A medium-sized diving duck. The male is easy to pick out, showing a deep rusty head, pale grey body set off by a black breast, and a broad pale bluish band across the bill. The female is much plainer, appearing grey-brown with faint pale markings on the head. Both sexes show a gently sloping forehead and a dark grey bill with a lighter band near the tip. In flight it looks generally grey and lacks any bold white wing stripe. It occurs on marshy, reed-edged lakes as well as open reservoirs, and in winter may move to coastal waters when inland sites freeze. Often seen in flocks and frequently mixes with Tufted Ducks in winter. It feeds mainly by diving.