How do birds fly?

Birds have a lot of special features, like feathers, beaks and wings, which other animals do not have. These unique characteristics are what make birds able to fly.

One thing that really helps birds fly is that they are lightweight. Bird bones are very light, because they are mostly hollow. Inside a bird bone is a honeycomb-like structure. Many bird bones are also fused together. This means birds need fewer muscles to move, which results in less weight. One very important bone that birds have is a keeled sternum, which looks like a keel on a boat. The keel provides the anchor to which bird wing muscles attach. Because the keel is very large in proportion to the bird, the chest muscles found there are also huge. This gives the bird leverage to fly.

Just like an airplane wing, a bird’s wing is curved from front to back in a shape called an airfoil. As the bird flaps, air flows faster over the top of the wing than it does the bottom. Fast-moving air has less pressure than slow-moving air, so there is more pressure pushing up on the wing than gravity pushing down. This causes lift, and lift is the force that gets a bird in the air.

Feathers are important to bird flight as well. Feathers allow birds to “catch” the air and create lift. Tail feathers act as a rudder in a boat to help steer and stay balanced. Tail feathers can also be used to create drag by pointing them downward to help birds slow down or land. Feathers also provide birds with thrust to move forward. Flapping would only allow the bird to move up instead of forward. As the wings beat, the flight feathers actually twist to provide thrust.

Birds can use different types of flight to get around. These are gliding, hovering, soaring, and flapping. The most common type of flight is flapping. The bird’s wing changes shape during the up and down stroke. Flapping flight is basically like rowing a boat. Soaring and gliding requires little effort from the bird. To glide, a bird stretches its wings out and sails along without flapping, dropping slowly toward the ground. Soaring is like gliding, except that a bird finds warm, rising air to carry it upward. Hovering is a special type of flight that hummingbirds do best. Hummingbirds are able to move their wings in a figure eight pattern that lets them hover.