duck, common name for wild and domestic waterfowl of the family Anatidae, which also includes geese and swans. It is hunted and bred for its meat, eggs, and feathers. Strictly speaking, duck refers to the female and drake to the male. Ducks are usually divided into three groups: the surface-feeding ducks—such as the mallard, wood duck, black duck, and teal—which frequent ponds, marshes, and other quiet waters; the diving ducks—such as the canvasback, scaup, scoter, eider, and redhead—found on bays, rivers, and lakes; and the fish-eating ducks, the mergansers, with slender, serrated bills, which also prefer open water. The surface feeders take wing straight up, while the divers patter along the water's surface in taking off. Ducks make long migratory flights. At the time of the postnuptial molt, the power of flight is temporarily lost, and most of the Northern Hemisphere drakes assume "eclipse" plumage similar to that of the female. The ancestor of all domestic breeds (see poultry), except the Muscovy of South American origin, is the mallard, Anas boscas, which is found in Europe, Asia, and North America. In the mallard drake a white ring separates the bright-green head and neck from the chestnut breast, the back is grayish brown, the tail white, and the wings have blue patches. The wood duck, Aix sponsa, smaller than the mallard, nests in hollow trees; the drake is a varicolored, iridescent ornament to lakes and ponds. The blue-winged, green-winged, and European teals (genus Querquedula ) are small ducks that fly with great speed. The canvasback, Fuligula vallisneria, is hunted widely for its palatable flesh. It has a chestnut head and neck, black bill and chest, and whitish back and underparts. A swift flier, it is also an expert swimmer and diver. It breeds from the Dakotas and Minnesota north and winters on the coastal waters along the entire continent. In northern countries a portion of the down with which the eider ducks line their nests is systematically collected, as are some of the eggs; since the eiders lay throughout the season, these are soon replaced. The mergansers, genus Mergus, also called sheldrakes or sawbills, are usually crested. They include the goosander and the smaller red-breasted merganser, both circumpolar in distribution, and the North American hooded merganser, similar to the Old World smew. Because their fish diet gives their flesh a rank taste, they are called by sportsmen "trash ducks." Ducks are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Anseriformes, family Anatidae.