The Children's Book of Birds

by Olive Thorne Miller

Nearly all birds have some of their bones hollow, and air-sacs, or pockets, under the skin. These sacs they can fill with air and make themselves light, so that those who live in the water cannot sink, but float like a cork.

Men who study the way birds are made do not yet know all the uses of the hollow bones and air-sacs. That is one of the things left for you young folk to find out.

Birds who get their food in marshes, or the edge of the water, have long legs for wading. They have also long necks, so they can pick up food from the ground.

Birds who swim have webs between the toes, that turn their feet into paddles.

Birds have very large gullets. In many cases the gullet leads into a place called the crop, where food is kept before it goes into the stomach. Sometimes the food is made soft in the crop, and then fed to the young ones, as I told you.

Birds have no teeth, yet they eat hard seeds, like acorns and grains of corn. To break these up, and get them ready for the stomach, they have a gizzard, which is a sort of grinding-mill. And to help in the work of grinding they swallow small stones.

One of the wonderful things about birds is the height at which they can live, and not only live, but fly. A man cannot go higher than twenty-two or twenty-three thousand feet, while moving about or exercising, because the air is so rare he cannot breathe. The highest a man was ever known to go and live, it is said, was less than thirty thousand feet, and that was in a balloon, where he did not move.

But birds go a good deal higher than this, and can fly—which is violent exercise—at that height. It is thought by some that the thinness of the air may be the cause of the great speed with which birds fly in that region. But there is still much to be found out about this.

Besides the marvels of flight, birds have other powers almost as strange. Many of them can fly under water with perfect ease, and, more than that, they can, when they wish, sink slowly till nothing is left above water but their beaks, to breathe. And they can stay so as long as they choose, keeping still in one spot, without moving.