The black-necked swan (Cygnus melancoryphus) is a swan that is the largest waterfowl native to South America.
Adults average 102 to 124 cm (40 to 49 in) and weigh 3.5-6.7 kg (7.7-14.8 lbs). The wingspan ranges from 135 to 177 cm (53 to 70 in). The body plumage is white with a black neck and head and greyish bill. It has a red knob near the base of the bill and white stripe behind eye. The sexes are similar, with the female slightly smaller. The cygnet has a light grey plumage with black bill and feet. The black-necked swan was formerly placed in monotypic genus, Sthenelides.
The smallest member in its genus, it is found in freshwater marshes, lagoon and lake shores in southern South America. The black-necked swan breeds in Chilean Southern Zone, Patagonia, Tierra del Fuego and on the Falkland Islands. In the austral winter, this species migrates northwards to Paraguay and southern Brazil. The wetlands created by the Great Chilean earthquake like Carlos Anwandter Nature Sanctuary in Cruces River have become important population centers for the black-necked swan. source