Beak

A bird’s hard, projecting mouthpart, formed by the jaws and covered in keratin. Its shape and strength support feeding, grooming, defense, and other functions.

Rhamphotheca: The keratinized sheath covering a bird’s upper and lower jaws. This sheath forms the beak’s hard outer surface and grows throughout a bird’s life.
Filter feeding: A feeding strategy that separates small food particles from water or sediment. Baleen-like structures on some beaks strain food from water.
Theropoda: A diverse group of mostly bipedal dinosaurs that includes modern birds. Bird beaks evolved within theropod dinosaurs.
Darwin’s finches: A group of Galápagos songbirds whose species differ in beak form and ecology. Their beak variation is a classic case of adaptation to different food sources.
Mammalian jaw: The paired bones and muscles that form the mouth’s movable framework in mammals. Unlike a bird beak, a mammalian jaw typically bears teeth rather than a keratin sheath.
Tomia: The cutting edges along the margins of a bird’s beak. Their shape helps determine how a beak grips, cuts, or tears food.
Granivory: A diet based primarily on seeds and grains. Seed-eating birds use beak edges and leverage to crack or husk seeds.
Archaeopteryx: A Late Jurassic feathered animal with both avian and non-avian dinosaur features. Its toothed jaws contrast with the toothless beaks of most living birds.
Crossbill: A finch whose crossed bill tips help extract seeds from conifer cones. Its unusual beak demonstrates a close match between form and feeding technique.
Rostrum: A projecting snout or beaklike structure in animals, including some fishes and invertebrates. The word can describe projections outside birds’ specialized beaks.

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