The beak, bill or rostrum's an external anatomical structure of birds which's used for eating and for grooming, manipulating objects, killing prey, probing for food, courtship and feeding young. The term also refers to a similar mouthpart in some cephalopods, cetaceans, pufferfishes, turtles, Anuran tadpoles and sirens. Anatomy Beaks vary significantly in size and shape from species to species. The beak's composed of an upper jaw, called the maxilla, and a lower jaw, cal… (More on Beak)