Birds in Flight E-Book

W. P. Pycraft

• Herausgeber: BookRix
• Kategorie: Lebensstil
• Sprache: Englisch
• Veröffentlichungsjahr: 2014

Beschreibung

THERE are hosts of people who have a genuine love of our native birds without yearning to possess their skins, or desiring to acquire the reputation of being "Ornithologists." They would call them all by name if they could, but seek, alas! In vain, for some book wherein they will find some magic phrase which will enable them to identify every bird they meet by the wayside.

Leseprobe

W. P. Pycraft

Birds in Flight

BookRix GmbH & Co. KG80331 Munich

Birds in Flight

By

W. P. Pycraft

Kingfisher and Young

Preface.

There are hosts of people who have a genuine love of our native birds without yearning to possess their skins, or desiring to acquire the reputation of being “Ornithologists.” They would call them all by name if they could, but seek, alas! In vain, for some book wherein they will find some magic phrase which will enable them to identify every bird they meet by the wayside.

Most of our native birds have learnt that “discretion is the better part of valour,” when in the neighbourhood of Man. Hence one gets but too often no more than a fleeting glance at their retreating forms, which, from frequent encounters, have become familiar, yet they leave no more than a vague image in the memory. “What bird was that? I have often seen it but have never succeeded in taking it unawares.” This is a question, and its comment, often put to me.

Those who are in this quandary, and they are many, are always hoping to find some book which will enable them to correctly name the retreating forms. That book will never be written. In the following pages an attempt is made to aid such enquirers, and at the same time the difficulties of the task are pointed out.

It is hoped, however, that this attempt will find a welcome among those for whom it is made. If it helps them to understand something, at least, of the absorbing and fascinating problems which the study of flight in the animal kingdom presents, it will at least have served some useful purpose.

The pursuit of the flying bird will inevitably stimulate a desire to know more about the bewildering changes of plumage presented at different seasons of the year, as well as by the striking differences which often distinguish the two sexes, and the immature birds. The endeavour to satisfy this desire will open up a new world. Those who would pass to this knowledge should possess themselves of the “Practical Handbook of British Birds.” Though most severely practical, and designed for the serious student alone, even the beginner will find interest in the description of these several plumages, and much else beside that it is essential to know.

Now that the study of flight is so much to the fore, some may turn to these pages in the hope of gaining useful information on the theme of mechanical flight. Some help they may find. But it was not for this that they were written. The flight of an aeroplane and the flight of a bird have little in common—at present; though something may be learned by the study of gliding flight and soaring, which of course have their place in this book. But anatomical details and mechanical formulæ, necessary to the serious student of flight, would have been entirely out of place here, and they have been omitted.

My task has been by no means easy. But it has been enormously helped by the extremely skilful and beautiful work of the artist, Mr. Roland Green. Where birds are concerned, few artists in the past, and very few in the present, have shown any ability to combine accuracy in drawing with ingenuity of composition and faithfulness in colouring. Mr. Green has shown this rare combination; his coloured plates and line-drawings speak for themselves.

W. P. PYCRAFT.

London, September, 1922

CHAPTER I. Concerning Wings.

"Divinity within them breeding wings wherewith to scorn the earth."—Milton.

What a wing is—The quill feathers and their function—The skeleton of the wing—The muscles of the wing—The great air-chambers of the body—The Bat’s wing—The wing of flying Dragons—The wings of Dragon-flies and beetles.

The flight of birds has always aroused man’s envy and stirred his imagination. David longed for the wings of a dove: the writer of the Book of Proverbs tells us that “the way of an eagle” surpasses his understanding. Icarus, spurred on by dire necessity, actually, we are told, contrived to fly—but his maiden effort ended in disaster! To-day we have, in a sense, succeeded where he failed. But only because we have given up the idea of flight by personal effort, and make our aerial journeys in a flying machine.

That we owe much of our success to a study of the flight of birds is common knowledge, but the machine which has evolved as a consequence of this study pursues its way through the air after a very different fashion from that of the birds, for its vast body is thrust, or drawn, through the air by means of a propeller, driven at incredible speed, its immobile wings sustaining the weight. The wings of the bird, on the other hand, not only lift the body from the earth, but they sustain it in the air by their marvellously complex movements. And this is true, in varying degrees of bird, and bat, and butterfly: of dragon-fly and beetle.

Even they who must perforce dwell in crowded cities see daily the miracle of flight performed. For even here sparrows and pigeons, at least, are everywhere, and it is just because this is so, just because they have become so “common-place,” that their very presence escapes notice. Yet the wonder of their movements in the air might become a never-ending source of delight if only we went about our business with open eyes and minds alert.

Watch the wary sparrow spring from the ground and dart across the road, or up to the nearest house-top. How is it done with such incredible speed and accuracy?

To understand even the broad principles of flight, it is necessary to realize, at the very beginning, that the wing, in the case of the bird, or the bat, is a specially modified fore-leg. So also is the human arm and hand. But its transformation has not been so drastic as that of the bird, or the bat. Wherein the hand has been, as it were, completely re-modelled to fulfil the peculiar and complex functions demanded of it.

How should one describe the wing of a bird, as one sees it in flight?

The Dictionary, obscure and inaccurate as Dictionaries usually are, defines a wing as “the organ of a bird, or other animal, or insect, by which it flies—any side-piece.” Might not the impression one gathers of a wing, during flight, be defined as of a lateral extension of the body, presenting a relatively large surface, but having no appreciable thickness? That surface, examined in a dead bird, is seen to be formed, for the most part, of a series of parallel, tapering, elastic rods, fringed with an innumerable series of smaller, similar, but much shorter rods, closely packed, and linked together by some invisible means to form an elastic web? These we call the “quill,” or “flight-feathers.” The rest of the wing, and the body itself, is clothed with precisely similar structures, differing only in their smaller size. We call them “feathers” commonly, without realizing that they are the “Hall-mark” of the bird, for no other creature has ever been similarly clothed.

These quill-feathers play such a tremendously important part in flight that their arrangement, and relation to the underlying skeleton must be carefully examined by all who would understand the flight of birds. To begin with, then, note that they are so arranged as to overlap one another, the free edges of the quills facing the outer edge of the wing. Only by this arrangement would flight be possible, for on the upstroke of the wing through the air the quills act like the shutters of the sails of a windmill, allowing the wind to pass between them and so relieving pressure on the uplifting wing-stroke. On the down-stroke, the opposite effect is produced. The full force of the stroke is conserved, because, owing to the overlap, the several feathers are now pressed closely together to form an impervious sheet.

How are they fixed to the skeleton? To see this all the smaller feathers and the muscles, or “flesh” of the wing must be removed. It will then be found that the flight-feathers are divisible into two series. One, widely spaced, runs along the upper surface of the fore-arm: the other, closely packed, along what answers to the back of the hand. In effect this is but a single rod of bone, but it is composed of three elements, answering to three of the digits of the human hand—the thumb and the first and second fingers. But they are scarcely recognizable as such, for the thumb is reduced to a mere stump, while the two fingers have become welded together. The third finger, indeed, has become reduced to the palm-bone, and a short stump answering to the first finger joint. To this frame-work, which can be folded up into the shape of a Z when the bird is at rest, the quills are fixed by their base by means of slender, but very strong elastic tendons. In birds which have a long upper arm bone, like the Albatross, Gull, or Heron, there is a third series of long, almost “quill-like” feathers running from the elbow to the body, thus closing up what would otherwise be a gap between the wing surface and the body, rendering flight impossible.

Swans.     Heron.Geese.

The most important muscles of the wing are those which have to provide the power for the down-stroke of the wing. And these are the “pectoral” or “breast-muscles”—which form such dainty meat in a roast fowl. Owing to their great bulk the breast-bone itself would be insufficient to afford them attachment. This is furnished by the development of a deep, median keel, so that the breast-bone of a bird, such as a pigeon, bears a fanciful resemblance, when seen in profile, to the hull of a ship—unusually shallow—with a very deep keel. The front end of the breast-bone supports two slender rods of bone, and these in their turn support the long, sword-like blade-bone, and the “merry-thought.”

The general appearance of this frame-work for the support of the wing and its muscles can be seen in the adjoining illustrations. But it must be remembered that in their relative sizes and disposition these various parts present a very considerable range of differences. That these differences are correllated with different forms of flight goes without saying, but, be it noted, no one, as yet, has attempted to discover in what way they are related. Some of the readers of this book may, perhaps, be tempted to try and solve the problems which these differences present. To begin with, a collection of breast bones of different species of birds with their attached shoulder-girdles should be made, and these should be studied together with careful observations of the flight of the living bird. So far only a few comparisons of this kind have been made.