Black-headed Duck, Heteronetta atricapilla

The Black-headed Duck, (Heteronetta atricapilla), is a species of stiff-tailed duck from the subfamily Oxyurinae and the family Anatidae. It is the only member of its genus Heteronetta. Its habitat is swamps, lakes and marshes in Northern Chile, Paraguay, and Northern Argentina. This species is not considered threatened by the IUCN.

The Black-headed Duck is the most primitive member of its subfamily, and lacks the stiff tail and swollen bill seen in its relatives. Though resembling a fairly typical diving duck, its plumage and other peculiarities give away that it is not a very close relative of these, but rather the product of convergent evolution in the ancestors of the stiff-tailed ducks. The male has a black head and mantle and a paler flank and belly. The female is pale brown overall.

This duck feeds on water plants and insects. It is considered a brood parasite because the female never nests and lays her eggs in those of other birds instead, earning it the nickname Cuckoo Duck. Host birds are usually the Rosy-billed Pochard or other ducks, coots, and occasionally gulls and birds of prey. Unlike certain cuckoos, however, neither the chicks nor the adults destroy the eggs or kill the chicks of the host. Instead, after 21 days of incubation, the ducklings fledge and are completely independent.

Image Caption: Heteronetta atricapilla couple in breeding plumage photographed in Povo Novo, Rio Grande do Sul, Brazil, in November 2009. Credit: Claudio Dias Timm / Wikipedia (CC BY-SA 2.0)