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
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.