- Small, compact duck.
- Bill small, thick-based, and slightly drooping.
- Forehead and nape steep.
- Rather long, pointed tail held above the water.
Male DescriptionBreeding adult (Alternate plumage): Head white. Pale green spot on lores. White extending from neck to flanks. Throat, collar, and back black (throat actually iridescent blue). Chestnut breast and belly, darker in middle. Small black spot on side of chest in front of wings. White extending in two lines down back. Black spot surrounding eye. Second black spot in bump on nape. Tail and undertail coverts black. Bill gray. Leading edge of wing with large white patch in flight.
Non-breeding adult (Basic plumage): like female, but with white upper wing coverts.
Female DescriptionDark brown. Pale eyering. Broad white borders to speculum. Bill gray. Head square. White wing linings in flight.
Immature DescriptionLike female.