Any of several short-billed, somewhat gooselike, Old World ducks with long legs and an upright stance. They are smaller members of the duck tribe Tadornini (family Anatidae). The common shelduck (Tadorna tadorna), of Europe and Asia, is black and white with a reddish chest band; the drake has a knob on his red bill. The ruddy shelduck (Casarca ferruginea), ranging from northern Africa and Spain to Mongolia, is orangish, with a pale head and white wing patches. Drakes usually have melodious whistling calls and are aggressive. In North America, mergansers are sometimes called sheldrakes.