Size: L: 40cm. Wt: 800-850 g. Sexually dimorphic in colour, but not in size. This species is not seasonally dimorphic.

Male: head peaked, dark metallic purple; eye yellow; bill blue with black tip; breast sleek black; flanks white; back gray; tail blackish-brown.

Female: head and breast dark brown; bill pale gray, with a white patch at its base; body mottled brown.

Duckling: downy; blackish-brown on back, head, and upper breast; buffy on lower breast and belly; dark eye stripe from bill to nape; bill blackish with paler tip; legs and feet blackish.