Size: L: 45-60 cm. Wt: Males: 350 g. Females: 530 g. Males and females are dimorphic in size, and in colour. This species is not seasonally dimorphic.

Male: upperparts grey, with dark wing-tips; rump white; underparts white, with light streaking and spotting; tail square, with black subterminal band; bill black, hooked, with yellow cere; legs long, yellow-orange, with taloned feet

Female: upperparts brown, with brown wing-tips; rump white; underparts whitish or pale buff, with heavy brown streaking on breast and flanks, lighter streaking and spotting on belly; tail as in male, but brown, with dark subterminal band; bill and legs as in male

Juvenile: upperparts brown, with some chestnut, and brown wing-tips; rump white; underparts rufous, with heavy, dark brown streaking and spotting on breast, lighter on belly; tail as in female; bill and legs as in adults

Nestling: semialtricial and downy; first down mainly white, with buff on back, wings, and sides of head and neck; dark eye-patch; second down buffy brown above, paler on sides, and whitish below; irides blue-grey; bill hooked, cere and feet pinkish, becoming yellow