How Can Birds Fly? 

　　Birds are good at flying. Their fore limbs have changed into organs that are used for flying - the wings. The hind limbs of the birds are used for walking and supporting their bodies. The shapes of birds' bodies look like spindles, which can help them to reduce air resistance and to keep balance of during flying. The mouth of a bird is of a keratin bill and is used to get food, to comb feathers and to peck objects. Combined with its flexible neck, the mouth of a bird can function partly as the “hands of man”. 

　　Look at the pictures and understand all parts of a bird.