by Mina Arnold Young
Many books about birds tell us that birds evolved from reptiles and the reptiles' scales turned into feathers. If that had really happened we should see some reptiles with feathers too. Perhaps some people would even have feathers instead of toenails! But birds, and only birds, have feathers. The feathers on the wings and tail and outlining the head, neck, and body of a bird are called contour feathers. The larger contour feathers on the wings and tail are called quill feathers.
A contour feather is something like a fern leaf with hundreds of little branches growing out in two rows on opposite sides. These little branches are called barbs, and each barb is like a little feather. It has little branches growing out of each side too, called barbules. These in turn have little hooks growing out of them. The hooks fasten the feather together so it is hard for air to get through.
You can take a large feather, as a wing feather of a chicken, and pull two of the barbs apart. If you look very closely as you do so you may be able to see what looks like a little zipper separating. You would have to use a very strong magnifying glass to see the separate hooks. When a feather on a bird separates like that he either gives himself a hard shake or pulls the feather through his beak to get it hooked up again.
Counting every little barbule and hook, a large feather has over a million parts. How could a scale divide itself into that many parts, designed just right to help a bird fly?
The main flight feathers are attached directly to the bones of the wings. The contour feathers that cover the body have their own muscles which the bird can use to raise the feathers. In cold weather you may see birds with their feathers all fluffed out. This helps them to keep warm.
There are also little down feathers, not hooked together. They are under the contour feathers and also help to keep the bird warm. Many of these down feathers have been used to keep people warm too, in down jackets and sleeping bags.
The flight feathers on a large bird must withstand many pounds of air pressure as they lift the bird into the air. No other part of any animal body is as strong for its weight as a feather.
All birds get a new suit of clothes at least once a year. They shed their old feathers, which is called molting, and new ones grow in. Usually just a few feathers are lost at a time. The bird's wings and tail molt evenly, with the same number of feathers lost on each side, so the bird will not be lopsided in flying. A flicker's two middle tail feathers, which are unusually strong, do not come out until all the other tail feathers have been replaced. But swans, ducks and geese lose all their quill feathers at the same time. They cannot fly until the new ones grow in.
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