Ducks have elaborate courtship displays, each unique to its species. 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 United States 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.