The familiar mallard is the most numerous duck in Britain (3), and is the ancestor of the domestic duck (2). Both male and female mallards are easily identified by the presence of a dark blue band on the wing known as a 'speculum', which is bordered above and below with white (2). Males and females are distinct; males have a metallic bottle-green head, a crisp white neck-collar and a rich purplish-brown breast. The upperparts are grey, the flanks are somewhat paler, and the central feathers of the black tail are curled smartly upwards (2). In contrast, females are brown, with streaks of darker brown and buff (4). Juveniles are very similar to females, but lack the speculum (2). It is the female mallard who produces the well-known loud 'quack-quack' call; males produce a softer 'rhaeb', particularly when alert, and a 'piu' whistle during courtship (2).