[O.E.] A well-known swimming-bird, whose boat-shaped body and long neck and webbed feet adapt it to live in the water. Its body is covered with a thick and close plumage ; its coat of down is very thick; and it has a large supply of oil in an oil-gland which keeps its feathers from getting wet. Its fiat bill is supplied with rough plates around the edge, which form a good strainer, and so it can pick its food from the mud and water it takes into its mouth. Ducks are kept on farms- for the sake of their eggs and their flesh. The feathers are also of use for bedding, those of the eider duck (q. v.) being especially soft and fine. River ducks include the common domestic duck, the wood-duck, the mandarin or Chinese duck, and the
Muscovy duck, originally of South America. The steamer-duck of South America cannot fly, but swims swiftly.