Adult Description

Medium-sized diving duck.
Chunky body.
Large head.
Male white with black back and head, and circular white spot on face.

Male Description
Breeding (Alternate) Plumage: Head greenish-black. Bright oval white patch on side of face at base of bill. Sides, breast, belly, and secondaries bright white. Back, wings, and tail black. Short, triangular black bill. Eyes golden yellow.
Nonbreeding (Basic) Plumage: Like female, but with some black tinge at sides.
Female Description
Head chocolate brown. Back, wings, and tail slaty gray. Flanks, belly, and breast white. Eyes pale yellow to white. Short, triangular bill black with yellow tip of variable length.
Immature Description
Immature similar to female. First winter male similar to adult male, but has browner head, gray sides and chest, and smaller and less distinct white oval on face.