Resident on lakes, marshes and ponds where it feeds on invertebrates, frogs and fish. The plumage is blackish-brown with white head and neck. On the nape of the neck there is a yellow mark. Its wings are dazzlingly white in flight.
Females are slightly larger than males with similar but brighter colours.
Often congregates in quite large flocks in winter. A female may mate with up to ten males, each of which incubates a clutch and raises his own brood. He found that the female is able to present her males with a full clutch of 4 eggs at intervals of 9-12 days. The cocks were seen to approach the clutch with great care and carefully to preen, especially the breast feathers, so that they are quite dry and airy for the brood. Then he spreads his pale-green legs and lowers his breast slowly while supporting himself on his wings.