Size: L: 28 cm. Wt: 120 g. Males and females are similar. This species is seasonally dimorphic, and requires two years to acquire adult plumage.

Breeding Adult: mantle grey; wings grey on upperside, with white border on trailing edge; underwing coverts blackish; head with full, black hood; underparts and tail white; bill black; legs dull red

Winter Adult: similar to breeding adult, but head white, with dusky crown patch, and black spot behind eye

Juvenile: similar to first winter, but mantle with extensive blackish-brown, extending onto sides of breast

Nestling: semiprecocial and downy; down thick, soft, long; head and upperparts dark greyish-buff, with irregular patches of blackish- brown; underparts buffy; bases of all down feathers blackish-brown