Size: L: 50cm. Wt: 400-1100 g. Sexually dimorphic in colour; females tend to be smaller, but not obvious in field. This species not seasonally dimorphic.

Male: large, black, spatulate bill, longer than head; head dark green; breast and belly white; flanks chestnut; back with black, white, and blue markings; green speculum, bordered with white; tail mostly black.

Female: bill as in male, but orange; body mottled brown; some blue in wings; green speculum, bordered with white; tail brown.

Juvenile: males have white crescent in front of each eye.

Duckling: downy; bill reddish-brown; dark reddish-buff above; underparts greyish-white; legs and feet greenish-black.