Size: L: 45 cm. Wt: Males: 790 g. Females: 690 g. Sexually dimorphic in colour, and also somewhat in size. This species not seasonally dimorphic.

Male: head peaked, dark metallic purple; bill grey, with white band, and bordered in white; breast black, with white band separating it from grey flanks; back and tail dark grey.

Female: head pale brown, crown darker; whitish eye stripe; breast and flanks mottled brown; back dark brown.

Duckling: downy; upperparts very dark brown; underparts, face, forehead, wing edge, and back spots yellow; legs and bill dark; bill-tip pale; like Canvasback, but smaller.