Gadwall

The gadwall is a dabbling duck 47–58 centimetres long with a wingspan of 78–85 centimetres. The male is slightly larger, averaging about 990 grams against the female's 850. The breeding male is patterned grey with a black rear end, light chestnut wings and a brilliant white speculum, obvious in flight or at rest. In eclipse plumage the drake looks more like the female but keeps the male wing pattern. The female is light brown, much like a female mallard. (Wikipedia, general species account)

The gadwall breeds across northern Europe and the Palearctic and in central North America, and is strongly migratory, wintering south of its breeding range. It favours open wetlands such as steppe lakes, wet grassland and marshes with dense fringing vegetation, feeding mostly by dabbling for plants but diving more proficiently than other dabbling ducks and sometimes stealing food from diving birds. It nests on the ground, often some distance from water, forms only small flocks outside the breeding season, and is monogamous. (Wikipedia, general species account)