Male has bright blue bill, black cap that contrast with white sides to head and chin. Rich chestnut upperparts, upper breast and flanks; lower breast blacker; belly and ventral area white barred blackish on the flanks and extending onto the ventral area. Under tail coverts white, tail and flight feathers blackish. Legs bluish-grey. Male eclipse plumage is retained throughout winter when bill becomes greyish, crown browner, white cheeks speckled with black and all chestnut plumage becomes dark brown and grey. Female has blue-grey bill with dark brown cap and nape and buff-white cheeks with poorly defined dark brown line from base of bill to nape. Red-brown upperparts and upper breast; neck pale brown; white underparts barred and mottled with brown, particularly on the flanks and white under tail-coverts barred brown. Wings, tail and legs as in male. Non-breeding female similar to breeding but with greyer bill and red-brown areas brown. Juvenile is like winter female, but duller and paler with poorly defined cheek line and less barring on flanks.

Prefers lowland wetlands with emergent vegetation and suitable patches of open water, avoids flowing fresh water.

Any time of the year.

This is an introduced species from North America that relatively quickly colonised the UK. The UK population is considered resident.

This was quite a common breeding bird but because of the potential risk of hybridising with White-headed Duck in Spain it was decided to cull the British population, which was very successful. It is now a very scare bird.

Was common but now a very scare visitor (see UK status).