duck

Any of about 50 species of short-legged waterbirds with webbed feet and flattened bills, of the family Anatidae, order Anseriformes, which also includes the larger geese and swans. Ducks were domesticated for eggs, meat, and feathers by the ancient Chinese and the ancient Maya (see poultry). Most ducks live in fresh water, feeding on worms and insects as well as vegetable matter. They are generally divided into dabbling ducks and diving ducks.

Anatomy
The three front toes of a duck's foot are webbed and the hind toe is free; the legs are scaly. The broad rounded bill is skin-covered with a horny tip provided with little plates (lamellae) through which the duck is able to strain its food from water and mud.

Species of duck
The mallard Anas platyrhynchos, 58 cm/1.9 ft, found over most of the northern hemisphere, is the species from which all domesticated ducks originated. The male (drake) has a glossy green head, brown breast, grey body, and yellow bill. The female (duck) is speckled brown, with a duller bill. The male moults and resembles the female for a while just after the breeding season. There are many other species of duck including teal, eider, mandarin duck, merganser, muscovy duck, pintail duck, shelduck, and shoveler. They have different-shaped bills according to their diet and habitat; for example, the shoveler has a wide spade-shaped bill for scooping insects off the surface of water.