Best time to see: mid Sep to mid Apr

Key facts

Medium-sized diving duck found on freshwater as often as on sea

Habitat: freshwater lakes, reservoirs, sea and estuaries

Widespread winter visitor; breeds in Scandinavia and N. Scotland

Recognition

Male: black-and-white upperparts, glossy dark green head with large white patch between bill and eye; yellow eye; 45 cm

Female: grey with brown head (no patch), white collar and wing patches

Forms small loose flocks, often diving to feed on molluscs and crustaceans; flies strongly, with noisy wingbeats