The American black duck (Anas rubripes) is a large dabbling duck in the family Anatidae. It was described by William Brewster in 1902. It is the heaviest species in the Anas genus, weighing 720–1,640 g (1.59–3.62 lb) on average and measuring 54–59 cm (21–23 in) in length with a 88–95 cm (35–37 in) wingspan. It somewhat resembles the female mallard in coloration, but has a darker plumage. The male and female are generally similar in appearance, but the male's bill is ye