Size: L: 80 cm. Wt: 3600-4500g. Males and females similar.

Breeding: thick, black bill; crown and nape blackish; white, striped markings on neck; white mottling on black back and wings; white on breast and under wings.

Winter: bill greyish, crown and nape dark grey; throat and breast white; back mottled grey and white.

Juvenile: similar to winter adult.

Nestling: semiprecocial and downy; down thick, blackish-brown, with paler areas on throat, foreneck, breast, and flanks; belly and lower breast grey-edged, becoming white; iris dull reddish-brown; bill light grey, becoming blackish; legs and feet grey