; : f mut ai oh CTE LT é iI pe a Ayaaie at - i re My ee as Wort Uae i ALBERT R. MANN LIBRARY NEw YorkK STATE COLLEGES OF E AGRICULTURE AND HomE ECONOMICS AT CORNELL UNIVERSITY Cornell University Library The bird, its form and function, Sd Se AS en perorni in ; bird, about five feet in length, which inhabited the great seas during the Cretaceous period, some four millions of years ago. American ature Series Group II. The Functions of Nature THE BIRD ITS FORM AND FUNCTION BY C. WILLIAM BEEBE Curator of Ornithology of the New York Zoological Park and Life Member of the New York Zoological Society ; Member of the American Ornithologists’ Union and Fellow of the New York Academy of Sciences Author of ‘ Two Bird- Lovers in Mexico” WITH OVER THREE HUNDRED AND SEVENTY ILLUSTRATIONS CHIEFLY PHOTOGRAPHED FROM LIFE BY THE AUTHOR ha iY N i iad Ws RNY Ov rads Wh Gin SSF NEW YORK HENRY HOLT AND COMPANY 1906 Copyright, 1906 BY HENRY HOLT AND COMPANY Published September, 1906 ROBERT DRUMMOND, PRINTER, NEW YORK DEDICATED IN GRATITUDE AND ESTEEM TO Professor henry Fairfield Osborn BY HIS FORMER PUPIL THE AUTHOR PREFACE We find to-day some thirteen or fourteen thousand different forms, or species, of birds upon the earth. For many years ornithologists have laboured to name, and to arrange in some rational order, these multitudinous forms of bird life. Some such arrangement is, of course, a neces- sitvy—without a handle we should indeed be handicapped in studying a bird; but let us not forget that classification is but a means to an end. Far too many students of birds follow some such mode of procedure as this: When a new bird is found, it is shot, labelled, preserved in a collection and forgotten; or, if studying the bird with a glass, all effort is centred in finding some characteristic by which it can be named, and, succeeding in this, search is at once made for still another species, whose name can in turn be added to a list. Observing the habits, the courtship and_nest-building, and memorizing the song, is a third phase of bird-study— the best of all three methods; but few indeed have ever given a moment’s thought to the bird isel/. I have lectured to an audience of teachers, every one of whom was able to identify fifty birds or more, but not one among them knew the significance of the scales on Vil Vill Preface a bird’s foot. It is to bridge this gap that this book is intended—an untechnical study of the bird in the abstract. This, it seems to me, is the logical phase of bird life, which, with an earnest nature-lover, should follow the handbook of identification—the study of the physical life of the bird itself preceding the consequent phase of the mental life, with its ever-varying outward ex- pression. Far from considering this treatment exhaustive, one must remember that any chapter subject could easily be elaborated into one or more volumes. I have intended the book more as an invitation than aught else: for each to observe for himself the marvellously fascinating drama of evolution; to pass on from the nature stories of ideal- ized composite animals and birds to the consideration of the evolution of all life; to the tales of time and truth which have been patiently gleaned by the life-long labours of thousands of students. Whenever possible I have illustrated a fact with a photograph from a preparation or from a living bird, believing that, where verbal exposition fails, pictorial interest will often fix a fact in the memory. First of all we must consider a few of the more important and sig- nificant of the bird-forms of past ages; because no one who is interested in living birds from any standpoint should be entirely ignorant of a few facts concerning the ancestors of these creatures. Otherwise it is as if one, entirely ignoring the rest of the plant, studied certain leaves and flowers, knowing not whether they came from tree or vine. Preface ix In my treatment of the various phases of the bird’s physical life I have been considerably influenced by the many questions which I have heard asked by visitors to the New York Zoological Park. The short list of books in the Appendix will indicate the sources whence much more detailed information may be obtained by those who desire it. Some two dozen of the illustrations are from outside sources, and for permission to use these I am indebted to Dr. William T. Hornaday, the American Museum of Natural History, Prof. A. Smith-Woodward, Prof. R. S. Lull, A. E. Brown, Esq., Mr. R. H. Beebe, Mr. T. H. Jackson, Mr. Harold Whealton, and Mr. E. H. Baynes; and for the use of specimens to Dr. F. A. Lucas, Dr. Robert Ridgway, and Dr. Jonathan Dwight, Jr. Unless otherwise indicated, the illustrations were taken by the author. The work of Mr. Walter King Stone in the paint- ing for the frontispiece and a number of text cuts is gratefully acknowledged; and for the skilful printing of many of the photographs my thanks are due to Mr. E. R. Sanborn. To my wife, for constant and valuable help, criticism, and suggestion in all departments of the book, I render my sincere appreciation. To take a few dead facts and clothe them with the living interest which will make them memorable and full of meaning to any lover of birds, and at the same time to keep them acceptable in tenor and truth to the most critical scientist—this has been my aim. x Preface A few chapters of this volume have already appeared in print in “Outing,” “Bird-Lore,” and the “New York Evening Post.” Cc. W. B. New York Zoo.ocicaL Park, May, 1906. CONTENTS CHAPTER PAGH ANCESTORS! 82. occstiniets untuk neeliiens areas e chain (eee eaioe « kosace Bak anes 1 TT CE BATHERS 22-55 hte teen! alin stunt ain ak parr ng epee eH apaeey aE Maoh aie aasne oes 19 Ts "Tar FRAMEW ORK Or THE BIRD? v5 ud eacsae Jkie Sear tine kee acne a mens 62 LY, CUR PSR ULE soit teh asa anions, on snc achat Gis aan ih melause amen eed ea 103 Ve (ORGANS: OF NUTRITION cakes ane matdahee lan ames wthauheease + vee Donate 116 Vive THE’ FOOD? OF JBIRDSs Graken @ slags a neniae eh 6 behtacnale or mesos fein MARS LAIN 142 Vi: lam BREATH OF AS BIRD 24.4064 evden soses Gees Gee ain see 165 VU. Muscims: AND NBR VES. 26.24.5.24 oe ed eacuilee tate dak alae ensada oud Seles 188 TNH BE ORNSB Sc aieesan, scat cre tates nen tay Sarena mee ats cues aNevare ye ca arA nade Leese tO () XM BREAKS AND: BIEESi. 20.a4 acu saiiieleg alabama een Mie eee te pee cee te O28 XT HBADS: AND NECKS. 46 .)ouu oni av gew ned pea estas weds Geass a aban g 252 Sy ae BODY OF AG BIRDS siie oh side Heal aad woe ncaamee Bae Had Sea ea enna MBBS SEEMS“ WINGS yes, salictilie m aque Wantaee a samenoeia Siaulmeeearnnaens Se ees OB 319 RLV A BEBE AND OLBGSince coun ealdinns aovenan cna ee eee acremaee aaa edge ee D8 DEVS MI CATIES ace teres care erat eaice aio AN aS YSN ves Wie ca ay chats macy neste Cee ct ch ed RS 398 XV Lan WGGssOr* BIRDSics.seciaulin sear dca + san Man ven wig ae ee ae 427 XVELS Tae - Bikt IN THE NGG. cci0 oi nen te een nee emee eee eee Seca len 462 AppeNDIX—Brief List of Useful Books. ... 2.0.0.0... 0... cece cece eee eee 483 SINDEN cite oii oa aed eu aiaere eas ola ceed ene saeasen Meee oe een sanes 485 xi THE BIRD CHAPTER I ANCESTORS ITH the exception of Astronomy, the science which most powerfully dominates our imagina- tion is Paleontology, or the study of the life of bygone ages. Of all things in Nature, the stars symbolize absolute immensity, their distances stretching out beyond our utmost calculation. So the revelations of Palzon- tology take us far beyond the sciences of life on the earth to-day, and open vistas of time reaching back more than five-hundred-fold the duration of the sway of mankind. Fossil bones—philosophically more precious than any Jewels which Mother Earth has yielded—are the only certain clews to the restoration of the life of past ages, millions of years before the first being awakened into human consciousness from the sleep of the animal mind. Until recently, Palzeontology has been popularly con- sidered one of the dryest and most uninteresting of the ’ologies, but now that the fossil collections in our museums are being arranged so logically and so interestingly, the most casual lover of Nature can read as he runs some of 2 The Bird the “poems hidden in the bones.” As Professor Huxley once said, “Paleontology is simply the biology of the past, and a fossil animal differs only in this regard from a stuffed one, that the one has been dead longer than the other, for ages instead of for days.” A great many more fossil mammals and reptiles have been discovered than birds, and the reason may perhaps be conjectured. The bones and bodies of birds were in former times as now very light, and if death occurred on the water, the body would float and probably be de- voured by some aquatic reptile. Then, again, when some cataclysm of nature or change of climate obliterated whole herds and even races of terrestrial creatures, the birds would escape by flight, and when death eventually came, they would be stricken, not in flocks, but singly and in widely scattered places as to-day. . For perhaps a million years in the past, birds have changed scarcely at all,—the bones of this period belong- ing to the species or at least genera of living birds. But in the period known as the Cretaceous, when the gigantic Dinosaurs flourished and those flying reptile-dragons— the Pterodactyls—flapped through the air, a few remains of birds have been found. Some of these are so com- plete that almost perfect skeletons have been set up, enabling us vividly to imagine how the bird looked when swimming through the waters of our globe, or flying through the air, perhaps four millions of years ago. The most remarkable peculiarity of these birds was the possession of teeth. Two of the most well-known examples are called Jchthyornis and Hesperornis. The Ancestors 3 bones of these birds were discovered by Professor Marsh imbedded in the rocks of western Kansas, and they are now preserved in the museum of Yale University. Pro- fessor Marsh tells us that Hesperornis, the Bird of the Fic. 1.—Restored skeleton of Ichthyornis (after Marsh). 1/2 natural size. West, “was a typical aquatic bird, and in habit was doubtless very similar to the loon, although, flight being impossible, its life was probably passed entirely upon the water, except when visiting the shore for the purpose of breeding. The nearest land at that time was the suc- 4 The Bird cession of low islands which marked the position of the present Rocky Mountains. In the shallow tropical sea, extending from this land five hundred miles or more to the eastward, and to unknown limits north and south, there was the greatest abundance and variety of fishes, and these doubtless constituted the main food of the present species. Hesperornis, as we have seen, was an admirable diver; while the long neck, with its capabilities of rapid flexure, and the long slender jaws armed with sharp recurved teeth, formed together a perfect instru- ment for the capture and retention of the most agile fish. The lower jaws were united in front only by cartilage, as in serpents, and had on each side a joint which admitted of some motion, so the power of swallowing was doubt- less equal to almost any emergency.”’ Hesperornis had numerous teeth set in grooves like those of serpents and crocodiles, but in Ichthyornis (‘Fish- bird,’ so called because its vertebre are biconcave like those of a fish) the teeth were in separate sockets as in alligators. The latter bird was not large, being about the size of a pigeon, and it had well-developed wings. It is interesting to compare Hesperornis with the group of penguins, both being highly specialized, although in ways so different, for an almost wholly aquatic life. Hesperornis swam by strong strokes of its great webbed, or lobed, toes, its wings dangling uselessly for genera- tion after generation, until all trace, save a vestigial humerus, of their bony support disappeared. Penguins, however, make but little use of their feet in swimming, only occasionally aiding the tail in steering; but they Ancestors 5 literally fly through the water by means of their flipper- like wings. The large size of the leg and toe bones of Hesperornis shows that great speed was attainable in the water, 4 - FRET Sa CITRATE, Sy reer ST ee Ge ae ee awe eee SCL ard Geli 222. StS ease ft, (7 £ tL abbenb arth on hoe Reinier ies a i map A POR BARD ee BEES Sat e e" Gir Fic. 2.—Lower jaw of Ichthyornis (after Marsh). 4/5 natural size. Fic. 3.—Lower jaw of Alligator. 1/6 natural size. The teeth are set in distinct sockets both in the extinct bird and in the living reptile. while only a single bone remained to show where the wings of its ancestors were situated. It is doubtful if it could stand erect upon land, being in this respect more helpless even than a grebe. Its nest, if it made one, must have been at the very edge of the shore, from which 6 The Bird it could wriggle or push itself with its powerful toes into the water. The thought of the untold generations of birds which must have preceded this toothed, wingless, feathered being, makes the mind falter at the vast stretches of time during which evolution has been unceasingly at work. When we examine the skull of Hesperornis we get a clew to the reason why this great creature, nearly as large as a man, succumbed when some slight change in its environment called for new adjustments in its habits of life. Its brain was comparatively smaller than that of any existing bird; and this absence of brain power im- plied a total lack of that ingenuity, so prominent in the crow, which, when man alters the face of the land, changes its habits, and with increasing wit holds its own against guns and traps. When Hesperornis passed, it was succeeded by birds much smaller in size but of greater wit—loons and grebes —which hold their own even to the present day. When in the depth of the winter, a full hundred miles from the nearest land, one sees a loon in the path of the steamer, listens to its weird, maniacal laughter, and sees it slowly sink downward through the green waters, it truly seems a hint of the bird-life of long-past ages. We must now pass back, as nearly as can be estimated, over two millions of vears, through the ages when the Tquanodonts and Megalosaurs lived, long before the first serpents had evolved and about the time when the first timid forerunners of the mammals made their appear- ance,—tiny insect-eating creatures which were fated to Ancestors x remain so long subordinate to the masterful giant reptiles. This was about the middle of the Jurassic period, and in deposits of this epoch have been found remains of the very first birds of which we know anything. Two specimens have been discovered and named Arche- opteryx (ancient-winged-creature). From these two little stone slabs, one in the British Museum and the other at Berlin, we know that these birds were about the size of a crow. Instead of the broad, fan-shaped tail of modern birds, the tail of the Archwopteryx was a long, jointed affair like that of a lizard, and was fringed with large feathers—a pair growing from each of the twenty joints. The wings were not large, and instead of the fingers being concealed by feathers, there were three entirely free digits, each armed with a claw, in front of each wing. The skin-covered jaws were furnished with teeth, but the feet and legs were much like those of an ordinary crow. Taken all in all, this was a most wonderful discovery, linking birds and reptiles together, and proving beyond all dispute the fact of their common origin. Perhaps the most surprising fact was the remarkable development of the plumage of the wings and tail, showing that perfect feathers were in existence at least six millions of years ago. In the rocks deposited in very ancient epochs are found many footprints which were supposed to be those of huge birds, but it is more probable that they were made by certain three-toed reptiles which, like birds, walked or hopped on two feet. Indeed Nature seems to have made several abortive attempts to produce bird- 8 The Bird like creatures before she struck the right adjustments. Pterodactyls failed to become birds because they depended on a broad web of skin, like the wing of a bat, thus miss- ing the all-necessary feather-ideal; Dinosaurs began at the wrong end, learning to stand on their hind feet and to hop, but never the delights of flight. These offshoots sooner or later were forced to the wall, but Archewop- teryx seems to have been very near the true line of descent. But after all, what a meagre record we have of the un- told myriads of generations of birds which have succeeded each other through ages past! It is to be hoped that many more fossils may be discovered, for the hints given us in the anatomy of birds, and the glimpses of past his- tory which flash out from the development of the chick within the egg,—all this evidence is becoming ever more and more clouded and illegible. Having learned that birds are descended from a rep- tile-like ancestor, it is interesting to search among living reptiles for the one which most resembles birds, and we have no choice but to select the alligator-—cold-blooded, scaly, bound to the earth though he is. A second near relation is to be found in the group of long-extinct Dino- saurs. A complete record of past ages would show the ancestral stems of alligators, Dinosaurs, and birds grad- ually approaching each other until somewhere, at some time, they were united in a common stock. But we must guard against the notion that birds are descended from anv group of living reptiles; which is as fallacious an idea as that we Americans trace our direct descent from Fie. 4.—Archeopteryx preserved in the British Museum. The pelvic girdle, leg and tail show best in this specimen. 1/5 natural size. 9 10 The Bird the Chinese, or that mankind is descended from the chim- panzee or gorilla. For the purpose of making more clear and interesting the ways in which birds have become especially adapted to their surroundings and needs, we may consider Arche- opteryx as resembling closely the typical original bird- type from which all others have at least indirectly evolved; and thus having obtained a definitely fixed starting-point, we may consider how some of the more representative birds of the present day came to acquire their widely differing structure and characteristics.* The tree of evolution of reptiles may be compared to a growth where several great trunks spring from the ground close together, towering up separately but equally high; the topmost twigs of which are represented by the living species of serpents, turtles, lizards, and crocodiles respectively. A very different arboreal structure is pre- sented in the genealogical tree of the Class of birds. Here, from a short trunk, we have many radiating branches, widely spreading and with thickly massed twigs, confu- sedly intermingled; so sight are the divergences between adjoining groups and so equally do almost all share be- tween them various reptilian characteristics. It is not necessary to concern ourselves now with the processes of evolution, especially as scientists are still in doubt as to the exact methods. Let us read our Darwin, and hope for another, philosophically as great, to com- * There are one or two reasons for regarding -Archwopterys as merely the tip of a parallel branch, but one sprouting close to the base of the avian tree. h x preserved in the Berlin Museum. The skull, vertebra forelimbs and flight-feathers are remarkably distinct. 1/3 natural size. IL 12 The Bird plete the work, meanwhile adding our own mite of truth- ful observation to swell the whole, and help prepare the way for this other. For even Darwin’s theory of evolu- tion was but the consummation of theories of former years and centuries,—beginning with Thales and Anaxi- mander, in the days of early Grecian civilization: in- deed Aristotle, coming but two hundred years later, is the only name in the history of zoology worthy of a place with that of Darwin. From the fragmentary evidence afforded by Archeop- teryx we may conclude that this Bird of Old had a short, blunt, skinny bill of moderate size, furnished with teeth which would enable the owner to feed upon Jurassic berries and fruit, or more probably a carnivorous diet of lizards and insects. Its wings were weak, hinting that it was a flutterer rather than a true flyer, perhaps only sealing hke a flying squirrel from the summit of one tree to the base of the next. Even this would give it an immense advantage over its terrestrial and arboreal non-flying enemies. The three free fingers on each wing would allow it to climb easily, to pry into crevices for insects, or to draw a_berry-laden branch close to its bill. Doubtless it frequently walked or ran on all fours, the more probably from its weak-loined condition,—the bones of the thigh-girdle not being fused together as in modern birds. Its tail has already been mentioned—a_ long double-feathered appendage, composed of a score of little vertebrae jointed together,—as we will later see the true forerunner of the modern fan-like tails. Its Fic. 6.—Restoration of Archeopteryx (adapted from Smit). Notice the teeth, three fingers, and lizard-lke tail. 14 The Bird feet and legs were little different from those of perching birds of to-day, with strong toes well adapted to cling to a branch. Finally, from a cast of the brain, which fortunately was found with one of the fossils, we know that, although small, it was that of a true quick-witted bird. As yet science has no more to tell us. Our fancy may add an archaic attempt at song—a lizard’s croak touched with the first harmony, which was to echo through all the ages to follow; we may also imagine, if we will, leathery eggs deposited in a rotten knot-hole of a Jurassic conifer. In both islands of New Zealand well-preserved remains of giant birds have been discovered, to which has been given the name of moas. One species must have reached a height of ten or eleven feet, which would make it tower above the largest living ostrich. They were, in fact, not unrelated to these latter birds and, like them, were flightless (in some cases absolutely wingless), and they had great massive feet and legs. Native legends among the Maoris hint that these birds were in existence during the last few centuries before the coming of the white men. In South America also, giant birds lived in ages past. One, the Phororhacos, stood seven to twelve feet in height, with a head and beak like that of a gigantic eagle. Unlike all eagles, however, this bird could not fly and doubtless ran down its prey, as a chicken runs down a grasshopper. It is an interesting fact that in South America there lives to-day a bird known as the Seriema, which is prob- Ancestors Ls ably at least an indirect descendant of the Phororhacos. The Seriema defies exact classification, sharing characters of cranes, bustards, and eagles. Its beak and inner claw are like those of a bird of prey, while in form of body, and in the other claws of the toes, and in the legs it is crane-like. One of these birds which I have ob- served for years in captivity is as gentle and as fearless as a bird can be. It will chase insects and _field-mice outdoors in the Zoological Park, and will occasionally stalk solemnly into my office and, coming close to my desk, watch me closely. It has most beautiful gray- blue eyes, with long eyelashes (Fig. 199), and if the birds of past ages were as comely and as lovable as this interesting species, I regret that only their fossil bones are left to us. As the Seriema runs down and kills a mouse, so the giant Phororhacos, doubtless, overtook and slew creatures as large as a deer. Its skull (lig. 7) is drawn to the same scale as that of the living Seriema (Figs 8). The evolution which has gone on since these epochs of old, bringing into being the wonderfully varied forms of penguin, ostrich, albatross, peacock, and humming- bird, may be summed up in two words which it is well to know and remember,—Adaptive Radiation. This is the spreading out or radiating of bird-forms descended from the ancient stem, into all parts of the earth, each coming into contact with a particular environment, to adjust itself to which, its various organs and parts exer- cise different functions, until the friction of the “struggle for existence”? has moulded each to its particular niche. 16 The Bird If its lines lie in happy places, its race is established, and it pursues and flees, it fights and plays, it sings with joy or pants with fear, and Evolution marks another success in its inexorable movement onward and upward, —a new species is born! Earth has few secrets from the birds. With wings and legs there is hardly a spot to which they cannot and indeed have not penetrated. Some find food and con- tentment in the desolate wastes of the far North; others spend almost all of their life on or above the sea far from Fie. 7.—Skull of Phororhacos, drawn to scale with Fig. 8. 1/6 natural size. land; thousands revel in the luxuriance of reeking trop- ical jungles; a lesser number are as perfectly suited to the blazing dust of the desert; and there are birds which burrow deep into the very earth itself. Day and night; heat and cold; water, earth, and air, have all been con- quered by the thirteen or fourteen thousand species of birds which share the earth with us at the present day. These brethren of ours, whose clans have so bravely conquered the dangers of millions of vears, and at last have gained a foremost rank in the scale of living crea- Ancestors sr tures, now find themselves face to face with the culmi- nating effort of Nature,—Mankind. They cannot escape Fig. 8.—Seriema, a living descendant of Phororachos, with characters of Cranes, Bustards, and Eagles. 1/6 natural size. from us, though the least among them laughs to scorn our efforts at following through the air. Yet all must 18 The Bird return sooner or later to earth for rest and food, and thus all are at our mercy. Let us beware of needlessly destroying even one of the lives—so sublimely crowning the ages upon ages of evolving; and let us put forth all our efforts to save a threatened species from extinction; to give hearty aid to the last few individuals pitifully struggling to avoid absolute annihilation. The beauty and genius of a work of art may be recon- ceived, though its first material expression be destroyed; a vanished harmony may yet again inspire the composer; but when the last individual of a race of living beings breathes no more, another heaven and another earth must pass before such a one can be again. CHAPTER II FEATHERS given, but all fall short in some particular, or Ss‘! are weak in having exceptions. FEATHERED is the one word which always holds true. All birds have feathers, and nowhere else in the world are similar struc- tures found. A feather, like an egg, is perfect in its adaptation to the bird’s requirements, and also, like the egg, its structure is rather complicated. Structure and Development First let us look at the skin itself in which the feathers erow. To skin a bird is an easy matter, for the skin, or integument as it is called, is very slightly attached to the muscles underneath. The skin of a dove is almost like tissue-paper, and tears so easily that it is a marvel how the hundreds of feathers find a sufficiently strong attachment. Thin as is this skin, it is made up of three separate layers, but in order to make our feather-study enjoyable by not overburdening it with too many details, we will consider only the two more important layers of the skin—a deeper one, the dermis, and an outer, more horny covering, the epidermis. 19 20 The Bird A list of all the structures of animals which are prod- ucts of the outer layer alone would be a long and sur- prising one, and we would be very ready to grant the importance of skin. Such an enumeration would include all claws and talons, nails and teeth, the rattles of a snake, spurs, hairs, the scales of fishes and reptiles, Fic. 9.—Tarpon-scale, shark-tooth, and peacock-feather; showing diversity of structure derived from the skin alone. 1/2 natural size. spines, whalebone, beaks and feathers. Even the horn of a rhinocerus is only a solid mass of agglutinated hairs, while as the antithesis to this may be mentioned all down and feathers: the tiniest fluff from a humming- bird to the great pinion of a condor. If we examine a newly hatched dove or sparrow, the little, ugly, sprawling creature, at first glance, seems Feathers 21 to be entirely naked; but a closer inspection shows scanty tufts of down scattered irregularly over the body. This, like the set of milk-teeth in mammals, is useful only for a time, and is later pushed out by the second or true plumage. Even more numerous than the down- Fig. 10.—Brown Pelican nestlings, showing feather papille on body and wings. About 1/4 natural size. tufts are little pimples or dots, many hundreds of which cover certain parts of the skin. Each of these will event- ually give rise to a perfect feather—quill, vane, barbs, and all. The under layer of skin, or dermis, is very thin in birds, much more so than in reptiles and other animals. 22 The Bird The first intimation of the appearance of a feather, or of down, is shown by a thickened group, or pimple, of cells in this under layer of skin, which grows and presses upward toward the outer layer—the epidermis. This is exactly the way in which the scales of fishes and reptiles begin to form; and if, at this stage, the tiny projection should flatten out, the shining scale of a carp, the armor Fic. 11.—Sprouting feathers of a 12-day embryo chick. Magnified 25 diameters. of an alligator, or the cobble-scale of an iguana lizard might result. Indeed, in the feathers of a penguin we find transition stages of flat, almost unsplit feather- scales; while on the legs and feet of birds are reptile-like scales. The evolution of scales, hair, and feathers is a most interesting problem, most of the details of which are beyond the scope of this work. Suffice it to say that Feathers a3 in sharks, which are among the most primitive forms of fishes, the skin is covered with tiny denticles or spines, which consist of enamel and dentine, and which rest on small bony plates. This form of scale is the most ancient known, and the hint of teeth which the description con- veys is not misleading; for we find that in some of these voracious fishes the spines in the skin become enlarged near the edge of the mouth, merging imperceptibly into the rows of cruel teeth which, to a certain extent, are homologous with the teeth of all higher animals. In other fishes the denticles become flattened scales, and many of these fish have teeth of corresponding plate- like form. So it is interesting to know that the scales of fishes and reptiles, the feathers of birds, and the teeth of animals have all evolved from skin structures which at an early stage of growth bear considerable resemblance to each other. But, in our young bird, the slender finger of cells which reaches upward, and whose base at the same time sinks deeply into the dermis, does not broaden out, but splits longitudinally into a number of folds, which grad- ually dry apart and harden into the slender, silky fila- ments which we know collectively as down. At the base of, and in fact attached to, the little pro- jection which gives rise to the nestling down is a small circular body of cells, which grows but little while the down plumage is serving its use; but when the bird is ready for a coat of true feathers this lower cellular mass begins to grow upward into a second finger, or column, of cells, pushing the base of the down feather out of its 24 The Bird socket. This growth continuing, the down is lifted clear of the skin, being supported on the new structure, and Fic. 12.—Early stages in the development of a down feather, showing close resemblance to scale of fish or reptile. ee ic, 12a.—Later stages of Fig. 12, showing the first splitting up of the feather pulp. soon brushed off and lost. Thus, little by little, in shreds and tatters, the baby plumage is shed and replaced Feathers 25 by true feathers, which overlap, protecting the body from heat and cold, dust and rain. Fic. 12b.—Last stages in the formation of a down feather, showing the plumes well above the surface of the skin, as in a newly hatched chick. All greatly enlarged. At the time of the first moult, this succession of feathers can be observed in almost any young bird, being more noticeable in large species, which have very thick 26 The Bird or lengthened down, as gulls and ducks. A Red-winged Blackbird, or for that matter almost any passerine nest- ling, looks very odd when it rises up in the nest, gaping for food; the long gray streamers of down waving like an aureole around its head. In some water-birds this nest- ling down retains its usefulness for nearly two months, Fig. 15.—Feather from the head of a young Bobolink, with down still attached to its tip. ‘Twice natural size. The feathers which replace the down are, when they first appear above the skin, rolled tightly and bound up in the thin tissue of the horny sheaths, so that they resemble a bundle of withes wrapped together in a cloth. In many young birds the feathers remain in this condi- tion until they are nearly full grown, and a young cuckoo Feathers 27 or kingfisher is a curious-looking object, most of the bird’s body seeming to be tiled with small, bluish sticks. Fic. 14.—Tip of feather from the crown of a young Song Sparrow, showing connection with down. Magnified 25 diameters. Fie. 15.—Duck Hawk moulting into juvenal plumage, with the natal down coming away in shreds and tatters. 1/4 natural size. When the folds of the developing feathers are sufficiently dry, they burst their sheaths and rapidly spread out. 28 The Bird The appearance of a young kingfisher or heron may be completely changed within a few hours time, so quickly and simultaneously does the first suit of feathers unroll. The condition of young birds when hatched varies greatly in birds of different groups. Nestlings are, in many ways, like human babies, and there are as many differences in the one class as there are in the other, Fie. 16.—Growth of an Ostrich feather from sheath to plume. 1/5 natural size. between those from different countries, only Nature does for the little birds what parents do for the babies. We see American babies wrapped in furs and blankets, wheeled in carriages, and rocked to sleep; while a tiny savage is strapped tightly to its mother’s back, and as soon as possible allowed to run where it pleases, find its own toys and develop its little muscles, gaining a degree of health and strength which many a civilized child would envy. So with birds, the highest—such as crows and thrushes—are hatched almost naked and must be warmed Feathers 29 and cuddled and fed for many weeks, before they learn to take care of themselves; while birds lower in the scale—as our quail—are born covered thickly with down and with wings nearly feathered, and in a few days can fly and find their own food. So a bird naked at birth is very helpless, one covered with down is more capable of taking care of itself, while Fig. 17.-—Nestling Ningfisher with feathers still in their sheaths. 2/3 natural size. the few which are completely feathered when hatched may be said to have no chickhood except in the egg. In the Crested Screamer (Fig. 264) the down-like character of the body-feathers of the adult birds may be a hint of the plumage of very ancient types of birds such as Archeopteryx. Now we are ready to begin our study of the perfect feather itself, and we will, for once, have to disregard our rule of starting with the simpler form—the scale of 30 The Bird a reptile—and working up to a feather; for, if we except the down, there seems to be no connecting link left. Fic. 18.—Young Brown Pelicans; hatched naked and helpless (altricial). 1/4 natural size. Fic. 19.—Young Red Jungle Fowl one day old; hatched covered with down and able within a few hours to help itself (precocial). Almost natural size. Although that old, old fossil bird Archwopteryx still retained reptile-like teeth, fingers and tail, it had Feathers ai feathers which were apparently as perfect as any we may examine to-day. When some form of scale had once changed so that it was of use in flight, the hollow elastic vane took first place at once, and all intermediate stages, which perhaps had been acquired merely for warmth, went to the wall. A creature could have flight if pro- vided with perfect feathers, or it could retain its scales and find existence possible along the old reptilian planes of life, but no awkward scale-flutterer could long be tolerated. All through the evidences of evolution we find instances like this,—a change for the better beginning slowly, through many channels, then the one best suited forging ahead with inconceivable swiftness, and crushing out all other less adapted structures. Hence the rarity | of ‘missing links.” Feathers are certainly among the most beautiful objects in Nature; and when we learn a little about their structure, they will be still more interesting. No matter how closely we may examine them, with hand-lens or microscope, their beauty and perfection of structure only increase. If we study a feather, say from the wing of a pigeon, we see that its whole structure is subservient to two characteristics—lightness and strength. What won- derful elasticity it has! We can bend the tip so that it touches the base and it will spring back into shape with- out breaking. If we look closely, we will see that each feather is composite—feathers within feathers. The quill gives off two rows of what are called barbs which together form the vane of the feather; each of these barbs has two 32 The Bird rows of barbules, and these give rise to a series of curved hooks, known as barbicels, which work into opposite series of grooves, so tightly that air cannot force its way through the feather. When the wings are pressed down- ward, the phenomenon flight is made possible by the accumulated resistance which the flight-feathers offer to the air. At the lower end of our pigeon’s feather, bar- bicels are present only near the quill. Therefore the Fic. 20.—Two interlocked barbs from the vane of a Condor’s wing-feather, show- ing barbules and barbicels. Magnified 25 diameters. tips of the barbs are loose and fluffy, unconnected and useless for flight. This is the condition in all down and in the feathers of the ostrich and cassowary. We might naturally think that feathers stiffened by so many close rows of interlocking barbicels would be useful in many ways beside flight. But fluffy feathers are evidently just as efficient in keeping warmth in and rain out as the other kind; so Nature, economical to the most micro- scopic degree, has lessened the number of, or has never provided, barbules and barbicels wherever a feather is not needed for flight or steering. Feathers 23 The two lines of barbs which grow out on each side of the quill are very elastic and so intimately hooked to each other that they will bend some distance before sepa- rating. If we ever tried to force our way through a Fig. 21.—Model showing interlocking barbules and barbicels of feather, greatly enlarged. bramble of sweet-brier or blackberry-vines, we can more readily appreciate how these barbs and the interlocking barbules clutch each other. The thorns in the bramble catch our clothes and, when we move, the elasticity of the long stems tends to make them hold the tighter. We notice that one line of barbs—that along the inner curve of the quill—is much longer than that on the outer curve and we might think the air would force this 34 The Bird 3 upward and escape beyond the edge. So it would, if it were not for the arrangement of the feathers on the wing, which overlap like the tiles on a roof, each vane over- lying and holding down the long barbs of the feather in front, while, above and below, other shorter feathers help to bind the whole tightly, thus enabling the bird at every stroke to whip a wingful of air downward and backward. A feather and its parts, like all the rest of the bird, is composed of cells—empty and hollow ones in this in- stance, as we can easily see for ourselves by placing a barb from a pigeon’s feather in a drop of water and looking at it under a low-power magnifying-lens. The network of horny cells is very plain. It is a simple matter to say that a feather consists of quill, barb, barbules, etc., but to appreciate the wonder- ful complexity of this structure let us make a little cal- culation. Suppose we have a wing-feather from a com- mon pigeon with a vane about six inches long. If we have patience enough to count the barbs on one side of the quill, we will find there are about six hundred of them. So the vane of the entire feather has twelve hundred of these little side featherlets. One of these, from a narrow part of the vane, will show under the micro- scope about two hundred and seventy-five pairs of bar- bules, which multiplied by the number of barbs on that side amounts to three hundred and thirty thousand. Making a very low estimate of the whole vane, we have nine hundred and ninety thousand separate barbules on this one feather, and when we think of the innumerable Fig. 22.—Feathers illustrating conditions where barbicels are unnecessary and are hence reduced or entirely lost, causing downiness. 3/5 natural size. (a) Primary of Pigeon—an important flight-feather; hence possessing a stiff” vane. (b) Under wing-covert of a Great Blue Heron; downy portion was over- lapped by the adjoining feather. (c) Wing-covert of Owl; the downy edge makes possible the all-important noiseless flight of this bird. (d) Feather of Ostrich; the power of flight being lost, the feathers are downy throughout the entire vane. 35 36 The Bird finer hooklets, and then the number of feathers on the pigeon’s body, we can echo the exclamation of Solomon: “The way of an eagle in the air” is “too wonderful for me!” Another beautiful adaptation to flight is seen in our Fig. 23.—Feathers of Condor and Emeu. The aftershaft in the former is reduced ao ea at the base of the vane; in the latter it equals the feather feather. The upper part of the wing must of course be perfectly level, with no projections to catch the air and retard motion. So, on the upper side of the feather, we notice that the lines of barbs spring out flush with the flattened quill-top, while below, the shaft projects promi- nently from the vane. The obliquely forward direction in which the barbs grow, the change in shape of the Feathers a7 quill—round where the body or body-feathers conceal it, square where it supports the vane,—and many other niceties which we can each detect for ourselves, show how exquisitely exact is the adaptation of a feather to its uses. Fic. 24.—Powder-down patch on the breast of a live Great White Heron. 2/3 natural size. Growing from the under side of the quill, at the be- ginning of the vane, is a tiny feather known as the after- shaft. In an ordinary down-feather of a young bird this is of considerable size, but it is either small or entirely absent in an ordinary feather. It reaches its greatest development in the emeu and the cassowary, where it is 38 The Bird as long and as perfect as the main feather. The origin and use of this feather-double is not known. Parrots, herons, and some other birds have a most convenient arrangement—a kind of automatic clothes- cleaner and valet combined. Concealed by the long body- plumage are several dense patches of down-feathers which grow quite rapildy, but instead of constantly increasing in length, the tips break up into a fine, white, greasy powder. This works its way through the entire plumage, and is doubtless of use in keeping the feathers in good condition and the body dry. Most of the birds possess- ing this convenience are comparatively free from lice, so this natural dressing may be as unpleasant to these ver- min as camphor-balls are to clothes-moths. The forms and textures of feathers are innumerable, and the uses to which they are put, more than we would ever imagine, but these will be spoken of under the chap- ters treating of the different parts of the body where they are found. Arrangement In examining a nestling we will notice that the feather- dots are not scattered at random over the surface of the skin, but grow in lines and tracts, whose limits are very sharply defined. In an adult bird, say an English Spar- row, this is even more noticeable. If we part the feathers on the centre of the breast, a broad, bare area is seen, with only a thin scattering of soft downy feathers. Under the wings are other naked spaces, and several more are on other parts of the body. The most ancient birds were Feathers 39 probably covered uniformly with scale-feathers, but as these increased in length there was less need for an un- broken covering, the feathers of one portion overlapping and protecting the surrounding parts, and besides, for ease in active motions, bare patches of skin were required. It has been found that the arrangement of the feathers on a bird’s body varies in different groups, and, such variation being rather characteristic of these larger divi- Fia. 25.—Nestling Crow, showing feathered and infeathered portions of the body (pteryle and apteria). 1/2 natural size. sions, pteryvlosis—as it is called—is of some importance in classification.. Penguins only, of existing birds, have feathers growing uniformly on all parts of the body. In the ostrich, which has given up flight and taken to run- ning, the body feathers have grown over almost all the bare spaces which existed in its flying ancestors. There are two marked exceptions due to the present habits of these birds. Like the camel, when resting, these giant birds lean upon their breasts. This portion of the body 40 The Bird is provided with a thick, callous pad, which, by constant use, is thus kept bare of feathers. In addition, the under sides of the degenerate wings are also free of plumage, owing no doubt to the continual close application of these organs to the sides of the body. The other bare areas are almost obliterated, but the legs are bare, thus allowing perfect freedom in action. Some birds, such as vultures and cassowaries, have lost all feathers on the head and neck, or other portions of the body, from various causes, as for cleanliness, or, in some cases, probably for ornament. This will be spoken of more in detail in a later chapter. Moult The waste of internal tissues and organs in animals is repaired by means of the blood which brings them fresh material and carries away worn-out cells, as it traverses arteries and veins. Entire parts, as the tails of tadpoles, may even be absorbed; but, in general, skin structures when old and worn out are cast off and renewed from the lower, or derm, layer. This takes place in various ways. The skin, even to the covering of the eyeballs, may come off entire, as is the case among snakes, or por- tions peel off and tear away, as in lizards. Warm-blooded animals also shed, or cast, their outside covering; mam- mals shedding their coats of hair, and birds their feathers. In the latter class this process is called moulting. The nestling down and the feather which replaces it can hardly be considered as separate structures, as the Feathers 41 same channel perforates both and the nutriment pith which supplies the down traverses the hollow quill of the succeeding feather.