- Large, stocky duck.
- Male bold black-and-white with brightly colored head: black body, white chest, light blue crown and nape, greenish face, and bright red-orange bill with large round orange knob outlined with black.
- Female brown with black barring.
Male DescriptionBreeding (Alternate) Plumage: White neck and chest. Yellowish buff wash over upper breast. Mostly black body. White sides of rump. Large white patches on forewings. Forehead, crown, and nape pearl blue. Cheeks iridescent pale green. Bill bright red with white tip; large yellow or orangish swollen knob at base of upper bill. Feathers stick up as two small triangular black sails on back. Legs bright yellow, with dusky webs and black nails.
Nonbreeding (Basic) Plumage: Resembles female in being brownish, but has blackish wings and white forewing patch. Bill duller than in breeding; lobe smaller and with dark brownish spots.
Female DescriptionMostly deep reddish brown, barred with black. Feathers on sides and flanks have black crescent or U-shaped black bars and dark centers. Bill is gray, and not enlarged like the male's, with a rounded edge of feathering at the bill base. Feet greenish gray to yellowish, with dark webs.
Immature DescriptionImmature like adult female. First-year male similar to female, but has pale chest, a light eyeline, and an unswollen, orange or yellowish bill.