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DUCK,
name collectively applied to numerous species of birds of
the waterfowl family Anatidae. Ducks differ from geese and swans
of the same family by their shorter necks and legs and other anatomical
differences. Ducks inhabit all continents except Antarctica and
most of the world’s islands. The legs of most ducks are
placed far apart and toward the rear, making them awkward walkers
but efficient swimmers. The underplumage, or down, which is buoyant
and insulating, is kept water-resistant by frequent preening with
oil from a gland, called the uropygial gland, at the base of the
tail feathers. Ducks, with the exception of mergansers, have spatulate
bills lined with bony notches, or lamellae, for straining plant
and animal matter from water.
Some island species have lost the power of flight, but most
ducks of northern continents are highly migratory. In a few species,
the sexes are alike in color, but in most the males are brighter
and more boldly patterned.
Ducks have elaborate courtship displays, each unique to its
species. Pair formation in most northern hemisphere ducks takes
place in winter: hence, unlike most birds with seasonal plumage,
males wear their bright plumage in winter, and briefly assume a
femalelike “eclipse” plumage during the summer.
Nests of most species are on the ground, containing from 4 to 12
eggs, surrounded by down feathers plucked from the female’s
breast and belly. Ducklings are able to swim and feed themselves
soon after they hatch. Some species, such as the wood duck, Aix
sponsa, of North America, nest in holes in trees, and will
accept artificial nest boxes. Their ducklings can jump from their
nests without injury, and take to the water soon afterwards.
Distances covered by migrating ducks vary with the species.
One arctic duck, the spectacled eider, Somateria fischeri,
winters at sea off Alaska. Long distance champion among American
ducks is the blue-winged teal, Anas discors, which
nests in most of North America and winters from the southern U.S.
south to Argentina.
Experts disagree about the classification of ducks into subfamilies
and tribes, but the hundred or so species include a number of obvious
groups. Most familiar are the dabbling or surface-feeding ducks,
which include the MALLARD, Anas platyrhynchos,
ancestor of most domestic ducks. Members of this group live primarily
on fresh water, where they glean plants and small aquatic animals
from the surface or from shallow bottoms that they can reach without
diving. The pochards, including the CANVASBACK, nest on fresh water,
but winter, often in very large flocks, both on inland lakes and
along the coasts; they feed by diving. Another group of diving ducks,
including the goldeneyes and the BUFFLEHEAD, nest in tree holes.
The mergansers are specialized for catching fish; the edges of their
bills have sharp, toothlike serrations for holding slippery prey.
Most marine of the North American ducks are the eiders and scoters,
which nest in the far north and winter predominantly at sea.
All except one breed of domestic duck are derived from the
mallard, originally tamed in the Old World. The exception is the
muscovy duck, Cairina moschata, a large species
of the American tropics. Wild muscovies are mostly black, but the
commonest domestic variety is white, with knobby, naked red skin
around the face and bill. It and the turkey are the only domestic
birds that originated in the New World.