The Screamers are related to ducks, geese and swans as members of the Anseriformes order of birds. They are generally believed to be more primitive forms of the order like the Magpie Goose (Anseranas semipalmata) of Australia. However, Sick says that the fact that they have abandoned the filtering technique of eating suggests that they are, in fact, more evolved than their duck and goose cousins.

They eat vegetation and are heavy birds weighing in at over 4 kilos. Being so large and obvious it might be surprising that they have not been hunted closer to extinction but the Screamer's great defense is that its spongy meat tastes awful. Indeed, hunters hate them because they act as sentinels and, when disturbed, emit screams that can be heard over 3 kilometres away.