Small individuals of this species are the smallest waterfowl on earth, at as little as 160 g (5.6 oz) and 26 cm (10 in). White predominates in this bird's plumage. Bill short, deep at base, and goose-like.
Male in breeding plumage is glossy blackish green crown, with white head, neck, and underparts; a prominent black collar and white wing-bar. Rounded head and short legs. In flight, the wings are green with a white band, making the male conspicuous even amongst the huge flying flocks of the Lesser Whistling Duck, which share the habitat. Female paler, without either black collar and only a narrow or nonexistent strip of white wing-bar. In non-breeding plumage (eclipse) male resembles female except for his white wing-bar. Flocks on water bodies (jheels), etc.
The call is a peculiar clucking, uttered in flight
It is largely resident, apart from dispersion in the wet season, but Chinese birds make long-distance migrations to winter further south. It nests in tree holes, laying 8–15 eggs.
This is an abundant species in Asia, although the slightly larger Australian race appears to be declining in numbers.[citation needed]
Found on all still freshwater lakes (jheels), rain-filled ditches, inundated paddy fields, irrigation tanks, etc. Becomes very tame on village tanks wherever it is unmolested and has become inured to human proximity. Swift on the wing, and can dive creditably on occasion.[citation needed]