LESSON XIX.

THE BIRDS OF OTHER DAYS.

“Thy flitting form comes ghostly dim and pale,As driven by a beating storm at sea;Thy cry is weak and scared, as if thy mates had sharedThe doom of us: thy wail—what does it bring to me?”

“Thy flitting form comes ghostly dim and pale,

As driven by a beating storm at sea;

Thy cry is weak and scared, as if thy mates had shared

The doom of us: thy wail—what does it bring to me?”

—Dana.

OLD FASHIONS IN FEATHERS.

It was an often-repeated saying of the great Linnæus that “Nature never makes a leap.” By this he meant that the law of nature is a law of gradations, and that in the long up-growth of organisms, the steps are short between the various classes of living things. The work of creation is harmonious, and moves from one grade of organization to another,with the easy transition of carefully shaded colors, or the ascent of the scale from note to note. But this creative harmony began very long ago, and in the innumerable ages which have rolled by with their train of living things, many types have been lost. Enough remain to fill us with wonder and admiration, when we see how the organism of one creature has been changed and adapted in some other succeeding animal.

We quoted in the last lesson the remark, “a bird is but a glorified reptile”; and, far apart in type as we might at first glance consider an eagle and a crocodile, or a lizard and a dove, it is not very difficult to trace, by the help of fossil forms, the similarity of organism and the steps in the process of change. Reptiles and birds belong to the class vertebrates; the backbone is then the first distinguishing feature. In the reptile, the spinal column with well-defined vertebræ passes from the head to the tail.[42]In the bird we find the vertebræ of the neck well marked, and more numerous than in the reptile; the shoulder-plates, breast-bone and hip-bones are largely developed, forming the box-like body of the bird, and embracing the backbone. In a similar fashion we often find certain insects in which one of the rings of which the jointed body is composed is developed far more than any of the others.

In the tail of the bird, we find the vertebræ flattened and crowded together into a triangular stump, while the tail of the reptile is extended, pointed, and supple. The reptile hasfour limbs; in the bird the two front limbs—the hands of the reptile—are changed to wings. The long-toothed jaws of the reptile become the horny beak of the bird. The reptile has scales and the bird has feathers, but there are spots on the reptile bare of scales, and on the bird bare of feathers.[43]

The sea had its inhabitants long before the land was populated, and the first vertebrates, the fish, were citizens of the sea. Before the earliest reptiles came, there were amphibians, which lived more readily in the water than on the land; then followed land reptiles, and finally flying reptiles. In like manner, the first birds were chiefly aquatic or swimming birds; then came huge, unwieldy walking birds, and finally flying birds. The earliest birds also diminish the distance between themselves and the reptiles, by the possession of teeth. In regard to feathers, we find that the plumage of the first birds was coarse and scanty, and consisted chiefly of quill feathers. The legs of all birds are covered with true scales such as the reptiles have.[44]

When we look at the reptile and the bird, the differences that seem most startling are between the wings of the bird and the fore-feet of the reptile, and between the scales of the reptile and the feathers of the bird. When we find the fossil form of one of the first flying creatures, we see that the huge wings were made of parchment-like skin, stretched upon the arm and fourth finger, which extended in claws in front of the membrane. If we examine that curious flying mammal, the bat, we shall see a similar construction, one finger of thebat’s fore-leg extending beyond the wing into a hooked claw, by which it can hang itself up for rest, or upon which it can walk, going on all fours, in a clumsy fashion.

Now, if we take the bones of a bird’s wing, we shall find that it has a large, thick upper bone, corresponding to the upper bone in our own arm; then the next section has two smaller bones, one slightly curved and one straight, to match the bones in our arm from the elbow to the wrist; and then in that small, pointed first section, we find three finger-bones. If we lay all these bones in their order we shall find a very good arm and hand. But now take these bones and construct from them a leg, and we shall notice that any arm is a modified and reduced leg. In nearly all animals the fore-legs are smaller and more symmetrical than the hind-legs. In the reptile family the fore-leg looks very like an arm and hand.

To return to the case of the bird and the reptile, we find that the first bird-like flying creatures, were not birds but reptiles of a bat-like construction; while the first biped creatures, supposed from their footprints to be birds, were not birds but biped reptiles. An enormous space of time separated biped reptiles from real birds.

The remains of the earliest birds seem to have been less well circumstanced for preservation than those of other animals, for very few are found; and of the first animal that can really be called a bird, for many years only part of a single specimen, and that lacking nearly all the head and breast-bone, was known. Enough, however, of the specimen remained stamped on the Bavarian slate to show that thishad been a feathered flying creature, with two slender legs, and feet suitable for perching upon trees. It was of about the size of a crow, and had a very singular tail. This tail was long and formed of extended vertebræ like the tail of a lizard, and from every joint grew a pair of large quill feathers.

Such a tail must have greatly hindered the creature’s flight, and in fact in the many years that passed before the existence of the next birds of which fossil forms remain, a new fashion of tails had come in; the huge court-train had vanished, and birds appeared with the closely crowded vertebræ of the tail, only sufficient to support the tail feathers.

But the print on Bavarian slate is not the only fossil of our long-tailed bird of early days. A feather was also found imprinted on stone, and then about 1880, a very complete specimen, showing that the jaws had teeth, and that the bird had claws. “A fearsome fowl, surely!”

The bird next found was aquatic, about the size of the nearly extinct penguin, but wingless. In the chalk shale of Kansas, birds of the size of pigeons, with short wings, but especially remarkable for having teeth in the old reptile fashion, have been found. Modern birds have lost their teeth, finding it more convenient to depend upon gizzards for crushing their food! A bird very nearly the size of a swan has been taken from the New Jersey marl.

It is only when the first age of the last world-building period opened, that we find a huge bird as large as an ostrich. This bird was not alone as a giant of the race; there seem to have been other species, too bulky to fly, but able to swim,and no doubt capable of running swiftly on land, aided by the rowing motion of their wings.

As the ages move on, more birds appear, having affinities with yet existing types. In some, the jaws had bony points and serrated edges, showing that the birds were fish-eaters, aquatic in their habits, and possessed of webbed feet. Birds allied to the gulls and kingfishers were numerous, and shortly after them came specimens of the flamingo tribe; and still we see that the aquatic birds, the birds that had their living from the all-bountiful sea, were most numerous.

It must not be concluded that of all these birds perfect specimens have been found. In some cases eggs, feathers, nests, footprints, or stray bones have been the only traces. The extinct bird frequently has had to be reconstructed from small portions of its body. Each succeeding age of the last world-building period has produced new birds. In France the strata from the first age of this period have yielded many species. The ancient beds of lakes have been especially rich in bird remains, as lying in the undisturbed ooze, the fragile bodies were less exposed to destruction. Very many of these birds of ancient days represented forms now living,—as barn-yard fowls, storks, woodcock, crows, and falcons. Possibly the birds were not more numerous in the Miocene than in the succeeding age, but its numerous lake beds, and other circumstances may have been more favorable to the preservation of the remains.

A great many fossil birds and remains of birds have been found in the caves of the succeeding eras. Many varieties of birds are still given to inhabiting caves, or any quiet andshady place. No doubt “the temple haunting martlet” haunted caves before temples were built, and swallows that now multiply in chimneys and eaves must have gone for shelter to the crevices of the rocks in ages before men displayed architectural talent. Thus the caves of the ancient world had numerous bird inhabitants, while the captured bodies of birds were no doubt carried to their cave-dens by carnivorous animals.

The division of “sub-fossil birds” embraces birds that have existed during the human period, but have now disappeared. In what are called the “kitchen-middens”[45]of Denmark, and in the lake dwellings of Switzerland, in recent fens and peat mosses, and in various islands, as Madagascar, New Zealand, and the Canaries, the remains of the great auk, the capercallzie, the dodo, the crested parrot, and in New Zealand the huge dinornis have been found. Within the historic period various other birds have been exterminated, and are now represented only by ancient drawings, stuffed skins, or relics of their nests and eggs.[46]

FOOTNOTES:[42]These differential characteristics apply only to existing species of birds and reptiles.[43]See Nature Reader, No. 3, Lessons 28-30.[44]This adaptation does not indicate any descent of the bird from the reptile.[45]The word means “kitchen refuse heap” and is applied to shell-heaps mingled with bones, found along shores and recognized as traces of ancient human habitations.[46]See Nature Reader, No. 3, Lesson 39.

[42]These differential characteristics apply only to existing species of birds and reptiles.

[43]See Nature Reader, No. 3, Lessons 28-30.

[44]This adaptation does not indicate any descent of the bird from the reptile.

[45]The word means “kitchen refuse heap” and is applied to shell-heaps mingled with bones, found along shores and recognized as traces of ancient human habitations.

[46]See Nature Reader, No. 3, Lesson 39.

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