A North American diving duck. Males are mainly black and white, females are brown, and the back of the head has a small peak.
Breeding males are black and white, with a purple or green sheen on the head in some light. Females are mostly brown and may have a white patch beside the bill.
It dives for mollusks and aquatic insects and also eats aquatic plants and seeds. Outside the breeding season it gathers on lakes, ponds, bays, and estuaries.
An extinction-risk assessment has not been added yet.