A young robin weighs about two grams when it hatches, but within about eleven days it is more or less fully grown. Beaks and bills Instead of a mouth, birds have a hard beak or bill. Beaks are adapted for many tasks - some for building nests, some for breaking nuts, some for catching insects, some for extracting worms from deep mud. The shape depends largely on the kind of food the bird eats. Birds of prey have hooked bills for tearing flesh.
Ducks have broad, flat bills for sifting food from water.
Swifts and swallows have gaping beaks for catching insects in flight. Robins are among the most familiar of all garden birds, with their bright red breasts. Many of the small birds you see in cities once lived in fields and woodland. But most city birds belong to the huge group called passerines or perching birds. There are over 5000 different passerines, but all are quite small and have a foot with three front toes and one hind toe - ideal for perching.