A bird's beak, also known as a bill, is a hard, pointed structure that birds use for various functions, including eating, grooming, and building nests. Beaks come in different shapes and sizes, adapted to the bird's diet and habitat. For example, hummingbirds have long, slender beaks for sipping nectar, while eagles have strong, hooked beaks for tearing flesh. The beak is made of a protein called keratin, the same material found in human nails and hair. Birds do not have teeth; instead, they use their beaks to grasp and manipulate food. The shape of a bird's beak can provide insights into its feeding habits and ecological role.