Size: L: 35 cm. Wt: 300-350 g. Males and females are similar. This species shows some seasonal dimorphism.
Breeding Adult: upperparts dark brownish-olive; head and neck black; underparts slate grey, with white streaks on flanks; outer undertail coverts white, innner ones black; bill red, with red forehead shield and yellow tip; legs yellow, often with orange proximally
Winter Adult: similar to breeding adult, but bill dull red, with dull forehead shield and yellowish tip
Juvenile: upperparts dark brownish-olive; head and neck greyish, with white throat flecked with black; underparts grey, with white central patch on breast, and white streaks on flanks; bill dusky red; legs dark greenish
Nestling: precocial and downy; down on body thick, short, black, sparser on head and forewing; skin on crown and over eye shows blue and pink; skin on forewing pink; bill red with yellow tip; legs blackish-green