The birds smooth, streamlined shape helps it move swiftly through the air. The skeleton is very light- many of the bones are hollow. Birds, with their powers of flight, are found in almost every part of the globe. A few birds, such as ostriches and penguins, cannot fly. Instead, the ostrich can run very fast, up to 50kph, and the penguin uses its wings as flippers for swimming.

All birds lay eggs with hard, waterproof shells .Birds are warm- blooded animals with bodies covered in feathers. Birds walk on their two hind legs. The hind legs and feet are covered in scales. The mouth is a horny beak or bill. The birds smooth, streamlined shape helps it move swiftly through the air. The skeleton is very light- many of the bones are hollow. The body and wings are covered in feathers, which are light but strong. The lungs lead into a series of air sacs which improve the birds oxygen supply when flying, as well as making its body lighter. In some birds the air sacs even extend into the legs.