Marisa R. took the time to answer your question.

Most living birds can fly; all are descended from ancestors, possibly dinosaurs, that could fly. The bodies of birds are therefore highly modified for efficiency in flight. The finger and wrist bones of the arm are fused (glued together) to form a strong support for the large feathers of the wing. Fusing of bones for strength and lightness is also found in other parts of the birds skeleton. Many bones of adult birds are hollow rather than filled with marrow (as the bones of people are) and are connected to a system of air sacs (bags) spread through out the body. The sternum, or breast bone is relatively huge and it supports some of the major muscles used in flying. Try to find this bone the next time you eat chicken or look for it in your Christmas turkey.

Pierre Kerr, ac210@freenet.carleton.ca, added a few more bits of information.

Birds and airplanes have a few things in common. The Compton's Encyclopedia provided some more facts

{picture from Comptons}

A flying bird is perfectly streamlined. Like a jet airplane, its body is slender and tapering. All the feathers point backward from head to tail. The wings have delicately curved leading edges and thin trailing edges. The legs of many birds, like airplane wheels, can be drawn up under the body. There are no projecting ears on the head. Even the nostrils in some birds point backward. The air comes out of them like the exhaust from a jet, moving to the rear.

{Wing picture from comptons}

Men have long been studying the flight of birds and trying to imitate it. Not until the 20th century did engineers fully understand the principles of flight that birds have been using for millions of years. The wing feathers most important in pushing a bird forward are the primaries. They are attached to a single bone that corresponds to the first and second fingers and the hand bones joined together. The secondaries are the feathers of the inner wing. They are attached to the lower arm. They play an important part in supporting the bird in the air. The primaries and secondaries can be used separately. Attached to the upper arm are thetertiaries.

Each wing feather overlaps the one next to it, starting from the base of the wing outward. On the downstroke of the wing the air pressure on the underside forces these feathers into an airtight fan. Speed and forward motion are gained. On the upstroke the wrist joint is bent, and all the primaries and secondaries turn on edge, like the slats of a venetian blind. Thus the wing is lifted with the least wind resistance.

Slow-motion pictures show that as the wings move downward, forward, then quickly upward, the wing tips move through a figure-eight pattern. The tail feathers act as a brake and as a rudder for steering. In addition to forward flying, birds soar and hover. Soaring means gliding on wind currents. Hawks and sea birds soar when they are looking for food below them. Hovering means hanging in the air over the same spot with tail lowered and outspread and wings fluttering rapidly.

How a bird flies is not a simple things to understand, but we hope what we gave you has helped a bit. Remember, it took birds millions of years to figure out how to fly, so don't worry if it takes you an hour or so. You may want to look at a wonderfule book in your library called

Why is the sky blue, by Jack Long, catalogue number 508 LON. It also explains how birds fly. Thanks for your question.

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