Comb Duck and Knob-Billed Duck (Sarkidiornis melanotos) -
Comb ducks are one of the largest species of duck, and they are the only members of the genus Sarkidiornis. There are two subspecies of comb duck. They differ only slightly by size and color. These ducks are common in pan-tropical regions of Madagascar, southern parts of Asia and northern parts of Argentina.
Male ducks have a large knob on their beaks and are larger than females. Juveniles are more mottled and their feathers are duller brown. As they mature, their wings become black and iridescent, and their breasts and undersides become whiter. They live and feed in groups, eating mostly water vegetation and sometimes fish. Unlike many other ducks, they prefer to perch in trees.