Size: L: 60 cm Wt: 900-1100 g. Males and females are similar. Seasonally dimorphic. This species requires four years to reach full adult plumage.
Winter Adult: mantle and wings grey, with dark gray wing-tips and white primary tips; head and breast with heavy, pale brown mottling; flanks, belly, and tail white; bill yellow, with red spot; legs dark pink
Third Winter: similar to winter adult, but may have brown flecks through mantle and wings
Second Winter: mantle mostly clear grey, with some light brownish patches; wings mottled pale grey-brown, with dark tips and no white primary tips; head and underparts mottled and speckled pale brown; tail dark; bill pinkish, with black tip or subterminal ring; legs pale pink
First Winter: mantle and wings brown or light grey-brown, with scaly appearance, and dark brown or grey-brown wing-tips with no white primary tips; head and underparts heavily speckled and mottled brown or buff; tail dark brown or grey-brown; bill black; legs pale pink