The class Aves is the birds. Birds are vertebrates with feathers, modified for flight and active metabolism. There are a few kinds of birds that don't fly. Modern birds have the following traits:

• horny beak, no teeth

• large muscular stomach

• feathers

• large yolked, hard-shelled eggs.

• strong skeleton Birds provides extensive care of their young until it is grown, or gets some other bird to look after the young. The birds are divided into 30 orders.