- ISBN: 9780836889536 | 0836889533
- Cover: Hardcover
- Copyright: 12/15/2007
Maybe people keep birds as pets because they can do what humans can only dream about - fly. Explore how their special bones, air sacs, muscles, and feathers make this feat possible. In addition, discover why these winged creatures have two stomachs and how they can sleep without falling off branches in Birds. Book jacket.