This species is gregarious, and at favoured sites, the flocks of a thousand or more birds arriving at dawn are an impressive sight. As the name implies, these are noisy birds with a clear three-note whistling call.
This species has a long grey bill, long head and longish legs. It has a white face and crown, and black rear head. The back and wings are dark brown to black, and the underparts are black, although the flanks have fine white barring. The neck is chestnut. All plumages are similar, except that juveniles have a much less contrasted head pattern. The call is a loud we-weoo.
Range and habitat
The habitat is still freshwater lakes or reservoirs, with plentiful vegetation, where this duck feeds on seeds and other plant food.
This is an abundant species. It is largely resident, apart from local movements which can be 100 km or more.