Birds and Flight思维导图

Turn to page 18. Why do birds have feathers? Feathers keep birds warm. They also help them to fly by giving their wings and bodies a special sleek shape. Each kind of bird has feathers of a different color and pattern. Males are often brighter than females. Their good looks help them to attract the mates. Which bird can fly backwards? Humming birds are the helicopters of the bird world. They can fly in all directions. Backwards, forwards, sideways, up and down. They can even hover on one spot. Why can't penguins fly? Well, penguins can't fly because their wings are too small to keep their heavy bodies up in the air. But penguins are very good swimmers and divers. They use their wings as paddles in the water. Birds fluffie down feathers trap warm air next to their skin. And much the same way as a duvet keeps you warm and bed. Humming birds are among the world's smallest birds. The bee hummingbird lays its egg in a nest the size of a walnut. Birds can fly by flapping their wings up and down or by gliding on still outstretched wings. Ostrages are too big to fly, but they can run at twice the speed of the fastest Olympic runners. Most birds can fold their wings up close to their bodies, but penguins can't. They always hold their wings stiffly out to the side.