Size: L: 55 cm Wt: 550-600 g. Males and females are similar. Seasonally dimorphic. This species requires four years to reach full adult plumage.

Winter Adult: mantle and wings light grey, with grey wing-tips and large, white primary tips; head and breast white, with extensive, light speckling; flanks, belly, and tail white; bill yellow, with red spot; legs pink

Third Winter: similar to winter adult, but may have some brownish markings on wing coverts and tail; bill may have small, subterminal blackish markings

Second Winter: mantle whitish, with faint brownish markings and some clear grey; wings whitish, with buffy speckling and white wing-tips; head and underparts whitish, with faint buffy speckling; tail white, with faint barring; bill flesh-coloured, with subterminal black band; legs pale pink

First Winter: mantle, wings, head, and underparts white, may have faint buff, or light brown speckling; tail white, with faint buff, or light brown barring; bill black; legs pale pink