Duck - biology. I INTRODUCTION Duck, a water bird with webbed feet, short legs, and a broad, flat beak. Ducks belong to the same family--waterfowl--as geese and swans. But most ducks have smaller bodies and shorter necks and legs than geese or swans. In general male ducks are brighter in color and more boldly patterned than female ducks, whereas in geese and swans both sexes look alike. Male ducks are called drakes, female ducks are called hens or ducks, and baby ducks are called ducklings. II RANGE AND HABITAT Ducks live on all continents except Antarctica, and they inhabit most of the world's islands. Most ducks live near ponds, rivers, wetlands, or other places with freshwater. Some ducks inhabit saltwater bays, river mouths, or seas. Ducks that nest in cold or temperate (mild) climate zones usually migrate to warmer waters for the winter. Some fly from Alaska or northern Canada all the way to Central or South America. Eider ducks inhabit cold, northern waters of the Atlantic and Pacific oceans year round. III KINDS OF DUCKS Experts disagree on the classification of ducks, but there are some obvious groupings based on physical characteristics or behavior. There are about 150 species of ducks. Ducks that live free in nature are known as wild ducks; ducks kept as farm animals or pets are domestic ducks. A Dabbling, Diving, and Perching Ducks Two of the largest groups of ducks are the dabbling ducks and the diving ducks. Dabbling ducks feed largely near the surface of the water. They prefer shallow waters where they can upend their bodies to reach food on the bottom. They are often found in ponds, creeks, and shallow lakes. Diving ducks plunge underwater to feed and may dive deep. They prefer deeper, more open waters, such as large lakes, bays, and seas or oceans. Mallards are the most familiar dabbling ducks in North America, and the most common ducks in the world. Other common dabblers are gadwalls, pintails, teals, and wigeons. Shelducks are common surface-feeders of Africa, Asia, and Europe, although they are not usually classified as dabblers. Diving ducks include canvasbacks, goldeneyes, redheads, ring-necked ducks, and scaup. Other ducks that dive but are not classified as divers include mergansers and ruddy ducks. The stiff tail feathers of the ruddy duck act like a rudder when the duck swims underwater. Perching ducks have long tails and short legs and can sit in trees, although they rarely do. The wood duck is an example of a perching duck. It builds its nest in trees or logs. Diving, dabbling, and perching ducks are sometimes classified as a subfamily. Other subfamilies include whistling ducks; stiff-tail and freckled ducks; shelducks; and eiders, scoters, mergansers, and other sea ducks. B Domestic Ducks People raise domestic ducks for meat and eggs or keep them in backyards as pets. Ducks and geese were domesticated at least two thousand years ago. Except for the Muscovy duck, all breeds of domesticated ducks derive from the wild mallard, the first duck to be domesticated, probably in Europe. The white Pekin and the brownand-white Saxony are domestic ducks bred from the mallard. The Muscovy, which was domesticated in Central or South America, is a large duck with greenish black feathers and red wattles. IV PHYSICAL CHARACTERISTICS Ducks swim, feed, rest, and sometimes build nests in water. They are excellent swimmers and move about better in water than on land. They have webbed feet that act like paddles in water but cause them to waddle awkwardly on land. Diving ducks have large feet, which help them swim fast underwater. The feet of ducks have many blood vessels that keep their feet warm and enable them to walk on ice comfortably. The legs of diving ducks are placed far back on their bodies. This placement helps the ducks dive but makes it difficult for them to keep their balance on land. To take off for flight, diving ducks flap their wings and run across the top of the water until they become airborne. Dabblers have larger wings than divers and are able to spring into flight directly. Ducks have lots of soft inner feathers, or down. The down is water resistant, and it traps air to keep the duck warm and afloat. Ducks keep their down waterproof by frequent preening. Using its bill the duck takes oil from a preen gland at the base of its tail feathers and rubs the oil over its feathers. The down of the eider duck is used for filling pillows and quilts because of its softness and elasticity. Ducks vary in color, but most are brownish overall with areas of grey, black, or white. The males are generally more brightly colored than the drab females, especially in spring when their bright colors help males attract a mate. In some species the males lose their bright feathers in late summer or autumn, after the mating season. The heads of some male ducks have a greenish or purplish sheen in sunlight. The male mallard's head, for example, appears green, while the male ring-necked duck's head appears purple. Some ducks have a colored patch on their wings called a speculum. In mallards the speculum is blue. In green-winged teals it is green. The most colorful duck in North America is the wood duck. The male wood duck has highly iridescent feathers of green, purple, black, white, and blue. The female is similar to the male, but her colors are duller and she has a white ring around her eye. Both sexes have a crest of feathers on top of their head. Ducks also vary in size. The pintail is the largest North American duck in length. Pintails grow as long as 64 to 76 cm (25 to 30 in), including their tail feathers. But the mallard is the largest in weight, reaching about 1 kg (2 lbs). The green-winged teal is the smallest North American duck, with a length of 35 cm (14 in). V FEEDING AND DIET Dabbling ducks feed largely on water grasses, pond weeds, seeds, and insects and other small invertebrates near the water's surface. Some dabblers tip their upper bodies into the water while they eat, leaving their tails sticking into the air. Others use their beaks to skim the surface of the water. Some dabblers also eat seeds, grass, or insects on shore. Divers eat less plant matter and more animals than dabblers do. The animals in their diet include clams, mussels, and other shellfish; small crustaceans; fish eggs; and fish. Sea ducks and mergansers also feed primarily on fish and other marine animals. Ducks, except for mergansers, have a broad bill with a rounded tip. The edges of the bill are lined with bony notches, or lamellae, that strain plant and animal matter from water. When ducks feed they push their tongue against the top of their mouth to squeeze water through the lamellae, leaving the food behind. Mergansers are fish-eating ducks with slender bills that are notched on the edges like the blade of a saw. These saw-toothed beaks help the ducks catch and hold their slippery prey. VI COURTSHIP AND REPRODUCTION Ducks form pairs long enough to mate, but most species find new mates each year. In a few species, including buffleheads and whistling ducks, the pairs form longlasting bonds. The male ducks perform courtship displays in fall and winter to attract females. These displays involve head and tail shaking; wing flapping; quacks, whistles, and other sounds; and raising or lowering the body in the water. The male mallard, as part of his display, dips his head underwater and brings it up suddenly while spurting an arc of water toward the female. The female duck generally selects the nesting site, and she often returns to the same site year after year. Most ducks build nests on the ground, often in dense grasses, rushes, or other plants that grow near the water's edge. The plants hide the nest from predators. Wood ducks nest in holes in tree trunks or logs, or in nest boxes provided by humans. Whistling ducks, goldeneyes, and buffleheads also nest in tree holes. Female ducks often pluck feathers from their breast to line the nest. The female generally lays 6 to 12 eggs and incubates them until they hatch, about four weeks later. The ducklings are able to swim and feed themselves within a day after they hatch. The female watches over her ducklings until they are able to fly. In some species the males also help care for the young. VII CONSERVATION Two North American duck species are considered threatened under the Endangered Species Act: the spectacled eider and Stellar's eider. Both are sea ducks that live in the coastal waters of Alaska and Canada. Scientists do not know for sure why their numbers have declined. Other sea ducks that breed in the north, including scoters and long-tailed ducks, also declined in number during the 20th century. Oil spills and other forms of water pollution are harmful to ducks. Lead in coastal waters is suspected of reducing the number of eiders. Habitat loss also poses a major threat to ducks and other waterfowl. Many North American ducks breed in wetlands and potholes on the prairies of the Great Plains. As wetlands were drained for farmland and pasture, many of these breeding places were lost. During droughts these breeding areas dry up, and ducks fail to reproduce as a result. Ducks, like other waterfowl, tend to follow the same path, or flyway, year after year when they migrate. There are four main flyways for waterfowl in the Americas: the Atlantic, the Mississippi (along the Mississippi River), the Central (between the Missouri and Mississippi rivers), and the Pacific. During migration ducks stop along the way at wetlands or other water sites to rest and feed. Today, these stopovers are few and far between. Maintaining them is important for conserving waterfowl. Scientific classification: Ducks belong to the family Anatidae of the order Anseriformes. Most of the dabbling ducks belong to the genus Anas, including the mallard, which is Anas platyrhynchos; the black duck, A. rubripes; the gadwall, A. strepera; the pintail, A. acuta; the American wigeon, A. Americana; the Northern shoveler, A. clypeata; and the green-winged teal, A. crecca. Many diving ducks belong to the genus Aythya, including the canvasback, which is Aythya valisneria; the ring-necked duck, A. collaris; and the lesser scaup, A. affinis. The wood duck is classified as Aix sponsa, the ruddy duck as Oxyura jamaicensis. The many other genera (plural of genus) that ducks belong to include Bucephala (goldeneyes and buffleheads), Dendrocygna (whistling ducks), Melanitta (scoters), Mergus (common and red-breasted mergansers), Somateria (most eiders), and Tadorna (shelducks). Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
