It is a fairly large species, at up to 89 cm (35 in) in length. The males weigh 4–8 kg (8.8–17.6 lb) and the much smaller females weigh 2.6–3 kg (5.7–6.6 lb). Other than size, sexes differ considerably in appearance. The striking male has a large back marking over the crown down the face to the chin with a bluish-grey neck. On the male, a chestnut band on the lower chest which is separated from the white belly by a thin black band. The female is much more of a subdued brownish color overall, with no bold black markings and has a face lined with faint slate-gray markings. In flight, the species reveals a white primary wedge on the otherwise dark upperwing, a feature obscured when the species is standing.