Includes over 140 species of waterfowl: includes ducks, geese and swans.
All species in the order are highly adapted for an aquatic existence at the water surface. All are web-footed for efficient swimming and a bill structure adapted for water feeding.
The ancestors of the Anseriformes developed the characteristic bill structure that they still share. The combination of the internal shape of the bill and a modified tongue acts as a suction pump to draw water in at the tip of the bill and expel it from the sides and rear; an array of fine filter plates called lamellae traps small particles, which are then licked off and swallowed.
All Anseriformes have this basic structure, but many have subsequently adopted alternative feeding strategies: geese graze on plants, the saw-billed ducks or mergansers catch fish.