Size: L: 40cm. Wt: 350-400g. Sexually dimorphic in colour; males slightly heavier than females, but not noticeable in the field. This species not seasonally dimorphic.

Breeding Male: head dark grey, with white crescent in front of eye; body speckled brown; green speculum, bordered with black; blue on wing; bill black.

Eclipse Male: body and head more mottled; similar to female

Female: body mottled brown; head and neck paler; green speculum, bordered with black; blue on wing; bill greyish-black.

Duckling: precocial; down brown above, yellow below, with small yellow patches on either side above thigh; rear edge of wing yellow; sides of face yellow with dark eyestripe from bill to nape, broken in front of eye; short dark streak on ear coverts; bill and legs blackish