any of several small, round ducks with short wings and long, spiky tail feathers, of the tribe Oxyurini, family Anatidae (order Anseriformes). A common and typical stifftail is the ruddy duck (Oxyura jamaicensis) of North America. In most species the drake has shiny reddish plumage and a bright-blue bill in breeding season; at other times he is drab. Hens are plainly coloured birds with a line or two crossing the face. A stifftail uses its specialized tail feathers for steering underwater in search of food. Stifftails can scarcely get about on land; like most waterfowl, they sleep on the water. The drake has an expansible esophagus and an air sac in the neck that he inflates (and, in some species, beats upon with his bill) during his noisy, elaborate courtship display. Stifftails usually build substantial nests of reeds in marshes. The eggs, averaging four or five to a clutch, are rough-surfaced and relatively the largest laid by waterfowl. The drake helps rear the young-a rare trait among ducks
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