Males much larger than females. Web only between fourth and third toes. Bill almost straight. Both mandibles grooved. First quill longest. Tail graduated. Tarsus transversely shielded in front and behind. Hind toe moderate. At breeding season male assumes a distinct plumage, with a ruff of long feathers. Scarcely two ruffs in full plumage are alike in colour. Polygamous. Almost the whole of the Old World.