The beak, bill, and/or rostrum is an external anatomical structure found mostly in birds, but also in non-avian dinosaurs and some mammals. A beak is used for eating and for preening, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young. The terms beak and rostrum are also used to refer to a similar mouth part in some ornithischians, pterosaurs, turtles, cetaceans, dicynodonts, anuran tadpoles, monotremes, sirens, pufferfish, billfishes and cephalopods.
