Size: L: 55 cm Wt: 650-700 g. Males and females are similar. Seasonally dimorphic.
Summer Adult: mantle and wings light grey, with darker outer primaries, forming dark wedge on underwing in flight; head white, with black forehead, crown, and nape; underparts and tail white; bill heavy, pointed, red with black tip; legs black
Juvenile: similar to summer adult, but with dark spotting throughout coverts of upperside of wing, and through tail; head markings dusky; bill may not have dark tip
Nestling: semiprecocial and downy; down soft, long; upperparts buffy grey, with small blackish-brown markings on back and wings; underparts white or buffy; throat dusky; bill red, with dark patch near tip; legs blackish-pink