Adult Description

* Large, slender diving duck.
* Long, thin, orange bill.
* White patches in wing visible in flight.
* Male with bright white sides and iridescent green head.

Male Description
Breeding (Alternate) Plumage: Head iridescent greenish black. Neck, underparts, and sides white. Back and tail gray. Black line along sides of back. Outer part of wings black. Bill scarlet-orange.
Nonbreeding (Basic) Plumage: Head rusty brown with short, ragged crest. Chin white. Breast, back, wings, and tail slaty gray. Belly and flanks white. Bill scarlet-orange. White patch in wing visible in flight. Like female, except crest on head may be shorter and wing has larger white patch.
Female Description
Head rusty brown with short, ragged crest. Chin white. Breast, back, wings, and tail slaty gray. Belly and flanks white. Bill scarlet-orange. White patch in wing visible in flight.
Immature Description
Immature resembles adult female.