1. A bird has streamlined body. Its bones are light and strong.
2. They are hollow and have air spaces between them.
3. The hind limbs of birds are modified as claws, which help them to walk and to perch.
4. The breast bones are modified to hold massive flight muscles which help in moving wings up and down.
5. Birds have special flight muscles and the forelimbs are modified as wings.
6. The wings and tail have long feathers, which help in flying. Birds show two types of flight: gliding and flapping
