The Coscoroba Swan, Coscoroba coscoroba, is the smallest species of swan. However, it is still a fairly large species of waterfowl, averaging 4.2 kg (9.3 lbs), 1 m (3.3 ft) long and 1.57 m (5.2 ft) across the wings. Like all other swans it belongs to the family Anatidae. Since it is only distantly related to the other swans, the Coscoroba Swan is placed in the monotypic genus Coscoroba.
The Coscoroba Swan has white plumage except for black tips to the outer six primary feathers, although this black is often barely visible on the closed wing. In flight, the black wing tips are conspicuous. The bird has a red beak, legs and feet. They look somewhat more like geese than swans. The female looks almost identical to the male. The cygnet is a patchy color, with brown and gray hues. The Coscoroba Swan is also lacking the black mask that other swans have where their lores are between the eyes and beak. They look like a very small swan in body and look like a goose in the head.
The Coscoroba Swan breeds in South America from southern Chile and central Argentina south to Tierra del Fuego and the Falkland Islands. In winter it flies north to central Chile, northern Argentina, Uruguay and the south east tip of Brazil.
The habitat is well-vegetated swamps and lagoons, where it lives mainly on grasses and small water plants, but also mussels and fish. The population is estimated as 100,000 birds.
The female incubates the eggs, while the male stands guard and aggressively helps to protect the fledglings against predators after hatching. Coscoroba Swans live to an age of approximately twenty years.