The screamers are a small family of birds, the Anhimidae. For a long time they were thought to be related to the Galliformes because of similar bills, but they are truly related to ducks (family Anatidae), and most closely to the Magpie Goose (which some DNA evidence suggests[ are closer to screamers than to ducks). The family is exceptional within the living birds in lacking uncinate processes on their ribs.
They are large, bulky birds, with a small downy head, long legs and large feet which are only partially webbed. They have large spurs on their wings which are used in fights over mates and territorial disputes; these can break off in the breast of other screamers, and are regularly renewed. Unlike ducks they have a partial moult and are able to fly throughout the year. They live in open areas and marshes with some grass and feed on water plants.
Both the Southern and the Horned Screamer remain widespread and are overall fairly common. In contrast, the Northern Screamer is relatively rare and consequently considered near threatened. They are seldom hunted in because their flesh has a spongy texture and is riddled with air-sacs, making it highly unpalatable.

Genus Anhima.
Horned Screamer
Anhima cornuta

Southern Screamer or Crested Screamer, Chauna torquata
Northern Screamer or Black-necked Screamer, Chauna chavaria