The slow moving air under the paper forces the paper up through the fast moving air on top of the paper, creating lift. When you see a bird, try to notice what color and shape each part of the bird is. For example, if you saw the bird shown below, you might say it was brown. But if you looked at it carefully, you would notice its back, wings, and tail are brown, but its crown is black and white, its bill, legs, and feet are orange, and its breast and belly are light gray. You can also tell a lot about a bird's feeding habits by the shape of its bill.
Woodpeckers have strong, straight, chisel-like bills for drilling into wood to catch insects.
The length of a bird's legs and shape of its feet are also clues to bird identification. Leg and feet shapes also provide information about where a bird lives, how it captures its food, and how it moves from place to place. Perching birds have toes for grasping. Pressure on the inside of the foot causes the toes to lock around a perch. That is how chickadees can sleep without falling off the branch.