棉凫是鸭科中体长最瘦小的水鸭，它的体长大约是30到31厘米，体重大约是190到312克，被称作“世界上最小的鸭子”。

Cotton Pygmy goose is known as the "world's smallest duck" , with a length of 30 to 31 cm and a weight of 190 to 312 grams.

在繁殖期的时候，雄鸟全身的羽色有黑绿色的光泽，头部、颈部和下体是白色，双翼是绿色，并且有白带，雌鸟的羽色则比较淡;在非繁殖期的时候，雄鸟的羽色和雌鸟的类似。

The male bird has a black-green sheen on his plumage, with white head, neck and lower body and green wings with white markings while female bird has lighter plumage during the breeding season. And the plumage of theirs is quite similar during the non-breeding time.

最近几年，随着生态环境的改善，四川成都的鸟友也能拍到棉凫的身影。2021年12月底，由成都观鸟会发起的成都2021年年度鸟评选结果揭晓，棉凫在24种提名鸟类中以39.13%的得票率胜出，成为成都2021年年度鸟。

Cotton Pygmy-goose has also been seen in Chengdu, Sichuan province, in recent years with the ecological environment improvement. It also won the title of Chengdu 2021 Annual bird with 39.13% of the votes among the 24 nominated birds in the annual bird selection.