Native of southernmost South America.
Lakes, marshes, water, and land.
White feathers with striking coral red legs and beak. There is no sexual dimorphism. Webbed feet.
Their buoyancy on water is due to air held in plumage. Body plumage is continually covered by oil from the preen gland. They are very careful not to get water under their plumage. These birds have flapping flight and are unable to glide or soar extensively. They are flightless for some weeks after the breeding season, when flight feathers moult simultaneously.
They stand in the water while mating. Release of ovum in the female and sperm in the male can vary with external factors. For example, if there is bad weather during mating period, clutches are smaller and the eggs are often infertile. Nests are made in dense swamp vegetation on the water. The female lays 1 egg per day until clutch is complete. The female covers the incomplete clutch with her own down feathers. Only the female incubates the eggs. Incubation begins with the laying of the last egg and lasts 21-43 days. Hatching occurs September through December. The young have downy brownish or grayish plumage. The young are precocial.
The coscorobas are actually an intermediate between whistling ducks and true swans. They have different calls, accompanied by definite movements such as for pair information, contact call, warning call, and a call to attract others.