wingspans of as much as six inches, sphinx moths, also known as hawk moths, are agile fliers that generally feed by hovering before flowers and sipping nectar with their long tongues. The majority are nocturnal and concealingly patterned in brown, but a few fly during the day. The larvae of most species have a horn or spine at the rear of the body and are called hornworms. Feeding on crop plants such as tobacco and tomatoes, some of the caterpillars are serious agricultural pests. Cerisy's sphinx moth is marked with two distinct eyes pots located on its hind wings. A close relative, lacking the black centers in its blue eyespots, is known as the blind sphinx.

Spicebush

Lindera benzoin

A shrub that flourishes in moist eastern woodlands, spicebush bears tufts of tiny yellow flowers in early spring, long before the leaves appear. Wreathing the branches, the blooms exude the spicy perfume for which the plant is named. Its attractive oval leaves, also aromatic when crushed, turn bright yellow in the fall, then drop away to reveal the year's crop oflittle red berries. The fruits have been used since colonial times as a substitute for allspice, and the leaves for a fragrant tea.

Spider

Though spiders may look like insects, they in fact belong to a separate group of animals called arachnids, which also includes the daddy-Ionglegs, mites, ticks, and scorpions. In contrast to insects, which have six legs and a three-part body, spiders have eight legs and a two-part body. They range in size from the three-inchlong tarantulas of the Southwest to species that are practically microscopic. Most spiders have eight eyes, and all have poison fangs, used to subdue prey, as well as spinnerets, small organs at the tip of the abdomen that produce silk. Most spiders use their silk to spin webs for entangling insect prey, and some webs-especially those of the orb weavers-are complex and beautiful creations. But not all species make webs. Some hunt for prey on foot; jumping spiders pounce on their victims; and crab spiders hide in flowers to ambush unsuspecting insects looking

for nectar and pollen. Whether or not they spin webs, all spiders use silk to make cases for their eggs, and many spin strands for ballooningdrifting long distances on the wind.

Spiderwort

Tradescantia

Natives of moist woodlands and prairies, some 60 species of spiderworts grow wild in North America. All have three-petaled blue, purple, pink, or white flowers, borne in loose clusters atop their stems. Producing long, narrow, grassy leaves, some spiderworts are erect and up to three feet tall, while others sprawl weakly across the ground. Pine spiderwort, found in parts of the Southwest, and western spiderwort, which ranges from Montana to Texas, were cooked as vegetables by American Indians. But the plants are more valued now as garden flowers, despite the fact that they sometimes develop into aggressive, persistent weeds.

Spike

Simple, branched inflorescence.

Spikelet

Inflorescence arrangement in grasses, sedges, and so on.

Spills

The accidental release of a liquid chemical, such as oil, into a body of water can have far-reaching impacts on the environment because spills may disperse widely or even mix with the water.

Spire

The upper whorls of a snail shell; may be few or many.

Spirea

Spiraea

Our several species of spirea are moisture-loving shrubs that thrive in damp places. A few are low or creeping evergreens, but most-including the attractive steeplebush, an eastern native and popular ornamental-are deciduous shrubs up to six feet tall. Spireas form thickets of erect stems clothed with oval, tooth-edged leaves; in summer they bear masses of five-petaled pink, white, or reddish blooms in dense clusters at the ends of the branches.

Spittlebug

Concealed by the masses of protective white foam that give these little insects their name, spittlebugs live in meadows and weedy places, where they feed by sucking the juices from plants. After molting several times, spittlebugs leave their bubbly hideaways as adults-now called froghoppers because they resemble tiny frogs and hop if disturbed. The foam makes the immature insects easy to find, but froghoppers usually slip away unnoticed.

Sponge

Best-known for some species' soft, absorbent skeletons, used for household cleaning and bathing, sponges are simple animals found in the sea and sometimes in fresh water. They live attached to rocks and other hard surfaces and are so plantlike in appearance that they were not recognized as animals until the 19th century. A typical sponge has no mouth, stomach, gills, or heart. Its body consists, instead, of a chamber with many pores in its walls and a large opening at the top. Water, laden with food particles, flows in through the pores and is expelled through the top. Some species, such as the bath sponges, have skeletons of a fibrous material called spongin. Others have skeletons made up of limey or glassy spines, called spicules. Sponges vary tremendously: they can be globular, branched, vase shaped, fingerlike, or simple, irregular crusts. Their colors range from drab browns to brilliant reds and yellows.

Spoonbill

Ajaia ajaja

One of the most spectacularly beautiful of our large wading birds is the roseate spoonbill, a resident of the Gulf Coast from east Texas to southern Florida. Named for its bright pink plumage and long, flat, spoon-shaped bill, the bird feeds in a manner all its own. It swings its keenly sensitive bill from side to side in shallow water, snapping it shut on small fish, shrimp, and insects that it detects by touch. Like other members of the ibis family, roseate spoonbills are usually found in flocks. The birds nest in colonies among shrubs and mangroves, often sharing island rookeries with herons, egrets, and other waders. Spoonbills are often seen flying in long lines at dusk, their slender necks extended, as they head to their roosts.

Spore

The tiny reproductive body that disperses and gives rise to a new organism. Just as flowering plants rely on seeds for sexual reproduction, so others depend upon singlecelled spores as a means of asexual reproduction. When ripe, spores are dispersed by wind and water, and if conditions are just right, they germinate. Spore-bearing structures dot the undersides of fern fronds, while the spores of mushrooms are visible as a telltale dust. Bacterial spores serve an additional function by providing protection during dormant periods; some are so resistant to harsh conditions that they can survive for hours in boiling water.

Spot-mapping method

Bird Biology Avian Conservation term.

A census procedure that plots on a map individuals seen or heard in a surveyed area. The survey is usually conducted over a period of days or weeks in a season, and individual territories or home ranges are then demarcated by examining the clusters of observations. Used in Breeding Bird Census.

Spring

Whether freezing cold or boiling hot, mere trickles or gushing torrents, all springs are sources of water flowing from the ground. Most are found where the top of an aquifer comes in contact with the surface of the land, often on slopes or at the bases of cliffs. Springs also occur where fissures allow water under pressure to rise to the surface-sometimes forcefully, as in geysers and artesian springs. Our largest springs, which can yield millions of gallons of water per day, pour from underground channels dissolved in limestone. Many, such as those in Florida, are natural wonders; others are celebrated for the supposed curative properties of their mineral content, as are those in the Ozarks.

Springtime

Spring is one of the four seasons of the year and is the transition from Winter to Summer. It is (also by convention) counted as the whole months of March, April, and May in the Northern Hemisphere and September, October, and November in the Southern Hemisphere.In Spring, the weather begins to warm significantly, causing new plant growth to spring forth, giving the season its name.

)Snow (if any) begins to melt, and rivers and streams swell with runoff and spring rains. Most flowering plants bloom this time of year, in a long succession beginning even when snow is still on the ground, and continuing into early summer. In normally snowless areas, "spring" may begin as early as February during warmer years, other areas may not see "spring" at all until May or even June, or December in the outer regions of the North. Flooding is also most common in and near mountainous areas during this time of year due to snowmelt, many times accelerated by warm rains. Springtime is seen as a time of growth, renewal, of new life (both plant and animal) being born, and of the cycle of life once again starting. It is also used more generally as the start of better times.

Spring beauty

Claytonia

Each year from March through May, spring beauties brighten damp woods and fields in both the East and West. Their slender 6- to 12inch stems, each bearing a pair of long, narrow leaves, are topped with delicate, rose-veined pink or white flowers. The display is especially pretty where the plants grow in large patches. Most species of spring beauty sprout from tubers that look like tiny new potatoes and taste like chestnuts. American Indians gathered them for eating, and they are still prized by wild-foods enthusiasts. But the plants should be harvested only where they are plentiful.

Spring peeper

Hyla crucifer

One of the best-loved signs of spring in the East is the chorus of spring peepers echoing from marshes and ponds. In the first warm days of the season, these tiny tree frogs gather to mate. Each male, just over an inch long, inflates his throat pouch to produce a high-pitched whistle; the calling of hundreds has been likened to the jingling of sleighbells. When mating is over, the adults return to the woods, leaving their eggs to hatch into tadpoles. Though the spring peeper is one of the most abundant frogs in the East, adults are seldom seen during the rest of the year. Equipped with adhesive discs on the tips of their toes, the little frogs easily climb high into the treetops in their quest for insect prey. On warm days in the fall, before they go into hibernation, lone males are sometimes heard calling deep in the woods.

Springtail

Though primitive and wingless, springtails have a unique mechanism for becoming airborne: most species have a hingelike structure on the underside of the abdomen that, when released, catapults them several inches through space. Among our smallest insects, springtails make up for their size by sheer abundance; millions can often be found on a single acre of forest floor. While most are too small to be easily seen, some species gather in such masses that they are impossible to overlook. One of these, the tiny, dark-blue snow flea, often swarms on the snow in mild weather; another, the seashore springtail, is frequently found floating on tide pools. Most springtails feed on decaying plant matter, fungi, pollen, and even bacteria, but a few are pests in greenhouses and mushroom cellars.

Spruce

Picea

Handsome evergreen trees that are most numerous in the North, spruces have the neatly tapered profiles of classic Christmas trees. So do firs, which the spruces resemble in many ways, but the two kinds of trees are easily distinguished. Spruce needles, which are stiff and prickly, leave peglike stubs when they fall from the twigs, while fir needles are softer and leave no stubs. Also, spruce cones hang down from the branches, while fir cones stand erect. Our most abundant species are black spruce and white spruce, both of which range from Alaska to New England. The tallest, the Sitka spruce of the Pacific Northwest, can exceed 200 feet and live for 800 years. Perhaps our loveliest species, admired for its silvery sheen and often planted as an ornamental, is the blue spruce of the Rockies. The wood of the spruces is used for everything from paper to pianos, and the twigs have even served as an ingredient in beer.

Spurge

Euphorbia

Despite their immensely varied appearances, most spurges share one trait: the plants contain a bitter, often poisonous milky sap. As a result, cattle refuse to eat the acrid foliage of some of the spurges, which have overrun much western rangeland. Caper spurge, on the other hand, is cultivated by gardeners because it is said to repel moles and gophers. Snow-on-the mountain, another common spurge, looks like a pale version of its subtropical relative the poinsettia.

Squall line

A row of thunderstorms that may extend for hundreds of miles, a squall line is visible as a wall of storm clouds that advances well ahead of a cold front pushing into warm, humid air. Accompanied by gusty winds, thunder and lightning, rain, and sometimes hail and tornadoes, the squall line usually passes over quickly. Within a few hours, however, temperatures are likely to plummet with the arrival of the cold front.

Squid

The unlikely cousins of clams and snails, squids are marine mollusks whose shells have been reduced to internal remnants. They range from 2 inches to more than 50 feet in length, with eyes at the head end. Surrounding the mouth are 10 arms equipped with suction cups, including 2 longer tentacles used for seizing fish and other prey. Frequently found in large schools, squids swim by natural jet propulsion: by drawing water into their bodies and then expelling it through a funnellike tube, they shoot quickly backward. When threatened, squids release a cloud of inky fluid that serves as a smoke screen, allowing them to escape.

Squawroot

Conopholis americana

Like other members of the broomrape family, squawroot contains no chlorophyll and so cannot manufacture its own food. Instead, it takes nourishment from the roots of oaks and other trees in eastern woodlands. With its leaves reduced to small, brownish scales, squawroot looks like nothing more than clusters of pine cones lying on the forest floor. In late spring, however, it puts on a modest show, with small yellow, hooded flowers peeping out from between the scales.

Squirrel

Though chipmunks, prairie dogs, woodchucks, marmots, ground squirrels, and flying squirrels are all members of the squirrel family, the term squirrel means to most people the familiar nonflying, nut-gathering tree squirrels. Wherever there are trees, in fact-from the Great North Woods to the Mexican border-there is at least one kind of tree squirrel.

Bushy-tailed acrobats that leap from branch to branch and race up and down tree trunks (sometimes as if to play hide and seek), squirrels are not nearly so secretive as most other forest dwellers. All the more conspicuous because they are active during the day and around the year, the busy little rodents are usually searching for food. Opportunistic omnivores, squirrels feed on insects, birds' eggs, and even young birds, as well as mushrooms, fruit, bark, and the nuts and seeds they store for winter. While red, Douglas', and Abert's squirrels favor the seeds of pines and other conifers, gray and fox squirrels prefer acorns and hickory nuts. The various seeds and nuts are either buried singly (and later located by smell) or stored in large caches.

Squirrels sleep and raise their young in tree cavities, which they line with leaves and bark, or in bulky nests built high in the treetops. Made of leaves and sticks, the nests may seem flimsy and precarious, but they are sturdy enough to withstand wind, rain, and snow.

Stable age distribution

Bird Biology Avian Conservation term.

The proportions of the population in different age classes when the rate of increase has converged to a constant (which depends on the fixed schedules of survival and fecundity). The ratios between the numbers in the age classes are constants.

Stalactite

Among the most impressive features of limestone caves are the strange, often beautifully shaped stalactites, which hang like icicles from the ceiling. They are formed by the slow evaporation of mineral-laden water as it drips from the roof of the cave. Stalactites start out as tiny ringshaped deposits on cave ceilings; bit by bit they lengthen into tubes and gradually become wider. Some grow an inch a year; others take 100 years to add that much. Stalactites consist of a form of calcium carbonate. Naturally white, it is tinged red, yellow, or black by impurities. When the flow of water is sufficient, it drips from the end of the stalactite to the floor of the cave, creating an upward-pointing formation called a stalagmite. If the two continue to grow, they may eventually meet and form a column. Stunning cave formations can be seen at such places as Luray Caverns in Virginia and Carlsbad Caverns in New Mexico.

Stalagmite

See Stalactite.

Stamen

Male reproductive structure of a flower

Starfish

See Sea star.

Stargazer

Homely fish with upward-slanting mouths and eyes on the top of their heads, stargazers habitually lie half-buried in sand or mud on the ocean floor with only their eyes and lips protruding. They wiggle a fleshy lure on their mouths, and when small fish, crustaceans, or other prey venture near to investigate, they leap up and snatch a meal. Stargazers also have special organs behind their eyes that can produce powerful electric shocks, perhaps to stun their prey, and some are equipped with venomous spines that help keep hungry predators at bay.

Starling

Sturnus vulgaris

Introduced to New York City in 1890, the stocky, iridescent European starling promptly began to expand its range and is now found all across the continent. Well-adapted to agricultural lands in Europe, it had no trouble adjusting to farmlands in North America and has become one of our most abundant birds. Starlings generally feed in open country, probing in the soil for insects, larvae, seeds, and other food; but in the evening huge, noisy flocks often gather in cities to roost on buildings. Starlings build their nests in holes in trees, and in crevices in cliffs or on buildings; both parents incubate the clutch of four to six eggs. While starlings consume many harmful insects, these adaptable immigrants are a mixed blessing, not only because they damage crops but also because they compete with native songbirds for nesting sites. The starling's feathers, tipped with white and buff in the fall, turn glossy black in spring as the tips wear off.

Station

Bird Biology Avian Conservation term.

The area within which observations made from a point are recorded by the observer (or often synonymous with "point," see Point count method) or a monitoring station is an area of usually less than about 50 ha where intensive censuses, nest searching, and/or mist netting for birds are conducted.

Statistical bias

A difference between the expected value of an estimator and the population parameter being estimated.

Stereotypy

An Animal Behavior term, this is used to describe a stereotyped and monotonously repeated movement patterns, especially those shown by caged Animals such as the relentless pacing up and down of Bears and Lions in zoos and the tail-biting of farm pigs.

Stenotopic

Found in only one or a relatively small number of habitats.

Stickleback

These small fish of shallow lakes, coastal waters, and brackish estuaries are named for the stout spines that project from their backs. Numbering from two to nine, depending on the species, the spines are used as weapons against predators and, during the spawning season, against other sticklebacks. Normally dull-colored, the males don brighter hues when they are ready to breed. They build tubular nests of water plants, which they glue together with a sticky mucous secretion. Each male then gives chase to one or more females, nipping their fins to coax them into the nest to lay eggs. The pugnacious male carefully guards both eggs and young, using his stout spines to drive away intruders. Their unusual mating behavior, plus their generally aggressive temperament, make the sticklebacks popular aquarium fish.

Sticktight

Bidens

Producing small, dry fruits armed with barbed prongs, the sticktights have earned such nicknames as beggar's ticks and devil's pitchforks. Because they attach themselves so easily to fur, feathers, or fabric, the fruits ensure wide dispersal of the weedy plants. Some of these members of the sunflower family have yellow ray flowers on their flower heads and are called bur marigolds, but most have only a drab central button of disc flowers.

Stigma

Botany term. Receptive tip of female part of flower, the style.

Stilt

Himantopus mexicanus

With l0-inch-long red legs that do indeed resemble stilts, these strikingly patterned blackand-white shorebirds are easy to spot as they stride through brackish lagoons and shallow lakes. Black-necked stilts sometimes wade belly-deep

the water, using their long, tapered bills to pluck insects nimbly from the surface. They also glean on nearby mudflats. Breeding in small colonies, black-necked stilts lay clutches of three or four spotted eggs, sometimes in shallow depressions in the sand and sometimes on islets in the water. Talented bluffs, nesting stilts are well-known for their very convincing distraction displays, which include both broken-wing and broken-leg acts.

Stinkbug

Protected from predators by the foul odors that have earned them their name, the stink bugs are shield-shaped insects that are usually about half an inch long. Most are green or brownish, but some are boldly patterned. The majority feed on plant juices, which they suck through their long flexible beaks, and a number of species are crop and garden pests. A few, however, are predators, using their beaks to drain the body fluids of caterpillars and other insects. Many stink bugs are protectively camouflaged in shades of brown or green. But some other species-among them the crop-destroying harlequin bug (right)are easy to spot because of their bright, distinctive patterns.

Stingray

Like the skates and other rays, stingrays are flatbodied kin of sharks that move through the water by undulating their winglike pectoral fins. From one to seven feet wide, they also spend much time buried in the sand in shallow water. Bathers on both our coasts should regard even the smaller kinds as armed and dangerous: when disturbed, stingrays lash out with their long whiplike tails, which, armed with venomous spines, can inflict painful injuries.

Stinkpot

See Musk turtle.

Stipule

Leaflike or scalelike structure at base of leaf stalk.

Stochastic

Implies the presence of a random variable.

Stonecrop

Sedum

Hardy plants, including many that live in dry, rocky places, the stonecrops have thick, succulent leaves in which they store water whenever it rains, and so are able to survive times of drought. Many are popular as rock garden plants, producing dense clusters of small flowers in shades of pink, purple, yellow, and white, on stems up to two feet tall. The yellow-flowered wallpepper, or mossy stonecrop, often planted as a groundcover, has escaped cultivation to spread mossy mats of thick, tiny leaves over rocks, cliffs, and dunes. Orpine, also known as live-forever, is another garden escape that enlivens roadsides and waste places with purplish blooms. The widespread, similar-looking roseroot thrives even in such forbidding habitats as high mountaintops and arctic tundra.

Stonefly

Poor fliers, stoneflies seldom venture far from the streams and rivers in which they spend their youth. With wings folded flat along the back, the adults are most often seen crawling over leaves or rocks near the water's edge. The aquatic nymphs, which creep about under stones and feed on algae or small animals, are themselves a major source of food for fish. While the nymphs take four years to mature, the adult insects mate and die within a few weeks.

Stone sheep

Ovis dalli

Storms (Weather)

Atmospheric disturbances manifested in strong winds accompanied by rain, snow, or other precipitation and often by thunder and lightning.

Storm-petrel

Small, dark seabirds with white rumps, stormpetrels are swallow-size relatives of albatrosses and shearwaters. They are usually seen fluttering just above the waves, pattering the surface with their webbed feet as they search for small fish and other food. The birds nest in colonies, usually on remote islands, where each female lays a single white egg in a burrow. But even during the breeding season, storm-petrels spend the day at sea, returning to their nests only under the cover of darkness. Leach's and Wilson's storm-petrels are the most common species.

Storm surge

Driven by hurricane winds, storm surges are moving walls of water that can devastate lowlying coastal regions. They form as hurricanes move across the sea; howling winds drive seawater toward the shore and whip up the waves, causing them to swell to tremendous heights. By the time the storm reaches the coast, the sea level may have risen by 10 feet or more. If the storm surge strikes without warning, the results are likely to be calamitous, for its waters can wash away buildings, break levees, and flood the coastal lowlands for many miles inland.

Stotting

An Animal Behavior term, this is used to describe the adoption of a stiff-legged, bouncing gait by Deer that have spotted a predator. This may function as a warning to others or possibly to the predator that, having Been spotted, it has no chance of success.

Strategy

Environmental Law term. Long-range policy designed for a particular purpose.

Strategy

An Animal Behavior term, this is used to describe a mode of behavior adopted by an individual when it could, either actually or theoretically, behave in a different way. For example, males of some species may adopt either of two strategies, Territorial or Satellite. In theoretical discussions, an Evolutionarily Stable strategy is that which, if adopted by the whole population, cannot be bettered by immigrAnts adopting a different strategy.

Strawberry

Fragaria

Living for several years and spreading by means of runners, each one tipped with a plantlet that soon takes root, a single wild strawberry plant can expand into a large bed, half-hidden in the grass of a meadow or under the trees in open woods. Clusters of white five-petaled flowers appear in late spring or early summer and are soon followed by the familiar strawberries.

Not a true berry at all, the juicy red, edible portion of a strawberry is actually a much enlarged stem end-what botanists call a receptacle-and each of the "seeds" on its surface is a separate, tiny, hard fruit. Though smaller than the cultivated kinds, wild strawberries are unrivaled for flavor and sweetness. Relished by humans for desserts and preserves, they also are avidly consumed by a wide range of wildlife, from birds to bears. Wild strawberries, a favorite of many birds, grow so close to the ground that turtles and small rodents can reach them as well.

Stress

An Animal Behavior term, this is used to describe a physiological state induced in Animals by conditions they are unable to tolerate and cope with, such as pain or overcrowding. In mild form, the changes involved help the Animal to cope but, if more extreme, they have adverse or even lethal effects.

Stressor

Any chemical, physical, or biological entity that can induce adverse effects on individuals, populations, communities, or ecosystems.

Stridulation

An Animal Behavior term, this is used to describe the method of sound production used by some Insects in which they scrape together two parts of the body, such as a leg and a wing. The structures involved may be specially adapted to form a comb and a scraper so that a stereotyped rasping sound is produced.

Strip transect method

Bird Biology Avian Conservation term.

A procedure using a strip of land, or water, of fixed direction that is sampled visually and/or aurally by an observer. Counts may be one of the following: fixed distance (width) counts limited to a strip of set width for all or specially chosen species; variable distance (width) counts, with different, species-specific widths that are determined to reflect detection attenuation; or unlimited distance counts, in which all detections are recorded regardless of distance.

Striped bass

Morone saxatilis

Nicknamed rockfish, stripers, and greenheads, striped bass have long been popular food and game fish. They are native to Atlantic waters but were introduced to the Pacific in 1886 and now thrive along the West Coast as well. The adults live in the sea but spawn in rivers and streams, where the females lay eggs by the millions and where the young remain until they are mature enough to head for the ocean. Some populations, especially in the Southeast, are landlocked in lakes and dammed rivers and so spend their entire lives in fresh water. Olive to blackish above and silvery to white below, striped bass are marked from head to tail with bold horizontal lines. On the average, adults are two feet long and weigh about 10 pounds, but individuals occasionally exceed six feet and weigh over 100 pounds.

Sturgeon

Giant, slow-moving fish armed from head to tail with rows of bony plates, sturgeons look as ancient and primitive as in fact they are. These bizarre-looking fish spend their time cruising ponderously along the bottom. Fleshy, sensitive barbels dangle from their flat, pointed snouts, helping them find small fish, crustaceans, and snails, which they suck into their mouths. Sturgeons mature slowly but are large and longlived. The white sturgeon of the Pacific Coast, our biggest kind, sometimes grows to a length of 20 feet and lives for 75 years. Some species, such as the lake sturgeon of the Great Lakes and Mississippi Valley, live in fresh water year-round. But most, such as the Atlantic sturgeon, are saltwater fish that migrate up rivers to spawn. Their eggs have long been prized for making the choicest caviar, and the smoked flesh is eaten as well. But because North American sturgeons have declined in number due to dam building, pollution, and overfishing, laws now prohibit taking them for their roe. As a result, most of the caviar consumed in this country is imported.

Style

Botany term. Female reproductive structure of a flower.

Subclimax

A stage of succession along a sere prevented from progressing to the climatic climax (i.e., the steady-state community characteristic of a particular climate) by fire, grazing, and similar factors.

Sublime

Biological Philosophy term. A habit of appreciating nature as beyond human control, immense, powerful, awe-inspiring. Associated with mountains, cataracts, the ocean, stars. The standard sources are Longinus, On the Sublime, and Edmund Burke, A Philosophical Enquiry into the Origin of Our Ideas of the Sublime and Beautiful, 1757.

Subordinacy

An Animal Behavior term, this is used in describing the position of Animals that lose in fights or defer to other individuals (see Dominance).

Subsong

An Animal Behavior term, this is used to describe a quiet, less pure and less well-organized Song that is produced by Birds, mainly early in the breeding season before they have developed their full song.

Subspecies

Sub-division of a species, members of which are able to breed with other subspecies but seldom do so because of geographical isolation. Subpopulations within a species that are distinguishable by morphological characteristics and, sometimes, by physiological or behavioral characteristics.

Succession

Replacement of populations in a habitat through a regular progression to a stable state (climax).

Every habitat, whether pond, marsh, or meadow, changes over time in a predictable, orderly sequence known as succession. At each stage the reigning species of plants and animals alter the environment, making it suitable for new species to move in. Eventually, however, a point of equilibrium is reached, and no new species are introduced. This stage, known as the climax community, is self-sustaining and remains stable-sometimes for thousands of years-until an act of man or nature upsets the balance and the cycle starts anew. A field laid bare by fire, for instance, is an open invitation to new plant life. Hardy pioneering weeds usually are first to arrive, enriching the soil and providing shelter for other seedlings. As conditions improve, shrubs begin to grow, shading out the sun-loving weeds. If conditions are right, pines may next appear, only to be replaced in time by a climax community of broadleaf trees. Ponds, too, undergo changes, as layers of debris accumulate and plants encroach from the shore. Inevitably all ponds fill in, becoming marshes and then dry land.

Succession

Biological Philosophy term. "An orderly process of community development that is reasonably directional and, therefore, predictable [that] culminates in a stabilized ecosystem” A term perhaps first used by Thomas Pownall in 1784 ... and reintroduced in 1860 by Thoreau to describe the development of pine woodlands following the logging of hardwood stands in New England and used again in 1864 by George Perkins Marsh". Succession moves toward Climax.

Sucker

Thick-lipped freshwater fish found throughout North America, suckers have protruding, underslung mouths that are adapted for sucking worms, insect larvae, and other food off the bottoms of streams and lakes. Some, such as the chubsucker, are less than a foot long, while others, including the bigmouth buffalo (the largest member of the family), can exceed three feet in length and weigh over 70 pounds. In spring the abundant white sucker and many other species migrate to streams or to shallow areas in lakes for spawning. Each female sheds thousands of eggs, which hatch in about two weeks. Despite an abundance of tiny bones, suckers are often caught for their sweet, tasty flesh.

Sulfur

An abundant, yellow, nonmetallic element, sulfur is a highly reactive substance that combines to form hundreds of compounds. Coal, oil, and natural gas all contain sulfur compounds, as do ores such as pyrite and galena. Sulfur is also present in foods such as onions and cabbage. Important industrial compounds include sulfur dioxide, a preservative and bleaching agent, and sulfuric acid, a commercial chemical. Sulfa drugs, too, are made from sulfur compounds. Texas and Louisiana are our largest sulfur producers.

Sumac

Small trees or shrubs, sumacs are fast-growing plants with long, featherlike compound leaves that turn brilliant red, orange, or purple before dropping off in the fall. Their greenish flowers are borne in large, loose spikes that are followed by dense clusters of hairy red or smooth white fruits. The fruits are eaten by many kinds of wildlife, and those of the widespread staghorn sumac, named for its velvety twigs, and California's lemonade sumac can be brewed to make a refreshing tea. Other common species include smooth sumac, a pioneer plant that is quick to take root in abandoned fields and waste places, and shining sumac, which is sometimes planted as an ornamental. Although the sumacs are related to poison ivy, most are harmless. But one, poison sumac, contains a virulent sap that causes a severe rash.

Summer

Summer is defined by convention as the whole months of June, July, and August, in the Northern Hemisphere, and the whole months of December, January, and February, in the Southern Hemisphere. The unofficial start of summer is a matter of convention. In general, seasonal changes occur earlier in coastal regions, so countries close to the oceans go for an earlier start to summer than inland ones. Summer is commonly viewed as the season with the longest (and warmest) days of the year, in which the daylight predominates, through varying degrees. In the northern latitudes, twilight is known to last at least an hour, sometimes leading to the famous season of the midnight sun near the North Pole. In most countries children are out of school during this time of year, although dates vary. Summer is also the season in which many types of vegetation are in full growth.

Sun

Our sun is the source of energy for life. Solar energy drives the climate and weather systems of our planet. The sun is a huge ball of hydrogen (72%) and helium (28%) gases. Tremendous pressure and temperatures in its inner core fuses the hydrogen nuclei and forms helium, releasing enormous amounts of energy.

This energy travels at the speed of light and reaches Earth in slightly more than 8 minutes. Earth receives only about one-billionth of the sun's energy. About 34% of the solar energy reaching the troposphere is reflected back into space by clouds, dust, chemicals. Most of the energy reaches the troposphere as visible light, infrared radiation, and a small amount of ultraviolet radiation that wasn't absorbed by the stratosphere.

This unreflected solar radiation is turned into infrared radiation, or heat. Heat-trapping gasses like water vapor, carbon dioxide, methane, nitrous oxide, and ozone affect the speed at which this radiation is returned to space. Without these gasses, known as the natural greenhouse effect, heat would immediately return to space, making it almost as cold as Mars.

Sundew

Orosera

In the sunlight, inviting droplets glisten like nectar on the leaves of sundews. But insects lured to these carnivorous plants discover too late that they have been fooled: their bodies get stuck in the gluey fluid on the tips of fine surface hairs, then nearby hairs bend in upon them to complete the trap. The sundews, which thrive in bogs and damp sandy areas, then digest their victims and so obtain the nitrogen and other nutrients that are missing from the acid soils where they grow. The roundleaf sundew is our most widespread species.

Sunfish

Named for their iridescent colors, sunfish are a group of small lake and pond fish that are native to the East but have been transplanted to the West as well. Most are deep bodied, with a conspicuous flap at the rear of each gill cover. The bluegill and the common sunfish, or pumpkinseed, are favorites with children and beginning anglers because they are easily caught with simple equipment. Also included in the large and diverse sunfish family are crappies, black bass, and pygmy sunfish.

During the breeding season the males of all species use their tails to clear space on the bottom, making circular nests in which the females lay their eggs. The males then guard the eggs and fan them with their tails to keep them free of debris until they hatch.

Sunflower

Helianthus

Beloved for their radiant yellow flower heads, sunflowers are also valued for their seeds, the oil they yield, and the tubers that some produce. A number of species are found across much of the continent, and most are easily recognized by their tall, stiff stems and showy, daisylike blooms. Three to 10 inches wide, the flower heads of the wild species are smaller than those of the cultivated sunflowers (up to 18 inches across) but are still dazzling. The common sunflower, grown by American Indians in the Southwest since about 3000 B.C., is one of the few North American natives that produces a major agricultural crop. Jerusalem artichokes, another common species, are as much as 10 feet tall and have flowers that are 2 to 4 inches wide. They are grown for their edible tubers.

Sunrise

The brilliant reds and yellows that tinge the sky at sunrise and sunset are easily explained. Red and yellow light, which have longer wavelengths than other colors, are less likely to be scattered by particles in the air (such as dust and water droplets). And since light must pass through more atmosphere-and more particles-when the sun is close to the horizon, it is the reds and yellows that we see. Spectacular sunrises and sunsets often occur after volcanic eruptions because the volcanoes spew huge amounts of dust into the air. Ash from the gigantic eruption at Krakatoa in 1883, blown by the wind, created brilliant sunsets around the world for more than a year.

Supernature, or the Supernatural

Biological Philosophy term. The action of God in the world, e.g., divine grace or help in living a good life, divine revelation, or God's telling human beings the truth about Himself and the world in the Bible, divine intervention in history to select a chosen people or redeem humanity. See Nature.

Supernormal stimulus

An Animal Behavior term, this is used to describe an artificial stimulus which is more effective in eliciting a behavior pattern than the normal stimulus found in nature. For example, many Birds will attempt to sit on a huge model egg in preference to eggs of the usual size.

Supply (Water)

The provision or storage of water, or the amount of water stored, for a house, community or region.

Surfperch

Common fish off the Pacific coast, most surfperch-true to their name-live in the surf zone. They are a great rarity among saltwater fish, for the females produce live young, giving birth to four or more offspring at a time. Remarkably, many of the tiny fry are able to mate within a day or two of their own birth. The barred surfperch, marked with golden stripes, and the walleye surfperch, steely blue with black-tipped fins, are the most abundant species.

Surgeonfish

Acanthurus

Vegetarian reef-dwellers that look as gentle as they are beautiful, the surgeonfish nevertheless carry secret weapons: built-in switchblades. Scalpel-sharp spines, sheathed in folds near the tail, can be erected when the fish are disturbed; a swipe of the tail can then inflict deep cuts on a predator or a human diver. Surgeonfish are found from the Gulf of Mexico and the Caribbean to Bermuda, and some range north along the Atlantic coast as far as New York. Also called tangs (German for "seaweed"), these thin, oval fish use their front teeth to scrape algae from rocks and coral reefs. Surgeonfish begin as colorless larvae, but many change dramatically in hue as they mature.

Surplus killing

An Animal Behavior term, this is used to describe the habit of some predators of killing prey far in excess of their requirements. They do not then attempt to eat or to hoard the excess. This seems to occur mainly in occasional individuals confronted with large numbers of easily accessible prey, for example, a Fox coming upon a Gull roost on a night too dark for them to fly off.

Survey

An enumeration or index of the number of individuals in an area from which inferences about the population can be made.

Survival

The proportion of newborn individuals alive at a given age.

Survival of the fittest

Biological Philosophy term. As the environment changes, those members of a species who, by accidental genetic variation, happen to have traits best fitted to the new environment are most likely to survive long enough to generate offspring. Illegitimately extended to human societies in Social Darwinism.

Sustainable development

Development that meets the needs of the present without compromising the ability of future generations to meet their own needs." In other words, development is essential to satisfy human needs and improve the quality of human life. At the same time, development must be based on the efficient and environmentally responsible use of all of society's scarce resources - natural, human, and economic.

Swallow

Streamlined birds with long, pointed wings, swallows are swift flyers that nimbly snap up insects in midair. In cooler weather, when insects are unavailable, tree swallows sometimes feed on berries and seeds as well. All species are social, feeding in flocks and sometimes nesting in colonies. And all are migratory; some winter in the South, but most travel thousands of miles to the tropics. Besides the purple martin, our largest swallow, seven other species breed in North America and display a variety of nesting styles. Tree holes are home to tree swallows and to the violetgreen swallows of the West, while bank swallows dig tunnels in sand banks, often in large colonies. Rough-winged swallows nest in drainpipes under bridges and in tunnels abandoned by other birds. Cup-shaped nests of mud are built by cave swallows and by the familiar, forktailed barn swallows. Cliff swallows construct gourd-shaped nests out of mud pellets, cementing them to cliffs, culverts, or buildings, including the Mission of SanJuan Capistrano in California, where the birds are famous for their predictable return each spring.

Swallowtail butterfly

Often large and dramatically patterned, swallowtail butterflies are named for the trailing extensions on their hindwings. Most of our two dozen or so species are black and yellow, blackand-white, or black and blue. Many of them look like other, foul-tasting species and so deceive predators. Their caterpillars also are protected in a number of ways. Some mimic vegetation or bird droppings, while others have large eyespots that make them appear far more fierce and formidable than they are. When disturbed, the caterpillars discharge an ill-smelling fluid from special glands near the back of the head. And those known as pipevine swallowtails feed on pungent roots that make them taste unpleasant to would-be predators who have not yet learned to avoid them by sight.

Swamp

In contrast to marshes, where grasses and reeds are the prevailing vegetation, swamps are wetlands that are dominated by trees. The constant supply of moisture in these wooded wetlands encourages the vigorous growth of many other plants as well, including shrubs, vines, epiphytes, and ferns. The kinds of trees found in swamps vary from place to place. In the Far North, for example, the most common trees are spruces, white cedars, and other conifers, while red maple is typical of swamps in the Northeast. In the Southeast bald cypresses draped with Spanish moss tower over many inland swamps, but only mangroves can survive in saltwater swamps along the coast. Thanks to the abundant moisture and lush vegetation, swamps are rich with wildlife. Insects proliferate and are consumed by countless fish, frogs, snakes, and turtles. Waterfowl of all kinds live there, and deer, raccoons, and other mammals are regular visitors. Humans have not always looked kindly on swamps. Early settlers regarded them as hindrances to travel and as breeding grounds for disease and dangerous animals, while modern developers often covet them as potential building sites. Such attitudes, however, are on the wane, and swamps are finally being appreciated as important habitats that deserve protection.

Swamp biome

A swamp is a area that features permanent inundation of large areas of land by shallow bodies of water, generally with a substantial number of islands, or dry-land protrusions. Swamps are usually regarded as including a large amount of woody vegetation. When a wetland area does not include such vegetation, it is usually termed a marsh. A mire (or quagmire) is a low-lying wetland of deep, soft soil or mud that sinks underfoot.

Swamps are generally characterized by very slow-moving waters, often rich in nutrients from decaying vegetation. They are usually associated with adjacent waterways. In some cases, rivers become swamps for a distance. Swamps are features of areas with very low relief, although they may be surrounded by mountains.

The most famous swamps in the USA are the Okefenokee and the Great Dismal Swamp. Swamps are characterized by rich biodiversity and specialized organisms. For instance, southeastern U.S. swamps, such as those mentioned above, feature trees such as the cypress, which are adapted to growing in standing water.

Swan

Cygnus

Graceful birds with white plumage and long, sinuous necks, swans are our largest waterfowl. They live on lakes, ponds, and estuaries and feed both by dipping their heads underwater to browse on aquatic plants and by grazing on vegetation along the shore. Bonded by noisy courtship rituals, swans, like geese, mate for life. They nest on huge mounds of dead plants, with both parents tending the eggs and young. Swans can be ferocious in defense of their offspring; they attack even dogs and humans who dare to venture near. The downy young, called cygnets, are brownish or gray and sometimes ride on the mother's back.

The tundra, or whistling, swan is the most abundant of the three species found in North America. It nests in the Far North and winters in marshes on the Atlantic and Pacific coasts. The trumpeter swan, named for its bugling call, lives on lakes in the Rocky Mountains and Alaska. Once endangered, it has increased in numbers in recent years. The mute swan, which, despite its name, can hiss and grunt, was introduced from Europe and is found on park ponds, especially along the East Coast and around the Great Lakes.

Sweet clover

Melilotus

On hot summer days sweet clovers fill the air with an unmistakable vanillalike aroma (it intensifies when the plants are dried). This scent alone distinguishes the sweet clovers from the true clovers. Found in waste places but also cultivated, sweet clovers produce tangles of branching stems up to 10 feet tall, covered with three-part compound leaves and topped from May to October with spires of white or yellow flowers. The plants are harvested for fodder, and a tea can be brewed from the fragrant blooms.

Sweet-fern

Comptonia peregrina

Though its foliage is fernlike, sweet-fern is in fact a flowering shrub related to the bayberry. Growing up to four feet tall, it has long, narrow leaves-dark green above and downy belowthat release a pleasant scent when crushed. Near

the tips of the branching stems are clusters of small catkins that mature into brownish fruits that resemble burrs. Sweet-fern, found in poor soils from Nova Scotia to Georgia, has long been used for home remedies and sachets.

Sweetgum

Liquidambar styraciflua

A native of moist bottom lands and swamps throughout much of the East, sweetgum is an important timber tree that yields a dark, attractive wood. It also exudes a fragrant resin that has been used for chewing gum and as an ingredient in perfumes and cosmetics. Growing as tall as 100 feet or more, the sweetgum is a handsome tree that is esteemed as an ornamental. It is easily recognized by its five- or seven-pointed, starshaped leaves, which in autumn turn a brilliant red; the corky wings that form along its twigs; and the spiny, spherical fruits that dangle from the branches all winter long.

Swift

Tireless, thoroughgoing aerialists, the fast-flying swifts spend more time on the wing than any other land birds-catching insects, drinking, courting, even mating while in the air. When not in flight, they cling to vertical surfaces with their sharp claws, since their tiny feet are not suited for perching. Widespread species include the chimney swift, a small, dark gray bird that nests in chimneys and hollow trees east of the Rockies. In the West the white-throated swift is often seen darting into rocky crevices, where large numbers roost at dusk. The black swift, also a westerner, often nests behind waterfalls.

Swordfish

Xiphias gladius

A magnificent warrior of the open sea, the swordfish is enormous in size, spirit, and stamina. It is streamlined from the tip of its long, pointed snout to the sleek arc of its tail and easily gives chase to all manner of sea life. Up to 15 feet long and weighing as much as 1,000 pounds, swordfish have been clocked at speeds of 60 miles per hour. While they have been known to charge boats and occasionally puncture their hulls, they are more likely to use their strong, sharp-edged swords (which may be five feet long) for decimating schools of mackerel and other small fish. Swordfish bills have even been found embedded in whale blubber-another testament to the creature's pluck. Highly popular game and commercial fish, swordfish live in temperate to tropical waters of the Atlantic and Pacific oceans.

Sycamore

Platanus

The most massive deciduous tree on the continent-the American sycamore-occasionally reaches heights of 170 feet or more, with a trunk 14 feet in diameter. Its western relatives, the California and Arizona sycamores, are more modest in size but, at up to 100 feet, are still among the tallest trees in the valleys and canyons that they favor. Sycamores are easily distinguished by their unique bark-it flakes away in jigsaw-puzzle patterns, exposing the ghostly pale underbark and giving the trunks a mottled appearance. Also distinctive are the sycamores' fruits, which are tightly packed into balls that commonly hang from bare branches all winter long. In the wild the giant trees flourish beside streams, while in cities the species known as the London plane tree is often planted along streets.

Symbiosis

An Animal Behavior term used in North America for associations between species, including Parasitism and Commensalism, but limited in Europe to associations where both species benefit (Mutualism).

Sympatric

Occurring in the same place, usually referring to areas of overlap in species distributions.

Synchrony

An Animal Behavior term, this is used to describe the occurrence of the same behavior in different individuals at the same time. Synchrony may occur because both are responding to external cues, such as daylength or the presence of a predator, but sometimes it also arises through Social facilitation.

Syntopic

Pertaining to populations or species that occupy the same macrohabitat.

Syzygy

The arrangement of three celestial bodies in a straight line in the heavens is known as syzygy. The sun, moon, and earth, for example, line up every two weeks during the new moon and the full moon. Since ancient times, many strange phenomena have been attributed to syzygy: astrologers place special significance on the alignment of planets, and a recent theory speculates that the syzygy of Jupiter, the earth, and the sun can cause volcanic eruptions and other cataclysms.

Taiga

Just south of the arctic tundra, a vast forest of spruces, firs, and other conifers encircles the globe. Known by its Russian name, taiga, the forest is also called the great north woods. It occupies an area that was scoured by glaciers during the last ice age and now is dotted with hundreds of bogs and lakes and crisscrossed by networks of streams. During the long, cold winters, the thin layer of surface soil is frozen solid, and summers are just warm enough to turn it into sodden muck. Despite such harsh conditions, the evergreens thrive; flocks of crossbills, grosbeaks, and other birds feast on the plentiful supply of conifer seeds; and lynx, moose, and other mammals eke out an existence in this wooded wilderness.

Taiga biome

Taiga is the Russian word for forest and is the largest biome in the world. It stretches over Eurasia and North America. The taiga is located near the top of the world, just below the tundra biome. The winters in the taiga are very cold with only snowfall. The summers are warm, rainy, and humid. A lot of coniferous trees grow in the taiga. The taiga is also known as the boreal forest. Did you know that Boreal was the Greek goddess of the North Wind? The taiga is the biome of the needleleaf forest. Living in the taiga is cold and lonely. Coldness and food shortages make things very difficult, mostly in the winter. Some of the animals in the taiga hibernate in the winter, some fly south if they can, while some just cooperate with the environment, which is very difficult.

The taiga doesn't have as many plant and animal species as the tropical or the deciduous forest biomes. It does have millions of insects in the summertime. Birds migrate there every year to nest and feed.

Here is some information about the temperatures and weather in the taiga. The average temperature is below freezing for six months out of the year. The winter temperature range is -65 to 30° F. The winters, as you can see, are really cold, with lots of snow.

Temperature range in the summer gets as low as 20° F. The high in summer can be 70° F. The summers are mostly warm, rainy and humid. They are also very short with about 50 to 100 frost free days. The total precipitation in a year is 12 - 33 in. The forms the precipitation comes in are rain, snow and dew. Most of the precipitation in the taiga falls as rain in the summer.

The main seasons in the taiga are winter and summer. The spring and autumn are so short, you hardly know they exist. It is either hot and humid or very cold in the taiga.

There are not a lot of species of plants in the taiga because of the harsh conditions. Not many plants can survive the extreme cold of the taiga winter. There are some lichens and mosses, but most plants are coniferous trees like pine, hemlock and fir. Coniferous trees are also known as evergreens. They have long, thin waxy needles. The wax gives them some protection from freezing temperatures and from drying out. Evergreens don't loose their leaves in the winter like deciduous trees. They keep their needles all year long. This is so they can start photosynthesis as soon as the weather gets warm. The dark color of evergreen needles allows them to absorb heat from the sun and also helps them start photosynthesis early.

Evergreens in the taiga tend to be thin and grow close together. This gives them protection from the cold and wind. Evergreens also are usually shaped like an upside down cone to protects the branches from breaking under the weight of all that snow. The snow slides right off the slanted branches.

The taiga is susceptible to many wildfires. Trees have adapted by growing thick bark. The fires will burn away the upper canopy of the trees and let sunlight reach the ground. New plants will grow and provide food for animals that once could not live there because there were only evergreen trees.

Animals of the taiga tend to be predators like the fox and wolf and members of the weasel family like the wolverine, minks and ermine. They hunt herbivores like red squirrels and voles. Red deer, elk, and moose can be found in regions of the taiga where more deciduous trees grow.

Many insect eating birds come to the taiga to breed. They leave when the breeding season is over. Seed eaters like finches and sparrows, and omnivorous birds like crows stay all year long.

Take

Endangered and Threatened species term.

From Section 3(18) of the Federal Endangered Species Act: "The term 'take' means to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct."

Talc

The softest mineral known, talc is also called soapstone because of its smooth, greasy feel. It ranges from whitish green to gray in color and is found in fibrous layers in certain metamorphic rocks. Talc is most familiar as the basic ingredient in talcum powder, but since antiquity it has been quarried for a wide range of other uses. The Assyrians and Egyptians carved talc into seals and amulets, while today it is widely used in industry as a lubricant and an electrical insulator and is an ingredient in rubber and paper. Chemically unreactive, talc is also ground for filler in soap, crayons, paint, and other products. Vermont, New York, Texas, and Montana are among the leading talc producers, and large deposits occur in parts of Canada.

Talus

The accumulation of rock fragments that piles up at the foot of a cliff or, in some areas, a mountain slope is known as talus. The buildup of debris is slow but steady, often block by block, as pieces of rock break from outcrops near the top of the cliff or slope. While weathering and erosion start the process, gravity completes it, pulling loosened rocks from the faces of cliffs or down mountainsides. Since the rocks often break into smaller pieces along the way, talus ranges from gravel-size pebbles to enormous boulders. In certain places, particularly the arid areas of the West, rock slides produce much of the talus found at the base of mountain slopes, where it presents a daunting challenge to hikers.

Tamarack

See Larch.

Tanager

Piranga

Among the most brightly colored North American birds are our four species of tanagers, which, like their equally colorful tropical relatives, are creatures of the forest. The scarlet tanager, so brilliant that it is sometimes called the firebird, lives in deciduous forests in the East, while the summer tanager prefers oak and pineoak woodlands in the South. Wooded areas in the mountainous Southwest are home to the hepatic tanager, and the western tanager-the only species in which the males are mainly yellow rather than red-nests in western forests of oaks or pines.

During the breeding season birds of all four species build cup-shaped nests of twigs and grass well out from the trunk on horizontal branches in trees. The greenish or yellowish females alone incubate their clutches of three to five eggs, but both parents share in the care and feeding of the young, with insects forming the bulk of the diet. As winter approaches, male scarlet and western tanagers acquire a duller plumage similar to that of the females, and all species migrate south.

Tanoak

Lithocarpus densiflorus

Intermediate between chestnuts and oaks, the tanoak is a tree that produces erect spikes of flowers resembling those of the chestnuts, but bears acorns exactly like those of the oaks. On mountain slopes in California and southern Oregon, this handsome evergreen sometimes attains a height of 100 feet or more, though at high altitudes it commonly grows as a shrub. While the tanoak is seldom harvested for lumber - its reddish -brown wood tends to split and warp as it dries-Ieatherworkers at one time gathered its tannin-rich bark for tanning hides.

Tansy

Tanacetum vulgare

A garden escape that thrives in fields and along roadsides throughout most of North America, tansy is a vigorous herb up to four feet tall with finely divided, dark green ferny foliage. It is sometimes known as bitter-buttons, an allusion both to its yellow buttonlike flower heads, which are borne in dense, flat-topped clusters, and to the intense aroma and bitter flavor of the entire plant. The strongly scented leaves were once used to flavor omelettes and sausages and, considered a natural insect repellent, were rubbed on meat to discourage flies. Tansy also has a long tradition of use in folk medicine, with its supposed powers ranging from the prevention of miscarriage to the cure of kidney disorders.

Tarantula

Big and hairy, with leg spans of five inches or more, tarantulas are our largest spiders. Most of them live in the Southwest, where they spend the daylight hours hiding in burrows and other dark places. At night, however, they roam about and hunt for insects or, in the case of the larger species, mice, lizards, and other small vertebrates. The tarantulas' eyesight is poor and they cannot hear, but their hairs are sensitive and detect vibrations from prey and foe alike. Although the males have relatively short life spans, females have been known to live for 20 years or more. Basically reclusive and seldom aggressive, tarantulas can nevertheless deliver a mildly poisonous, though very painful, bite.

Tar pit

Commonly known as the La Brea Tar Pits, these unusual pools of thick natural asphalt located within the city limits of Los Angeles, California, are a treasure trove of animal fossils. The tar pits, formed by seepage from underground petroleum deposits some 20,000 years ago, served for millennia as wildlife death traps. Lured by inviting pools of water that collected on the surface, thirsty mammals, birds, and other creatures became mired in the deadly tar, sinking slowly to their deaths. Since 1906, when an ancient bear was exhumed, the remains of more than a million creatures-including mastodons, mammoths, saber-toothed cats, camels, sloths, bison, and birds-have been recovered from this sticky mass grave. The tar pits are part of Hancock Park, and the fossils are on view in a nearby museum.

Tarpon

Megalops atlanticus

A popular game fish along the Atlantic Coast, especially south of Cape Hatteras, and in the Gulf of Mexico, tarpons are well-known for their fighting qualities. When hooked, a tarpon immediately begins a series of spectacular twisting leaps, presenting a thrill and challenge to sport fishermen. Although these huge relatives of herrings can reach a length of eight feet and weigh 350 pounds, they are seldom taken for food: their coarse, oily flesh is considered poor eating. Their silvery scales, however, as big as silver dollars, are used in jewelry and other decorative work. Extremely prolific, the females lay as many as 12 million eggs at a time. The hatchlings begin life as transparent, ribbonlike larvae that look nothing like the adults.

Tarsal gland

Tufted, discoloured hair patches found between the hock and the hoof on the inside of each hind leg in deer. These areas are a source of scent used for communication. Also Metatarsal gland.

Taxis

An Animal Behavior term, this is used to describe a movement in which an Animal orients its body with respect to a stimulus, perhaps moving toward or away from it or taking a particular angle to it as in compass orientation.

Taxonomy

The science of classification, assigning names, assigning living things to the proper genus and species. See Classification.

Teal

The small, fast-flying teals are ducks that prefer the shallow water of marshes and weedy ponds, where they can easily dip down to feed on aquatic plants and, occasionally, snails and other small animals. Each year large numbers gather in the prairie pothole country of the West and build their nests in dense vegetation near shore. The males depart soon after mating, leaving the females to incubate the eggs and tend the ducklings on their own. The green-winged teal, one of the commoner species, presents a spectacular show during migration: huge flocks fly in formation with the precision of well-trained drill teams as they head for the southern states or Mexico. Often feeding on mudflats, the green-wing also forages in fields and woodlands. Its close relative, the bluewinged teal, flies farther south and is more aquatic. Aside from the colors of their wing patches, these two species can be identified by the males' head markings: green-wings have green ear patches, while white crescents mark the cheeks of blue-wings.

Teasel

Dipsacus

The sharp spines that arm the leaves, stems, and flower heads of the teasels make them difficult to handle but extremely useful to weavers: the pincushionlike flower heads of one species, fuller's teasel, have been used since ancient times to tease, or to raise the nap on, newly woven woolens. Flourishing on wastelands, fields, and roadsides across much of North America, teasels grow up to six feet tall and produce lavender flowers. Their paired upper leaves are joined at their bases to form little cups around the stems. Early herbalists valued the rainwater that collects in these basins, using it to cool inflamed eyes and to "render the face fair.”

Teleology

Biological Philosophy term. Seeing natural things in terms of purpose: eyes are for seeing, wings are for flying. It was one of the major efforts of science to break this habit in order to clear the way for deeper insights into nature, specifically into evolution.

Temperature (Weather)

In meteorological terms, temperature refers to the degree of heat or cold of the air as measured by a thermometer.

Template

An Animal Behavior term, this is used to describe a suggested sensory or neural recognition system that guides learning of Song in young Birds and ensures that they learn only those sounds appropriate to their species.

Tendril

The slender, modified leaf or stem structure which assists climbing in some plants.

Tent caterpillar

Malacosoma

The larvae of medium-size brownish moths, tent caterpillars are destructive pests that cause serious damage to forest and orchard trees. In early spring, just as the leaves begin to unfurl, masses of voracious, hairy caterpillars hatch from egg masses that were laid on twigs the previous summer. The larvae of many species spin communal silken nests in the crotches of branches and, on their forays from these protective tentlike structures, sometimes completely defoliate the trees in which they live.

Termite

Among the most destructive insects, termites are dreaded by home owners because of their remarkable ability to eat wood. Although they are more closely related to cockroaches, termites are sometimes called white ants because they look like pallid versions of those insects. They also resemble ants in behavior, for they are social creatures that live in huge, highly organized colonies. While some live in fallen logs or the wood of buildings, most live in the ground and tunnel to their food source. At the heart of each colony is the royal couple, a king and an oversize, egg-laying queen. Soldier termites defend the colony, and legions of blind workers gather food, build tunnels, and care for the young. In spring, swarms of winged termites leave their nests and fly off to start new colonies.

Tern

Graceful relatives of the gulls, terns are slender, long-winged birds that live along seacoasts and near inland waters. They are often seen hovering in midair, poised to plunge headfirst into the water to grasp fish and other prey in their long, pointed bills. Most terns have deeply forked tails and range from 8 to 22 inches in length. While many have white bodies and black caps, some, such as the black tern of inland marshes, are largely black. Terns nest in crowded, noisy colonies, placing their eggs in shallow scrapes in the sand, or on flimsy platforms of marsh grass. Both parents incubate the eggs and feed the downy young.

Widespread species include the common tern, a swift, buoyant bird of inland lakes and coastal beaches, and Forster's tern, which looks similar but favors marshlands over seashores. Another, the arctic tern, is famous for its longdistance migrations of up to 22,000 miles a year. The least tern, our smallest species, nests on sandy beaches and is now endangered due to coastal development. Terns are sometimes called sea swallows because of their forked tails. Arctic terns breed in the Far North but travel all the way to Antarctic waters for the winter. Royal terns can tolerate close quarters, nesting just inches from their neighbors; many thousands of pairs often manage to squeeze onto a small, sandy island.

Terrapin Malaclemys terrapin

A turtle of salt marshes and estuaries along the East Coast from Cape Cod to the Gulf of Mexico, the diamondback terrapin is named for the deeply incised rings on its upper shell, which is four to seven inches long. The diamondback often floats just below the surface of the water with only the tip of its snout exposed. It feeds on snails, crabs, and plant shoots. Several times a year, females leave the water to dig nests in sandy banks or dunes and lay clutches of 4 to 18 eggs. When the young hatch, they immediately scramble down to the marsh to take cover in dense vegetation. Once hunted to near extinction for their tasty meat, terrapins are also threatened by faxes, gulls, and other predators. Diamondback terrapins feed by day and bury themselves in the mud at night.

Territory

Animals of many kinds stake out and defend territories-areas of living space from which they exclude others of their kind as they vie for food or mates. These areas range in size from a few square inches to many square miles and may be used for feeding, mating, nesting, or all three. Pairs of golden eagles, for instance, lay claim to territories of 35 square miles or more and vigorously defend them against any other golden eagles that dare to venture in. While most birds proclaim their territories with song, foxes, wolves, and other mammals use scent or urine to mark the boundaries of their private domains and discourage others. Any area defended by one or more individuals against intrusion by others of the same or different species.

Territory

An Animal Behavior term, this is used to describe an area occupied by one or more individuals of a species and defended against the intrusions of others (see also Home Range).

Territory-mapping

Bird Biology Avian Conservation term.

See Spot-mapping method.

Thallus

Unspecialized vegetative body of a lower plant.

Thermal

When sunlight heats a patch of open ground, the air above it also becomes heated and begins to rise, creating a column of ascending warm air called a thermal. The air cools as it rises, and water vapor contained in the thermal eventually condenses, becoming visible as a puffy cumulus cloud. Hawks and other birds often take advantage of thermals to soar high in the sky in their search for prey.

Thistle

The tall thistle of the eastern and central states, with stems as much as 12 feet high, and the shorter pasture thistle, with fragrant magenta flower heads up to three inches across, are just two of our many native thistles. But the ones that most commonly infest fields and roadsides are a couple that arrived as stowaways in seeds shipped from Europe: the bull thistle and the misnamed Canada thistle. Both have spiny leaves and prickly flowers in shades of pink and purple. The tufts of silky threads on the fruits, which help them parachute to new areas, are avidly collected by goldfinches, who line their nests with thistledown. In the past, herbalists used thistles to treat intestinal and urinary problems, and thistle tonic was popularly used as a pick-me-up.

Thorax

Middle section of an insect's body.

Thornapple

See Jimsonweed.

Thrasher

Long-tailed birds that nest in low thickets and forage on the ground, thrashers nevertheless announce their presence with loud songs. Though they are less talented as mimics than their cousins the catbird and the mockingbird, their warbled melodies are just as sweet. Ranging from the East Coast to the Rockies, the brown thrasher is the most widespread member of the group. Brown above with a pale, streaked breast, this secretive bird digs for worms and insects under the cover of dense shrubs but sings from the highest treetops. Our other thrashers are birds of the West. The curve-billed thrasher, for example, is common from Texas to Arizona and nests amid the protective spines of cholla cacti. The sage thrasher, a smaller version of the brown thrasher, builds its sturdy, cup-shaped nest in sagebrush thickets.

Threat

An Animal Behavior term, this is used to describe a behavior shown in Agonistic situations which signals that the Animal may attack. DominAnts may threaten rivals who then withdraw, or an individual in a conflict between attack and escape may threaten instead of performing either of these actions.

Threatened

Endangered and Threatened species term.

The classification provided to an animal or plant likely to become endangered within the foreseeable future throughout all or a significant portion of its range.

Thrips

Some 600 species of thrips are found in North America, but most of these insects are so tiny that they are visible only as little black specks moving about on leaves and flowers. The banded thrips are beneficial because they feed on such pests as mites and aphids. Most other kinds, however, are pests that suck the sap of garden flowers, grains, onions, pears, and other plants and often spread diseases.

Thrush

Outstanding songsters, the thrushes produce clear, flutelike notes that carry long distances through the woodlands, their favored habitat. One species, the hermit thrush, is considered by many to have the loveliest song of any North American bird. Mainly brown with spotted or speckled breasts, the thrushes are insect eaters that spend much of their time searching for food in the leaf litter on the forest floor. But all add fruit to their diet, especially during the fall migration and in winter. The females lay their distinctive blue eggs (spotted in some species, unspotted in others) in sturdy nests built of twigs, grass, and dead leaves and usually reinforced with mud. Most spotted thrushes, including the familiar wood thrush, the veery, Swainson's thrush, and the gray-cheeked thrush, winter in the tropics. The hermit thrush, however, nests in boreal and mountain forests and winters in the southern states. The varied thrush, an orange-breasted bird, lives year-round in western coniferous forests.

Thunderstorm

Thunderstorms are punctuated by bolts of lightning that streak across the darkened sky. It is hardly surprising that thunderstorms were once thought to be caused by angry gods, for their violent winds, torrential rains, flashes of lightning, and roaring thunder do indeed seem like celestial temper tantrums. Typically, however, a summer thunderstorm begins calmly enough, with a mass of warm, moist air rising skyward and cooling rapidly. The moisture condenses, forming huge, threatening clouds whose inner turbulence results in the buildup of electrical charges. When the charges become strong enough, they are released as bolts of lightning, and the blazing heat of the lightning causes the surrounding air to expand with tremendous force, creating the racket that we call thunder. Drenching rain follows, and in some cases thunderstorms produce hail and tornadoes as well.

Thwarting

An Animal Behavior term, this is used to describe the situation where an Animal is stopped from performing a behavior pattern by some external barrier or the absence of the expected stimulus. In such circumstances, as in Conflict, Animals may perform Displacement activities.

Tick

Relatives of mites and spiders, ticks are tiny parasites that attach themselves to the skin of animals or humans and gorge on their blood. They are found on shrubs and other vegetation, where they wait for prospective hosts to pass by. Once attached, a tick is tenacious and hard to remove because the entire head is embedded under the skin. Some species of these minuscule pests transmit serious illnesses, including Lyme disease, tularemia, and Rocky Mountain spotted fever.

Tickseed

Coreopsis

Little flat fruits, each with two short bristles, give the tickseeds their name. (Even the scientific name means "buglike.") But the most distinctive feature of these plants is their bright, golden flowers. One to three inches across, they usually consist of eight petallike rays with notched tips, surrounding a brown or purplish center. North America is home to many tickseeds, including one, the giant coreopsis of coastal California, that grows as a small tree up to 10 feet tall.

Tidal wave

See Tsunami.

Tidepool

When the ocean's tide recedes, isolated pockets of water-tidepools-are left behind in natural basins among the rocks. These rich and picturesque habitats usually teem with an amazing array of sea life, from sponges and sea stars to periwinkles and rubbery-fronded algae. Although their waters seem tranquil and protected, tidepools are in fact a demanding environment in which only the hardiest of creatures can survive. Alternately drenched by high tide and then partially drained when the tide goes out, they can be as warm as bathwater in summer and icy cold in winter. Beneath the hot sun evaporation sometimes makes their water unbearably salty, while sudden downpours can make it too dilute for most creatures to endure. Yet many of them do survive, making tidepools fascinating places to explore.

Tiger beetle

Slender, long-legged insects with bulging eyes, tiger beetles are named for their predaceous way of life. They are frequently spotted on sandy tracts as they await passing insects, which they seize in their sickle-shaped jaws. The larvae also are hunters; lurking at the top of deep vertical burrows, they are quick to snatch unwary passersby. Because many species are resplendent in iridescent blue or green, they are popular with collectors, but swift runners and fliers, tiger beetles are a challenge to catch.

Tilefish

Deep-bodied fish with blunt snouts, tilefish have fleshy triangular flaps on top of their heads and dorsal fins that extend along almost the full length of the back. They live in deep, warm waters near the edge of the continental shelf and forage on the bottom for crabs, mollusks, and other invertebrates. Our best-known species is the Atlantic tilefish, which can reach a length of three feet and weigh more than 30 pounds. First discovered in great numbers in 1879, the fish suddenly-and mysteriously-began dying by the millions three years later. Subsequently it staged a slow comeback, and the mild-flavored fish is now commercially harvested once more.

Tine

A point or branch of an antler.

Titmouse

Small, stocky birds that are equally at home in woodlands or cultivated lawns and gardens, titmice frequently visit feeders and commonly nest in birdhouses. Whether breeding in tree cavities or man-made shelters, the crested songsters raise broods of up to eight young. In winter these nonmigratory birds, relatives of chickadees, travel in small groups as they search for insects, fruit, and seeds. The tufted titmouse, the most familiar of our species, prefers eastern forests, while the plain titmouse favors oak, pinyon, and juniper woodlands in the West. The Southwest is home to the bridled titmouse; the most distinctive of these predominantly gray birds, it has a black-and-white facial pattern that resembles a horse's bridle. Tufted titmice, active, gregarious birds, are familiar visitors at feeders from Michigan to New England throughout the winter months.

Toad

Unlike their mainly aquatic cousins the frogs, toads are amphibians that spend most of their lives on dry land. They are also stouter than frogs and can afford to be more sluggish as well, since their tough, warty skin secretes a poison that deters predators.

Toads have long, sticky tongues that can dart out and back instantly, zapping insects and other small prey. In spring males call out to females and mate with them in pools of rainwater. The eggs, contained in long strings of jelly, hatch into aquatic tadpoles that eventually metamorphose into adult toads. North American species range in size from the one-inch-long oak toad of the Southeast to the nine-inch-long marine toad of Texas and South Florida, which is big enough to prey on mice. Much more widespread are the American toad and the common, or Woodhouse's, toad, both the size of a human fist. Smaller and more secretive are the spadefoot toads, which spend most of the daylight hours buried in the soil. Toads, though oft maligned, are useful to gardeners. They use their sticky tongues to snap up insects and, because of their enormous appetites, provide a natural means of pest control. It has been estimated that a toad can eat 200 insects in a single night.

Toadfish

At least as homely as their namesake, toadfish have broad, flattened heads and wide, gaping mouths and make occasional croaking sounds. Most are marine fish about one foot long that cruise the bottom in search of mollusks, crustaceans, and small fish, which they snap up in powerful jaws lined with sharp teeth. Some kinds, called midshipmen, are ornamented on their sides with rows of light-producing organs that suggest the portholes of ships lit up at night.

Toadstool

See Mushroom.

Tornado

Rotating columns of air several hundred metres in diameter that whirl destructively at speeds of up to 800 kilometres per hour, and are usually accompanied by a funnel-shaped cloud. As terrifying as they are short-lived, tornadoes are among the most destructive storms. No one knows exactly how these so-called twisters develop, but it is known that they occur only when a mass of cool, dry air overruns warm, humid air, producing thunderstorms and extremely turbulent wind conditions. A funnel of spinning air develops on the underside of a cloud, lengthening into a slender column that rises and falls in the air and threatens to touch ground-and once it does touch, the havoc begins. Roaring like a freight train and whirling at up to 300 miles an hour, the deadly column of wind and debris becomes a violent engine of destruction that uproots trees, hurls huge objects through the air, and flattens entire towns. As the twister passes over buildings, low pressure inside the funnel causes them literally to explode. Unlike hurricanes, which can last for days, tornadoes are usually over in a few minutes to an hour, and their paths of devastation are relatively short and narrow. One notable exception occurred in 1925, when a giant tornado roared some 220 miles through the Midwest, killing nearly 700 people. The Midwest is, in fact, the world's most tornado-prone area. Here enormous cold air masses from Canada collide with warm, moist air from the Gulf of Mexico, creating ideal conditions for major twisters.

Tortoise

Gopherus

Our three native tortoises are land-dwelling turtles adapted for digging in the soil. Equipped with stumpy, elephantine hind limbs and heavily scaled forelegs that are flattened for scooping sand, they excavate long tunnels with large chambers at the end. These burrows may house one tortoise or many, and the turtles may even share their quarters with an assortment of other animals, including opossums, raccoons, and snakes. Tortoises also dig shorter, temporary tunnels, which provide refuge from heat, drought, or cold. Famous for their lumbering gait, tortoises emerge from their burrows by day to eat grass, leaves, and other vegetation. If threatened, they retreat into their high-domed shells-a defense that has not prevented one species, the desert tortoise of the Southwest, from becoming endangered. Our other species are the gopher tortoise, found in the Southeast, and Berlandier's tortoise of southern Texas.

Touch-me-not

Impatiens

Touch the ripe seed capsules of these wild annuals and you will discover the secret of their name: the pods burst apart on contact and scatter their seeds far and wide. Common in moist woodlands and ravines throughout North America, touch-me-nots grow up to eight feet tall on thick, succulent stems. Also known as jewelweeds, they bear spurred orange or yellow flowers that dangle like little gems from the ends of delicate stalks. The seeds of the touch-menots have a pleasant nutty flavor, and the plants' juice, rubbed on the skin, is said to relieve the miseries of athlete's foot and poison ivy.

Towhee

Pipilo

Long-tailed, sparrowlike birds, towhees are ground foragers that spend most of their time in the underbrush noisily scratching for insects and seeds and kicking up dirt and dry leaves in the process. They also conceal their cup-shaped nests close to the ground and lay clutches of two to six speckled eggs. Several towhees are native to North America, but only the rufous-sided towhee breeds in both the East and the West. Its song is unmistakable, for this rusty-flanked bird trills a distinct drink-your-tea. Common western species include the canyon and the California towhees, muted brown birds found in suburban shrubbery and chaparral in parts of the Southwest and along the coast of California; and the green-tailed towhee, a highly migratory bird of western mountains.

Toxic Substances (Water)

Substances that have or may have an immediate or long-term harmful effect on the environment or human health. Toxic substances from industrial and agricultural activities often enter water and have been linked to health problems in animals and humans.

Tracks

Hoofprints etched neatly in the mud beside a stream, or a dotted line of little round impressions in the snow-signs such as these are often all we see of the wild animals that live around us. Unlike birds, squirrels, and domestic animals, which are accustomed to humans and are active during the day, most of our wild neighbors are shy and nocturnal - the events of their lives hidden under the cover of darkness. When dawn arrives, these elusive creatures return to their hiding places. But they leave behind tracks and other signs that offer clues to what they are and what they have been doing. For those who know how to read them, tracks tell tales-from the simple record of a deer walking to a pond for a drink, to dramatic evidence of life-and-death struggles between predator and prey. One might, for example, make a revealing series of discoveries while walking through a snowy field: first, a set of tracks left by a creature whose larger hind feet landed in front of the smaller forefeet-the sure sign of a bounding gait. Since the tracks in this case are too large for a squirrel, one might reasonably conclude that they were made by a cottontail.

Farther along, the tracks abruptly change direction and are spaced farther apart, indicating that the rabbit has reacted to something and increased its speed. Its tracks are then joined by others-the larger, four-toed footprints typical of a feline or canine predator. The presence of claw marks on the toes rules out a bobcat or other member of the cat family (their claws are retracted when they run), and the tracks are too large for a fox. So they must have been left by a dog, a wolf, or a coyote. At any rate, a chase was obviously in progress. Some distance down the trail the suspense is ended at a patch of snow disturbed by a scuffle and reddened by drops of blood. From there the tracks of only one animal continue-those of the four-toed hunter. Just as the tracks of dogs, foxes, wolves, and coyotes-all canines-are similar to each other, those of other kinds of animals show resemblances as well. Deer, elk, caribou and mountain sheep, for example, all leave the two-part imprints of cloven hooves, and the tracks of most birds show three narrow toes in front and one in the rear. Muskrats, marmots, opossums, and raccoons leave tracks that look like little five-fingered handprints. Beavers do too, except that their hind feet are webbed, an unmistakable clue that distinguishes their tracks from the others. Bounding tracks, like those of rabbits and hares, with the footprints of the larger hind feet ahead of the smaller forefeet, are also typical of squirrels and several kinds of mice. In this case the size of the tracks is an important clue to the animal's identity. Besides birds and mammals, a host of other creatures leave tracks. Snakes glide along the banks of streams or "side-wind" through desert sand, and sea turtles lumber across beaches to lay their eggs. Even invertebrates such as beetles and millipedes make methodical little trails in the sand, and marine snails trace unbroken lines through the mud at low tide. Tracks are not the only signs that animals leave behind. The shape and size of droppings, for example, often reveal what creature made them, as well as what was eaten. Feeding signs also tell tales: the heaps of pine-cone fragments left by red squirrels at their favorite dining sites, for example, or rotting logs tom open by skunks. Many other c1ues-a bed of flattened grass where a deer has spent the night, tender twigs nipped off by a rabbit, and a gnawed, pointed stump left by a beaver that has felled a tree-all tell us something about the kinds of creatures that visited a place, as well as what they did. Because we see them so rarely, we are apt to assume that many animals-especially nocturnal mammals-are simply not there. But tracks remind us that these secretive creatures are indeed present, and often abundant, and that they are as much a part of the wildlife around us as the birds and squirrels we see by day.

Tradition

An Animal Behavior term, this is used to describe a behavior complex shared by individuals in a population and passed from one generation to the next through individuals learning from each other.

Tragus

Pointed inner ear outgrowth found in some bat species.

Trail following

An Animal Behavior term, this is used to describe a response found in certain species, especially Ants, in which workers lay Pheromone trails from the nest to sources of food, and other workers are able to reach the food simply by following the trail.

Trailing arbutus

Epigaea repens

Nestled amid oval evergreen leaves, the nosegays of fragrant white or pink blooms on trailing arbutus make their first appearance in March and were traditional heralds of spring until overpicking eliminated the plant in many areas. As its name suggests, trailing arbutus is a creeper that hugs the ground, especially on acid soils in northeastern and middle Atlantic woodlands. This diminutive relative of mountain laurel and rhododendron, also known as mayflower, is now protected by law in many places and is honored as the state flower of Massachusetts.

Transect

Bird Biology Avian Conservation term.

A cross section of an area along which the observer moves in a given direction (see Line transect, Point transect, Strip transect method).

Transportation (Industry)

The transportation industry comprises all businesses involved in conveying people or goods from one point to another by way of air, land or water.

Trapdoor spider

These close relatives of tarantulas live in vertical tunnels that they dig with toothlike spines on their jaws. Lining the burrow with waterproof silk and topping it with a silk-hinged lid, a trapdoor spider creates an ambush site, a nursery, and a fortress all in one. When it senses the vibrations of a passing insect, the spider rushes out to snatch its prey. The female's several hundred eggs hatch in the burrow, where the spiderlings spend most of the first year of their lives. When danger threatens-frequently in the form of parasitic wasps-the adult simply braces itself against the tunnel walls and holds the trapdoor shut.

Treatment (Water)

The treatment of wastewater or contaminated water using chemical, physical or biological agents to make it safe for drinking and other uses.

Tree

5,000 years of age. But while these record holders boast superlatives, our lesser trees likewise are tremendously varied and intriguing. Needles and leaves, cones and flowers Trees are typically defined as woody perennial plants, at least 15 feet tall, that have a single main stem. They are further divided into two large groups: broad-leaved trees and conifers. Oaks, maples, and chestnuts are familiar examples of broad-leaved trees, which are also called deciduous since most drop their leaves in autumn. Some of the conifers, such as spruces and firs, have slender needlelike leaves, while others-cedars, for example-have scaly foliage. Because most conifers stay green all year, ever green is commonly used as a synonym - though a few drop their needles in the fall, just as hollies and some other broad-leaved trees retain their foliage year-round.

An additional difference is in reproduction: most broad-leaved trees reproduce by means of flowers, whereas conifers bear their seeds in woody cones. Some flowering trees, such as chestnuts and magnolias, produce conspicuous, showy blossoms that fill the air with fragrance. But on many others, such as oaks and elms, the flowers lack petals or sepals and are so tiny that they are easily overlooked. Even when a tree is growing most vigorously, the bulk of the wood in its trunk and branches is already dead. Nonetheless, a tree is a highly efficient pump, transporting many gallons of water from soil to leaves every day. At the center of the trunk is the heartwood, which supports the tree as it grows up toward the sun. Sapwood encircles this core and is filled with tiny tubes through which water and dissolved minerals travel up from the roots. Beneath the bark (the outer coat that protects the tree from injury) is a thin layer of living cells that produce the growth rings we see on cut trunks. Here too is another set of tubes that transport food from the leaves to all parts of the plant.

A tree's roots, of course, are fundamental to its survival, for they not only collect water and nutrients but also anchor the plant in the soil. Some penetrate deep into the earth-a mesquite's roots may reach depths of 80 feet-but as a rule, they run within the top few feet of soil. Tiny hairs near the growing tips of the roots take in the water that passes up through the trunk and into the leaves. The leaves (including those of the conifers) are highly productive factories: they collect solar energy, using it to convert water and carbon dioxide into the energy-rich sugars that fuel the tree's growth. An important by-product of this process, known as photosynthesis, is oxygenwhich all living things require. Newsprint, turpentine, lumber, cherries, medicines, and more-life as we know it would be unthinkable without these and hundreds of other products from trees. But just as important is their environmental impact. Water evaporates from their leaves, cooling and humidifying the air. The leaves work as filters, too, helping to cleanse the air of pollutants. Trees also help conserve soil, prevent flooding, and-perhaps most important-playa crucial role in maintaining the balance of gases in the air. But quite simply, trees enrich our lives with their beauty. The trees of North America-whether the elegant and fragrant spruces; stately oaks, the very symbols of strength; or crab apples, their blossoms tinged with pink-are among the most impressive members of the plant kingdom. And with over 800 native species and millions of acres of forests, it is not surprising that some of those trees hold world records. The tallest trees on earth, for instance, are the California redwoods, which stretch to heights of 350 feet and more. The General Sherman Tree in Sequoia National Park is the largest living tree, with a height of 275 feet and a trunk 37 feet thick. The world's oldest trees also are American: some of the gnarled bristlecone pines that grow on desolate mountaintops in the Far West are close to
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Treehopper

Small, agile jumping insects, treehoppers are noted for their strange, even bizarre, forms. Some, for example, are shaped like thorns, allowing them to blend in with spiny plants; another, the buffalo treehopper, has two pointed projections on its back that resemble the horns of a bison. Treehoppers live on plants, especially trees and shrubs, where the females lay their eggs in slits cut into the stems or twigs. After hatching, the nymphs mature quickly on a diet of plant juices, often to the detriment of the host. The nymphs of one kind, the locust treehopper, secrete honeydew, attracting ants that in tum protect them from predators.

Tree line

High on our western mountains, and on a few eastern ones as well, there is a kind of boundary called the tree line, or timberline-above which no trees can grow. At and just below this line the few trees that manage to survive are stunted and contorted by the wind, often with branches growing only on their leeward sides. Above the tree line the wind, cold, and short growing season make it impossible for trees to survive at all. In this zone, called alpine tundra, only the hardiest low-growing plants, such as sedges, grasses, and a few flowering perennials, can endure the harsh conditions. Another kind of tree line-and another kind of tundra-are found not on mountaintops but near the top of the world. North of this line, which stretches across Alaska and northern Canada, trees cannot grow due to cold temperatures and the permanently frozen subsoil, called permafrost, in which trees cannot take root.

Trends (Weather)

Trends identify similarities over time. For example, observations of climatic data, such as precipitation and temperature, are used to determine changes in our climate. Any general directions and tendencies in these data over the long-term are referred to as trends.

Trial and error

An Animal Behavior term, this is used to describe a form of learning, also called Instrumental conditioning, in which an Animal comes to associate performance of a behavior pattern with its consequences so that, for example, a response which by chance yields reward will be repeated more often.

Trifoliate

A leaf divided into three sections.

Triggerfish

The colorful triggerfish live among coral reefs in warm coastal seas. Up to two feet long, they have deep bodies that are flattened from side to side and small mouths with protruding teeth. Triggerfish get their name from the stout lifesaving spines on their dorsal fins. When danger threatens, a triggerfish darts into a rock crevice, where it wedges itself securely by snapping a spine upright. A second, shorter spine-the trigger-locks the first one into position, making it impossible for predators to extricate the fish from its hiding place.

Trillium

Among the most easily identified of all spring wildflowers, the trilliums, whose name derives from the Latin for "three," produce their parts in triplicate. A whorl of three leaves circles a stem that can rise to a height of two feet (though the dwarf species may reach only about six inches). Above this ring of leaves each stem is topped by a single flower with three green sepals and three pointed petals. The blossom may be white, pink, maroon, or yellow. Appropriately, the yellow species usually smell pleasantly of lemons, while the purpleflowered stinking Benjamin, aptly named, has a foul odor. Particularly abundant in moist woodlands in the Southeast, trilliums range across most of eastern North America and the Far West. They are sometimes called wake-robins because they come into bloom just as robins are heading north in spring.

Trilobite

Creatures that lived in prehistoric seas from about 575 million years ago until their disappearance some 350 million years later, trilobites are among our most common fossils. Aptly described by Indians as "little water bugs in the rocks," the fossils reveal that trilobites, as their name implies, had bodies that were divided lengthwise into three distinct lobes. Most had large, compound eyes and numerous legs and lived by crawling or burrowing on the ocean floor. The smallest of these bottom dwellers were scarcely I inch long, while others ranged up to 18 inches in length.

Tripletail

Lobotes surinamensis

So named because of the taillike lobes on their anal and dorsal fins, tripletails are fish of warm and temperate waters from Cape Cod to the Gulf of Mexico. The young, which live in bays and estuaries, rely on mimicry for protection: their flattened bodies, yellowish-brown color, and habit of swimming on their sides make them look like dead leaves floating on the water. The adults, which live farther offshore, can be up to three feet long and weigh as much as 50 pounds.

Trophic

Pertaining to food or nutrition.

Trophic level

The position in the food chain determined by the number of energy-transfer steps to that level.

Trophic structure

Organization of the community based on feeding relationships of populations.

Tropical Rainforest biome

The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches of rain falls yearly.

About 1/4 of all the medicines we use come from rainforest plants.

comes from a tropical vine, and is used as an anesthetic and to relax muscles during surgery. Quinine, from the cinchona tree, is used to treat malaria. A person with lymphocytic leukemia has a 99% chance that the disease will go into remission because of the rosy periwinkle. More than 1,400 varieties of tropical plants are thought to be potential cures for cancer.

All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don't branch out for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect the them from water loss and freezing temperatures. It also makes it difficult for

and plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers.

Trout

Salmo

Considered by many to be the kings of freshwater game fish, trout thrive in cold, clear streams and lakes. (Some species spend part of their lives at sea but return to fresh water to spawn.) The demands of anglers have resulted in the spread of trout well beyond their original ranges, and various kinds are now found from the Arctic to mountainous regions in the South. Voracious carnivores, the fish eat everything from insects to small animals that fall into the water-and they can, of course, be tempted by artificial lures. Some grow to a length of 36 inches and weigh more than 30 pounds. Trout are usually light colored, with black or brown spots. On brown trout, however, most spots are reddish orange, and the rainbow trout adds a red stripe to its sides during spawning season. For sheer drama, however, nothing surpasses the aptly named cutthroat, which has a bright red dash on each side of its lower jaw.

Trout-perch

Percopsis

Though they share structural similarities with both trout and perch, the trout-perch in fact are closely related to neither. Our two species both are small freshwater fish of northern lakes and streams. The larger of the two, the six-inch-long trout-perch, has a silvery, translucent body covered with rough, saw-toothed scales. It is also the more widespread, ranging from Alaska to Quebec and south to Missouri and Kentucky. The smaller fish, known as the sandroller, is found only in the Columbia River basin in the Pacific Northwest. Both species feed by night on insects, crustaceans, and shellfish.

Truffle

Though European truffles are the ones famous among gourmets, the tasty subterranean fungi also grow in North America. (They are especially common in California and Oregon.) Ranging from pea-size spheres to irregular balls several inches across, they are usually black, brown, or white. Truffles flourish near hardwood trees, taking nutrients from their hosts' roots and supplying minerals in return. Their pungent aroma attracts rodents, deer, and foxes, which eagerly unearth and devour these prizes.

Tsunami

Terrifying and often catastrophic, tsunamis are huge waves caused by volcanic eruptions, submarine landslides, or earthquakes on the ocean floor. These triggering events, which occur most often in the Pacific Ocean, send powerful shock waves through the water. On the open sea these waves appear as swells racing across the surface at speeds of up to 600 miles per hour. But when such a wave approaches the shallows near shore, drag on the bottom causes it to decrease in speed and increase dramatically in heightsometimes to 100 feet or more. Slamming the coast with horrifying force, a tsunami can demolish buildings, hurl ships ashore, and cause death and destruction far inland.

Tube worm

Marine relatives of earthworms, tube worms live in protective tubes built of sand, mucus, and other materials. Parchment worms, for instance, make U-shaped, papery tubes (open at both ends) in mud or sand and live by filtering food particles from seawater passing through the tube. Another kind, the feather dusters, extend brightly colored tufts of food-catching tentacles from one end of their tubes, attaching the other to shells or seaweed.

Tufa

A light, porous form of limestone, tufa is deposited when water rich in calcium carbonate flows into lakes or hot springs and begins to evaporate. Along the shores of Searles Lake in southern California, for example, eerie tufa cones rise some 75 feet into the air, while in other areas the mineral completely encrusts the surfaces of rocks. Though often beautifully colored by impurities, tufa is too soft and crumbly for ornamental or commercial use.

Tuff

A product of volcanic eruptions, tuff is a kind of rock made up of tiny particles of ash that have been compacted by pressure or fused together by intense heat. It sometimes contains fossils of animals that were overwhelmed by the ash. Large deposits of tuff are often sculpted by erosion into deep canyons, tall pillars, and other fanciful forms. At Frijoles Canyon, New Mexico, ancient Indians carved cliff dwellings into the soft tuff that makes up the canyon walls.

Tulip tree

Uriodendron tulipifera

The stately tulip tree, also called the yellow poplar, is a North American native with only one close living relative, a species that grows in Asia. Although it thrives throughout most of the East, this giant among broad-leaved trees attains its greatest size in the Ohio River valley and the southern Appalachians. There tulip trees can exceed ISO feet in height, supported by magnificent, arrow-straight trunks up to 6 feet in diameter. The greenish cup-shaped blossoms that cover the trees in spring are splashed with orange and do indeed resemble tulips. In autumn oblong cones of winged seeds remain on the branches long after the leaves have fallen.

Tumbleweed

Forming globes the size of beachballs, the tangled stems of the various tumbleweeds roll and bounce for miles across windswept plains. They begin as most other plants do-anchored in the soil. But after flowering, the tumbleweeds wither and snap free from their roots. What seems a frailty is actually a strength, however, for breaking loose in this way allows the plants to scatter their seed as they bounce along, sowing themselves far and wide. Two of our most common tumbleweeds are immigrants from the Old World: tumbling mustard, which has spread over much of the northern plains, and saltwort, or Russian thistle, which tumbles all across the West.

Tuna

The ultimate in streamlining, tunas have robust, torpedo-shaped bodies that taper dramatically and end in a deeply forked tail. Two rows of triangular finlets in front of the tail are a distinctive feature. Swift, powerful swimmers, tunas ply both warm and cool seas-in summer they are found as far north as Newfoundland in the Atlantic, and British Columbia in the Pacific. All

Tunas are able predators that swim long distances in large schools as they search for fish (especially the closely related mackerels), squid, and crustaceans. Female tunas lay eggs by the millions. The fry, about the size of houseflies upon hatching, take several years to reach maturity. Tunas are among the most-prized commercial and sport fish. The largest, the massive bluefins, sometimes grow to 14 feet in length and weigh more than 1,500 pounds. Other popular species include the three-foot-long skipjacks; yellowfins, named for their black-bordered golden finlets; and albacores, which are sold as white meat tuna.

Tundra

In the Far North, beyond the evergreen forest that stretches from Alaska to Newfoundland, is a vast expanse of arctic tundra. Here no trees can grow and only the hardiest low-growing plants are able to survive. In the dark, frigid winter, only a few animals-many of them outfitted in white- manage to find food: arctic foxes, for example, hunt lemmings, and snowy owls seek ptarmigan and other prey. In spring and summer, when temperatures often rise above 50 degrees, the tundra wears a bright mosaic of lichens, sedges, shrubs, and wildflowers. While the subsoil (called permafrost) remains frozen, the surface is soggy and marshlike, attracting legions of clamoring waterfowl and shorebirds from points south. Here they nest and, in uninterrupted daylight, feed on an abundance of insects, seeds, and berries. Another kind of tundra-one defined by altitude rather than latitude-is found above the tree line on our highest mountains. Here also, harsh conditions permit only a few small, tenacious plants to survive. They are grazed by elk and mountain goats, while golden eagles soar on high in search of marmots and ground squirrels.

Tundra biome

Did you know that the Arctic Tundra is the world's youngest biome? It was formed 10,000 years ago. Located at latitudes 55° to 70° North, the tundra is a vast and treeless land which covers about 20% of the Earth's surface, circumnavigating the North pole. It is usually very cold, and the land is pretty stark. Almost all tundras are located in the Northern Hemisphere. Small tundra-like areas do exist in Antarctica in the Southern Hemisphere, but because it is much colder than the Arctic, the ground is always covered with snow and ice. Conditions are not right for a true tundra to form. Average annual temperatures are -70°F.

Tundra comes from the Finnish word "tunturia", which means a barren land. The ground is permanently frozen 10 inches to 3 feet down so that trees can't grow there. The bare and sometimes rocky ground can only support low growing plants like mosses, heaths, and lichen. In the winter it is cold and dark and in the summer, when the snow and the top layer of permafrost melt, it is very soggy and the tundra is covered with marshes, lakes, bogs and streams that breed thousands of insects and attract many migrating birds.

The main seasons are winter and summer. Spring and fall are only short periods between winter and summer. The tundra is the world's coldest and driest biomes. The average annual temperature is -18° F. Nights can last for weeks when the sun barely rises during some months in the winter, and the temperature can drop to -94° F . During the summer the sun shines almost 24 hours a day, which is why the Arctic is also called the Land of the Midnight Sun. Summer are usually warm. Temperatures can get up to 54° F , but it can get as cold as 37° F. Average summer temperatures range from 37° to 60°F.

The Arctic tundra is also a windy place and winds can blow between 30 to 60 miles per hour. The tundra is basically like a desert when it comes to precipitation. Only about 6 - 10 inches of precipitation (mostly snow) fall each year. Below the soil is the tundra's permafrost, a permanently frozen layer of earth. During the short summers the top layer of soil may thaw just long enough to let plants grow and reproduce. Since it can't sink into the ground, water from melting permafrost and snow forms lakes and marshes each summer.

There is barely any vegetation in the tundra, only about 1,700 different species, which isn't very much. These are mostly shrubs, sedges, mosses, lichens and grasses. There are about 400 varieties of flowers. The growing season is only about 50 to 60 days long. There are no trees, except for some birches in the lower latitudes. The ground is always frozen beneath the top layer of soil, so trees can't send their roots down. Plants do grow on some parts of the tundra but only as low carpets about 3 inches high. Most plants grow in a dense mat of roots which has developed over thousands of years. The soil is very low in nutrients and minerals, except where animal droppings fertilize the soil.

Surprisingly there are animals in the tundra. Although there isn't a lot of biodiversity, only 48 species of land mammals are found on the tundra, there are a lot of each species. These consist of slightly modified shrews, hares, rodents, wolves, foxes, bears and deer. There are huge herds of Caribouin North America (known as reindeer in Eurasia) which feed on lichens and plants. There are also smaller herds of other ungulates. Wolves, arctic foxes, and wolverines are the predators of the tundra. Smaller mammals are represented by mice, shrews and lemmings. There aren't many different species of insects in the tundra, but black flies, deer flies, mosquitoes and "no-see-ums" (tiny biting midges) can make the tundra a miserable place to be in the summer. Mosquitoes can keep themselves from freezing by replacing the water in their bodies with a chemical called glycerol. It works like an antifreeze and allows them to survive under the snow during the winter. The marshy tundra is a great place for migratory birds like the sandpipers and plovers.

The tundra is one of Earth's three major carbon dioxide sinks. A carbon dioxide sink is an area which takes in more carbon dioxide than it releases. Carbon dioxide is a greenhouse gas that contributes to global warming. During the short summer tundra's plants take in carbon dioxide, sunlight and water in the process of photosynthesis. Plants normally give off carbon dioxide after they die and decompose. But because of the short, cool summer and freezing winter temperatures, plants can't decompose. Remains of plants thousands of years old have been found in the tundra permafrost. In this way the tundra traps the carbon dioxide and removes it from the atmosphere. Today global warming is melting the permafrost of the tundra and every year several feet of tundra are lost. As the tundra melts, the plant mass decomposes and returns carbon dioxide to the atmosphere.

The tundra is a very fragile environment. The extremely cold temperatures makes it a difficult environment to survive in during the winter, and plants and animals have a hard time coping with any extra stresses and disturbances. More people moving to the tundra to work in the mines and oil rigs have created towns and more roads. Some animal's movements to traditional feeding and denning grounds have been disrupted by these obstacles. When they try to pass through a town they are often scared away or shot. With their feeding patterns disrupted, many polar bears have starved. The Alaskan oil pipeline was built across a caribou migration route. In some places the pipeline has been raised above the ground so the caribou can pass under it. Pesticides have been used to control the hordes of insects. Thousands of migrating birds come to the tundra because of the abundant insects. Through the food chain the pesticides reach many of the animals that live on the tundra.

Pollution from mining and drilling for oil has polluted the air, lakes and rivers. The land around some nickel mines in Russia has become so polluted that the plants in the surrounding area have died. Footprints and tire tracks can be visible for many years after they were made. When the sun hits the ruts it causes the permafrost to melt. This causes erosion and the ruts get bigger, and eventually the ruts turn into gullies. Tracks made during WW II have grown so large that some of them are now lakes.

The tundra is not a cold and useless wasteland. It is a very fragile environment and the plants and animals that have made their home on the tundra biome have made some incredible adaptations to the long, cold winters and the short but abundant summers. They live on a precarious edge and the smallest stresses can bring about their destruction.

Tupelo

Nyssa

Also known as black gums and sour gums, tupelos are trees that thrive in the moist soils of river bottoms and swamps throughout much of the East. In spring bees are attracted to their inconspicuous but nectar-rich greenish-white flowers and produce a crystal-clear honey that is prized for its purity. When fall arrives, the tupelos are among the first trees to change color; their oval, glossy green leaves tum to a vivid scarlet that contrasts dramatically with the year's crop of blue-black cherrylike fruits.

Turkey

Meleagris gallopavo

Benjamin Franklin defended the wild turkey, his choice for our national bird, as "more respectable" than the thieving, scavenging bald eagle. But the eagle won out of course, and the turkey became not our national bird but the traditional symbol of Thanksgiving. Agile, swift, and wary, the wild turkey is about as comparable to the domestic variety as a nimble fox is to an overweight dog. Like their cousins the pheasants and grouse, wild turkeys are adept at making winged escapes but prefer to flee on foot. (They can nearly outrun a human.) The four-foot-long birds resemble their smaller relatives in courtship as well. Gobbling and strutting, the colorful males swell their bright red wattles and fan their tails to attract the attention of the females. When not courting, the birds forage by day for acorns, seeds, and insects and retire to the trees at dusk. Wild turkeys once were plentiful in woods throughout the East and south into Mexico, but over the years hunting and habitat destruction nearly wiped them out. In recent decades, however, these quintessentially American birds have been restored to much of their original and rightful domain.

Turnover

The process of local extinction (e.g., on islands) of some species and their replacement by other species. The turnover rate is the number of species eliminated and replaced per unit time.

Turnstone

Arenaria

Stocky, robin-size shorebirds, our two turnstones are named for the way in which they forage near the water's edge: they search for snails, worms, crustaceans, and other fare by flipping stones, shells, and bits of debris with their short, stout bills. In spring the ruddy turnstone also digs in sand for horseshoe crab eggs. The black turnstone nests only on the coast of Alaska, but the ruddy turnstone breeds in arctic regions worldwide. Females abandon the North before their young can fly, leaving the males to tend their offspring until they are ready to migrate. Winter finds the black turnstone along the Pacific coast, while the ruddy turnstone heads for Atlantic, Pacific, and Gulf shores.

Turret shell

A widely distributed family of marine snails, turret shells typically have long, narrow, conical shells. Ranging from one to six inches in length, they look much like miniature dunce caps. But some members of the family, called worm shells, are less orderly in their growth. One end of the shell remains tightly twisted and turretlike. But after this normal start, the shell elongates in loose meanders that are suggestive of a worm. Some turret shells live on the seafloor; others live inside sponges.

Turtle

The only reptiles with shells, turtles have flourished for millions of years on land, in fresh water, and at sea. One secret of their success is their two-part suit of armor-the upper carapace and lower plastron-into which most can pull their heads and legs for protection. Turtles have no teeth but use their tough beaks to feast on a varied diet of plant and animal life. The females of all kinds, including even sea turtles, dig nests in moist sand or soil. There they deposit their eggs, cover them, and leave them to be hatched by warmth from the sun. Cold-blooded creatures, turtles are most abundant in temperate and tropical regions. Some 50 species inhabit North America, with the greatest variety found in the South. Freshwater species range from the diminutive mud turtles to the gigantic alligator snapper. The plodding, stout-legged gopher tortoises are among our several land turtles, while loggerheads are perhaps our best-known sea turtles.

Tusk shell

The curved and tapered shells of these marine mollusks are open at both ends but otherwise resemble tiny elephant tusks. The foot of the creature that inhabits the tusk protrudes from the wider opening and anchors the shell in sand or mud on the sea floor; the pointed end projects into the water. Tusk shells eat one-celled prey that they snare with threadlike tentacles. Indians in the Pacific Northwest used one species of these distinctive shells as wampum.

Typical intensity

An Animal Behavior term, this is used to describe the tendency of Animal signals to be performed at the same intensity regardless of the Motivation of the signaler. It is thought to have evolved through Ritualization as a means to reduce the ambiguity of signals or to hide the motivation of the signaler where it is disadvantageous to indicate this to other Animals.

Ultimate factors

Aspects of the environment that are directly important to the well-being of an organism (for example, food). Ultimate factors are concerned with fitness.

Ultrasound

An Animal Behavior term, this is used to describe sounds beyond the limit of Human hearing (about 20,000 cycles per second. Such sounds are used in communication by many Animals but, because they bounce back from objects, they are particularly effective in Echolocation.

Ultraviolet (UV) Radiation

Invisible electromagnetic radiation with a frequency between that of visible violet light and X rays. Most of the ultraviolet component of sunlight is absorbed by the ozone layer of the atmosphere, but UV-B radiation can cause sunburn and skin cancer and UV-A radiation can cause photosensitivity reactions and possibly skin cancer.

Umbel

Umbrellalike inflorescence.

Umbrella sedge

Cyperus

With stems that are triangular in cross section, the umbrella sedges resemble other members of the sedge family, but they are distinguished by their floral clusters. The flowers themselves are small and inconspicuous, but the clusters rise from a ring oflong, leafy bracts that radiate from the top of the stem like the spokes of an umbrella. The most famous of these wetland plants is the papyrus, which supplied the ancient Egyptians with a paperlike material. Closer to home are the nutgrasses, persistent weeds of moist fields and meadows that grow up to three feet tall and produce tiny yellow or purple flowers.

Underbrush

Underbrush is any small shrubbery found underneath or near a tree or forest. Underbrush is normally located in damp or humid climates and prefers shaded areas but can also be found in sunny plain areas. Underbrush also houses a unique variance of colorful and textured foliage. The plants range from dark greens to pale yellows and often contain oils which are likely to start fires. These fires occur mostly in arid, windy regions. Many animals also make their homes in the underbrush. Field mice and small birds commonly make their homes out of small twigs and pieces of foliage that have died or gone dry. This often draws the line between life and death for these small animals as the dense plants protect them from the view of predators. Snakes are also one of the common animals that reside within the grasses of the underbrush. These include both poisonous and harmless species; this is one of the reasons people tend to stay away from brushy areas. When underbrush is found beneath a large tree(s), the foliage is often created from stunted trees or other larger plants whose growth has been interrupted due to the interference of the larger surrounding foliage. This is often the cause of the common misconception that underbrush can only be found under a thick forest canopy of trees (such as that of a forest or wood). As long as there are surrounding, larger trees, underbrush is still an occurance.

Undertail Coverts

This undertail coverts part of the underside of the bird, and refer to the area extending from the area between the birds legs, and continuing under the base of the tail.

Underwing

Catocala

Widespread across North America, underwings are robust moths with drab forewings that conceal a colorful secret. Hidden beneath them are the smaller hind wings, which on most species are brightly banded with yellow, orange, and other hues. Dull though they are, the forewings provide excellent camouflage as the moths rest by day, pressed against the trunks of trees. And the patterned hind wings serve to startle predators when, with a flash, the moths take flight.

Ungulate

Hoofed Animals. Many familiar farm animals, and their wild relatives as well, are ungulates-mammals with hooves. Made of a tough hornlike substance, hooves are, in effect, heavy-duty fingernails that cover and protect the toes. While horses have only one hoofed toe per foot, cattle have two, and pigs have four. Moose in the north woods, pronghorns on the prairie, and sheep and goats in the barnyard are other well-known examples of animals with hooves.

Unicorn plant

Proboscidea

The long, gracefully curved seedpods of these plants-their unicorn "horns"-are curiosities today, but to American Indians they were a source of both food and fiber. When young and green, the pods were eaten fresh or pickled for later use; when mature and dried, they were split into strips and woven into baskets. Though once cultivated, the plants still survive in fields and waste places. Growing upright or in sprawling mats with sticky, hairy leaves, the unicorn plants bloom all summer long and bear clusters of trumpet-shaped pink or yellow flowers.

Uniformitarianism

Biological Philosophy term. One side of a nineteenth-century geological argument about the forces that have shaped the earth; in this case, the notion was that, with the exception of volcanoes and earthquakes, the earth has been shaped by the slow, almost imperceptible working of natural processes which are still going on and can be measured. The issue is this: if the laws are uniform, we can see back beyond the last major cataclysm and so can reliably talk about millions of years in the past. See Catastrophism.

Updraft

When wind meets an obstacle, it is deflected skyward, creating an updraft. Birds save energy by gliding on updrafts just as they do on the rising columns of warm air called thermals. Migrating hawks, for example, take advantage of updrafts along mountain ridges, while on seacoasts gulls soar effortlessly on those caused by buildings or cliffs. In high western mountains updrafts sometimes blow insects far above the tree line, where they are eaten by alpine birds.

Uranium

A silvery radioactive element, uranium is vital to the nuclear power industry and is used in manufacturing. Most uranium is derived from the ore uraninite, also known as pitchblende because of its coallike luster. It occurs as well in a few brilliantly colored (and sometimes fluorescent) minerals, such as carnotite and autunite. Uranium is mined in Canada and parts of the Southwest.

Urban (Water)

The government issues water quality guidelines, but it is the local municipalities that are accountable for the quality of urban water.

Urban wildlife

Aside from pigeons, squirrels, and such all-toofamiliar pests as rats, mice, flies, and cockroaches, one might reasonably ask what else in the way of "wildlife" our cities and towns have to offer. In fact, a surprising array of creatures survive and even flourish in urban areas. But as is true in the country, many of them come and go under the cover of darkness and live in secret places-behind walls, in pipes and tunnels, on high ledges, or in abandoned buildings. Raccoons and opossums, for instance, often hide out in parks during the day, sleeping in tree cavities or hollow logs, and emerge at night to raid garbage pails. In many areas such unlikely city critters as coyotes and red foxes are occasionally seen prowling the streets at night for rats, mice, and scraps of edible refuse. Roosting by day in tunnels or under the eaves of buildings, bats also come out at night to feast on the insects that swarm around streetlights. Descendants of wild rock doves, which nest on cliffs, pigeons make their homes on the clifflike facades of buildings, while flat gravel roofs are preferred nesting sites for nighthawks, and chimneys are inhabited by chimney swifts. Both kestrels and bam owls roost in abandoned buildings, the former capturing sparrows by day and the latter hunting rats by night. Even the endangered peregrine falcon has been known to nest on the high ledges of skyscrapers. And such fragile tropical birds as parrots and parakeetsescapees from indoor cages-manage to thrive in southern cities. A few amazed onlookers have even spotted them in the urban Northeast.

Urban wildlife is much more abundant and diverse than one would think. In coastal cities, for example, herring gulls routinely raid the fish markets for scraps. Even amid downtown bustle, robins take advantage of a Don't Walk sign, their nest kept warm by the electric lights. On the West Coast a busy harbor provides a sheltered winter home for sea lions.

Utilitarianism

Biological Philosophy term. The Puritan Cotton Mather: "What is not useful is vicious," that is, whatever cannot be eaten, worn, sold, or otherwise used by human beings is evil. The term is in quotation marks to distinguish this use of it from the Utilitarian school of philosophy.

Valerian

Valeriana

Though several native species of these healing herbs live in moist places across the northern states, it is an introduction from Europe, a garden escape, that is best known. Flourishing along roadsides, where it grows up to four feet tall, valerian has feathery leaves and produces sweetly scented clusters of tiny flowers. Belying the fragrance of its blooms are the plant's foulsmelling roots. Even so, valerian roots, whether native or naturalized, have traditionally been used as a sedative and are still sometimes prescribed for nervous disorders and insomnia

Valley

Long depressions in the surface of the earth, valleys are erosional features formed by rivers or glaciers. The shape of a valley gives a clue to its origins. Deep, steep-sided, U-shaped valleys, like those seen in the mountains of the West, for example, were excavated by glaciers during the last ice age. In contrast, rapidly flowing rivers carve V-shaped valleys as their waters actively

scour the bed. In places such as the Grand Canyon where a river is cutting through solid rock, steep-sided canyons or gorges form. In low-lying areas, where a meandering river wends across a plain, the valley has a broad, relatively flat floor with gently sloping sides and is periodically inundated by floods.

Variable circular plot

Bird Biology Avian Conservation term.

See Point count method.

Variable-distance method:

Bird Biology Avian Conservation term.

see Strip transect method, Point count method.

Variance:

A statistical measure of the dispersion of a set of values about its mean.

Ventral

The lower surface.

Venus flytrap Oionaea muscipula

The only carnivorous plant of its kind in the world, the Venus fly trap thrives in sandy savannas near the coasts of North and South Carolina. The acidic soil there is deficient in nitrogen, but the fly trap overcomes this shortage by attracting insects to its hinged leaves. When an interloper touches the trigger hairs on a leaf, the trap snaps shut and the plant's digestive juices start flowing to extract nitrogen from the prey. In about 10 days the leaf reopens, set for its next victim.

The Venus fly trap bears clusters of small white or pinkish flowers at the top of I2-inch stems. Since each cluster produces an abundance of seeds, the plant has withstood the collection of millions of specimens that are sold each year as botanical oddities. Development of its native habitat, however, poses a real threat to the survival of this unique species.

Verdin Auriparus f1aviceps

At home amid the drought and scrub vegetation of the American Southwest, this small, yellowheaded songbird is an expert at survival in the desert. It flits about in search of insects among the paloverdes and mesquites, apparently getting all the moisture it needs from the insects and berries that it eats. The verdin chooses a thorny cactus or shrub in which to build its large, globular nest. Constructed of hundreds of intertwined twigs, the nest is lined with feathers, spider silk, and soft plant fibers, making it well insulated for the comfort of the young. A small entryway and prickly surroundings discourage intruders.

Vervain

Verbena

While the familiar garden flowers known as verbenas are mostly from South America, many of their equally colorful wild relatives, called vervains, are found all across North America. They were regarded as sacred by American Indians, whose medicine men used them to treat a variety of ailments. Most common is blue vervain, up to four feet tall with spikes of violet flowers that brighten meadows in the East and throughout much of the Great Plains. Hoary vervain, similar in appearance, is found mainly in the central states, where it accents the wide open spaces with streaks of lavender.

Vertebrate

Mammals, birds, reptiles, amphibians, and fish are all vertebrates-animals with backbones. Made up of bone or cartilage, the backbone surrounds and protects the spinal cord, the main conduit of nerves that runs from brain to tail. To allow flexibility, the backbone is divided into segments called vertebrae (hence the word vertebrate). Among the other characteristics shared by vertebrates are skulls, internal skeletons, and bodies with right and left sides that are mirror images of each other. All other animals, such as insects, mollusks, and crustaceans, lack backbones and are called invertebrates.

Vetch

Vicia

Though many are common roadside weeds, the vetches have earned a place in the farmer's field as well. Cow vetch is grown as fodder for livestock and is also planted as "green manure"when plowed under, it restores nitrogen to the soil. Another vetch - the broad, or fava, beangrown for its edible seeds, is one of the world's oldest cultivated crops.

The vetches have weak stems that either sprawl across the ground or climb other plants with the aid of tendrils growing from the tips of their feathery compound leaves. The dainty flowers, which have been compared to little butterflies, range from white to pink, purple, and blue. Members of the pea family, the vetches produce crops of distinctive pea-type pods that contain the plants' seeds.

Viburnum

Elegant shrubs that beautify woodlands, especially in the East, the viburnums are prized by landscapers everywhere. Their showy, three- to five-inch clusters of white or pink flowers, often pleasantly scented, have the quaint look of oldfashioned lace caps. The berrylike fruits that follow-bright yellow, orange, red, or shiny blue or black -are truly eye-catching, inspiring such curious names as nannyberry, mooseberry, wild raisin, possumhaw, and highbush cranberry. The leaves, always in opposite pairs, vary in shape from species to species. Hobblebush, for example, has heart-shaped leaves; arrowwood's leaves are oval; and those of the highbush cranberry resemble maple leaves.

Viceroy

Basilarchia archippus

Masterful mimicry protects this large, conspicuous butterfly from enemies. Brightly patterned with orange and black, the viceroy looks almost exactly like the monarch butterfly, an insect that is distasteful to birds. Though the viceroy is perfectly edible, the resemblance is enough to keep birds away from it. The butterfly is protected at other stages as well. Its eggs, laid on leaves, blend with the leaves' galls, and in autumn the caterpillars prepare for the cold of winter by wrapping themselves in bits of foliage attached to branches, where they remain until spring. The viceroy butterfly's black line across each hind wing, as well as its smaller size, differentiates it from a monarch butterfly.

Vacuum activity

An Animal Behavior term, this is used to describe the occurrence of a behavior pattern in the absence of the external stimulus normally required for its elicitation, for example, prey capture when no prey organism is present, or courtship in the absence of a mate. Few instances have been described because the complete absence of a stimulus is hard to demonstrate.

Video

Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images which represent scenes in motion. Video technology was first developed for television systems, but has been further developed in many formats to allow for consumer video recording. Video can also be viewed on a computer through the Internet.

Vigilance

An Animal Behavior term, this is used to describe the state of an Animal determining the likelihood that it will detect an unpredictable event in the environment such as the appearance of a predator. Feeding Animals look up often to maintain vigilance, but less so in groups where the presence of more pairs of eyes makes it less necessary.

Vine

In the competition for sunlight, vines have a distinct advantage over other plants. Their ability to climb-by using neighboring plants, cliffs, buildings, trellises, and other objects as supports-allows them to reach the sunlight quickly. Trees and shrubs, in contrast, need much more time for their stems to become sturdy enough to achieve any substantial height. Vines climb in a number of ways. Ivies have tiny clinging rootlets or adhesive discs, which enable them to ascend flat surfaces such as cliffs or walls. Grapes and passionflowers hoist themselves up with coiling tendrils. Clematises use twining leaf stalks, and wisteria winds its entire snakelike stem around poles or tree trunks. Rambler roses use yet another technique: they hang onto their supports with sharp thorns.

Violet

Viola

Each spring, these delicate little wildflowers tint the land with blossoms of blue, white, yellow, and of course, violet. The blooms- five petaled with a nectar-filled spur-are pollinated by bees. But many species also produce petalless, self-fertilizing flowers, often hidden underground, that yield an abundance of seeds. Some, like the common blue violet, have heart-shaped leaves, but on others they look like lances, arrowheads, or on the birdfoot violet, an avian foot. Rich, moist soils are the preferred habitat, but some adapt to dry grasslands (the prairie violet) or even arid regions (the desert violet).

Viper's bugloss

Echium vulgare

Called a wildflower by some and a weed by others, viper's bugloss brightens waste places all summer long. Also known as blueweed, it bears tubular blue flowers with long red stamens. The blooms grow on short curved spikes along the upper part of two-foot hairy stems. The first part of the plant's common name refers to the shape of its fruits, which supposedly resemble a viper's head and gave the plant its reputation as a remedy for snakebite. The second part, bugloss, is from the Greek for "ox tongue," perhaps because of the leaves' rough texture.

Vireo

These little insect-eating birds resemble the warblers with whom they often migrate. Vireos, however, have somewhat thicker bills, search more slowly and carefully for food, and are not nearly as colorful. Eleven species breed in North American woodlands and thickets, where they construct cup-shaped nests that are suspended from the forks of tree branches.

Most of these songsters spend the winter in the tropics, but Hutton's vireo, a drab bird of the Pacific Coast and the Southwest, remains on its breeding grounds all year round. The most common species are the warbling vireo, whose drowsy song can be heard across most of the continent during the summer months, and the red-eyed vireo of the eastern states and southern Canada, whose repetitive aria has earned it the nickname preacher bird.

Virginia creeper

Parthenocissus quinquefolia

A widespread, vigorous vine, Virginia creeper flourishes in sun or shade, clambering up trees and walls or sprawling across the ground. The plant's twining tendrils are equipped with adhesive disks that release a gluey resin when they touch a potential prop. In fall the five-fingered leaves furnish one of the first signs of the season, turning from bright green to brilliant red. The fruits-dark blue berries with scarlet stalksprovide food for birds and other wildlife.

Viviparity

An Animal Behavior term, this is used to describe the embryonic development within the Mother and receiving nourishment from her, as in all Mammals and some other Animals of various groups.

Volcanic neck

A volcanic neck is a plug of solidified lava that at one time filled the vent of a volcano. After volcanic activity ceased, the enclosing rock of the volcano's cone eroded, leaving the plug of rugged rock intact. Volcanic necks often stand as massive, craggy towers that loom over their surroundings. In Monument Valley, Utah, for example, Agathla Peak rises abruptly to a height of 1,400 feet. In some areas these imposing structures are the only clues to the existence of longvanished volcanoes.

Volcano

Floods of molten magma; boulders hurled into the air; lethal clouds of fiery ash and caustic steam-all these and more can be part of a volcanic eruption. The mountains that result, known as volcanoes, owe their existence to huge subterranean reservoirs of magma, or molten rock. The gas-rich magma accumulates in chambers a mile or more beneath the surface, and when its pressure reaches a critical point, it bursts out through fissures in the earth's crust. Depending on the chemical makeup of the magma, it may emerge relatively quietly, producing rivers of red-hot lava, or it may erupt with exzplosive force, sending ash, pumice, and boulders high into the sky. Volcanic peaks build up gradually as a result of repeated eruptions. Explosive eruptions often produce the classic cone shape, while domeshaped mountains (like those in Hawaii) are formed by gentler flows of viscous lava.

Most volcanoes occur at the boundaries of the earth's giant crustal plates. Such is the case along North America's Pacific Coast, where active volcanoes smolder from Alaska southward. In 1980 Mouilt St. Helens in Washington blew up with devastating force, causing dozens of deaths. denuding forests, and clogging lakes and rivers with debris. Nearby, Mount Rainier steams quietly beneath its ice cap, a reminder that it-and other seemingly dormant peaks in the vicinity-may erupt again one day.

Vole

Often called field mice, voles are rodents with shorter tails and smaller ears than true mice. Many, such as the widespread meadow vole, live in open fields, where they scoot from place to place along well-maintained pathways in the grass. Red-backed voles and woodland, or pine, voles live in forests, where they tunnel through leaf litter or burrow in the ground. Active day and night around the year, voles even tunnel under snow in search of seeds, grass, roots, and bark. Like their close relatives the lemmings, they reproduce prolifically and from time to time experience population explosions that can increase their numbers tenfold. Because of their abundance, voles are a mainstay in the diets of foxes, owls, and a host of other predators.

Volunteerism (Action and Learning)

Thousands of citizens carry out valuable, unpaid work to help contribute to environmental protection and conservation-including such activities as daily climate observations, ecological monitoring, and a variety of stewardship initiatives.

Vulture

Big black, bald-headed birds that feed primarily on carrion, vultures are masters of the air. They often soar high in the sky for hours on end as they scan the countryside for food. Their beaks, though only slightly hooked, nevertheless serve well for tearing flesh, and their featherless heads are easily cleaned after probing inside large, messy carcasses.

Vultures do not build nests but lay their eggs on rock ledges, in hollow logs, or on the ground. Both parents care for the young, which are unable to fend for themselves until about three months old. The turkey vulture, often called the turkey buzzard, has a six-foot wingspan and is found from coast to coast. It has a red head and holds its wings in a V as it soars. The black vulture, a slightly smaller bird with a more southerly range, has a black head and soars with its wings held straight out, flapping them often.

Walking catfish

Clarias batrachus

Found in the muddy ponds and canals of south Florida, walking catfish not only walk but also breathe air. Iftheir ponds dry up, these astonishing fish simply haul themselves out and use their stiff pectoral fins to wriggle overland in search of new homes. Breathing through lunglike sacs, the fish can stay out of water for hours or even days and are often seen crossing roads on rainy nights. Accidentally introduced from Asia, walking catfish are considered undesirable aliens because they compete with native fish for food and habitat.

Walkingstick

Remarkable mimics, the long, slim, wingless walkingsticks bear such a close resemblance to the twigs on which they live that the insects are virtually impossible to spot. Of the 20 or so species in North America, one kind reaches a length of six inches (our longest insect), but it, too, is nearly invisible. These creatures feed only at night and are all but motionless by day, but in years when they are abundant, their voracious appetite for foliage can seriously damage trees.

Wallflower

Erysimum

Far from inconspicuous, wallflowers are bold and showy, decorating dry hillsides, prairies, and mountain meadows with bright clusters of four-petaled, usually yellow or orange blossoms. Members of the mustard family, these sun lovers have strap-shaped leaves and, after flowering, bristle with long, slender seedpods. Western wallflower, a well-known species, is prized for its lovely pompoms of golden blooms.

Walnut

Juglans

Tall, stately trees with spreading branches and feather-shaped compound leaves, walnuts of several species thrive on rich bottomlands in the East and along stream banks and ravines in parts of the West and Southwest. The largest, the black walnut, commonly reaches a height of 100 feet or more; it ensures itself adequate growing space by releasing a natural herbicide, juglone, from its roots. Its nuts, notoriously hard to crack, are nonetheless a popular ingredient in confections, and its wood makes fine furniture. Butternut, another common species, yields a yellow dye traditionally used by countryfolk.

Walrus

Odobenus rosmarus

Long white tusks distinguish walruses from seals and sea lions, but otherwise, they have much in common with their smaller kin. Equipped with flippers and a thick layer of fat, walruses live in icy arctic seas, where they dive for clams and starfish. They also haul themselves out onto land and ice floes, where they move about with the help of their hind flippers. Male walruses are huge-some grow to a length of 12 feet, weigh more than a ton, and have tusks up to 3 feet long. The smaller females have tusks too, but theirs are thinner and shorter than the males'. While walruses sometimes use their tusks to defend themselves against polar bears, they use them more often to break through ice or haul themselves out of the water. Gregarious creatures, walruses congregate in herds of 100 or more and, like seals and sea lions, visit traditional breeding grounds to perpetuate their kind. Walruses, contrary to popular belief, do not use their tusks to pry shellfish from the ocean floor.

Wapiti

Cervus elaphus

Also called elk, wapiti once roamed across much of North America but now are found mainly in the Rockies and along parts of the Pacific Coast. Except for moose, they are our largest deer; Wapiti, an American Indian word for "white," refers to the animal's buff-colored rump. Bulls can reach a shoulder height of about five feet, weigh 1,000 pounds or more, and produce antlers with a span of five feet. Traveling in herds between the high country in summer and sheltered valleys in winter, wapiti forage on grasses, twigs, and leaves. During the fall mating season, the males' loud bugling calls and antler-crashing fights echo through the countryside as they compete for harems. Wapiti fawns, born in the spring, are able to walk and travel with the herd only minutes after birth.

Warbler

Favorites among bird-watchers, the warblers are sometimes called butterflies of the bird world because of their small size, bright colors, and sprightly movements. Our 50-odd species, collectively called wood warblers to distinguish them from unrelated old-world warblers, winter mostly in tropical areas and nest in forests, swamps, and thickets all across North America.

Two of our loveliest species are also among the most commonly seen: the yellow warbler, a bright canary yellow, and the American redstart, strikingly patterned with black and orange, nest not only in wild places but also in city parks and gardens. Most warblers build cup-shaped nests in trees or shrubs, but the waterthrushes, ovenbird (named for its covered nest), and Wilson's warbler nest on the ground, while the prothonotary warbler makes its home in tree cavities.

With a few exceptions, warblers are undistinguished singers, but all are accomplished insect hunters. Many capture their prey on the wing, but others-among them the black-and-white and pine warblers- use their thin, sharply pointed bills to probe the crevices in tree bark. Since warblers dispatch vast numbers of harmful insects each year, their spring migrations are anticipated as eagerly by farmers and foresters as by bird-watchers.

Wasp

Of the more than 3,500 species of wasps found in North America, the best known are the social wasps, such as hornets, paper wasps, and yellow jackets. They live in colonies with strict social organizations and inhabit papery nests made of chewed plant fibers. But the majority of wasps lead solitary lives. While many nest in underground burrows, the more specialized mud dauber and potter wasps build nests of mud. Most solitary species are hunters that paralyze prey with their stings (only females have stingers), then leave the prey sealed in their nests as food for their developing larvae. Still other wasps are parasites that lay their eggs on caterpillars and other live hosts.

Waste (Water)

Wastewater is water that has been used for a human activity and allowed to run away-usually into the environment or into a treatment facility.

Waste Management

Disposal, processing, controlling, recycling, and reusing the solid, liquid, and gaseous wastes of plants, animals, humans, and other organisms. It includes control within a closed ecological system to maintain a habitable environment. Some of the waste materials involved are hazardous while others are simply so voluminous that their permanent disposal becomes a problem.

Water

A colourless, odourless and tasteless liquid compound made up of hydrogen and oxygen. In environmental terms, water is one of the three main components of our physical environment-which also includes land and air. Water in general refers to rainwater, groundwater, seas, lakes, rivers, etc.

Water conservation

Water conservation means reducing water usage or using water more efficiently, in order to reduce pollution and health risks, lower water costs, and extend the useful life of the existing supply and waste-treatment facilities.

Water quality

The quality of water as determined by its chemical and bacterial composition. To ensure the safety of drinking water, maximum allowable limits exist for all potentially harmful contaminants.

Watercress

Nasturtium officinale

In the cool water of springs and gentle streams, watercress spreads like a ruffled green carpet. Though the plant can survive in damp soil, it also grows as a true aquatic, with its leaves wholly or partially submerged. Its clusters of small white flowers, however, are held well above the water's surface. Colonists brought watercress to America as a remedy for scurvy (the foliage is rich in vitamin C), but today it is popular as a peppery addition to salads and soups.

Waterdog

See Mudpuppy.

Waterfall

From modest cascades along mountain streams to the thundering walls of water where rivers plunge over cliffs, waterfalls are almost always impressive. Some occur on the edges of high plateaus or along fault lines, while others are the legacy of glaciers that long ago carved their way down mountain slopes. After the ice melted, the shallow tributary glaciers that fed into far larger ones often left hanging valleys, from which rivers now empty into the deeper valley below. Yosemite Falls in California, among the loftiest in the world, for example, tumbles from a hanging valley for a total drop of nearly half a mile.

Ageless as they may seem, waterfalls undergo constant change. Some wear away their ledges grain by grain until they become gentle slopes, while others-those that plunge from hard cap rock to softer rock below-undermine their ledges chunk by chunk, gradually working their way upstream. Niagara Falls has been doing this for the last 10,000 years and, in that time, has traveled seven miles from its original site.

Waterfowl

Any bird that frequents the water, or lives on or near rivers, lakes, seas, etc.-some of which are long-legged waders and others web-footed swimmers. The term is especially common for swimming game birds.

Water hyacinth

Eichhornia crassipes

With clusters of lavender flowers perched atop rosettes of glossy green leaves, the water hyacinth is one of our prettiest aquatic plants. It is surely the most prolific, for in the warm waters of Louisiana, Florida, and Texas, 10 plants can multiply to smother an acre of lake or river in just eight months. This tropical transplant floats on air-filled bladders on its leafstalks, its dangling roots absorbing nutrients directly from the water. And it wanders freely, choking waterways and suffocating fish as it goes. Although the water hyacinth maintains its reputation as a pest, it has gained new ecological status in the South: planted in man-made lagoons, it now serves many cities as a wastewater purifier.

Waterlily

Nymphaea

Like jewels adrift on the surfaces of ponds and slow-moving streams, waterlilies are among the best-loved aquatic plants. Anchored by thick rootstocks in the mud below, the underwater stems terminate in large oval leaves, or pads, and graceful blossoms that float on or project above the surface. Once the flowers fade, they sink underwater, where their seeds ripen, float away, and settle to the bottom to take root. Our most common species-the white, or fragrant, waterlily-opens its six-inch blooms only in the morning, while the pygmy waterlily opens its smaller, scentless white flowers only in the afternoon. White to pale pink in the North, waterlilies also come in yellow, blue, and violet in the South.

Water snake

Nerodia

Often mistaken for the venomous cottonmouth, or water moccasin, which shares their aquatic habitat, water snakes look more dangerous than they are. Large and irritable, they strike if provoked, but their bite is not poisonous. Water snakes feed on fish and frogs and often bask on branches that overhang streams and ponds. The largest is the six-foot green water snake of the South. The four-foot northern, or common, water snake ranges from the Gulf Coast to Canada.

Waterspout

Whirling columns of water vapor and air, waterspouts develop beneath cumulus clouds as they pass over lakes and seas. As in tornadoes, a swirling funnel dips down from the base of the cloud and dances along the surface, sucking up water and disturbing anything in its path. Waterspouts are sometimes accompanied by strong winds, which can present a real hazard to boaters. Most, however, are short-lived and are no stronger than land-based dust devils. A waterspout's characteristic trunkshaped funnel dips down into the Gulf of Mexico, creating a spectacular summer sight from the water's edge.

Water table

In most areas an underground reservoir of water (known as ground water) saturates soil and porous rock, percolating down until it reaches an impermeable layer. The uppermost level of this reservoir is called the water table, and its depth beneath the surface rises and falls depending on the season, the amount of precipitation, and how much water is being removed through wells. Where the water table intersects the surface of the land, springs and swamps-and sometimes lakes-can form.

Wave

The ripples produced by a frog jumping into a pond have much in common with the 20-foot swells stirred up by storms at sea, for all waves are caused by some form of energy disturbing the water's surface. Boats, animals, earthquakes, and even the gravity of the sun and moon can produce waves, but most are set in motion by the wind - the force and duration of which determines the size of the waves. As waves move along the water's surface, the water itself does not move with them; it simply rises and falls as the waves pass by, as do objects floating on the water. Ocean waves change dramaticallyas they approach shore. The shallowness of the water forces them to rear up and form steep crests that spill over as breakers.

Waxwing

Bombycilla

Named for the red tips, like bits of sealing wax, on some of their wing feathers, waxwings are sleek, crested birds clad in soft grayish brown. Both the sparrow-size cedar waxwing and the slightly larger Bohemian waxwing complete their attire with black masks and yellow-tipped tails. Cedar waxwings are sociable birds that travel in flocks to seek out fruit-laden trees. Although waxwings eat some insects, they feed mainly on berries and other fruits. And like many other fruit-eating birds, they travel in flocks, roaming the countryside in a constant quest for edibles. The cedar waxwing, a bird named for its fondness for the berries of red cedars and other junipers, nests in midsummer or later, when fruit trees are heavy with morsels for the young. While cedar waxwings are widespread, Bohemian waxwings live mainly in the western mountains. In winters when food is scarce, however, they sometimes wander far to the south or east.

Weasel

Mustela

Agile and high-strung, our three weasels are small but deadly predators. The well-named least weasel is only 8 inches long, while the largest, the long-tailed weasel, rarely exceeds 16 inches. The third species, the ermine, or shorttailed weasel, is about a foot long. All are brown above and white below, but most ermines and northern populations of least and long-tailed weasels turn white in winter. The ermine and the long-tailed weasel keep their trademark-a black tip on the tail-year-round.

Weasels feed primarily on small mammals and birds, killing their prey with quick, wellplaced bites on the back of the neck. Shy and mainly nocturnal, these long, slender, shortlegged creatures are adept at snaking among boulders and into hollow logs; their prey, in fact, find few havens into which the fast-moving animals cannot follow. Although notorious as a menace to the chicken coop, weasels are appreciated for keeping rodents under control.

Weather and Meteorology

Meteorology is the science that studies the processes and phenomena of the atmosphere. Weather is the state of the atmosphere at a given time and place with regard to temperature, air pressure, humidity, wind, cloudiness, and precipitation. The term weather is used mostly for conditions over short periods of time.

Weather

The condition of the atmosphere in a given place-hot or cold, calm or windy, rainy or clear-and how it changes from day to day are known as weather. Climate, in contrast, is the average condition of the atmosphere over years. Plants and animals, for the most part, are adapted to climate, but the daily changes in weather affect their lives as well. A cold snap in autumn, for example, can cause trees to drop their leaves prematurely, just as unseasonable warmth in February can stimulate early blooming. Wind storms can blow migrating birds far off course, and ice storms, by locking up seeds and other foods, sometimes cause animals to starve.

Weed

The nemesis of farmers and gardeners, weeds are usually defined as plants growing where they are not wanted. Weeds steal water, light, and nutrients from cultivated plants, harbor diseases and insect pests, and can be poisonous or just plain unsightly. On the plus side, weeds deter erosion, help enrich the soil, and provide food and shelter for wildlife. Some, such as clover and dandelions, considered weeds in lawns, are also cultivated as crops. Many of our most familiar weeds, such as crabgrass and purple loosestrife, were introduced from abroad.

Weeping willow

Weeping willows, though native to China, are common in the East and Far West, where they add a touch of elegance to the banks of ponds and lazy rivers.

Weevil

Sometimes called snout beetles because of their long, down-curved beaks, the weevils are a large, widespread group of insects that includes some of our worst agricultural pests. With sturdy mouthparts at the tip of the snout, the females bore into nuts, seeds, buds, and other plant parts to lay their eggs. The acorn weevil, for instance, deposits its eggs inside acorns while they are still on the oak tree. When the larvae hatch, they devour the inner meat of the acorns; then, after the nuts drop to the ground, the adult weevils leave the empty shells. Other weevils mature inside kernels of rice and grain. The granary weevil, for example, causes great damage by laying its eggs in harvested wheat.

Wentletrap

With their name derived from the Dutch for "spiral staircase," wentletraps are among the most beautiful of sea shells. Delicately ribbed and usually white, the whorls of the shells taper to graceful spires that have an elegantly sculptured look. The snails that dwell inside these handsome structures are carnivores that feed primarily on sea anemones. But wentletraps are not safe from predators themselves; fish sometimes swallow them whole. When danger threatens, the snails emit a pink-purple dye.

Wetland

Wetlands are land where the water table is at, near or above the surface, or which is saturated for a long enough period to create such features as wet-altered soils and water-tolerant vegetation. They include bogs, fens, marshes, swamps and shallow open water. Wetlands are threatened by human development and water pollution. From the soggy arctic tundra to the steamy Florida Everglades, North America is well endowed with wetlands- places where the land is soaked with water. Known more specifically as bogs, marshes, or swamps, wetlands can be freshwater or saltwater, smaller than an acre or hundreds of square miles in extent. All are rich and productive habitats that teem with birds, fish, insects, plants, and other wildlife and deserve to be carefully protected. Wetlands with trees are called swamps. In a Florida swamp, alligators lurk beneath the towering bald cypresses. In contrast, marshes have no trees. Dominated by grasses and sedges, they are important nurseries for birds, fish, and other wildlife.

Whale

Titans of the deep, whales include the largest creatures on earth. One, the 100-foot-Iong, 150ton blue whale is the largest animal that has ever lived, surpassing even the colossal dinosaurs. But many other whales are not nearly so big: dolphins and porpoises, which are actually small whales, rarely exceed 10 feet. Though they look like fish, whales are mammals-the descendants of ancient land animals that gradually adapted to life in the sea. The body became streamlined, the front legs were transformed into flippers, the hind legs virtually disappeared, and the tail came to resemble that of a fish. Whales breathe air through blowholes on top of the head, where a plume of vapor can sometimes be seen as they exhale. Highly intelligent, with a sense of hearing much more refined than our own, whales communicate with each other using a complex repertoire of sounds.

Whales fall into two broad categories. The toothed whales, equipped with peglike teeth, travel in groups called pods and feed on fish and squid. The largest is the 60-foot-Iong sperm whale, with a bulky square forehead and a disproportionately narrow lower jaw. Among the smaller toothed whales are the dolphins, porpoises, and killer whale, as well as the beluga, or white whale, and the narwhal, distinguished by its long, spearlike tusk. The other group, called baleen whales, has no teeth. Instead, thin plates of baleen, or whalebone, in their mouths filter plankton from the water. The largest whales-the blue whale and the 80-foot fin whale-are baleen whales, as are the somewhat smaller humpback whale (which has no hump) and the gray whale, whose migrations along the Pacific Coast can be watched from shore.

Whelk

Among the many snails found in the waters off North America are the large, spindle-shaped whelks. They thrive in both cold and warm seas, where some kinds are active predators and others live as scavengers. Whelks lay their eggs in strings of papery capsules, which can be found stranded above the high-water mark on many beaches. One of the most dramatic shells to wash up along our Gulf and southern Atlantic coasts is the lightning whelk, a species that reaches a length of more than one foot.

Whip-poor-will

See Goatsucker.

Whip scorpion

Mastigoproctus giganteus

Named for their whiplike tails, these arachnids look as fearsome as real scorpions. When disturbed, they release a pungent vinegarlike spray that has earned them the alternate name of vinegaroons, but in fact whip scorpions are harmless to humans. They live in the South, where they hunt by night for slugs, insects, worms, and other small creatures. During the day, whip scorpions hide under logs or rocks and sometimes burrow into sand.

Whipsnake

Masticophis

Slender and speedy, whipsnakes are hard to catch and harder to handle. They deliver a mean (though nonvenomous) bite, thrash around wildly when held, and zip away in a flash when released. Sometimes called coachwhips, whipsnakes are found all across the southern United States. They spend their days hunting for rodents, birds, frogs, and other snakes, often looping their bodies on top of prey to pin it down.

Whiptail

Cnemidophorus

Slim-bodied and long-tailed, whip tails are lizards that flit along rapidly, jerking their heads from side to side. But while their nervous movements are distinctive, whiptails are of greatest interest because of their unusual reproduction. Some species consist entirely of females and reproduce by parthenogenesis-they lay fertile eggs without ever mating. Ranging from 6 to 15 inches in length, whip tails have patterned bodies, commonly marked with stripes or spots; large rectangular scales cover their bellies, while those on their backs are granular. Whiptails prefer deserts or dry woodlands and feed on insects, scorpions, and spiders. Western whiptails like to dash across open ground and are very hard to catch. Their sensitive noses can detect buried insects, which the lizards dig up and eat.

Whitefish

Pale silvery relatives of salmon, trout, chars, and graylings, whitefish thrive in cool northern lakes and streams. The fine flavor and great abundance of these freshwater fish once made them popular and lucrative commercial catches. The lake whitefish population has decreased dramatically in recent years, however, especially in the Great Lakes, where overfishing and pollution have taken their toll. But in places where cool waters have remained pristine, summer anglers and ice fishermen alike still pursue these delicately flavored sport fish.

Whitefly

Tiny insects with a waxy white powder covering their wings and bodies, whiteflies look a bit like miniature moths. Even the largest kinds are only one-eighth of an inch long, and so they appear as little more than specks on the leaves of the plants that they attack. Thriving outdoors in the warm climate of the South, whiteflies suck the sap from plants and often cause extensive damage to citrus and other trees. Indoors, the greenhouse whitefly-perhaps the most destructive species-is an unwelcome visitor to houseplants, which wither and die when they become infested with the insects.

White-footed mouse

Peromyscus

These active, long-tailed little mice with brown backs and white feet and underparts are found throughout North America in forests, fields, and brushy deserts. Nocturnal in habit, white-footed mice venture out in the evening to gather seeds, nuts, and berries, resting during the day in burrows, in crevices among rocks, in logs, or even in old birds' nests. Several kinds also invade houses, particularly in winter. Of the many species found in North America, the deer mouse is the most common and, indeed, is one of the most widespread of all our mammals. Extremely prolific, it produces two to four litters of up to eight young each year. The pinyon mouse, a denizen of chaparral and dry woodlands in the West, is distinguished from other white-footed mice by its unusually large ears. The biggest species is the California mouse, whose length, including the tail, may exceed 10 inches.

Whooping crane

See Crane.

Whorl

A 360 degree turn of a snail's shell.

Wild America

Wild America is a series of films created in the 1980s by producer/host Marty Stouffer. It is a science television series that focuses on the wildlife creatures and wild lands of North America.

Wildflower

Anyone who has admired the pink pouchshaped blossoms of the showy lady's slipper-a wild orchid that grows on the forest floor-or who has driven through the Southwest when bluebonnets are drowning the countryside in a sea of color can attest to the surpassing beauty of wildflowers. While many think of them as shy and delicate plants of remote places, wildflowers are in fact as close at hand as the nearest roadside or vacant lot.

Indeed, wildflowers flourish in virtually every habitat all across the continent. Literally thousands of species are found in North America, with some 2,700 kinds of wildflowers living in the state of Texas alone. Some, such as buttercups and dandelions, grow like weeds in almost every dooryard, but others are vanishingly rare: the entire population of the Maguire daisy of central Utah, for example, is a mere five plants. But while the beauty of wildflowers is certainly alluring to us, their shapes, textures, colors, and scents are designed to ensure their perpetuation.

Native wildflowers are exquisitely attuned to their environments, often adopting ingenious strategies for coping with less-than-ideal conditions. Carnivorous species, such as the pitcher plants and sundews, trap and digest insects, thereby flourishing in boggy, nutrient-poor soils that few other plants can tolerate. Beechdrops, pale parasitic wildflowers, survive in the shade of the forest floor by tapping into the roots of the overhanging trees.

Among the most spectacular-and successful- wildflower adaptations is that of the desert ephemerals. Their seeds sprout only after rain or snow has moistened the desert soil. But then they rush to maturity within a few weeks, flowering, dying, and leaving seed that lies dormant until the rains return.

Just as impressive is the summer show staged on the arctic tundra. In this harsh northern habitat, where the growing season lasts but weeks, many wildflowers sprawl across the ground in colorful mats. As delicate as they appear, however, these ground huggers are surprisingly hardy. The arctic forget-me-not, for instance, grows in dense pincushionlike clusters, an adaptation that protects the plant from fierce winds.

Equally successful are the many immigrants from foreign lands. A few, such as foxgloves, probably came as garden flowers and escaped into the wild. Many more arrived as impurities in agricultural seed or as hitchhikers in imported hay or in ballast that was dumped by visiting ships. Some were unable to compete with native wildflowers, but many gained a foothold, and a few-Canada thistle, for instance, and purple loosestrife-became aggressive pests, colonizing millions of acres.

The intoxicating fragrance of honeysuckle on a summer evening, the slick yellow petals of buttercups, and the spurred blossoms of the columbines are all engineered to attract pollinators. Bees, the most common agents of pollination, are drawn to sweetly scented flowers, while carrion flies are attracted to early spring bloomers such as skunk cabbage, which waft an odor reminiscent of rotten meat. Moths, nocturnal fliers, visit heavily scented, usually white blooms that are easy to locate under the cover of darkness. The color and shape of flowers also provide clues as to how they are pollinated. Honeybees favor blue and yellow flowers that have petals modified into landing platforms. In addition, dark lines on petals, like the lights on an airport runway, tell the bees where to find nectar and pollen. Hummingbirds and butterflies visit long, tubular blossoms, many of which are bright red, a color that bees see as black.

Wildflowers are a link with the lore of the past. Long used for medicines, folk remedies, dyes, and foods, they have, over centuries of familiarity, acquired common names that remind us of simpler times. Fleabane, a member of the sunflower family, for example, was used to repel fleas in the days when insecticides were unavailable, and the roots and leaves of soapwort were lathered into suds on many frontier laundry days. A syrup made from coughwort leaves was long a favorite remedy for colds, and Joe-pye weed preserves the name of a Massachusetts Indian who, in the late 18th century, used this wildflower to cure colonists of fevers. Roundleaved hepatica, a staple of herbal practitioners, was also known as liverleaf because of an old belief that a plant's outward appearance was a sign of its healing properties.

Though the use of wildflowers in home remedies and crafts is now largely a thing of the past, they still can be appreciated for their simple beauty. While a great number of species are accessible within a short walk of almost any front door, human activities have brought many others to the brink of extinction. The greatest threat is suburban development - l,000,000 acres of countryside is lost in this way every year. Fortunately, some cities and towns are trying to route development around sensitive habitats. Individuals can make a contribution by getting to know local varieties, learning the lore and legends they have inspired, and awakening others to the beauty and charm of wildflowers.

Wild ginger

Asarum

Though not related to the spice of the same name, wild ginger releases a similar fragrance when its leaves and roots are bruised. In spring dull brownish ground-hugging flowers appear beneath the large heart- or kidney-shaped leaves. The urn-shaped blooms, which flare at the mouth with three pointed lobes, emit a foul odor that offends humans but attracts pollinating flies. These woodland plants were used as a digestive remedy by American Indians, which explains one of their nicknames, Indian ginger.

Wild lettuce

Lactuca

These coarse, weedy relatives of the familiar salad green bear sharply toothed, deeply lobed leaves and clusters of yellow, white, or blue flowers that look like little dandelions. Up to 10 feet tall, the wild lettuces are plants of roadsides, fields, waste places, and woodland clearings. Their milky sap, reminiscent of the juice of the opium poppy, was prescribed by generations of doctors as a sedative and painkiller until chemical analysis revealed that "lettuce opium" is, after all, not a narcotic.

Wilderness

Biological Philosophy term. Nature untamed, untouched by humankind, potentially hostile, indifferent, destructive, but also awe-inspiring, sublime, exhilarating.

Wildlife

Wild animals and vegetation, especially animals living in a natural, undomesticated state. Wildlife is all non-domesticated plants, animals, and other living things. Domesticated wildlife are plants, animals, and other living things that have been removed from nature and raised in an environment that is more or less controlled. Domestication, act of taming, or controlling, wild plant and animal species and producing them for human benefit, is performed often and has an impact on the environment, both postive and negative.

Wildlife is a very general term for life in general. Humans have historically tended to separate themselves and their society from wildlife in a number of ways; besides the obvious difference in vocabulary, there are differing expectations in the legal, social, and moral sense. This has been a reason for debate throughout recorded history. Humans have often declared certain animals to be sacred, and in modern times concern for their welfare is a growing concern. It is viewed as unacceptable when humans engage in the cruel exploitation of wildlife for human benefit or entertainment.

Wildlife Film

A wildlife film or nature documentary is a presentation about animals or other non-human living creatures, usually concentrating on film taken in their natural habitat. Such programmes are most frequently made for television, particularly for public television and science channels, but some are also made for the commercial television networks. Wildlife and natural history films have boomed in popularity and have become one of modern society's most important sources of information about the natural world. Yet they have been largely ignored by film and television critics and scholars. Most programs or series focus on a particular species or family of animals. Although most take a scientific and educational approach, some present animals purely for the viewer's pleasure. Although almost all have a human host or presenter, the role varies widely, ranging from explanatory observer to extensive interaction or even confrontation with animals. Well-known nature documentary makers and presenters include Marty Stouffer and Marlin Perkins. Most documentaries are for television and are usually of 25 or 50 minutes duration, but some are made as full-length cinematic presentations.

Wind

Movements of air in the atmosphere-windsare produced when air is heated by the sun, expands, and rises, permitting cooler, denser air to rush in and take its place. These movements can be as gentle as the breezes that rustle leaves or as powerful as gales that uproot entire trees. While winds can blow in any direction, in our latitudes they generally travel from west to east. These prevailing westerlies help in predicting the weather. If it is raining a few hundred miles west of a place today, for instance, rain will probably fall in that place tomorrow. Both wildlife and the environment are constantly affected by winds. They carry the seeds and pollen of plants, assist birds in their migrations, whip up waves at sea, and help sculpt the land through erosion.

Wind chill (Weather)

Wind chill describes the way we feel as a result of the combined cooling effects of temperature and wind. Wind chill is most commonly calculated using the Siple-Passel formula, and expressed as the rate of heat loss in watts per square metre, or likened to the equivalent temperature on a calm day.

Windflower

See Anemone.

Winter

Winter is one of the four seasons. It is the season with the shortest days and the lowest temperatures. Depending on place and culture, what is considered to be the start and end of winter vary. Contemporary thinking takes winter to be the months of December, January, and February in the Northern hemisphere and June, July, and August in the Southern hemisphere. Meteorological winter is the season having the shortest days (which vary a great deal) and the lowest temperatures. Nighttime predominates the winter season, and in some regions it has the highest rate of precipitation, as well as prolonged dampness due to permanent snow cover in such areas. Measured, winter begins on the shortest day of the year, and each day of winter has more sunlight than the previous one.

Outside the equatorial areas, winter is cold and (particularly in the Northern Hemisphere) snowy. Winter is by convention counted as the whole months of June, July and August in the Southern Hemisphere and December, January and February in the Northern Hemisphere.

The three-month period of the shortest days and weakest solar radiation occurs during November, December and January in the Northern Hemisphere (May-July in the Southern).

In reality, the three-month period associated with the coldest average temperatures typically begins somewhere in late November or early December in the Northern Hemisphere. If "winter" is defined as the statistically coldest quarter of the year, then the astronomical definition is too late by almost all local climate standards. No matter, winter is the only season that spans two calendar years in the northern hemisphere. In other words, there are very few temperate climates in which the vernal equinox is on average colder than the winter solstice. The tilt of the earth's axis relative to its orbital plane has a dramatic effect on the weather. The popular belief that winter is caused by the Earth being farther from the Sun than in summer is not true. In fact, in the Northern Hemisphere, winter occurs when the Earth is its closest to the Sun.

The earth is tilted at an angle of 23°27' (23 degrees 27 minutes) to the plane of its orbit, and this causes different latitudes on the Earth to directly face the Sun as the Earth moves through its orbit. It is this variation that primarily brings about the seasons. When it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. During winter in either hemisphere, sunlight hits that hemisphere at an oblique angle. This effect is compounded by the larger distance that the light must travel through the atmosphere, allowing the atmosphere to dissipate more of this already limited heat.

Winter Bird Population Study (U.S.):

Bird Biology Avian Conservation term.

A program involving census of wintering birds by counting and mapping, but not depending on persisting occupation of territories or home ranges.

Wintergreen

Gaultheria procumbens

A dwarf creeping shrub less than six inches tall, wintergreen spreads a carpet of oval, shiny evergreen leaves across sandy woodlands from Newfoundland to Alabama. In midsummer waxy, bell-shaped white flowers dangle among the leaves and are followed by tasty, bright red berries-a favorite winter food of grouse and other wildlife. The pungent oil that suffuses the plant is used as a flavoring in candies and chewing gum and in balms that soothe sore muscles.

Witches' broom

The clusters of spindly shoots that sometimes spring from the branches of forest trees and shrubs really do resemble the broomsticks that witches were supposed to mount and fly. And so it is not surprising that our ancestors believed that witches not only caused their growth but also used them as resting places during their

Witches' broom is a symptom of disease in plants; these unusual growths have inspired much folklore and legend.

travels. In fact, these abnormalities are a symptom of plant disease. The condition is caused by a number of agents, including viruses, fungi, and insects, and it appears on conifers as well as alders, birches, cherries, and other plants.

Witch hazel

Hamamelis

Shrubs that are native to eastern woodlands and stream banks, both of our witch hazels are sometimes referred to as winterbloom. The nickname is appropriate, for common, or American, witch hazel unfurls its tassels of ribbonlike yellow petals as late as December, and vernal, or Ozark, witch hazel blooms in January or February. The woody fruits that follow are hard capsules that literally explode when they are ripe, shooting shiny black seeds more than 15 feet away. The familiar soothing lotion called witch hazel is made from the leaves and bark of the plant, and its forked branches have been used as divining rods.

Wolf

Canis

Though the sound of wolves howling in the night is enough to send chills down the spine, their reputation as ferocious enemies of man owes more to fiction and folklore than to reality. Wolves, in fact, go out of their way to avoid humans. Even so, they have been hunted so persistently over the years that one of our two species, the red wolf of the Southeast, has virtually disappeared. The other-the gray, or timber, wolf-whose domain once included the South, now lives only in northern wilderness areas. Resembling large, wide-faced German shepherd dogs, gray wolves vary in color from white on the arctic tundra to gray or black in forested regions. They travel in packs, working cooperatively to bring down such big game as deer, moose, and caribou. Though wolves are usually regarded as unbeatable in their quest for prey, they often fail to subdue their intended victims. Wolves are no match for a healthy adult moose, for example, and so must routinely select individuals that are old or sick.

Highly intelligent, wolves behave according to a complex set of social rules. The pack is led by a dominant male, and each member knows its place within the group. Wolves communicate by means of postures and scents, as well as an array of yelps, whines, and growls, and they all work together to rear the cubs, which are usually produced only by the dominant pair. Timber wolves roam North America's northern woodlands night and day in pursuit of prey.

Wolverine

Gulo gulo

Dark brown with dull yellow stripes on its forehead and sides, the wolverine, at up to 60 pounds, is one of the largest members of the weasel family. Though much smaller than any wolf or bear, it is nevertheless among the most formidable predators of the arctic tundra and far western mountains. A solitary hunter on the prowl both night and day, this tough, muscular creature plods relentlessly after prey. Incredibly strong for its size, the wolverine can bring down quarry as big as deer. Smaller animals are also fair game, and insects, birds' eggs, berries, and carrion supplement its diet. Despite its strength and prowess, the wolverine needs large wilderness areas in which to range and is intolerant of people; wherever humans modify the land, wolverines quickly disappear.

Woodchuck

Marmota monax

Unlike most other marmots, which live in high mountains, woodchucks prefer lowland forests and meadows across Canada, the Northeast, and the Midwest. They have prospered in many agricultural areas and are often considered pests.

After fattening on tender plants-alfalfa and clover are favorites--woodchucks hibernate in their burrows in winter. Although they are the groundhogs of Groundhog Day, most remain underground long after February 2. The young, born in spring, are ready to venture into the outside world within a month. During the summer these stocky rodents can be seen standing in fields, ready to duck out of sight with a loud whistle at the first sign of danger.

Woodcock

Scolopax minor

A stocky, snipelike bird of the East, the American woodcock is best known for the elaborate and unique aerial display that the male performs in early spring to attract a mate. He struts back and forth across his territory and then, with wings whistling, takes to the air. Flying in wide circles, he sings a bubbly song and, still singing, zigzags back to earth like a falling leaf. If successful, he is greeted by a suitably receptive female. Woodcocks build their nests on the ground, where the birds are camouflaged by streaked, brownish plumage that blends with the leaf litter. They use their unusually long, thin, sensitive bills to probe for earthworms in damp meadows and swampy woods.

Woodland

Biologically, a woodland is a treed area differentiated from a

. In these terms, a forest has a largely-closed canopy; the branches and foliage of trees interlock overhead to provide extensive and nearly continuous shade. A woodland, with sunlight penetrating between trees. Some types of woodland are essentially

with shrubs and scattered trees.

A woodlot is a closely-related term, which refers to a stand of trees generally used for firewood. While these woodlots often technically have closed canopies, they are so small that the

is such that they are ecologically more woodland than forest.

Woodpecker

Famous for the rat-a-tat drumming with which they punctuate the peace and quiet of forests, woodpeckers are well equipped for life on tree trunks. Sharp claws and stiff, prop like tails hold the birds in place while muscular necks and stout bills work in concert to drill holes into bark. Drilling is a way of life for these birds: it is used both for excavating nest holes and for finding insects, which are lapped up with a long, sticky tongue. Woodpeckers also drum on hollow branches to proclaim territory and communicate with mates. A few members of the family, however, are nonconformists. The northern flicker feeds on the ground, where its favorite food is ants; sapsuckers drill holes in bark to drink the sap that oozes out; and acorn woodpeckers drill holes in trees-and utility polesas storage spaces for the acorns they eat.

Most of our 22 species are black-and-white with a dash of red on the males' heads. The smallest and one of the commonest is the sixinch downy woodpecker, found from coast to coast. Since our largest species, the 20-inch ivory-billed woodpecker of the Southeast, is probably extinct, the honor for top size now goes to the crow-size pileated woodpecker.

Wood rat

Neotoma

Native to woodlands and other wild places, these furry rodents live up to their nickname, pack rats, for they nest in structures (sometimes huge) that are built of all sorts of odds and ends. (Desert-dwelling species ward off enemies by using plenty of cactus spines in their construction.) Wood rats often raid campsites at night, gathering coins and other shiny trinkets to incorporate into their fortresses. Leaving a twig or pebble in place of the purloined prize has earned them yet another nickname, trade rats.

Wood sorrel

Oxalis

Delicate plants with cloverlike leaves, wood sorrels grow in moist, shady woodlands. The white blossoms of the common wood sorrel are striped with pink, but there are yellow- and purpleflowered species as well. Because of their pleasantly sour taste, the leaves are often added to salads. Herbalists have long used the plants for treating a variety of ills, but it is now known that overindulgence in the foliage inhibits the body's ability to absorb calcium. Wood sorrel often forms a thick ground cover in the moist forests that it inhabits.

Wood stork

Mycteria americana

The large, long-legged wood stork is a wading bird that lives in the marshes and swamps of the Southeast. It feeds in shallow water, using its long, probing bill to catch fish, frogs, and other prey. Mostly white, the wood stork has a blackish, scaly-looking, unfeathered head that has earned it the nickname flinthead. Despite its homely face, it is graceful on the wing, soaring with its long neck and legs extended. The gregarious wood stork breeds in large colonies, building a flimsy nest of sticks and twigs in a tree or other swamp vegetation. Since it depends on falling water levels to concentrate its prey in small pools, it does not nest at all in very wet years when prey is dispersed over a wide area. Because of habitat destruction, our only native stork is now listed as endangered.

Woolly bear

Isia isabella

Black at both ends and brown in the middle, the familiar woolly bear is the caterpillar of the Isabella tiger moth. It is most often seen in autumn, crawling across the ground in search of a safe place to hibernate for the winter. Like the caterpillars of most other tiger moths, the woolly bear is covered with stiff bristles. When disturbed, it curls up quickly, and the bristles make it difficult for predators to pick up. Not at all fussy about its diet, the woolly bear feeds on the foliage of a wide variety of plants, including grasses, and is common from coast to coast.

Wrasse

Found mainly in warmer waters, wrasses are a diverse group of brightly colored fish. Typically they have narrow bodies-from three inches to a few feet long-and pointed snouts; all have pharyngeal, or throat, teeth, used for crushing crabs, sea urchins, and other food. (Some of the smaller kinds pick parasites off other fish.) The tautog, a common Atlantic wrasse, is popular with anglers: found from Nova Scotia to South Carolina, it lurks around breakwaters and other rocky areas. The California sheephead, with a distinctive hump on its head, favors the kelp beds and rocky shores of the Pacific.

Wren

Nine species of wrens-all of them small, stocky brownish birds that often perch with their tails cocked over their backs-are native to North America. The best known is the house wren, which nests in parks, farmyards, and orchards from coast to coast. Tenacious and aggressive, it is a welcome springtime visitor that fills the air with bright, bubbly song. The Carolina wren, the largest eastern species, is a rusty brown bird that happily nests in baskets, mailboxes, and other man-made cavities, as do most other wrens. The starling-size cactus wren is a husky bird with a boldly spotted breast. Noisy and conspicuous, it flits along the desert floor, picking among rocks and brush for insects and other food, and builds its nest in the well-armed safety of a spiny cactus.

Wrentit

Chamaea fasciata

These secretive West Coast songbirds are more easily heard than seen: the males sing yearround, but wrentits seldom venture from their home turf in dense scrub thickets or chaparral. Mated wrentits form devoted pairs, preening each other's feathers and foraging together for insects and berries. They also roost side by side, sometimes fluffing their plumage and leaning against each other so that they look like a single little gray-brown ball of feathers.

Xeric

Referring to habitats in which plant production is limited by lack of water.

Xerophyte

Plants that are able to live in places where fresh water is in short supply-deserts and salt marshes, for example-are called xerophytes. Succulents such as cacti and agaves store water in their stems and leaves to weather times of drought. Other desert plants, known as ephemerals, germinate during the rainy season only, completing their entire life cycle- from seed to flower to seed - in a matter of weeks. Many xerophytes have waxy coatings or dense, feltlike coverings of hair that protect them from the sun and wind and slow down water loss. Others react to the blazing sun by folding their leaves, positioning them so that the sun's rays strike less surface area, or dropping them altogether during dry spells.

Yarrow

Achillea millefolium

A tolerance for drought and an ability to thrive even on poor soils have made yarrow a common weed of waste places throughout North America. Growing up to three feet tall, it is clad with finely cut foliage that has a pungent aroma, as do the flat-topped clusters of small white-or sometimes pink-flowers that appear in summer. Yarrow is said to have been used by the ancient Greek hero Achilles (hence the plant's generic name) to stanch the blood of warriors' wounds. American colonists and the Indians used it as a healing herb: both drank yarrow tea to treat digestive ills and reduce fevers, and yarrow poultices were recommended for healing wounds, cuts, and burns.

Yellow rattle

Rhinanthus

Flourishing as far north as the Arctic Circle, yellow rattle colors fields, moist alpine meadows, and thickets with spikes of bright golden blossoms. Each of the tubular flowers protrudes from a swollen green base, which matures into a bladderlike, seed-filled pod. When stirred by the wind, the dry, ripened pods do indeed make a rattling noise. Up to 24 inches tall, our most common species, also known as rattlebox, is in bloom from June to September.

Yellowwood

Cladrastis kentukea

Named for its handsome timber, yellowwood is a slow-growing, long-lived tree that is found in isolated pockets in parts of the Southeast and Midwest and is nowhere abundant. It favors the rich soils of river valleys and streamsides, where it sometimes reaches a height of 60 feet. In early summer, yellowwood produces long, drooping clusters of fragrant, creamy white flowers, which are followed by papery seedpods two to three inches long. The featherlike compound leaves turn bright yellow before dropping from the tree in autumn. The durable wood, when available, is coveted for gunstocks.

Yeti

The Yeti is the same creature as the Abominable Snowman, which is also called Yeti. The Snowman is an obviously mythical creature said to live on Mount Everest and other mountains of the Himalaya range of Asia. Reports of such a creature have also come from remote parts of China and the Soviet Union. According to legend, the Abominable Snowman is a hairy beast with a large, apelike body and a face that resembles that of a human being. It supposedly has long arms that reach to its knees, and it is reported to walk erect on its thick legs. Legend says that the Snowman sometimes attacks villagers. There is no direct evidence that the Yeti exists, even though individuals have photographed “Snowman” tracks in the snows near Everest. In North America, similar reports describe a creature usually known as Bigfoot. See Bigfoot.

Yew

Taxus

Shade-tolerant trees and shrubs with flattened, evergreen needles, yews are easily distinguished from other conifers by their red berrylike fruits. Largest of the three species native to North America is the Pacific yew; up to 60 feet tall, it is found in far western forests from southern Alaska to California. Its durable, reddish wood is used for archery bows, canoe paddles, and hand tools. Another northerner, Canada yew, is a low woodland shrub; though the foliage of all yews is poisonous, Canada yew is heavily browsed by moose and deer. florida yew, a 30-foot tree, grows only in northwestern Florida.

Youth (Action and Learning)

Young people between the ages of 15-25 years may contribute to environmental knowledge through their own studies and carry out activities aimed at protecting or restoring the environment. Many are active in environmental discussion groups that provide valuable input to decisions and strategies.

Yucca

while yuccas are most common in the deserts of the Southwest, these dramatic plants range all across the southern states and even as far north as Montana. A few, including the renowned Joshua tree of California's deserts, are tall and branching. But most are shrubs with trunkless ground-level clusters of daggerlike leaves that have inspired such names as Adam's needle and Spanish bayonet. The yuccas produce tall spikes of white to purplish, cup-shaped flowers. These open after dark and are pollinated by a type of moth that lays its eggs exclusively on yuccas.

Zebra longwing

Heliconius charitonius

Our only member of a group of tropical butterflies called heliconians, the zebra longwing flies slowly, almost feebly, through wooded areas in the South. It seems to know that its bold blackand-yellow pattern warns predators that it is distasteful- the result of feeding on the poisonous leaves of passionflowers. Unlike most butterflies, the adults feed on pollen rather than nectar and gather at night in communal roosts.

Zinnia

Though the cultivated zinnias that grace our gardens are all descended from a Mexican ancestor, several species of wild zinnias thrive on dry, rocky slopes and grassy plains in parts of the South and West. Like most members of the sunflower family, their blossoms are characterized by a ring of petallike ray flowers surrounding a central disk. The plants, which commonly grow from 4 to 20 inches tall, are in bloom from early spring through midfall.

Zooplankton

The general term for all of the very small animals that swim or float at or near the water's surface.