WE The Child's Book of NATURE THE STORY OF THE BIRDS come now, in our story of Animal Life, to the great family of birds. Nature's richest gift to the animal world was the gift of flight to the reptiles which became birds. The hideous monsters that first began to fly, with great toothed beaks and scaly, tufted tails, have all perished. Some flying animals remain still, sailing on outstretched rafts of muscle; and there are fish in the ocean which, leaping from the waves, sail far and fast by the aid of wing-like fins. But true flight belongs only to the birds and the bats. The bats skulk through the air at nights as if ashamed of their strange performance; but the birds fill the air with life and song from early morning till the sun goes down, as if to show that nowhere beneath the clouds is there a place where Nature's children may not flourish and be happy. A1 BIRDS THAT CANNOT FLY LTHOUGH we our CONTINUED FROM 1382 selves cannot fly, we are able, in a general way, to understand what happens when a bird flies. The wings of the bird displace the air with every beat they make. They force the air downwards and backwards. But every time the air resists before giving way; it resists all the time that it is being pressed by the wings, and that resistance of the air enables the bird to rise. It is the resistance of the water to our strokes that enables us to swim; it is the resistance of the water to the screw-propeller that causes the big ship to be driven through the waves; and it is the resistance of the air to the bird's wings when pressed down that causes the bird to rise in the air and to go forward. In order that the bird may exert this downward and forward pressure it has enormous muscles. The muscles of the flying birds are far bigger, considering their size, than the finest muscle of a giant man. The strongest muscle of the bird is that which pulls the wings down. That is the flesh on the breast of the bird. It is attached to a breast-bone shaped like the keel of a ship. But when the wings have come down, they have to be drawn up again ready for the next stroke. This drawing up of the wings is done by two smaller muscles hidden in the flesh of the breast. The great muscle of the breast is also attached to the under side of the wings, to draw them down and to cause the bird to rise and go forward. The smaller muscles are continued into strong tendons which pass through a hole in each shoulder-joint, and are fixed to the upper side of the wings, so that these may be raised when the downward stroke has been made. All these muscles work in turn to enable a bird to change the position of its wings so that it may catch the breeze, and sail or hover; or, of course, to turn in a new direction. When the wings are forced down, all the feathers are spread out flat to prevent the air from passing between them; but when the wings are being raised, the feathers open out to let the air pass through, so preventing the bird from being tired by too great an effort to force up its wings against the pressure of the air. Thus we see that the action of a bird's wings is controlled by the most wonderful and perfect living machinery. There are other aids to flying which a bird possesses. It has an oil-gland from which it draws oil to lubricate its feathers. This is specially valuable to sea birds, which must have their feathers water-tight; but it is of service to the birds of the air also, for the oil upon their feathers makes them less porous, and causes them to offer a greater resistance to the air when they are making the important downward-forward stroke. Another important thing is the system of air-vessels, or air-sacs, with which a bird is provided. The bird has huge lungs, but beyond these run the air-sacs, some birds having them continued right into their bones. It was at one time supposed that these sacs were filled with gas, to make the bird light, as gas makes a balloon light. That is not the fact. These air-sacs do help to make the bird lighter, but not through gas. The air in them is warmed by the great heat of the bird's body, and as hot air is lighter than cold air, so the presence of a quantity of warmed air in the body of the bird must help to sustain it in its flight. CANNOT FLY, AND ARE BIRDS THAT Seeing how great is the perfection to which flying birds have attained, so that they can fly from country to country in the course of a single night, and race the fastest ships and trains, we may wonder that all birds do not fly. Some, however, forgot how to fly so long ago that there is now very little evidence of their ever having flown. The greatest of all birds, the moa, which lived chiefly in New Zealand, but also to some extent in Australia, had no wings at all. There are no moas left alive now. They were hunted by the natives until not one moa survived. They were plentiful up to the middle of the eighteenth century, and some natives of New Zealand, who were in England fifty years ago, told stories of their grandfathers having hunted the giant bird. There were some small varieties of moas, but the giants of the family were fourteen to sixteen feet high-taller than the tallest elephant, and as tall as a good-sized giraffe. They had enormously thick legs and toes, the bones being like those of an elephant. But they are all gone, and the other birds which cannot fly are in danger of following them into extinction. Madagascar's great bird, the æpyornis, which laid an egg a yard in length and two feet six inches round, which could hold more than two gallons, is, like the moa, as dead as the dodo. How animal. Be that as it may, there is little doubt that the moa, the ostrich, the cassowary, the apteryx, the rhea, the emu, and the penguin all started fairly like the other birds, and had their chance with them. But early in their history we find the old story repeated. Most birds had to fly to pursue their food, or to escape flesh-eating enemies. They had a hard life of it then, and, making the best of it, they gradually developed wings and learned to fly. The birds which do not fly descend from birds which found pleasanter quarters, where food was abundant on the ground, and where there were no savage beasts to kill them. Although they had learned to fly, they had now no need to do so. They neglected the use of their wings. Slowly, in the course of long ages, the wings lost their power to raise them above the ground. The wings got smaller and smaller, until to-day, in the case of the ostrich, they serve only to balance the bird as it runs, in the same way that hands serve to balance us when we walk and run. RUNS LIKE AN EXPRESS TRAIN INSTEAD OF FLYING When we think of this we must remember that the wings of all birds, big or little, flying or flightless, are only hands which have been changed into wings. They had arms, and wrists, and hands, and fingers, just as we have. But these changed and became covered with feathers, to form the wonderful instruments which carry the flying birds up into the clouds. THE OSTRICH, WHICH The most famous of the birds which do not fly now alive is the ostrich, because it is the biggest, and gives the best feathers. It differs from the other big birds because these have three toesindeed, one has four-while the ostrich has only two toes. Its home is in Africa and Arabia, but it used to live in India, and the egg of one has been discovered, very, very old, in Southern Russia. The height of the ostrich is between six and eight feet, the neck being long and flexible. When wild, it shuns men, and prefers the company of giraffes and zebras and deer. As it has lost the power of its wings, it has developed the power of its legs. These are very thick and strong. When it begins to run, it races away like an express train, at the rate of THE FLIGHTLESS BIRDS LOST THE It is probable that all the great flightless birds of our day descended from birds which could fly, though there are in the wing of the ostrich the slender claws of a limb which suggest that the ostrich's wings were, once upon a time, not wings at all, but the supports of a four-footed It was A living specimen of any of these birds would be worth a fortune. The huge bird is the extinct moa. taller than an elephant. The bird which looks like an emu is the extinct æpyornis. Its egg would hold two gallons. The penguin-like bird is the great auk. There is not now one living in all the world. The dodos lived and died in Mauritius, where sailors ate them. They were the biggest pigeons in the world, larger than a swan. The solitaire looks like a tiny-winged goose, but was a pigeon. All these birds forgot how to fly, and perished. Its The ostrich does not run straight, but in curves, so the hunter, by taking short cuts, can get up to it. Then the ostrich, if it be a male, will fight. feet are its weapons. You may judge how strong are its feet and legs when you know that the ostrich can carry two men on its back. It strikes forward with its feet, and can inflict a terrible injury. This shows us how unreal are the stories in the school books of the ostrich running away and burying its head in the sand as soon as it sees an enemy, believing that because it cannot see neither can it be seen. The ostrich does no such thing; nor does it leave its eggs to be hatched by the sun. Stupid the ostrich may be, but it makes a very good parent. Three or four hens lay their eggs together in a rough nest, which is made simply by a hollow in the sand. The ostrich's egg is very big, but the male ostrich is a big bird, and can cover sixteen of them. If there be more than that, he simply pushes them out of the nest, and frequently more wasted eggs are found lying about the nest than have been hatched. The hatching lasts forty-two days. The birds do not leave the eggs in the sand. The male sits on them throughout the night, and the hen sits on them during the day. Sometimes the hen may cover the eggs over with sand, and leave them in the sunshine for a few hours during the day, but this rarely happens. WHEN THE YOUNG OSTRICHES COME OUT OF THE EGGS AND BEGIN TO EAT STONES The birds have sense enough to know that if left unprotected the eggs would be fried or boiled by the sun, so they use sand as a shield when leaving them. When the chicks are hatched, they eat nothing but a few stones for the first two or three days. When they are able to run about, the father bird guards them affectionately. Many ostriches are tamed and kept on ostrich farms, in South Africa and in the South of France. The big ostriches are wanted for their feathers. At certain periods of the year the birds are collected together, and taken one by one into big yards to have some of their feathers removed. Eighteen or twenty long white feathers are cut from each wing; then eight or nine fancy feathers, and a few long black ones, and some short feathers. The bird suffers no pain. If it did, it would take a fever and die. Nor are more feathers removed than the ostrich can spare, for in that case the bird would be cold, and die. The business of the ostrich farmer is to keep his birds in good health, and it pays him to be kind. Ostriches are to be seen in nearly all the zoological gardens. There they eat the most extraordinary things. One ostrich, which died, was found to have swallowed many large stones, seven nails, a scarf-pin, an envelope, thirteen copper coins, a silver coin, fourteen beads, two small keys, a part of a handkerchief, a silver medal, and a small metal cross. This one did not die from what it had eaten, but one which swallowed part of a parasol did. THE HE RHEA Bird, which stole part of A A bird which much resembles the ostrich is the rhea. It has three toes, but is so like the other bird that it is called the South American ostrich. It lives only in South America. In nothing else does it more resemble the ostrich than in its appetite. It will eat almost anything which can be picked up. When a railway was being built in the wilds of South America, there was quite a famine of steel nuts and bolts the rheas used to creep up to the works and steal all that they could find. Of course, in such a big place as South America, the rheas are not all alike. Some lay quite small eggs; others lay large eggs. Some have horny crests to the head, like the cassowary. When the families of the rheas are being made up, they have battles, like the giraffes. The young males are driven away, then the old ones fight among themselves for the females which they desire to possess. They twist. their long necks together, and bite as hard as they can, kicking and stamping all the while, as they prance round in a circle. When an ostrich kicks an ostrich, or when a rhea kicks a rhea, not much damage is done. Use and nature have made them ready for such treatment. 1426 Ostriches gained their present shape when there were no enemies from which they could not escape by running. They never learned to fly. They can run faster than a horse; but their wings are small, and serve only to balance the body as they race over the ground. The ostrich has at the end of its wing-bones two slender claws, which are believed to be remnants of front limbs which its ancestor had when it existed as a four-legged animal. |