Ducks & Geese

About 170 species. Waterfowl with webbed feet, dense insulating down and a bill lined with lamellae for straining food from water; in geese the same structure crops grass instead. Most species moult all their flight feathers at once and are flightless for several weeks, which confines them to open water where they can escape by diving. The young are precocial and leave the nest within a day of hatching.