Published: 5 December, 2007

A bird's wing flatness helps it take to the air

How do wings on birds make them fly?

How wings make birds fly is kind of hard to explain. But you might be surprised to learn that you have already felt what it feels like to have a bird wing. Have you ever tried to move your open palm through the water really fast? Wide, flat objects, like your hand, or a paddle, are hard to move fast against water, aren't they? It feels like the water is pushing back against you. Or have you put your hand outside the window while driving in a car and felt the air rush against it? You can see-saw your hand up and down in the wind. In both cases you can feel the water or the air push against the flat palm of your hand. But if you turn your hand sideways, you can slip your hand through the water or air easily, right? These observations can help you understand how wings make birds fly.

In order to fly, an animal has to interact with air in a special way. The animal needs to have a structure that is wide and flat when looked at in one direction, and very thin when looked at in the other direction, kind of like your hand, but even wider and thinner, like a bird wing! When a bird is flying, their wings are flat so that the air flows easily around it in the direction the animal flies (like your hand cutting through the water or air). But something special and tricky happens here. As the air flows over the wing, the air flows faster over the top then the bottom, because the wing is slightly curved on top. This means there will be more air on the bottom side (because this air is moving more slowly). When there is more air on the bottom (a scientist would say there is higher "pressure") that leads to a push. And since the push happens against that wide flat part of the wing, this push lifts the animal. So a bird wing slices into the air in the forward direction, and gets pushed up from below; the net result is a flying bird!