This very large duck which has a long serrated bill for catching fish. The male has a green-black head with a hooked red bill, and a salmon pink to white body. The female has a dark brown head, a sharply defined white throat and dark collar, a smooth downward-pointing crest, and blue-grey plumage. The juvenile has a striped face and brown-greyish body.
It feeds by diving from the surface of the water to take fish. It nests in a hole in a tree near water, and lays 8-11 eggs in 1 brood from April to May. It can live for up to 8 years.
Seen all year round, and it is found in small groups in winter, whilst in summer breeding pairs prefer upland reservoirs and fast-flowing streams with stony shores. A very shy bird, and easily scared off even from a long distance.