The digestive system of birds is complex for the size of most birds. A small bird can eat up to twenty percent of its body weight daily. Birds have an extremely high metabolism so to keep up with the requirements bird must eat a large amount of food. The digestive system of the bird begins with the beak and tongue. Evolution has eliminated the teeth in birds.
Birds have a very strong beak.
The beak and the tongue are modified according to the diet and the environment of the bird. The long curved beak of a hummingbird is suitable for drinking nectar. The beak grows constantly and must be worn down by climbing and cracking nuts. When a bird eats it uses its beak and tongue to gather food. Since a bird has no teeth, chewing time is eliminated.