Bird bills serve a variety of purposes. They allow birds to feed, preen feathers, collect material for nests, enact courtship displays, and provide defense from predators or rivals.
Bills are composed of an interior bone structure covered in keratin, a fibrous structural protein also found in human hair and nails. The upper bill is somewhat flexible.
Bird bills are well adapted to specific diets. Thicker, conical bills enable birds to crack open nuts. Bills with sharp edges allow birds of prey to tear apart their catch. Birders use bill or beak shapes to identify bird as well as their prey.
