Size: L: 65 cm. Wt: 1050-1250 g. Males are somewhat heavier than females. Seasonally dimorphic. This species requires four years to reach full adult plumage.

Breeding Adult: mantle and wings pale gray; wing-tips black, clear-cut and confined to outer primaries, with white spots which may be lacking or partially worn; head, underparts, and tail white; bill yellow, with red spot; legs pinkish

Juvenile: similar to first winter, but mantle with more regular, scaly pattern, and head and underparts darker and more heavily streaked, nearly same color as mantle

Nestling: semiprecocial and downy; down long, soft; upperparts and throat buffy grey, with small blackish-brown spots on head and throat, and small dark streaks around eye and at sides of throat; upperparts mottled with irregular, blackish-brown blotches; underparts whitish to buff; bill black, with pink tip; legs pinkish