Background color of Great Bittern is clayey-buff; each feather is black-brown mottled. Forehed, crown and nape are black-brownish. There are no differences in seasonal and age plumages. Bill, legs and skin near eyes are greenish-yellow; legs are slightly greener than bill; claws are black-brown, eyes are yellow. Sizes: wing 320-350, tail 113-116, tarsus 96-102 mm.