ae és ore aoe ety gore mony CORNELL UNIVERSITY LIBRARY FROM A FUND RECEIVED BY BEQUEST OF WILLARD FISKE 1831-1904 FIRST LIBRARIAN OF THIS UNIVERSITY : 1868-1883 CORNELL UNIVERSITY LIBRARY LABORATORY OF ORNITHOLOGY LIBRARY Gift of DATE DUE GAYLORD PRINTED IN U.S.A. ANIMAL LIFE AN EVOLUTIONARY NATURAL HISTORY GenerAL Epiror: W. P. PYCRAFT ZOOLOGICAL DEPARTMENT, BRITISH MUSEUM VOL. I A HISTORY OF BIRDS Cornell University The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924022531242 T HOME LESSON IN PROTECTIVE COLORATION THE BITTERN A A HISTORY OF BIRDS W. P. PYCRAFT ZOOLOGICAL DEPARTMENT, BRITISH MUSEUM WITH AN INTRODUCTION BY SIR RAY LANKESTER, K.C.B., F.R.S. AND NUMEROUS ILLUSTRATIONS AND DIAGRAMS METHUEN AND CO. 36 ESSEX STREET W.C. a My Orn, Qu 613 aks AS07670 First Published in 1910 CAROLO EDUARDO FAGAN PLURIMA ET JUCUNDissIMa MEMORIA DEDICATUS EST HIC LIBER PREFACE Y aim in writing this book isto present the study of Bird Life from the point of view of the Evolutionist ; to set forth, in broad outline, the evidence now generally regarded as bearing on that most fascinating pro- blem, the birth and growth of the various types of birds— whether regarded as large groups, or as geographical races. The external beauty of form and colour which birds pre- sent, has so far proved a serious distraction, so that Ornitho- logists, captivated thereby, have paid but little heed to the possible factors to which these features are due. At any rate, since the master mind of Darwin himself laid the foundation for this wider study of Bird Life but little progress has been made. It is hoped, however, that this volume will prove a stimulus to renewed efforts to penetrate some, at least, of the many mysteries to which he called attention. The purpose of this book, then, is obviously to present the Study of Birds as one of living organisms, moulded in part by an inherent constitution, and in part by that “struggle for existence” which is the lot of every living thing—a struggle with environment, animate and inanimate. This being so, it is obvious that anything more than the barest account of ana- tomical details would be out of place here. True, these “anatomical details’’ are the essence of the whole matter, but though this be so their bearing on the question at issue, at present, is not measurable; and accordingly those who seek in these pages for information of this kind will seek in vain. My expert critics will doubtless discover many omissions in this book. I am aware of many: but I have had perforce to select, and I have chosen those facts which seemed best to vii viii A HISTORY OF BIRDS serve my needs. Furthermore, I have written, not for the expert but rather for those who, like myself, have a keen love of birds—but who have so far had no opportunity of studying them from this point of view. My friends being all busy men I have not dared to trouble them with appeals for help in my self-imposed task, but I am deeply indebted to Professor J. Arthur Thomson for help in laying the foundations, and to Mr. H. Eliot Howard for kindly criticism on my work in the course of its progress. For many of the illustrations in these pages I am indebted to the courtesy of the Council of the Zoological and Linnean Societies, and of the Norfolk and Norwich Naturalists’ Society. My thanks are also due to Mr. A. J. Bishop, Dr. Bumpus, Mr. J. G. Millais, Mr. A. R. Momber, the Hon. Walter Rothschild, Major Trevelyan, Miss E, L. Turner, and to Messrs. Black, Jack, Sotheran and Rowland Ward. Finally, I desire to accord my best thanks to my friend Mr. G. E. Lodge for his splendid interpretation of the themes illustrated by his brush ; these have never before been so vividly and realistically handled, and they should do much to bring home the lesson they are designed to teach. W. P. PYCRAFT Lonpon November, 1909 CONTENTS PREFACE List oF ILLUSTRATIONS IN THE TEXT List oF PLATES INTRODUCTION List oF AUTHORS QUOTED CHAPTER I INTRODUCTORY - o General characters of structure—feathers, glands, the skeleton, the respiratory system, the lungs and air-sacs, the digestive system, the circulatory system, the muscular system, the nervous system, the senses. CHAPTER II PHYLOGENETIC - - Birds and their position in the animal kingdom. Relationship to the reptiles, and the evidence thereof. Archeopteryx—the first bird. Hesperornis and early specialisation. Ichthyornis, The Pro-aves. CHAPTER III PHYLOGENETIC (continued)—THE CLASSIFICATION oF Birps IN BroaD OuTLInE—THE Main LINES OF THE EVOLUTION OF THE CLASS AVES - - Archornithes and Neornithes. The position of the Ostrich tribe in the system. What the structure of the bony palate reveals. Palzo- gnathe and Neognathe. The classification of the Palzxo- gnathe and of the Neognathe. A hypothetical ancestor. The Grebes and Divers, Penguins and Petrels, Steganopodous birds, the Accipitres, the Anseres, the Alectoromorphe,—the Game-birds, Cranes and Rails, Plovers, Pigeons, the “ Coraciiform”’ birds; the Passeres. Numerical strength. CHAPTER IV CEcoLoGIcaL Peculiarities of distribution. Continuous and discontinuous areas. Zoo- geographical regions. The northern and southern hemispheres and the origin of life. Some British birds and the lessons they teach in regard to the migration of animal life from north to south, Factors in the formation of isolation areas. The haunts of birds. ix 30 41 61 x A HISTORY OF BIRDS CHAPTER V SeasonaL Lirg, RELATIONS TO MorsTuRE, TEMPERATURE, ETC., AND TO Pgriopic CHANGES IN THE COSMOSPHERE The bleaching effect of light. Desert forms. The effects of a saturated atmosphere. Arctic conditions. Size and latitude. Storms and drought. CHAPTER VI MIGRATION - if Kinds of migration. Routes. The height at which birds fly. Speed. Lighthouses and their influence. Erratic migration. Causes of migration. Meaning of migration. CHAPTER VII RELATIONS TO THE ANIMATE ENVIRONMENT Relation to plants. Birds and pollination. Birds and spread of seeds. Birds in relation to other animals. The perils of nestling birds. Birds and “ civilisation ”’, CHAPTER VIII PecuLiar INTERRELATIONS Ostriches and Zebras. Rheas and Guanacos. Oxpecker and big Game. Egrets and Elephants, Bee-eaters and Bustards. Penguins, Alba- trosses and Petrels. Osprey and small birds. Chaffinch and Missel-thrush. Burrowing Owl and Prairie-dogs. Petrels and “Tuatera Lizard”. Puffins and Rabbits. Skuas and Gulls. Frigate-birds and Gannets. Cuckoos and their dupes. The causes of parasitism. CHAPTER IX Puases or Sociat Lire . Gregarious birds. Curious sleeping habits. Pelicans fishing. Wood- peckers and food stores. Significance of gregarious habits. CHAPTER X THE RELATIONS OF THE SEXES a * = - The division of labour in nest-building. Manifestations of sexual activity. Forms of this activity. Plumage displays. “Sdcaleli.” Wind-bags and display. Tournaments. Weapons and their uses. Dancing. “Gardening.” Song. Instrumental music. Where the sex réle is reversed. CHAPTER XI REPRODUCTION—NIDIFICATION - The first nest-builder. Origin of nests. Primitive nests, Burrowing. Simple nests. The nests of the Thrush tribe. Complex nests. Pensile nests. Mud nests. The remarkable nests of Tree-swifts, Colonies. Variability in nesting sites, Se i Strange nesting sites. Nest-building and instinct, PAGE 80 89 106 124 135 143 173 CONTENTS CHAPTER XII REPRODUCTION—CONCERNING Eccs - Number of eggs ina “clutch”. Shape of the egg. Size. Texture and thickness of the shell. Colours of eggs. Origin of the colours. Patterns of coloration, Colours of eggs in relation to classification. Coloration in relation to environment. White eggs and their mean- ing. Structure and composition of the egg. CHAPTER XIII REPRODUCTION (continued)—CARE OF THE OFFSPRING - Brooding and “ brood-spots”’. Care for the sitting female. The remark- able case of the Hornbill. The brooding of the Emperor Penguin. Brooding of Egyptian Plover and of Megapodes. Forsaking eggs. Osprey and care of eggs. Transportation of eggs by parents. Pre- cautions against floods. CHAPTER XIV Care or OFFspRING (continued) - ee - The care of the young undertaken by the male alone, and by the female alone, or by both parents. The remarkable case of the Sand-grouse in procuring water for their young. The strange case of the trans- portation of the young in the Woodcock. Feeding customs. Sanitation of the nest, The callousness of Eagles, The coloration of nestlings. CHAPTER XV NESTLING BIRDS AND WHAT THEY TEACH : - The differences between young birds and young reptiles. Nestling birds and the systematists. The clothing of nestlings. Primitive nest- lings. Precocious flight. Helpless nestlings. The coloration of nestling birds and its significance. CHAPTER XVI Tue Lire-HIsToRY OF BIRDS—AN CECOLOGICAL SUMMARY Embryology in outline. No hard-and-fast line between embryonic and post-embryonic characters. Plumage phases. Some puzzling facts with regard to adult characters. The plumage of Thrushes. Signs of maturity. Nuptial liveries. Coloration and its evolution, Moult- ing. Abrasion phenomena. The age of birds. Mortality. Play of birds. CHAPTER XVII VARIATION: CONTINUOUS AND DisconTINUOUS—INTER-BREEDING Paucity of information on variation in birds. The work of J, A. Allen. Relation of variation to natural seléction. Barrington’s work. Colour variation. Dimorphism. Mutation. Albinism and Melan- ism. Swallows. 213 223 235 262 291 xii A HISTORY OF BIRDS CHAPTER XVIII AcQuIRED CHARACTERS—THE PROBLEM OF PARENTAL MODIFICATIONS The remarkable case of the Hoatzin and the bearing thereof on the problem of parental modification. The results of feeding experi- ments, and changes of light and temperature on Flamingoes and Tanagers, : CHAPTER XIX NATURAL SELECTION AS APPLIED TO BIRDS The theory of ‘* Natural Selection ” applied to birds. Modes of selection. Inter-specific selection. Pigs and Penguins. Skuas and natural selection. Protective coloration. Winter whitening of Ptarmigan. Mimicry among birds. Protective resemblance and aggressive re- semblance. Importance of inter-specific selection on the evolution of species. Intra-selection. CHAPTER XX ARTIFICIAL SELECTION The evolution of the domesticated races of Pigeons, Fowls, etc. Rever- sion of domesticated races to the wild, ancestral type. Physiological and morphological species. Fertility and the test of species. CHAPTER XXI SEXUAL SELECTION Darwin and the theory of sexual selection. The evidence on which his theory was based. Objections to the theory of Alfred Russel Wallace, and of H. Eliot Howard. Sexual selection in absence of secondary sexual characters. Consciousness in display of the effect produced, or to be produced. The factors which incite display. The part which sexual selection does play. CHAPTER XXII IsoLATION—SPATIAL AND PHYSIOLOGICAL AND DETERMINATE EVOLUTION - Isolation and natural selection in evolution. Natural selection and the origin of species. Isolation and geographical distribution. Varia- tions blastogenic. Romanes and Isolation. Physiological selection. Inter-breeding species. Island forms. Species formation in high altitudes. Discriminate isolation. Determinate evolution. CHAPTER XXIII STRUCTURAL AND FUNCTIONAL ADAPTATIONS—SHAPE AND SYMMETRY The factors determining shape. The remarkable asymmetry of Owls’ ears. The wing. The shoulder-girdle and sternum. The pelvic girdle. The pelvic limb. Some puzzling features in the pelvis of Struthious birds. The pectineal process and its homologies. -Types of feet. Feathers and adaptation to arboreal life. PAGE 3IL 318 335 343 354 366 CONTENTS CHAPTER XXIV ADAPTATIONS (continued)—ORGANS OF EXTREME PERFECTION - The significance of certain peculiar modifications of the trachea. Re- ciprocity in development. The apparent over-elaboration of organs as illustrated by Woodpeckers and Kingfishers. Diastataxy. CHAPTER XXV ADAPTATIONS (continued)—THE ALIMENTARY CANAL AND VASCULAR SysTEMS) - - . e The form of the beak in relation to the food. Modifications of the tongue. The alimentary canal. Modifications of the crop and gizzard. The convolutions of the intestines. Peculiarities of the vascular system, CHAPTER XXVI CONVERGENT EVOLUTION AND PARALLEL DEVELOPMENT The evolution of the Owls and diurnal birds of prey. Night-jars and Owls, Swifts and Swallows. The Cariama, Cranes and Storks. The Plover tribe and the Rails. Gulls and Petrels. The Diving Petrels and the Auks. The remarkable transformation of the skeleton in the Auks and Diving Petrels. Homoplasy a factor in the evolution of birds. The problem of the New World Vultures. xili PAGE 400 411 439 LIST OF ILLUSTRATIONS IN THE TEXT ILLUSTRATION I. 2. To. It. 12. 33 DracraMs ILLUSTRATING THE STRUCTURE oF A FEATHER. (After Pycraft) - - : - From The Book of Natuve Study. Contour FraTHERS (PHEASANT AND Emu) SHOWING THE Hypo- RHACHIS OR AFTER-SHAFT. (After Pycraft) - From The Book of Nature Study. A DEVELOPING FILOPLUME SHOWING THE RAMI WHICH LATER DIS- APPEAR, AND THE MAIN SHAFT WHICH REMAINS TO FORM THE “FILopLuME”. (After Pycraft) - From The Tr tions of the Li: Society. . PreryLosis oF Acanthidositta chloris SHOWING THE FEATHER Tracts. (After Pycraft) - - - “ By permission of the Editors of The Ibis. . Wine or A Birp, SLIGHTLY DIAGRAMMATIC, TO SHOW THE ARRANGE- MENT OF THE “ QUILL” oR ‘“‘ FLIGHT-FEATHERS”. (After Pycraft) DISSECTION SHOWING THE LUNGS AND ArR-SAcS OF A Birp. (After Strasser) - - - - - - TyPES OF THE Caca, or BLIND Gut, oF RHEA, OwL AND MarTINETA TINAMOU - - = By permission of the Editors of The Ibis, and of the Zoological Society. . SKULLS OF NESTLING PENGUIN AND EMU To SHOW THE SUTURES DIvIDING THE SEPARATE ELEMENTS OF THE CRANIUM From Specimens in the British Museum of Natural History. Hip-GIRDLES OF A DINOSAUR, AN EMBRYO Birp anp A NESTLING Emu. (After Marsh) > el Tue END OF THE SHANK AND MIDDLE Bones oF THE Foot (Tarso- METATARSUS) OF A YOUNG BrirRD COMPARED WITH THE SAME Bones 1n AN ApuLt Reptive (Dinosaur). (After Marsh) THE SKELETONS OF Two ExtincT FossiL Birps, HESPERORNIS AND IcHTHYORNIS - OnE oF THE Pro-Aves. (After Pycraft) - ss RESTORATION OF ARCHAOPTERYX. (After Pycraft) - xv PAGE to 12 13 18 23 31 33 34 36 39 42 xvi A HISTORY OF BIRDS ILLUSTRATION 14. 15. 16. 17. 18, 19. 20. ai. 22. 23 24. 25. 26. 27 28. 29 30. 31. 32. STAGES IN THE EVOLUTION OF THE AVIAN PALATE PHYLOGENETIC TREE OF DESCENT Tue Wuave-Heapep Stork (Balaniceps) Tue Rurous Tinamou (Rhynchotus rufescens) Wine FEATHER OF A CURLEW SHOWING THE In1TIAL STAGES IN THE DISINTEGRATION OF THE WHITE PARTS: AND A PoRTION OF THE QUILL FEATHER OF A GULL SHOWING THE SAME PROCESS Humine-strp FERTILISING FLowers oF Maregravia Nepenthoides. (After Wallace) Devices To SECURE A PERMANENT Foop SupPLY Poucu or Great BusTarD DISSECTED To SHOW ITs RELATION TO THE GULLET AND WinppiPE. (After Pycratt) Tus DispLay or THE GREAT Bustarp (Otis tarda) From Newton's Dictionary of Birds. Types oF WINDPIPES Nest oF THE HaMMER HEAD From Newton's Dictionary of Birds. Nest oF THE HumMinc-BirpD (Phathornis eurynome) From Newton's Dictionary of Birds. NEsT oF OVEN-BIRD From Newton's Dictionary of Birds. Hoarzin (Ofpisthocomus cristatus) From Newton's Dictionary of Birds. Wines or Nestiinc Hoatzin AND ComMMoN FowL, UPPER SURFACE Wines oF NestLinc AND ApULT HoarTzin, AND NESTLING OF Com- MON FowL, Upper Surrace. (After Pycraft) DIssECTION OF BEAK-SHEATH OF CORMORANT SHOWING VESTIGES oF NariAL APERTURE. (After Pycraft) THROAT OF HOUSE-SPARROW SHOWING THE DIFFERENCE PRODUCED BY ABRASION BETWEEN THE “ WINTER” AND “ SUMMER” PLUMAGES RED GAME COCKEREL - - - - By permission of the Editors of The Ibis. Buack PorisH Cock - - By permission of the Editors of The Ibis. Tyres or Comss. (After H. S. Davenport) Tue Sun-BITTERN IN DIsPLAy - From Newton's Dictionary of Birds. WinG oF ARCHOPTERYX, AND HAND oF YOUNG OSTRICH TO SHOW THE STRUCTURE OF THE WRIST PAGE 44 57 68 75 81 106 141 152 153 167 178 182 187 238 240 241 265 284 338 339 340 352 374 LIST OF ILLUSTRATIONS ILLUSTRATION 37. WiNG oF a LONG-RARED OwL SHOWING THE PoINTED TypE oF “WinG AssocIATED WITH STRONG Powers OF FLIGHT From The T? tions of the Lit Society. 38. Winc oF a ‘“ Woop-OwL” sHowinGc THE RounpEp Tyre. (After .Pycraft) , By permission of the Editors of The Ibis. 39. SHOULDER-GIRDLE AND STERNUM OF AN EaGte. (After Pycraft) From The P? dings of the Zoological Society of London. 40. SHOULDER-GIRDLE AND STERNUM OF A Cormorant. (After Pycraft) From The Proceedings of the Zoological Society of London. 41, SHOULDER-GIRDLE AND STERNUM OF A BOATSWAIN-BIRD. (After Pycraft) - 3 By permission of the Zoological Society of London. 42. TYPES OF PeLvic GIRDLES. (After Pycraft) From The Proceedings of the Zoological Society of London. 43. Types oF Birps’ Feet. (After Pycraft) From The Book of Nature Study. 44. Types oF SyRINX - - 45. FoRMS OF THE BEAK IN THE GENUS GEOSPIZA From The Transactions of the Zoological Society of London, 46. Upper SuRFACE OF THE WING oF a LITTLE STINT TO sHOW THE OVERLAP OF THE COVERTS; AND UPPER SURFACE OF A PoRTION OF THE WING oF AN OwL TO sHow “ DrastaTaxic”’ CONDITION. (After Pycraft) From The Transactions of the Norfolk and Norwich Naturalists’ Society. 47. TYPES OF BEaks 48. EAR APERTURES OF THE Owzs. (After D. Meinertzhagen) From The Tr tions of the Lt Society. 49. SKULLS oF OWLS, SHOWING THE ASYMMETRY OF THE SKULL OF TENGMALM’s OWL, AND THE CURIOUS DIFFERENCES IN THE FORM OF THE SQUAMOSAL IN THE YouNG TAwNy OWL AND YOUNG Burrowine Ow. (After Pycraft) From The Tr tions of the Li Society. 50. Types oF Toncugs. (After Lucas) PAGE 376 377 379 381 382 387 395 403 405 407 413 416 LIST OF PLATES Tue BitrerRN aT HomE, A LESSON IN PROTECTIVE COLORATION Frontispiece FACING PAGE PowDER-DOWN PATCHES ON THE BREAST OF THE HERON, EXPOSED BY PULLING ASIDE THE BREAST FEATHERS By permission of the Editor of British Birds, Wines or EuryLt@mus (A) anp Corrus (B) DissEcTED To sHOW DELTOIDEUS MUSCLES By permission of the Zoological Society. BLUE-NECKED CASSOWARY AND THE SECRETARY BIRD Map SHOWING ZOOGEOGRAPHICAL AREAS, ILLUSTRATING THE DISTRIBU- TION oF BIRDS By permission of Dr. R. Bowdler Sharpe. Care PeNncuins (SPENIScUS DEMERSUS) From a Photograph by A. R. Momber, Esq. ELEPHANTS AND EGRETS = - By permission of Messrs. Rowland Ward, Ltd. From Neumann's Elephant Hunting in Equatorial Africa BEE-EATERS AND BUSTARD By permission of Messrs, Rowland Ward, Ltd. From Neumann's Elephant Hunting in Equatorial Africa. Tue Peacock 1n DIsPLay From a Photograph by Reid, Wishaw. A STaGE IN THE DISPLAY OF THE LESSER BIRD OF PARADISE By permission of the Editors of the Ibis. THE NupTiaL DANCE OF THE PRAIRIE HEN - - By permission of the American Museum of Natural History. Buiack Cock ON THEIR PLAYING-GROUND From Game-Birds and Shooting Sketches. By permission of the Author. NEsT oF REMEZIA - : - From a Specimen in the British Museum. NESTS oF THE EDIBLE SWIFT - From Specimens in the British Museum, xix Io 26 49 63 117 124 125 145 147 149 157 184 186 XX A HISTORY OF BIRDS NEST oF THE HERRING GULL From a Photograph by Mr. A. R, Bishop. A Primitive Nest (NEST oF THE RINGED PLovER) From a Photograph by Major Trevelyan. Emperor PENGUIN BRooDING ITS YOUNG From a Drawing by Dr. A. E. Wilson. LapwinGc SeTTLinc Down on 1Ts Ecos - From a Photograph by the Rev. H. N. Bonar. WuittE-THROAT FEEDING ITs YOUNG From a Photograph by Miss E, L. Turner. Meapow Pieir REMOVING ExcRETA FROM ITS NEST - A BREEDING CoLONy OF GANNETS - From a Photograph by Messrs. Valentine & Co. FACING PAGE Igt IgI 216 225 225 229 248 A NestTINnG CoLony OF THE WHITE OR MoLLy-Mavk (DIOMEDEA IMMUTABILIS) ALBATROSS - 249 From The Avifauna of Laysan. By permission of the Hon. Walter Rothschild. NESTLINGS OF PIGEON AND FLEDGLING Barn Owt (from Photographs by Reid, Wishaw), anD or NESTLING CaPE BaRREN OR CEREOPSIS GoosE : From Specimen in the British Museum of Natural History. A NESTLING CASSOWARY AND A NESTLING Emu From Specimens in the British Museum. MESOPTYLE FEATHERS OF TAWNY AND BARN OWLS By permission of the Editors of British Birds. SHOULDER-GIRDLE AND STERNUM OF THE HOATZIN From Specimens in the British Museum of Natural History. A Factor IN THE STRUGGLE FOR EXISTENCE (PEREGRINE) From a drawing by G. E, Lodge. (Falcon Attacking a Rook.) ARTIFICIAL SELECTION AS ILLUSTRATED BY PIGEONS 254 258 270 313 318 - 336 ARTIFICIAL SELECTION AS ILLUSTRATED BY VARIETIES OF THE COMMON Fow. (Rep CocHIN AND Brown Lecuorn) - From Photographs by Reid, Wishaw. Tue AMHERST PHEASANT IN DispLay From a Painting by G. E. Lodge. THE GRASSHOPPER WARBLER IN DispLay From The British Warblers. By permission of the Author. Tue Kacu 1n Dispray From a Photograph in the British Museum. 340 344 347 353 LIST OF ILLUSTRATIONS xxi FACING PAGE Tue EvoLUTION OF THE PADDLE OF THE PENGUIN 385 After Pycraft. SECTION OF THE HEAD OF THE HELMET HORNBILL, SHOWING THE Dense Layer oF Horn AND Bony TISSUE FORMING THE CASQUE 422 From a Specimen in the British Museum. THe Trunk SKELETONS OF CHIONIS, THE DIvING PETREL AND THE FORK-TAILED PETREL 451 From Specimens in the British Museum of Natural History. THE TruNK SKELETONS OF THE GUILLEMOT AND DIVER, SHOWING MopiFicaTions INDUCED BY DIVING-HABITS 451 From Specimens in the British Museum of Natural History. SHANK OF THE LEG OF THE RED-THROATED DIVER AND OF THE GREAT CRESTED GREBE - - 452 From Specimens in the British Museum of Natural History. INTRODUCTION IVING things form an inexhaustible field of in- L terest and delight to Man, who is the outcome of an age-long process which has culminated in the production of the human mind with its unique powers of thought. This process has left, as it were, on the way to man, all the varied crowd of lower animals and plants which still survive to tell him whence he has come, and to enable him to arrive at an understand- ing of the secrets of his own nature. No wonder that natural history, the knowledge of animals, plants and stones, has from the earliest times been a serious pursuit, and perhaps we ought not to be astonished when the intimate and deep-seated relations of man with other living things is borne in mind, that the most fantastic beliefs about natural history have been current, and that it took a longer time to enable men to investigate animals without prejudice and the domination of childish and preposterous. imaginings than it did to start a reasonable examination of less elusive and exciting things, such as plants and the non-living objects of which our senses give us cognisance. The study of animals can never lose its special hold on the human mind, due to the animal’s direct appeal to man, its saying, as it were, ‘“‘ You are one of us, you know. We are close to you—very close to you: if you can understand my nature, my mechanism and XxXili xxiv A HISTORY OF BIRDS origin—snail, robin, squirrel, whichever I am—you will be near to understanding man’s nature, mechanism and origin—near to understanding—yourself/” And so there are endless books on the natural history of animals, their kinds, their structure, their mode of action, their habits, growth, reproduction, food, their relations to one another and to other living things. Any one book treating of animals in every possible way would be too large; moreover, our knowledge about animals is always growing and receiving quite new accessions, so that no one should complain of the number of such books, and every new one, if it is really a new one and written by a real ‘“‘ Knower” of animals, should be welcome. Mr. Pycraft’s series of four volumes called Animal Life is a really new book on animals, and its novelty and excellence is exhibited in the volume on Birds written by Mr. Pycraft himself. In the first place, let me say what may not be known to every reader, though well-known to all scientific zoologists—that Mr. Pycraft is a most competent authority on birds; he has devoted his life to them, and has studied with specially favourable opportunities their skeletons and their plumage and the stages in their growth, so as to add greatly to our knowledge. From the museum at Leicester he came to assist me in the University Museum at Oxford in 1892, and later was appointed to the staff of the Zoological Department of the British Museum, where I again had the oppor- tunity of seeing and appreciating his work. In the second place, the plan of the book on Birds (which will be followed in the other volumes on Mam- mals, on Reptiles, Amphibiaand Fishes and on Inverte- brates) is original. We do not start with a scheme of classification and then take up the groups one by one INTRODUCTION XXV and examine the different kinds included in each, but boldly, after an introduction on the general structure of birds, the phylogeny of birds is discussed, that is to say, their genetic relationship to the reptiles and the evidences thereof, and a “family tree” showing the main lines of the descent of birds and the relationships to one another of the numerous groups of birds is given. Then we have a chapter on Geographical Distribution followed by others on the Seasonal Life of Birds, on Migration, on Peculiar Interrelations (such as those of the Cuckoos), on the Relations of the Sexes (including courting, display, fighting, song and music). Then we come to chapters on Nidification, Eggs, Care of Off- spring, Nestling Birds and what they teach (a subject greatly studied by Mr. Pycraft), the Life-history of Birds, Variation, Natural Selection and Artificial Selec- tion in the case of Birds, Sexual Selection, Adaptations and Convergence of form in distinct groups (the latter better called ‘“homoplasy ”). These and similar topics are discussed by Mr. Pycraft at greater length than would be possible in a systematic treatise on birds of the usual scope. The survey of bird-life thus given is a very complete one, and many interesting features of it, liable to be too briefly treated in a book arranged on classi- ficatory lines, are here duly dealt with. The illustrations are of great value, for they are not old but new, and they are admirably executed. I may cite here a few of the more interesting views which Mr. Pycraft advances in the present volume. In regard to the subject of migration (see page 89), he has promulgated one or two new ideas. He holds that the trend of migration is, throughout the world, due north and south, as far as physical conditions render this possible. It appears as a consequence of this that xxvi A HISTORY OF BIRDS our Swallows (for example) do xof, as is supposed, on reaching Africa disperse some to West Africa as far south as the Gold Coast whilst others continue down the East Coast to the Cape. But that, on the contrary, our British birds, and those of France and Spain, go to West Africa only. Those that are found along the East Coast of that continent are birds which have been bred in Eastern Europe. It is significant in this con- nection that the Swallows of Northern Asia go south to India and Burma, those of North America to South Brazil. Our British migrants are held by Mr. Pycraft to be so many “local” races of their species. Hence, he be- lieves, has come about the extinction of many of our ‘British ” birds—Avocets, Spoonbills, Ospreys, Ruffs, Bitterns, etc. As the parent stock is killed down, here and abroad, no descendants are left to retyrn to the old haunts, for the Avocets, Spoonbills, Storks, etc., of the Continent are similarly so many “local” races, having no “inherent knowledge” (if one may use the term) of land outside their particular routes. That migration was and is possible only to such species as can obtain a livelihood outside their place of origin is very justly asserted by our author. Hornbills, Toucans, Birds of Paradise cannot migrate: outside their home- range they would starve. Hence when the areas they inhabit become over-stocked the surplus must perish. Those birds more fortunate, because less specialised in the matter of food, which find salvation in migration, were driven back periodically to the land of their origin by climatic conditions. Having, however, extended their range and hence their breeding area, they returned in greater numbers than those which departed. Hence the land of origin was less able than before to support INTRODUCTION XXVii the returning host, and hence migration became a fixed and necessary habit. The range and increased breed- ing area increased in waves mechanically. The exodus would naturally be to the new-found land of plenty. The birds of last year would return to their old breed- ing station: their young also. But these would be driven by the old birds further a-field and establish new colonies ; for it is well known that birds will drive away their young and jealously defend their appropriated breeding territory against all-comers. Mr. Pycraft makes a laudable attempt to combat the contention, which has been and still is urged, to the effect that small variations in animal colour and form can have no value as features for selection in the struggle for existence. He urges that even if this be true in many cases, yet such small variations will not be sup- pressed by selection adverse to them. They are free to take their course unless and until of such magnitude as to be either checked by natural selection or favoured by it. In illustration of his contention, he cites various facts in regard to the evolution of the skull and of par- ticular skull bones and other skeletal structures in birds. This view appears to me to be well worthy of con- sideration. In regard to the theory of sexual selection the original views of Darwin and those of Wallace are cited as well as the more serious criticisms of these views advanced by other observers. In the light of some recent work, Mr. Pycraft is led to hold that some slight re-setting of Darwin's views in their application to birds is necessary. Without endorsing his view of the absence of selective action in certain cases, I may draw the reader’s attention to his argument. Since it is now known that birds of the most sober hues affect displays of a character in- xxviii A HISTORY OF BIRDS distinguishable from those of birds in which such displays are made apparently for the sole purpose of exhibiting to the best advantage some specially modified or beauti- fully coloured patterns, it seems (our author contends) probable that such resplendent dress is to be regarded rather as a by-product of sexual selection—as a varia- tion allowed to assume a more or less extravagant form because unchecked by natural selection. That display is the result of sexual selection is not doubted by Mr. Pycraft, for even the most incon- spicuously coloured birds indulge in antics, more or less grotesque, when dominated by sexual desire. Any varia- tion in the direction of more resplendent plumage would thus of course be free to fulfil its potentiality unless, and until, checked by natural selection. The view advanced by Mr. Pycraft is in short this—that the ‘display ” is older than the resplendent plumage, and is not the consequence of its presence. Sexual selection is still regarded as operative, for there must have been degrees of splendour among the ancestors of the now resplendent species, and the brighter coloured would excite the females more effectively. Mr. Pycraft considers at some length the coloration of desert-dwelling forms of birds. | He emphasises the contention that natural selection is not the agent which has in the first instance determined that coloration. | confess that I should not have supposed that any one would contend that it has done so, any more than that the view could be supported that “natural selection ” has primarily started any of the variations of colour or form upon which it operates. Mr. Pycraft holds that there can be no question but that the peculiar physical conditions of a desert environment exercise a direct influence on pigmentation. It is very possible that INTRODUCTION xxix such a direct effect of one kind or another is in many ~ instances produced. But in all such matters one would like to see experimental proof and to have full chemical explanation of the details of the coloration and the way in which external conditions directly modify it. Mr. Pycraft thinks that a humid atmosphere undoubtedly causes an intensification of pigment inclining to melan- ism. That would be very important if it were experi- mentally demonstrated, but that seems not to be the case, nor is the chemical change by which such intensi- fication of pigment, or the production of independent black pigment, could be arrived at by the action of a humid atmosphere as yet suggested. Our author says that of course natural selection “may have” acted by securing elimination of all those individuals which were not physiologically affected by desert conditions, vzz., intense light and heat, or (I should be inclined to add) were not, owing to other causes, variations in the direction of sand-colour. In regard to the life-history of birds, Mr. Pycraft has drawn attention to a host of facts which have hitherto been ignored by leading Darwinians, though of first-rate importance from their point of view. Such are his own observations as to the coloration of nestlings and of immature birds showing the significance of striped nestlings and of the brilliantly coloured mouths of certain species. He gives very cogent reasons for regarding the ancestral bird as arboreal, and as gradually acquiring flight by “parachuting”. The view that the earliest birds were aquatic and that the wing was at one time a paddle is, however, still capable of defence. To arrive at anything like a preference between the two theories requires a very extensive survey of anatomical and palzontological facts, as well as a consideration of the XXX A HISTORY OF BIRDS various mechanisms of flight in animals and their rela- tion to other locomotor organs. It is distinctly a feature of Mr. Pycraft’s book that he has given a larger number of illustrative examples of adaptation to environment, of homoplasy and parallelism, than is to be found in any other book on birds. E. RAY LANKESTER LIST OF AUTHORS QUOTED Avcock, Dr., 116. LANKESTER, Sir Ray, 342, 453. Alexander, Capt. Boyd, 82. Latter, O., 130. Allen, J. A., 83, 85, 292. Lucas, F. A., 122, 431. Andrews, Dr. C., 112, 150, 290. Mittais, J. G., 157, 345. BarrineTon, R. M., 294. Mitchell, Dr. Chalmers, 410, 437. Bates, 423. Moseley, Prof., 449. Beebe, C. W., 81, 315. Murie, Dr., 149. Beddard, F. E., 47. Bonhote, J. L., 272. Ne son, E. W., 162. Bumpus, Dr., 293. Neumann, A., 125. Butler, A. G., 234. Newbigin, 199, 310. Newton, Prof., go, 103, 119, 136, 180, CuHapman, A., 326. 285, 301. Chapman, F. M., 95. Nicoll, M. J., 117. Clarke, Eagle, 96. Nutting, H., 162. Cunningham, J. G., 315. Ossorn, Dr. H. F., 453. Darwiy, C., 321, 335,337) 411. Davidson, W. R., 146. PaLMEN, Prof., 94. De Varigny, 346. Poulton, Prof. W. B., 323, 327: Dwight, Dr. J., 281. Pycraft, W. P., 410. ExuiotTt, Dr. D. G., 172. Ripuey, H.N., rio. Romanes, G., 355, 356; 357: FIELDEN, Col., 298. Rothschild, Hon. W., 162, 308, 309. Finn, F., 328. Forbes, H. O., 111. SaunpERS, H., 120, 297, 298, 301. Flirbringer, Prof. Max, 47. Sclater, Dr. P. L., 76. Seth-Smith, D., 171. Sharpe, R. B., 92, 101, 102, 363, 443. Gapow, Dr. H., 47, 251, 310, 312. Sorby, Dr., 198: Gatke, 96, 97. Giglioli, Prof., 303. Godman, Dr. F. D., 225. TENNANT, S., 95: Grant, Ogilvie, 147, 305. Giinther, Dr. A. vat 232. Ussuer, R., 87. Vernon, H. M., 318. Harvig-Brown, J. A., 298. Von Rosenberg, Dr., 218. Headley, F. W., 281. Howard, H. E., 290, 347, 348, 351. WALDO, Meade, 225, 285. Hudson, W. H., 114, 163, 323. Wallace, A. R., 100, 147, 193, 208, 329, 330. Jorpan, 251. Warren, R., 345. Whitaker, J. S., 81, 86, go. KELLOGG, 251. Wilson, Dr. A. E., 216, 217, 287, 320, Kerner, A., 107, III. 432. XXxi A HISTORY OF BIRDS CHAPTER I INTRODUCTORY General characters of structure—feathers, glands, the skeleton, the respira- tory system, the lungs and air-sacs, the digestive system, the circulatory system, the muscular system, the nervous system, the senses. BIRDS, IN BROAD OUTLINE HOUGH the bird and the mammal are alike descend- ants of the scaly reptile, they present no points in common, save that both are “warm-blooded”. Birds are essentially creatures of the air, mammals of the earth: yet, be it noted, some birds have lost the power of flight, while some mammals, in varying degrees, have acquired this; albeit only one group, the bats, have really mastered the art. Birds, in short, from the first were destined by Nature to possess the air, while mammals were, on the other hand, de- veloped along lines which made the earth their natural abiding place. And this fundamental difference explains the fact that, structurally, the birds present a remarkable degree of uniform- ity, while the mammals, on the other hand, display a wonderful diversity of form and structure. The mechanical requirements of flight rendered this structural uniformity inevitable; while, on the other hand, the terrestrial life of the mammals left open a wide range of variability in the matter of bodily shape, and this in time manifested itself, as the need arose, as, in the struggle for existence, some took to climbing trees, some to burrowing in the earth, some to the rivers, and some to the open sea, some to the burning deserts, and some to the wild fast- nesses of the sombre mountains, I 2 A HISTORY OF BIRDS By the accident of birth, so to speak, the career of the bird was determined by the shape of its fore-limbs. Though in course of time circumstances deprived these of all importance in certain species, so that they eventually became reduced to mere vestiges, as in many living birds, or even suppressed en- tirely as in the extinct Moas, the mammals, on the other hand, have in no case suffered a similar loss; but the hind-limbs, by way of contrast, have in not a few cases similarly vanished. In birds the fore-limb has in all cases served as an organ of flight; even where this member has been reduced to the merest vestige, it is clear that the modelling thereof is that of a wing. In the mammal, on the other hand, the fore-limb presents the most varied forms. Similarly, in the case of the hind-limb, that of the bird presents a wonderful uniformity of structure, being always used for the carriage of the body when on terra- firma, but this is far from true of the mammal. Notwithstanding the unquestionable uniformity of structure which birds present, this is apparent only when the fundamental structure is considered in relation to that of other groups. To the ornithologist birds display a marvellous range of variation, and in so far as coloration is concerned this is undoubtedly true. From the esthetic point of view birds hold an unique position, and fill a place in the world that adds more than is generally realised to its charm and habitability. They seem to display a joyousness in existence, an intensity of emotion, that is infectious; though, it is needless to remark, this mani- festation is not a universal characteristic of the group. The factor which, more than any other, has secured for birds the high place which they hold in the affections of men, is unquestionably that of flight. Thereby they ever keep themselves, as it were, before the public, and give life and beauty to the world around them. And this is true more especially of such species as seek their daily bread in the open, on the wing, or indulge in zrial evolutions apparently out of the sheer ex- uberance of spirit. There must be few who have not gazed with admiration at the hovering feats of the Kestrel, and still fewer who have not felt moved at the wild, Screaming flights of a flock of Swifts at dusk, while the marvellous spiral evolutions of the Skylark, accompanied by outpourings of song, have in- spired some of the finest poets who have ever lived. INTRODUCTORY 3 The vivid hues which so many species display must be reckoned as only slightly less important in this respect than flight. This fatal gift of beauty has from earliest times sub- jected the wearers to a rigorous persecution, not only at the hands of savage races, but of peoples boasting themselves civilised, among whom women have always been the worst and most heartless offenders. On account of the ceaseless persecution to which these defenceless creatures have been subjected to meet the demands of fashion, savage and “ civil- ised,” many species have become wiped out of existence, and of many more the doom is sealed ; the more beautiful of the Birds of Paradise and of the Humming-birds, for example, will, in another decade, have ceased to exist! There is more in this colouring of the plumage than meets the eye of the unobservant ; for whether we contemplate broad bands of vivid colours, sharply defined; or intricate patterns, fine as the most delicate lace work, we are confronted witha mystery which is so far insoluble—what determines the seg- regation and deposition of these pigments? The problem presents its greatest difficulties in such feathers as display, individually, intricate patterns, whether of sober shades or hues such as vie with, or even surpass, the rainbow in splendour. Take, for example, a feather displaying a series of fine concentric lines, divided by wider bands of white, or black, or red, as the case may be. These lines are not continuous, not organically complete, but formed by the exact relation, one to another, of a series of minute spots of pigment, each lodged in a separate filament, so that the several spots in each separate filament, when ranged side by side, form the several series of lines, straight or vermiculated, as the case may be. All that we can say is, that the spots in question are deposited simultaneously in each rod as the feather grows. But what controls the alterna- tions of the deposition of the pigment necessary to bring about so simplea pattern as that to which we refer? And what determines the changes of pattern in the different areas of the body? But birds have yet other attractions for us men. Graceful in their movements, and exquisite in their apparel, they are furthermore fascinating in their lives, for they display in their periods of courtship a singular vivacity, and in the care of their offspring a marvellous tenderness and solicitude. 4 A HISTORY OF BIRDS There is, in short, no single phase of their life-history which is not throbbing with interest. Nests, eggs, and young, ado- lescent and adult, at rest or in action, there is no phase which is not overflowing with matter for reflection, no single incident which is dull; and this is perhaps more than can be said for any other group of animals. Birds, like mammals, display a wonderful plasticity to environment, There is no spot on the earth’s surface which has not been made to provide a habitation for them, from the icy and storm-swept regions of the poles, to the equator: while by relatively slight structural changes, they have contrived to avail themselves of food supplies of the most varied description. The general homogeneity which birds present, when com- pared with the mammals, or the reptiles, is generally attri- buted to the fact that they are less ancient than either: though they may yet claim a respectable antiquity, since the earliest known bird dates from the Jurassic epoch. It is supposed by some that enormous periods of time are necessary to bring about the extinction of connecting-links, and the con- sequent formation of sharply defined groups, such as are to be met with among the mammalia. But it may well be that this work of extermination among the birds has been largely evaded, and homogeneity preserved, by their ability to escape from unfavourable conditions. With the mammals the avoidance of periods of stress, of whatever kind, has always been restricted. Migration has been limited by unsurmountable barriers ; at one time mountain ranges, at another of vast stretches of water. To this evasion of Fate most modern taxonomers owe their difficulties in their attempts to classify birds, that is to say, those who desire merely to establish so many well-defined groups which can be readily summarised in the form of a “Key”. Those, on the other hand, who have spent laborious days in the endeavour to trace the descent of the more or less well-marked groups of living and extinct birds, though hardly more successful than their less ambitious neighbours, must look to yet other and more subtle factors. First, and foremost, must be placed the fundamental modification due to the ex- igencies of flight, which all birds, without exception, share in common. Thereby the range of possible variation has been kept within very narrow limits, and secondly, there must be INTRODUCTORY 5. reckoned the phenomena of convergence and parallel develop- ment. In taking a bird’s-eye group of the Class Aves one may dis- tinguish a number of apparently well-defined groups, such as the Ostrich tribe, Diving-birds, Penguins, Petrels, Steganopodous- birds, e.g., Gannets and Cormorants, the Goose tribe, Storks, Birds of Prey, “ Game-birds,” Cranes, and the Limicole or “Shore-birds”: and against these may be set the Parrots, Cuckoos, a host of forms commonly known as “ Picarians,” including, for example, the gorgeously coloured Rollers, King- fishers and Bee-eaters, and the bizarre Hornbills, the Owls and Night-jars, the Swifts, and the jewel-like Humming-birds, the gaudy Toucans, and the Woodpeckers. Finally, we have the most puzzling of all, the “ Passerines,” of which the crows may be taken as typical examples, So far, any classification of this medley of forms, which shall express the lines of descent, has proved beyond attain- ment, though much towards this end has been done by the labours of such men as Huxley, Garrod, Forbes, Fiirbringer, Gadow, Beddard and Chalmers Mitchell. GENERAL CHARACTERS OF STRUCTURE The Feathers For the purposes of these pages a very general survey of the structural characters of birds will suffice. And this survey cannot well begin better than with a general account of the feathers, since these, as we have already remarked, are unique structures. In their nature they answer to the scales of Reptiles rather than to the hairs of Mammals. In addition to those which form the outer covering of the body, and hence are known as the “contour” feathers, there are several other forms of feathers. The most familiar of these are the “down feathers ” which play so important a part in commerce. These form, in many birds, such as the Goose tribe, Gulls, and aquatic birds generally, a dense underclothing answering to the under-fur of mammals, such as, for instance, the “ fur-seal,’ and after these come the “ filo-plumes” and “powder-down” feathers to be described presently. .6 A HISTORY OF BIRDS A typical contour feather consists of a central axis, and a vane or vexillum. The axis is divisible into two portions: (a) ILL. 1.—DIAGRAMS ILLUSTRATING THE STRUCTURE OF A FEATHER I. A contour feather showing the calamus or quill (C), the rhachis or shaft (R), and the web or vane (V) attached thereto. On the right-hand side of the vane is a portion showing the appearance presented under a low magnifying power, B = barb and Bs = barbule. II. A section cut across two barbs parallel with the barbules of the anterior series to show the method of interlocking. III. Shows a barbule of the anterior series (A) with its hooklets, and two barbules of the posterior series (B). a hollow “ calamus,” and (8) a solid rhachis or shaft. The calamus forms the lower portion of the axis and is inserted by its base \ Hy INTRODUCTORY 4 into the skin. Tubular in shape and semi-transparent, it en- closes a series of hollow, oblong cells fitting one into the other. During the growth of the feathers these cells contained the pulp, or nutrient matter out of which the feather is built up. The shrivelled end of.the last of these cells projects from a small aperture—the upper umbilicus—at the point where the quill passes into the “rhachis” or shaft. This is formed by a process of continuous growth of the dorsal surface of the calamus, and the resultant lateral edges of this projecting out- growth ultimately curl inwards, meeting in the middle line of the under surface of the feather and leaving a fine groove to mark the junction. The enclosed cavity is simultaneously filled with a closely packed mass of “ pith ”-cells, recalling “elder-pith,” giving stability and elasticity to this region of the axis. Along each’side of this rhachis, which has a quadrangular section, there runs, from the region of the upper umbilicus to the tip of the feather, a closely planted series of flattened lamine, terminating in a point, and these in turn support a double row of smaller lamine. The former are known as the rami or “ barbs,” the latter as the “radii” or barbules. The whole form the remarkably elastic fringe which runs along each side of the shaft, and which together form the “vane” or “vexillum” of the feather. This fringe must be more closely examined. On a super- ficial inspection it presents a homogeneous surface, but grooved withal by a number of fine, parallel lines. If an attempt be made to stretch this web in the direction of the long axis of the feather, it will be found that though at first resisting, it will eventually split, when, by drawing the fringe through the fingers the original unity will be restored. Ifa lens be now brought to bear on this surface, it will be found that the grooved or ribbed appearance of this vane is caused by the interspaces between the rami just described; interspaces which are more or less perfectly filled by the series of barbules which intercross. Under a high magnification of the microscope these barbules will be found to consist of two very distinct kinds, ranged one on either side of the barb. Those on the side of the barb pointing to the tip of the feather have the appearance—when examined separately—of flattened plates, cut up, from the middle out- wards, into a number of long, hooked filaments, while those 8 A HISTORY OF BIRDS of the opposite side of the barb take the shape of long scrolls, whereof the upper edge is the more deeply curled. When zx sziu the two series are so arranged that the hooklets are thrust down between the scrolls so that their curled edges are caught thereby. A reference to the accompanying diagrams will make these points clear. The number of these rami or barbs I II Ml ( i] i NY) ILL. 2.—ConTour FEATHERS SHOWING THE HYPoRHACHIS OR AFTER-SHAFT (A) I. Of a Pheasant, II, Of an Emu, depends mainly on the length of the feather. Along the inner web of a Crane’s quill feather 38 cm. long, Dr. Hans Gadow counted about 650 rami: he further estimated that every ramus of this feather bore about 600 pairs of radii (barbules), mak- ing nearly 800,000 radii for the inner web alone, and more than a million for the whole feather, The contour feathers of most birds bear what is known INTRODUCTORY 9 as an aftershaft (hyporhachis). This is a duplicature of the main shaft, but much smaller and more delicate, and springs from the upper umbilicus of the main shaft. In the Game- birds it is especially well developed, while in others it is reduced to a mere vestige, or is wanting be eae In the great feathers which form the “quill” or “ flight” feathers (remiges) of the wing, and in the tail ree (rectrices) the after shaft is invariably wanting. Among the Ostrich tribe it is present only in the Emus and Cassowaries, and here it is of great size, as large indeed as the main shaft. The contour feathers of the Ostrich tribe—save only in the Tinamous—it may be remarked, are peculiar in that their vanes are not held together to form a well-knit “ web,” the radii being degenerate, and failing to hold the vanes together; hence these vanes are said to be “discontinuous”. Down feathers differ from contour feathers in that the barbs, or cami, of the feathers are of great length and slenderness, and often all arise from a common base—the top of the calamus, instead of being ranged along each side of a long rhachis. The radii (barbules) of such feathers are represented by mere filaments, or sometimes by nodular swellings, which again may assume a pyramidal form. As touching “ filo-plumes” little is known!as to their mean- ing or purpose. There are the long hair-like threads which remain sparsely distributed over the body of a fowl when plucked. They grow in clusters of five or six, or more, about the bases of the contour feathers, and when examined micro- scopically are found to consist of a simple, solid axis, terminating in a few weak barbs and barbules. An examination of the late stages of growth, just before development is complete, however, shows that these are degenerate feathers, inasmuch as there will then be found a considerable number of barbs, arranged much after the fashion of the barbs of a down feather. Among these one will be found stronger than the rest, and this eventually is left, the rest disappearing. In some birds these filo-plumes play a conspicuous part in the coloration of the surface of the body, since in such cases they attain a great length, and develop relatively large vanes. These project beyond the level of the contour feathers and may form large white patches, as in the thigh patches of the Cormorants, or INTRODUCTORY II powder-down is luminous, and that the birds take advantage of this luminosity by raising the contour feathers so as to shed this light on the water wherein they may be fishing, and thereby lure their prey to within striking distance. As these birds do not fish by night, and the glow would be invisible by day, this theory may be regarded as exploded. The feathers of nestling birds do not differ structurally from those of adults in any essential particular, but they are remark- able for the very great range of degeneration which they dis- play. On the varying number of successive plumages through which nestlings pass before attaining to a dress which is structur- ally equivalent to that of the adult much will be said later. The nestling down feathers, it should be remarked, are known as “neossoptyles” to distinguish them from the “ tele- optyles,” or adult feathers—terms coined by Dr. Hans Gadow to serve a most useful purpose. The neossoptyles are made up (a) of feathers which im- mediately precede the contour feathers of the adult ; and (8) of feathers which are later succeeded by down feathers. The former are to be known as “ pre-penne,” the latter as “ pre- plumule ”. The pre-pennz may further be divided into “ protoptyles ” and “mesoptyles”; and while the nestlings of some species develop both, in others the protoptyles have become suppressed, while the mesoptyles are degenerate, and may be represented by little more than a few straggling, hair-like filaments, as in young Pigeons, or the nestling may remain absolutely naked until the appearance of the first “teleoptyles”. Only in some species of Tinamous are the mesoptyles really well developed, and here they very closely approach teleoptyles in structure, but are peculiar in that the after shaft is almost as large as the main shaft, a point wherein they agree with the teleoptyles of the Emu and Cassowary. This is a very remarkable and puzzling fact, because in the adult Tinamou the after-shaft is either feebly developed or wanting, and in the nestlings of the Emu and Cassowary, and the Ostrich tribe.in general, the after-shaft is degenerate, or absent! In the nestlings of certain Owls, ¢.g., Tawny and Eagle Owls, the mesoptyle plumage is worn until the first autumn, at least in so far as the trunk feathers are concerned, for the quill and tail 12 A HISTORY OF BIRDS feathers are of the true teleoptyle type before the birds leave the nest. These mesoptyles are, in such species, preceded by a peculiarly downy plumage made up of the protoptyle feathers. In the young Barn Owl the protoptyles are never developed, while the mesoptyles have so far degenerated as to be indis- tinguishable from protoptyles. That they are really mes- optyles is shown by the fact that, like all mesoptyles, they are thrust out upon the tips of the teleoptyles as soon as these develop (p. 271). In some birds, as ‘in nestling Game-birds and Owls, pre- penne only are developed. In others, as in nestling Hawks, the pre-plumule are larger, and play a more important part than the pre-penne. And from this there is but a step to the suppression of the pre-pennz altogether, as in the young of the Cormorant, wherein the nestling is clad only in pre-plumule. I II ILL, 4.—PTERYLosIs oF Acanthidositta chloris SHOWING THE FEATHER TRACTS Pi. cap. = Pteryla capitis. Pt.h, = Pteryla humeralis. Pt. sp. = Pteryla spinalis. Pt. f. = Pteryla femoralis. Pt. coll. v. = Pteryla colli ventralis. -.-..-. Pt. v. = Pteryla ventralis. (By permission of the Editors of The Ibis.) The feathers of birds are not evenly distributed over the body, as are the hairs of, say, the horse, but are gathered to- gether to form more or less sharply defined tracts (pterylz), leaving large bare spaces or “‘apteria,” though in many birds such apteria are covered with down feathers. The nature of these tracts may be seen in Ill. 4. Since they assume char- INTRODUCTORY 13 acteristic forms in different groups of birds they are of value for taxonomic purposes. The feathers on the wings of birds have a quite peculiar AMT. = membrane “QUILL” oR paragial Anterior . “\ FLIGHT-FEATHERS ” pata al pe bis bronc fosterior élastiaum. Vinculur ILL. §.—W1nG oF A BIRD, SLIGHTLY DIAGRAMMATIC, TO SHOW THE ARRANGEMENT OF THE arrangement, and this is true more especially of the great “flight” feathers or quills. These are arranged along the upper surface of the skeleton of the fore-arm and hand, being 14 A HISTORY OF BIRDS fairly well spaced on the former, crowded together at their bases on the latter (Ill. 5). The quills of the fore-arm, or “secondaries,” vary in number according to its length, never falling below six or exceeding thirty-seven, But the quills of the hand—the “ primaries” —never exceed twelve in number among Neognathine birds, and never fall below ten, though the tenth may be reduced to a mere vestige, known as a “ remicle”. The bases of these “quills,” and the surface of the arm generally, are covered by feathers arranged in definite order. These are known as the coverts, whereof four distinct groups are distinguished. The first of these are the major coverts. These are always large and strong feathers, and are closely attached to the bases of the quill feathers; the next row are known as the median coverts ; beyond these run from one to five ——rows of minor coverts, while beyond these come the marginal coverts, The same rows are represented on the under surface of the wing. Since these coverts present characteristic features in each of the great groups of birds, they are useful for taxonomic pur- poses; and this is more especially true of the manner in which those of the upper surface overlap one another. Thus, the major coverts always lie with their free edges turned towards the tip of the outstretched wing, and so also, very commonly, do the median series. The overlap is then said to be “ distal”. But the outermost median and minor coverts frequently have’ an opposite, or proximal overlap, that is to say, the free edges of the feathers face towards the body. The marginal coverts always overlap distally, But the details of this matter should be sought for in the special treatises on this subject rather than in these pages. While it seems impossible to discover any significance in the matter of this overlap in the smaller coverts, this is by no means the case with the great flight feathers and their coverts. With a distal overlap, as the broad surface of the wing is raised during the up-stroke in flight, the resistance of the air is reduced to a minimum, since it forces down the inner webs of these feathers and so escapes; but during the down-stroke, this re- sistance forces these inner webs upwards, driving one against another, and so forming a continuous, unyielding surface, as perfect as that afforded by the membrane of the wing of the bat. INTRODUCTORY 15 Where the arm (humerus) is long, as for example in the Alba- tross, the gap between the innermost quills of the fore-arm and the body, which would be formed during flight, is filled up by a series of long feathers which are related to the humerus much - as are the secondaries to the fore-arm. But with this difference, in the arm this series is double, one running along the upper, and one along the under surface of the shaft. But for this bridging, flight would be impossible. Glands Birds have no sweat glands. Indeed the only skin gland they possess is that known as the Oil-gland or Uropygium, which is situated above the bases of the tail feathers, and secretes a fairly abundant quantity of clear oil. In some birds this gland ends in a pointed nipple, e.g, Owls; in others it bears a tuft of feathers, eg., Ducks. As to the use of this gland: it may be remarked that it is now universally believed to serve as a reservoir for the secretion of oil which is used by the bird for the purpose of dressing the feathers. It is supposed to be applied by the beak, the bird turning the head backwards, and gently squeezing the nipple of the gland. The oil thus expressed is then applied to the feathers, individually, by drawing them through the mandibles, and thereby it is believed aquatic birds make their plumage waterproof. So deeply rooted is this belief, that he who would nowa- days presume to question its truth would be branded as a heretic, or worse. The late Charles Waterton had the temerity to cast doubt upon this thypothesis, and was promptly scorned for his pains; nevertheless, there are grave doubts as to the function of this gland. And these can be briefly set forth by one or two striking cases. To be of any use asa lubricant this oil must be very skilfully applied: yet there are many birds wherein this gland is well developed which could not possibly take up and spread so much as one drop of this precious fluid. The Scissor-bill is perhaps the most striking instance of this, for in this bird the lower is not only longer than the upper jaw, but both jaws, from the gape of the mouth onwards, are compressed to form a single blade as flat as a paper-knife. The Pelican is tongueless, and 16 A HISTORY OF BIRDS has a long unwieldy beak: how could this seize upon and distribute oil over individual feathers drop by drop? Simil- arly, the Shoveller Duck and the Petrels of the Genus Prion have the edges of the jaws fringed by very long, delicate lamella: how, with such an armature, could drops of oil be expressed from the gland and spread over the feathers: or how could this be done by the serrated beaks of such birds as the “Saw-billed Ducks” and the Darters? The Anastomus, or Open-bill Stork, and the Whale-headed Stork again, would surely find such a feat impossible. And these, be it noted, are all aquatic birds. On the other hand, the Bustards, many Pigeons and Parrots, and the Ostriches have no gland: yet they keep their feathers in as good condition as those birds which possess this organ. So copiously is this secretion said to be formed in the gland of the Concave-casqued Hornbill (Dzchoceros bicornis) that the feathers of the zeck ! are said to be stained yellow thereby ! Nevertheless, ninety-nine out of every hundred Ornitholo- gists are firmly convinced that they ave seen the oil squeezed from the gland, and witnessed its application. If, after all, it should be proved that this gland is zo¢ used as tradition assures us, what then is its purpose? So far no really satisfactory hypothesis presents itself. But the same is true of many other glands in other animals. It is possible, however, that it may have served, and may still serve, as a scent gland: though the odour may not be traceable by the olfactory nerves of the human subject, save in one or two cases. In the Hoopoes, for example, it gives forth a most offensive odour, while in the Musk Duck (Bizi#ra lobata) it sends forth a musky smell. The peculiar smell of Petrels is also appar- ently due to the secretions of the oil-gland. The Skeleton Birds show their reptilian ancestry in the skeleton more clearly than in any other part of the body, though even here the evidence has been largely masked by the modifications due to flight. The reptilian characters are more conspicuous in the pneumaticity of the bones, the structure of the skull, and the great number of the neck vertebra, and the structure of the hip- INTRODUCTORY 17 girdle and hind-limb. The shoulder-girdles are unquestionably reptilian, but this is not so patent as are the other characters. While in some birds, as in the Hornbills for instance, every bone in the skeleton contains spacious air-chambers, in others, the long bones at any rate—the bones of the wings and legs— are filled with marrow, and this is true even of such skilled performers on the wing as the Swallows. The peculiar char- acters of the shoulder-girdle, wing, and hind-limb will be dis- cussed later in these pages. The Respiratory System The respiratory system of birds presents some points which demand a brief notice. The Lungs In the first place the lungs are not suspended freely within the body cavity, but are closely affixed to the dorsal wall of the anterior portion of the thorax. In the second place they differ from the lungs of other vertebrates in that the respira- tory air is not simply drawn into the lungs and expelled again, but is rather drawn through them and passed into a series of large thin-walled chambers lying along each side of the body cavity, and known as the air-sacs. The air stored in these reservoirs serves not only for respiratory purposes, but also as regulators of the temperature, thereby compensating for the lack of sweat glands. The Pulmonary System of Air-sacs There are five pairs of these air-sacs. The first, or cervical pair, lie one on either side of the base of the neck and may give rise to a number of smaller cells which run up the neck, and even into the head; while small side branches may penetrate between the muscles of the neck, the vertebra, and the various cranial cavities: or they may form large inflatable sacs in the region of the throat, as in the Prairie-fow] and Frigate-bird. The second pair are known as the interclavicular sacs. In the Ducks they communicate one with another, while in the Storks they combine to form a single chamber. Lateral ex- tensions of these sacs form large axillary chambers ultimately penetrating the humerus and other of the wing bones, the a 18 large pectoral muscles, sternum. A HISTORY OF BIRDS and the body and keel of the The third and fourth pair are the “anterior and posterior intermediate sacs,” and are enclosed within the thoracic cavity, extending backwards more or less far into the abdominal cavity. ILL. 6.—D1ssEcTION SHOWING THE LUNGS AND AIR-SACS OF A BirD Pb. s. = Pre-bronchial sac. Ax. = Axillary sac bounded ex- ternally by the breast-muscles, seen here in section, S.s.= Partition dividing anterior inter- mediate sac (A.is.) from the sub-bronchial sac. P.i.s, = Pos- terior intermediate sac. O.s. = Oblique septum. H.s. = Hori- zontal septum. L. Ab. s. = Left abdominal sac. H.= Heart. G.=Gizzard. L.= Liver. In, = Intestine. (After Strasser.) The fifth pair form the “abdo- minal sacs”. Of large size, they are continued backwards to the end of the abdominal cavity. This elaborate system of air- chambers is further complicated in many birds by an extensive system of pneumatic cells extending between the muscles, and between the muscles and the skin,so that the bird is abso- lutely encased in a layer of air en- closed between the skin and the body. This emphysematous condi- tion is most perfectly developed in birds such as the Gannets, Screamers and Hornbills. The Naso-pharyngeal System of Air-sacs But there is yet another system of air-cells to be mentioned, which is known as the “tympanic” or “naso-pharyngeal system”. While in the majority of birds this is con- cerned merely with the supply of air to the bones of the skull, in the Adjutant Storks it gives rise to a_ very remarkable pouch which runs down the front of the neck as far as its middle. It can be inflated and deflated at pleasure, communicating as it does with the nasal chamber through an aperture in the floor of the orbit. The extraordinary air-pouches of the Great Bustard and the Emu may be mentioned here. That of the first-named forms \ INTRODUCTORY 19 a relatively enormous cavity, having extremely thin walls, lying immediately under the skin of the neck, and opening im- mediately under the tongue. Peculiar to the male, it must be regarded as a variation of the pouch described just now in the Adjutant. Only one other bird possesses a similar chamber, and this is the Musk Duck (Bzzzura lobata). But here the pouch is very small, and is lodged in a sac depending from the under- side of the lower jaw. The pouch of the Emu is formed by an evagination of the lining membrane of the windpipe, and makes its escape along the ventral aspect of the trachea, near its middle, where the tracheal rings for some distance are cut away, as it were, to permit of the exit of the pouch (p. 401). The pulmonary system of air-sacs make their first appear- ance in the embryo at about the eleventh day, as small vesicles from the surface of the lungs, formed by dilations of branches of the bronchial tubes. As they develop they push the peri- toneal membranes before them. Thus they acquire a two- layered wall—the outer serous layer formed by the peritoneum, the inner by the lining of the bronchial tubes from which they take origin. The Digestive System The digestive system of birds betrays its reptilian origin in many ways, but perhaps most markedly so in the arrange- ment of the annular and longitudinal muscular layers of the intestine, the longitudinal layer lying within the annular, while in. the mammals the reverse order obtains, the longitudinal layer, with the sevosa, forming the outer wall of the tube. In most birds the food is swallowed without any attempt at mastication, and passed backwards into the cesophagus. As «a rule this tube, in the region of the furcula, dilates to form a more or less globular or bi-lobed and thin-walled “crop”. Here, mixed with saliva and water, and warmed by the heat of the body, the food is softened and passed on to the stomach. This again is divisible into two distinct portions, an anterior, the “ Proventriculus,” with thick glandular walls, and a posterior, the “ Ventriculus” or “Gizzard,’ whereof the walls are thick and muscular, and furnished with a more or less rugous and indurated inner surface. In grain-eating birds the inner walls of the gizzard are furnished with a pair of apposed and greatly 20 A HISTORY OF BIRDS thickened pads, which, by means of spirally arranged muscular fibres, are made to rub together in opposite directions after the fashion of a pair of millstones. But this work of trituration is further aided by a mass of small stones swallowed, and retained by the gizzard, for this purpose. In the pigeons of the genus Prilopus there are four such pads, so that the gizzard is cross- shaped in section. In fish and flesh-eating, and in insectiv- orous and fruit-eating birds, the gizzard is feebly developed, the proventriculus and ventriculus passing insensibly the one into the other. The latter, in fish-eating birds, such as the Herons and Cormorants, may assume the form of a long oval sac extending along the whole length of the abdominal cavity ; while, by way of contrast, it should be mentioned that in other piscivorous forms, such as the Tropic-birds, Pelicans and Gannets, the gizzard or ventriculus is much reduced, the pro- ventriculus being in consequence of considerable size. In the Cassowaries and Emus and in Tanagers of the genus Euphones similar relations obtain between these two portions of the stomach; but in the Hoatzin, which has also a greatly reduced ventriculus, it is the crop which has become enlarged (p. 313). The inner lining of the stomach is naturally constantly wearing away and being reproduced, but in some birds this lining is suddenly cast off and ejected through the mouth as in the Starling, Missel Thrush, Little Owl, Cuckoo and Horn- bill. The Cuckoo and Trogons of the genus Harpactes are further peculiar in that the inner lining of the gizzard becomes beset with hairs, spirally arranged, derived from the caterpillars on which these birds feed. In birds of prey the fur and feathers of the victim swallowed, and in some grain-eating birds the husks, are formed into “pellets” and ejected through the mouth. The intestines, with the external digestive glands—the liver and pancreas—attached thereto demand little notice here. Suffice it to say that three portions thereof may be distinguished —the duodenum, a closed loop embracing the pancreas, and re- ceiving the hepatic and gall-ducts; the z/ewm or “small in- testines,” the longest portion of the gut, and the rectum, The last-named is shut off from the ileum by a special valve, the “jleo-cacal,” which, while it permits of the contents of the gut passing into the rectum, hinders any return thereof, INTRODUCTORY 21 The convolutions into which the small intestine is thrown, for the purpose of securing a greater length of gut, and con- sequent increased digestive surface, are of considerable value for taxonomic purposes, as Dr. Hans Gadow and Dr. Chalmers Mitchell have successively shown (p. 436). But the length of the gut, and the thickness of the walls thereof, are largely determined by the nature of the food to be assimilated. Thus, in purely frugivorous and insectivorous birds the gut is very short, while it reaches its maximum length in species which feed upon fish, carrion, grain and green vegetable matter. The lumen of the gut in short-gutted forms is generally very wide, while in piscivorous birds the walls of this canal are always very thick—a possible contrivance to lessen the danger of perforation by fish-bones. At the junction of the small and large intestines there may be found a pair of caca or blind diverticula, guarded by a valve which allows the semi-feecal matter to pass into these pouches, but prevents any backward movement into the small intestine (ileum). In some birds, such as the African Ostrich, Rhea (Ill. 7, p. 23) and the Gallinz these ceca are of relatively enormous size ; they are also very large in some of the Wading-birds (Limicole), in Owls and in Night-jars, Rollers, Bee-eaters and Cuckoos which are insectivorous. In fish-eating birds they are of relatively small size, and in some species are quite degenerate. In some species they are reduced to mere wart-like bodies, of which one may be wanting altogether, ¢.g., Herons and Petrels, or both may have com- pletely disappeared as in many Pigeons, Parrots, Kingfishers and the Swifts, for example. In Struthio and Rhea the aggregate volume of these ap- pendages, as Dr. Hans Gadow has pointed out, may surpass that of the rest of the intestinal canal. These pouches do not present any great range in the matter of shape. As atrule they are cylindrical. But in the Owls they assume the form of inverted Florence-flasks ; while in the Martineta Tinamou (Calodromas elegans) they assume a truly remarkable form, having the semblance of a bunch of grapes! (Ill. 7, p. 22). 22 A HISTORY OF BIRDS The caca appear to function as digestive organs when fully developed ; but in some cases they seem to have assumed a new character. Such instances appear to obtain in many cases where these organs would seem, judged solely by their small size, to be degenerate, as, for example, in Passeres. But here, as Dr, Chalmers Mitchell has pointed out, the walls of these extremely reduced organs contain lymphoid tissue, though what function they serve, whether secretory or excretory, is yet unknown. Theczca of the Owls similarly, at their ends, con- tain masses of lymphoid tissue, while in Ducks and Fowls this occurs in scattered patches. Thus, while some reduced caca are certainly degenerate and functionless, others, though re- duced, still play a more or less important réle in the meta- bolism of the body. But the presence of these organs presents some curious anomalies, which seem to show that although their develop- ment is correlated with certain kinds of diet, this relation is by no means always maintained. The diurnal birds of prey and the Owls afford the most striking illustration of this peculiarity. Both are now flesh eaters, and the former have apparently in consequence lost them, yet in the latter they are of large size. Some of the Owls, it is true, still partake freely of insect food, but so also do many of the smaller Falcons, which indeed live exclusively on this diet, yet they, like their larger brethren, are minus these organs. One must assume that they were lost before the insect diet became fixed, and so could not be re- developed. But it is clear that they are not essential to the digestion of insect food, and equally clear that the substitution of a carnivorous diet need not bring about their dissolution. The rectum, like that of reptiles, terminates in a cloaca di- vided into a series of more or less distinct chambers, the copro- dzeum, urodzum and proctodzum, into which last opens the “Bursa Fabricii,’ an organ of unknown function, peculiar to birds, and largest in nestlings; into the urodeum open the kidney and the genital-ducts. The coprodeum retains the fecal and urinary matter until ready for expulsion. The Circulatory System The main features of the circulatory system may be very briefly summarised. Inu. 7.—Types oF THE C&ca, or Buinp. Gut, or I. Ruea. II. Ow. III. Martineta TinaMou INTRODUCTORY 25 Birds differ from Reptiles and agree with the Mammalia in having a completely four-chambered heart, whereby the ad- mixture of arterial and venous blood is prevented. The heart _of birds, however, differs in important respects from that of mammals, Owing to their excessive activity the heart-beats of the bird are quicker than in any other animals, numbering 120 to the minute during rest, and during flight reaching a far higher figure. Ina bird which has just alighted the pulsations are beyond the count of the ear. Birds, like mammals, have but asingle aortic arch, but while in the former this is the left, in the latter it is the right of the originally double arch which persists. The corresponding arch of the opposite side, in both cases, gives rise to part of the subclavian artery. The carotid arteries exhibit some interest- ing modifications, but these appear, like so many other char- acters, to have no bearing, no traceable bearing, on the struggle for existence. And the same remarks apply to the femoral arteries which may be supplanted by the sciatic. Though attempts have been made to use these vessels for taxonomic purposes, they have been only partially successful. The Pen- guins alone among birds develop a rete mirable, which is, of course, connected with their diving habits, though other diving birds, it is to be remarked, have not developed a similar ar- rangement of the blood-vessels, which is met with again in the Cetacea among the mammals. An ingenious use of the veins supplying the intestinal mesentry has been made by Dr. Chalmers Mitchell, but the discussion of this, as of other peculi- arities of the vascular system, does not come within the scope of this work. During the work of brooding it is to be remarked the blood-vessels of the abdomen become greatly distended, and form large “inflamed” areas known as brood spots, which, applied to the surface of the egg during incubation, generate the heat necessary for the development of the growing chick. The Muscular System The muscular system of birds presents no characters which have any really important bearing on the problems with which this book is concerned. Nevertheless, interesting illustrations INTRODUCTORY 27 this purpose into three separate tendinous branches. In a number of species, however, wherein the ambiens was supposed to be wanting, Dr. Chalmers Mitchell found striking proofs that this muscle had suffered extensive degeneration, but that traces thereof were to be found in the shape of a tendinous band attached to the fibula and sending off three tendinous slips to the perforated flexors. More than this, in a dissection of two specimens of that aberrant bird the Hoatzin, he found in one case no ambiens above the knee, but the, so to speak, dismem- bered, distal end thereof forming a round ligament attached to the fibula, whilst its opposite extremity was split up into three branches, inserted after the manner just described. In the other specimen the belly of the ambiens was present, but the tendon thereof lost itself on the knee. The dismembered extremity thereof was found attached, as in the first-named specimen, to the fibula at the one end, and to the branches of the perforated flexor at the other. Thus there could be no doubt as to the evidence showing that the dissolution of the ambiens was ac- complished by slow degrees, the first stages commencing with the disappearance of the region between the knee and the crossing at the fibula. In a precisely similar way, it may be remarked, the hindmost thoracic ribs disappear, till at last nothing but the head attached to the synsacrum, and the terminal portion attached to the sternal rib next in front remains; finally, the head also disappears, leaving but a spicule of bone representing the sternal segment of the rib. Nervous System and Senses Though birds display a high order of intelligence the brain is devoid of superficial convolutions such as are found in the brains of the higher mammals. A slight furrow, however, apparently answering to the sylvian fissure of the Mammalian brain, may be traced in many birds. In the size of the brain, however, birds are in advance of reptiles; both the cerebrum and cerebellum being relatively much larger in the former. The sense of sight in birds is highly developed; thereby the soaring vulture detects the presence of food at immense distances, guided largely, no doubt, by the movements of others of its species nearer the feast, though these may be so far apart 28 A HISTORY OF BIRDS as to be invisible to human eyes. The hovering Kestrel again from a considerable height is enabled to detect the presence of creatures so small as mice on the ground beneath him. In the structure of the eye birds resemble the reptiles. In both the sclerotic coat is more or less cartilaginous, while the region surrounding the face of the eyeball lodges a number of overlapping, bony plates, which in Accipitres and Owls attain a large size, and gives this region of the eye a tubular shape. In the Woodpeckers and their allies, and in the Passeres, the region surrounding the entrance of the optic nerve also lodges — bony plates. In the Lammergeier the outer surface of the sclerotic region immediately surrounding the iris is of a vivid vermilion colour. No other bird has this region similarly coloured, and this may be cited as another of the many char- acters which birds—in common with other animals—display that appear to have no direct relation to the struggle for existence. Inaddition to the fovea centralts, answering to the “yellow spot” of mammals, the spot of most acute visuality, “ many birds,” says Dr. Gadow, “ possess a second foveze more towards ‘the outer or temporal side of the eye. One pair of these fovea seems to be used for monocular, the other for binocular sight, so that the whole field of vision of birds possesses three points where vision is most acute.” The exposed surface of the eye in birds is protected by a large semi-transparent membrane known as the nictitating membrane, This is formed by a reduplication of the con- junctiva, and worked by two muscles whereby the membrane is drawn over the eye from the outer lower towards the upper inner angle. In some birds, as in Owls, this is kept in constant motion, so that the iris is incessantly being covered and un- covered by this curious curtain. In other birds it is less often used, but in many, as in Corvidz, for example, it appears to be employed extensively during moments of pleasurable excite- ment. The eyelids are not conspicuous, and, as a rule, the lower lid only is movable, rising upwards to close the eye. Only in a few species are eyelashes present, such, for example, as the Ostrich and the Hornbills, where they are of exceptional length, and in the Amazon Parrots. INTRODUCTORY 29 The sense of hearing is acute in most birds, though there is no external auricle, such as is met with in most mammals; and herein birds and reptiles again agree. But in the Owls there are some species which develop prominent folds of skin of a very remarkable character, such as will be found described in chapter XXIII, p. 369. The structure of the ear will not be described in these pages, since this is a subject which belongs to the domain of comparative anatomy and is foreign to the purpose of this book. The sense of smell in birds is not, apparently, as a rule, very strongly developed. The evidence so far collected on this head is conflicting. The South American Vultures and the Petrels have both an unusually large olfactory chamber, yet, in the first-named at any rate, it has been satisfactorily demon- strated that their sense of smell is practically nil. They find their prey by sight. The Apteryx has the most complicated nasal labyrinth of all birds, and during feeding keeps up a con- stant sniffing sound, as if seeking to make up for its deficient sight by the use of its olfactory sense; and a piece of further evidence that this sense is well developed is the fact that the nostrils are placed at the extreme tip of the beak—a position found in no other bird. Nevertheless, experiments on captive specimens have produced no very striking evidence to show that their sense of smell is much better, if at all, than in other birds. Ducks are credited with a keen sense of smell, and in the days when duck-decoys were worked, it was the custom of the decoy-men to burn a sod of peat or other vegetable matter when the wind was blowing towards the fowl, in order that any suspicion of human scent might thereby be covered. Birds certainly possess a sense of taste, as is shown by the predilections of captive birds, for example, and the way in which gaudily coloured and nauseous insects are avoided. How much the tongue is used in this matter, and whether tongueless birds like Cormorants and Pelicans also possess a sense of taste, there is no evidence at present to show. The sense of touch in birds is confined chiefly to the beak: in reptiles, it may be remembered, the tongue is often used for this purpose. The beak of the Snipe, and of its near relatives, is singularly sensitive, being used as a probe for the discovery of food hidden in mud and swampy ground, CHAPTER II PHYLOGENETIC Birds and their position in the animal kingdom. Relationship to the reptiles, and the evidence thereof, Archzopteryx—the first bird. Hesperornis and early specialisation. Ichthyornis. The Pro-aves. T the outset it is well that a clear conception should be gained as to the relationship of birds with regard to. other classes of the Vertebrate kingdom: and this relationship can be established more clearly perhaps with regard to the birds than in any other group. Agile and restless to a degree unequalled perhaps in the animal kingdom, it may seem surprising to many to learn that nevertheless they owe their descent to the sluggish and cold- blooded reptiles : yet such is the case. Like the reptiles they are oviparous, though, unlike the reptiles, none-aré ovoviviparous. Furthermore, they differ from their humbler allies in that their eggs require a higher temperature to incubate. This is generally obtained by the brooding of the parent, though in certain exceptional cases this is secured by depositing the eggs in fermenting vegetable matter, or by the aid of sand heated by warm springs (p. 218). Structurally their reptilian character is abundantly plain. In the skeleton this is manifested in several ways. The skull alone would furnish sufficient evidence to prove this relationship, but happily many other parts of the skeleton can be made to bear no less striking evidence. These char- acters may profitably be reviewed, though briefly, here. First of all as to the skull. . Asin the reptiles this articulates with the vertebral column, or backbone, by means of a single condyle—a rounded boss of bone projecting from the floor of -- the skull immediately below the aperture for the exit of the spinal cord—while the bones of the palate and of the cranium 30 PHYLOGENETIC 31 are arranged on the same general plan as those of the reptile. In so far as the bones of the palate are concerned, this can be ILL. 8.—SkuLis oF NESTLING PENGUIN (I.) AND Emu (II.) To SHow THE Suture DivipING THE SEPARATE ELEMENTS OF THE CRANIUM The quadrate has been displaced in the case of the Penguin to show the base of the skull. These should be compared with that of Sphenodon, III., IV., the most primitive living Reptile. Al. = Alisphenoid. P. = Parietal. F. = Frontal. Sq. = Squamosal. S.o. = Supra-occipital. Q.= Quadrate. Qj. = Quadrato-jugal. Pt. = Pterygoid. Pa. = Palatine. Pm. = Premaxilla. Pt.f. = Post frontal. L. = Lachrymal. N. = Nasal. Jug. = Jugular. Max. = Maxilla. Vo. = Vomer. readily demonstrated at all ages in the bird’s life-history ; but this is not the case with the cranial bones, that is to say, with the elements which make up the brain case, inasmuch as these rapidly coalesce after birth obliterating all traces of their separate 32 A HISTORY OF BIRDS existence, and forming a smooth, highly polished box whose walls are permeated with air spaces. But in the ripe embryo, or better still, generally, in the nestling, this cranial box is found to be composed of a number of separate pieces correspond- ing closely with those of the reptile. Of these separate ele- ments there is no need to do more than give a very general account of those which have a direct bearing on the question at issue. As in the reptile, the fore-part of the floor of the skull is prolonged into a long parasphenoidal rostrum, at the base of which, in the majority of birds, will be found a pair of “besipterygoid processes”, These are peculiar to reptiles and birds, Largest in the more primitive types, such as the Ostrich tribe, Game-birds and Ducks for example, they have disappeared entirely among some groups, as in the Parrots for example; while in others some members possess vestiges thereof, and others no trace at all, as for instance among the birds of prey and the song-birds. The lower jaw articulates with the skull by means of an anvil-shaped bone, the quadrate, and this again occurs only among reptiles and birds. i But owing to the relatively enormous increase in the size of the brain, the cranium of the bird differs markedly from that of the reptile, inasmuch as the parietal bones, before fusion, have the whole posterior border interlocked by suture with the supra- occipital and lateral occipital bones, and to these the squamosal is attached, being fitted in, as it were, puzzle fashion, to fill up the gap left where they meet, and serving at the same time to partly cover the bones of the internal ear (Ill. 8). In the reptile, on the contrary, the brain is relatively small, so that the outer angle of the hinder border of the parietal is produced backwards into a long “ flying buttress” to serve for the attach- ment of the squamosal which is thus completely divorced from all participation in the cranial wall. In this particular then the bird really more closely resembles the mammal. The structure of the ear and the lower jaw are other characters which must be cited in this connéction. Evidence of no less importance is to be had by a study of the developing skull, but this is of an extremely technical character, and need not be cited here, Turning now to the skeleton of the trunk, we find that, in the young bird at least, the neck vertebre bear free ribs—in t PHYLOGENETIC 33 the adult they coalesce with the centrum, while in the nature of the ends of the body, or centrum, of the vertebra, reptilian blood is also evident. But this evidence might not, at first, appear so plainly as in the characters just referred to, since the majority of birds have now acquired what are known as “saddle-shaped” vertebra, or heteroccelous vertebree; that is to say, the two ends are unlike. Anteriorly the articular surface is columnar, posteriorly trans- versely hollowed, so that the columnar surface of the vertebra moves, laterally, on the hol- lowed surface of that next in front of it. But in the old Ich- thyornis like the modern reptile Hatteria, these surfaces were cup-shaped; while the Par- rots, Penguins and Gulls have cup and ball articulations to the vertebre, in the region of the thorax, and these are quite rep- tilian in type. Young birds, however, furnish much more emphatic ‘testimony on this point, for, in addition to the movable ribs of the neck verte- brz, we have the fact that, as in reptiles, these vertebrze do not possess, at any stage, ‘‘ Epi- physes,” as in the mammals, These epiphyses are flat discs of bone fitting on to the ends of the vertebrz, enabling new bony matter to be added between the enclosed space: growth com- A ILL. 9.—HIpP-GIRDLES OF A DINOSAUR (A), AN EmBryo Birp (B), AND A NEsTLiInG Emu (C) The hip-girdle of the embryo in the shape of the Ilium (Il) and the position of the bubis (P.) and Ischium (Is.) resembles that of the Dinosaur— a primitive or ancestral phase of de- velopment. In the nestling Emu the Ilium has greatly increased in length, and the Pubis and Ischium have rotated backwards. In less primitive birds the fissure between the Ilium and Ischium becomes almost com- pletely closed. pleted, these plates fuse with the main body of the centrum. The hip-girdle, especially during its embryonic stages, pre- 3 34 A HISTORY OF BIRDS sents a very striking resemblance to that of the Dinosaurian reptiles; and the shoulder-girdle no less emphatically bespeaks_ areptilian descent. The hind-limb again is built on a completely reptilian model, and this is seen in the peculiar character of the ankle-joint, and the nature of the tarso-metatarsal segment. Both in reptiles and birds the joint between the foot and the shank of the leg is formed by a hinge passing between the two rows of ankle-bones, and not, as in the mammals, by a hinge between the shank and the first or uppermost row. In the adult bird, however, no separate ankle-bones are traceable. To find these the embryo, or at least the nestling, must be examined. In the former several distinct tarsals can be made out, but in the nestling these are represented (a) by a mallet-shaped bone, and (6) by a flat disc. The first, or astragalus, fits on to the end of the shank, up the front of the shaft of which it sends a short spur; in a few weeks after hatching this as- tragalus fuses completely with the end of the shank, when all trace of its former existence is lost. The second is applied to the surfaces of the three metapodial or foot-bones, and this similarly fusing therewith b disappears rapidly as an indepen- JY dent element. This plate, as may be seen in the embryo, is made up of eS ae ee distinct elements, but these rapidly Foot (Tarsometatarsus) oF coalesce to form the plate, which A Youne Brrp (B, D) Com- .; : PARED WITH THE SAME Bones !1 turn disappears to form the top IN AN ApULT Reprite (Dino- of the “cannon-bone”. aed pa This “cannon-bone” or tarso- A. = Astragalus. metatarsus—the “tarsus” or scale- covered portion of the leg, in works on Ornithology—in the embryo, or nestling bird, is seen to be made up of three sepa- rate shafts or rods, answering to the similar bones extending from the ankle to the base of the toes in the human foot, for example, and consequently corresponding in number to the number of the toes. The dividing lines in the nestling bird IV PHYLOGENETIC 35 are extremely fine, but they can easily be seen. By the time the adolescent stage has been reached all trace of these separate bones has vanished, leaving the hard, pillar-like “cannon-bone,” which reveals no evidence of its earlier compound character. So much for the reptilian characters of the skeleton. But the Brain, Vascular and Urino-genital Systems similarly fur- nish proofs of the same derivation. So. closely do the birds and reptiles agree, indeed, that Huxley included them together under the term Sauropsida. But apart from the indubitable evidence to be obtained from existing birds, other and even more striking evidence is to be obtained from the remains of fossil forms. This evidence carries us back to Jurassic times, the oldest known fossil bird, Archeopteryx, having been obtained from the Lithographic slate of Solenhofen in Bavaria, This bird more nearly resembles the reptiles than any other known form. So much so, that undue and unwarrantable use has been made of the fact, many writers having endeavoured to show that it was more reptile than bird, a contention which becomes ridiculous when the facts are carefully considcred. Two specimens only of this remarkable bird are known— belonging to as many species—the first to be discovered being now in the British Museum of Natural History, the second in the National Collection of Berlin. With their specific distinctions we have nothing to do here, but both agree in having the jaws armed with teeth and a long tapering, lizard-like tail, but this, like the rest of the body, bore feathers. Of all the accounts, and there are many, that have been given of this patriarch of the bird-world only one can be re- garded as accurate, though on many occasions one or other of them have been described by men whose powers of interpreta- tion have in other ways been more severely tried. It is on their descriptions that the inaccurate, and sometimes grotesque figures which adorn text-books of comparative anatomy have been based. So profoundly impressed do these authorities appear to have been by the presence of the teeth, the long tail, the armature of claws on the wings—concerning which we shall have more to say—and the fact that traces remain only of the wing and tail feathers, and of the feathers of the leg, that they contended that these ancient types must have been clothed 36 A HISTORY OF BIRDS with scales as to the head, neck and trunk, the feathers being restricted to the parts on which they occur in the fossil! A contention as wildly improbable surely as it would be to insist that from the absence of all traces of muscles these primitive cyeatures had not yet acquired muscular tissue ! Nevertheless, we have, in this primitive type, not only a remarkable link in the chain of evidence as to the source from which birds derived their origin, but also a most valuable key to some essentially avian characters which would otherwise have had to be explained on mere conjecture. In so far as the reptilian characters are concerned the principal features are IcL, 11.—TuHE SKELETONS oF Two Extinct Fossiv Brrps, HEsPerornis (A) AND IcHTHYORNIS (B) In Hesperornis all that remains of the wing gga vestige of the humerus, seen in the figure lying across the ribs. . the teeth and tail. The former were small and appear to have been lodged in sockets, while the tail, on account of its length and the number of the vertebra, must unquestionably be regarded as reptilian. As to the avian characters, these will be dealt with later (p. 263). Not, unfortunately, until the cretaceous period do we meet again with bird remains, and these have now become stamped with the stereotyped avian characters in all save that the jaws still bore teeth. The two most conspicuous and most perfectly preserved of PHYLOGENETIC 37 these ancient birds were Ichthyornis and Hesperornis, from the cretaceous shales of Kansas. On account of the presence of teeth in the jaws these have been Rated in a distinct “Sub-class” of birds—the “ Odont- ornithes,” but it is open to question whether on such groungls this is justified. Ichthyornis may\ perhaps be, and generally is, regarded as the ancestral type of the present Steganopodes—the Gannets, Cor- morants, Pelicans, Tropic and Frigate-birds. In all save the teeth and the.peculiar character of its vertebrae, which were amphiccelous—reptilian characters—the skeleton of this bird had acquired all the characteristic peculiarities of the Class A ves, though we should expect, by the way, when the structure of the palate is better known, to find that it presents evenfore reptilian characters than are to be found in the living Struthious , birds. Hesperornis, on the other hand, represents one of the most highly specialised of all birds, after the toothed jaws are taken into consideration, having undergone the most radical changes of structure in adaptation to an aquatic life (p. 385). These two birds, Ichthyornis and Hesperornis, though not the only birds known from cretaceous rocks, represent the only complete skeletons yet discovered, and it is significant that they had already not only become adapted to different modes of life, but that, in the case of Hesperornis, this adaptation had attained a degree of spgcialisation exceeding that of any other known bird, with the exception of the Moa, fossil or recent. The existence of these two very different types—the one a bird of powerful flight, the other not only flightless but wing- less, only a vestige@@p the upper arm remaining—points con- clusively to a very extensive bird fauna at this remote period, though of the land birds naturally but few would be preserved, and these have not yet been discovered. Furthermore, when the whole of the available fossil material comes to be examined, it is evident that the differentiation ifito land and water birds took place in very remote times indeed, dating from the Jurassic period, if not earlier. It is to the earlier Jurassic formations then that we must look for traces of the pro-avian types, for an insight into the beginnings of the evolution of the bird. And here, probably, if anywhere, we 38 A HISTORY OF BIRDS must turn to find that process of differentiation at work which evolved the several types of land and water birds, of which our bird fauna to-day are the descendants. What these “ pro-aves” were like we can only dimly sur- mise; and all our inferences must be inspired by and based upon that strange, kite-tailed form, Archezopteryx. From what we know of the evolution of other types of vertebrates, we may safely assume that these ancestral birds were of small size, and were almost certainly also arboreal. And from the unmistakable signs of the shortening of the body in modern birds, the trunk, we may assume, was also relatively longer, as it certainly was in Archeopteryx. From these two inferences we may conclude with some degree of probability that these creatures, these birds “in the making,” had substituted leaping for climbing about the trees, and from this there was but a short passage to leaping from tree to tree. In these movements we may reasonably suppose the fore-limbs were used for grasping at the end of the leap. The use of the fore- limb for this work would naturally throw more work upon the inner digits, 1-3, so that the process of selection would rapidly tend to the increased development of these, and the gradual decrease of the two outer and now useless members. Corre- lated with this trend in the evolution, the axillary membrane, the skin between the inner border of the upper arm and the body, became drawn out into a fold, while a similar fold came to extend from the shoulder to the wrist, as the fore-limb, in adaptation to this new function, became more and more flexed. While the fingers upon which safety now depended were increasing in length, and growing more and more efficient, they were at the same time losing the power of lateral extension and becoming more and more drawn together by ligament and muscle, and more and more tending to become flexed upon the fore-arm, And the growth in this direction was probably accompanied by the development of connective tissue and mem- brane along the post-axial or hinder border of the whole limb, tending to increase the breadth of the limb when extended preparatory to parachuting through space from one tree to another, long claws being used to effect a hold at the end of the leap; though to a less extent, the hind-limbs were also affected by this leaping method of locomotion, resulting in the PHYLOGENETIC 39 reduction of the toes to four, and the lengthening and approxi- mation of the metatarsals, 2-4, to form a “cannon-bone ”. The body clothing at this time was prob- ably scaly, but with scales of relatively large size. Those covering the hinder border of the in- cipient wing, growing longer, would still retain their original overlapping arrangement, and along its hinder border would, in their arrangement, ap- pearance, and function, simulate the quills of modern birds ; as their length increased they became also fimbriated and more and more efficient in the work of carrying the body through space. There is less of imagination than might be supposed in this attempt at reconstructing the primitive feather, inasmuch as there is a stage in the development of the highly complex feather of to-day which may well represent the first stage in this process of evolution. Creatures such as are here conjured up would bear a somewhat close resemblance to the Archzopteryx; and it is contended that the discovery of earlier phases of avian de- velopment, the phases preceding Archzopteryx, will show that this forecast was well founded. But in Archeopteryx it is to be noted the feathers, so far as the impressions on the slab containing the remains of this bird enable us to see, differ in no way from the most perfectly developed feathers known to us. While the external form and mode of life of these primitive, hypothetical types was slowly changing, no less fundamental changes must have been taking place with regard to the inter- nal organs, more especially to the nervous, respiratory and vascular systems, changes in the direction of a larger brain in the one, and a more perfect system of oxygenating the blood in the other. This last was effected by the acquisition of a four-chambered heart, an approach to which has been made only in the Crocodiles among living reptiles. By the addition of this ILL. 12.-ONE OF THE Pro-AVES 40 A HISTORY OF BIRDS fourth chamber the high temperature and phenomenal activity of the birds came into being; but for reasons for which no explanation is yet forthcoming, the reptilian character of the blood corpuscles has been retained. That is to say, the red corpuscles still retain the nucleus in common with all the lower vertebrates, while in the warm-blooded Mammalia—also of reptilian descent—these nuclei have been lost. But whether these pro-aves are to be regarded as descended, in common with the reptiles, as a collateral branch of the same stock; or whether they sprang from some primitive but true reptile, is a point too subtle to be determined. CHAPTER III PHYLOGENETIC (continued) THE CLASSIFICATION OF BIRDS IN BROAD OUTLINE—THE MAIN LINES OF THE EVOLUTION OF THE CLASS AVES. Archornithes and Neornithes. The position of the Ostrich tribe in the system. What the structure of the bony palate reveals. Paleognathe and Neognathe. The classification of the Paleognathe and of the Neognathe. A hypothetical ancestor. The Grebes and Divers, Penguins and Petrels, Steg- anopodous birds, the Accipitres, the Anseres, the Alectoromorphe,—the Game- birds, Cranes and Rails, Plovers, Pigeons, the ‘‘ Coraciiform”’ birds; the Passeres. Numerical strength. RCHAOPTERYX naturally forms the starting-point A in any comprehensive system of avian classification, since it represents the lowest, because most reptilian, of the whole Class Aves. Moreover, on account of its many structural and peculiar characters, it is by common consent set apart in a separate sub-class—Archornithes—as distinct from the Neornithes, the sub-class which embraces all other known forms. Though the Struthious or Ostrich-like birds are, by modern systematists, regarded as the lowest, most primitive of this Neornithine branch or sub-class, they are not, by many, on this account looked upon as a natural group of birds; that is to say, as a group having a common origin. Rather it is held they must be considered as descendants of several dis- tinct stocks—four, or perhaps five isolated groups whose relation- ship to the remainder of the birds is necessarily a matter for conjecture rather than dogmatism. One of the strongest reasons among the older systematists for regarding this assemblage as one bound by ties of affinity was that all the members thereof had lost the power of flight, and with it the characteristic median plate, or keel, which, in flying birds, runs down the under surface of the sternum. Hence they were placed together to form the “Order Ratita ” 41 42 A HISTORY OF BIRDS or “raft-breasted” birds. And, by way of qualifying this arrangement, it was pointed out that in the structure of the palate these “ Ratite” differed fundamentally from all other birds, past and present. As a matter of fact the raft-like character of the breast-bone is of no real importance, no guide as to questions of affinity: it is a secondary, degenerate char- oe [-b / Apgwbeovige | al ILL. 13.—RESTORATION OF ARCHAOPTERYX (after Pycraft) acter, which has been independently acquired by many birds, though in no case so completely as in the “Ratite”. The structure of the palate is, on the other hand, of supreme import- ance in this connection. So far from being fundamentally different from that of flying birds, it is now clear, as the present writer has shown, that the palate in the flightless and flying forms is fundamentally similar. That this is so-a brief review of the main features of this palate, and its evolution, will make clear. In the Emu and Cassowary we have this palate in its simplest form. Its chief characteristic is the enormous size of PHYLOGENETIC 43 the vomer which is of considerable width, and extends forwards over the premaxillary and backwards as far as the middle of the pterygoids, embracing the anterior half of each by a pair of broad “feet”. The palatines, it will be noticed (Ill. 14), are short, articulating on the one hand with the vomer and pterygoid where they overlap, and on the other with the maxillo-palatines, which are of great size. The next phase of development is furnished by Rhea. The vomer is here also of great size but is deeply cleft in front, while the “feet” posteriorly are nearer together. Their rela- tion to the vomer is precisely similar to that which obtains in Dromzeus (Emu), though this fact is masked by the movement of the palatines which have shifted inwards, and in so.doing have come to rest under the junction between the vomer and ptery- goid, concealing this when the skull is seen from the ventral aspect. In their relative size and shape the palatines differ but little from those of the Emu, but the maxillo-palatines are relatively much wider as the palatine processes of the premaxilla are also much longer. The palate of the Tinamous carries us a stage further. The vomer is still large, and in its general conformation closely resembles that of Rhea. The palatines have, however, become relatively longer and rod-like; and while posteriorly, in their relation to the vomer and pterygoid, they agree with those of Rhea, anteriorly they have come into touch with the palatine processes of the premaxilla. The maxillo-palatines, it should be noted, have become relatively smaller than in Rhea. So much for these three stages in brief outline. Now compare any, or all three, of these palates with those of, say, a Gull and a Common Fowl. For clearness’ sake let the comparison be made with the skull of the Fowl (Ill. 14). One of the first things to be noted will be the greatly reduced size of the vomer, which indeed is now little more than a vestige. It will next be noted that this reduced vomer has lost all rela- tion with the pterygoid, and is borne by an ingrowing pair of plates from the palatines. These, moreover, it will be noticed, have now greatly changed, both in their relative position as well as in length and shape. Compared with those of Rhea and the Tinamous, they will be found to have extended forwards in the form of a pair of slender rods, wedged in between the palatine 44 A HISTORY OF BIRDS process of the premaxilla and the ma xillo-palatine processes, in this last matter resembling the Tinamous. Finally, they ILL. 14.—STAGES IN THE EVOLUTION OF THE AVIAN PALATE A, Dromeus. B, Gallus. C, Rhea. D, Tinamou. E, Larus. F, Portion of the palate of a Penguin to show the hemipterygoid. G, The hemipterygoid, ~ side-view. Vo. = Vomer. Mx. = Maxillo-palatine. Pt. = Pterygoid (I, Ill. A. Pc., Ill. C = Pterygoid), Pa. = Palatine. H. pt. = Hemipterygoid. will be found to articulate with the pterygoids by means of a true joint—opposed bones having glenoid surfaces. Now between the type of palate, as we have remarked, PHYLOGENETIC 48 exhibited by the Struthious birds and that of the “ Carinate” or flying birds, such as is seen in the Fowl, for instance, there appears to be a very wide gap. A study of the palate of the nestlings of the * Carinate” or Neognathine group, however, will show conclusively that this gap is apparent only, and not real. In the skull of the young Penguin, for example, the palatine and the pterygoid articulate, not by a joint, but by overlapping suture ; the pterygoid termin- ating, moreover, in a spike which just reaches the forked ends of the vomer ; so that, in so far as this contact between vomer and pterygoid is concerned, Carinate and Struthious birds agree. But as growth proceeds the pterygoid segments, at a point corresponding with the level of the hinder end of the palatine, and shortly after this segmentation the spike-like anterior ex- tremity of the pterygoid fuses with the palatine on which it rests, while a true joint is formed between the segmented sur- faces. When this process is complete, all record of the earlier connection between vomer and pterygoid is lost, so that the palate appears to differ fundamentally from that met. with in the Struthious birds. In some other species,*as for example in the Petrels, the joint formed after the segmentation of the pterygoids is formed between the pterygoid on the one part and the pterygoid and palatine on the other: that is to say, the anterior end of the pterygoid segments at the level of the hinder end of the palatine instead of tail-wards of this point (compare illustrations.) These two types of palate have been named by the author the Struthious “‘ Palzognathine” and the Carinate ‘‘ Neogna- thine”. Concerning the latter more must be said later: for the present it is sufficient to point out the fact that the one has been derived from the other—the Neognathine from the Palzo- gnathine. But this by way of a digression. We must return to the question of the relationship of these Palaognathine forms one toanother. Owing to the paucity of material this is a peculiarly difficult problem, and one which, for the present at least, must be regarded as unsolved. That the Emu represents the most primitive member of the group few will doubt. And with the Emus we must reckon the Cassowaries. The Ostrich of Africa is probably nearly related. In the palate it shows degenerate 46 A HISTORY OF BIRDS characters, while in the matter of the hind-limbs and hip-girdle it has undergone extreme specialisation (p. 391). In the pterylosis of the wing it shows more primitive characters, probably, than any other group. By many, the extinct A=pyornis of Madagascar is regarded asa close ally of Struthio : but until more is known of the palate this must remain open to question; especially since the form of the hip-girdle, and of the nature of the hind-limbs differs so conspicuously from that of Struthio, and agrees rather with that which obtains in the New Zealand Dinornis, The Rheas in the nature of the palate bear a striking similarity to Dinornis; but in the matter of the hip-girdle the two types differ fundamentally, Rhea, indeed, exhibiting characters in this region of the body that are absolutely unique (p. 392). By many, including the present writer, the Tinamous of the South American Continent are also to be included among the Paleognathe, being possibly allied to the Rheas. The remarkable Apteryx of New Zealand must, it would seem, be regarded as oneof the most aberrant of the Palaognathe, though, by some? it is regarded as allied to the Moas (Dinornis). The discovery of further and more complete remains, especi- ally of the skull, of an extinct type from the Lower Eocene of Western Europe, now known as Gastornis, promises to throw a flood of light on the subject of the evolution of the Palzeognathz (Ratite), though according to some these remains are those of an Anserine bird, a conclusion which is probably wrong. Only a part of the skull is known, but this shows that the cranial sutures were persistent, or at least slow to close, and further, that the post-orbital region of the skull, as in the Cassowaries, was of considerable length. The birds which exhibit the arrangement of palatine bones, here designated Palgognathine, should probably be regarded as representing some six or seven sub-orders (including Gast- ornis) of an Order Palaognathe. Time may show that these sub-orders must be further reduced, since Rhea, the Tinamous, fEpyornis and Dinornis may prove to be descended from a common stock. With the possible exception of Gastornis, the Palaognathz, both fossil and recent, are represented only by flightless forms, excepting only the Tinamous, which still retain the power of PHYLOGENETIC 47 flight. Gastornis may also have retained this power: at any rate it possessed a complete furcula. We must turn now to a broad survey of the “Carinate” or, as we prefer to call them, “ Neognathine ” birds—a formidable array, inasmuch as the remainder of the Class Aves is included in this review. By the older systematists these were fancifully arranged so as to form a linear series. That is to say, they believed it possible to group the forms with which we are now concerned in a continuous series, the several types being supposed to pass the one into the other. But in such schemes, it must be re- marked, the Struthious types were generally also included. Such schemes were of course founded on external characters alone. More philosophical methods of investigation have shown, however, that no such continuity exists; but that we are dealing, not with a linear series, but with an intricate and at present tangled system of branching. To trace out these ramifications endless patience and research is necessary ; indeed, the classifica- tion of the Class Aves on phylogenetic lines is one of the most difficult tasks which the ornithologist can be called upon to undertake. The attempt made by Dr. Gadow, based on, and inspired by, the monumental work of Professor Max Firbringer, has much to recommend it; and no less valuable is the later work of Dr. Chalmers Mitchell. Though founded on a single set of characters—the convolutions of the intestines—and not: offered as a solution of the problem of descent, this work shows a very remarkable grasp of facts and power of interpretation. The writer of these pages has endeavoured to blend the labours of these investigators in setting forth the main prin- ciples of the classification of the Neognathe, a classification which it is believed expresses more or less truthfully the phylogeny of the several groups. Briefly the Neognathz may be regarded as divisible into two great branches, traceable to a common stock. Each of these two branches again divides into two, giving us on the one hand what we must describe as the Colymbo- and Pelargo- morphine branches, and on the other the Alectoro- and Coracio- morphine branches. What the ancestral stock may have been like which gave 48 A HISTORY OF BIRDS rise to these two great branches we cannot, from lack of material, say as yet. That it was an offshoot from the Palzognathine stock is certain, and Dr. Mitchell contends that it is represented to-day by the remarkable aberrant Goose-like birds, Palamedea and Chauna, more commonly known as the “Screamers,” natives of South America. The descendants of this hypothetical Palamedia-like ancestor would seem to have given rise to a stock of great potentiality, which under the stress of the struggle for existence became more and more differentiated, more and more specialised as the necessity for adaptation to environment became more acute. These descendants, in short, gave rise to what we know to-day as the Neognathine birds, which, as we have already remarked, are divisible into two great groups. Let us pass, in brief review, the essential features of the differentiation of the Colymbo-pelargomorphine group. Of these, the oldest, the first to become differentiated from this generalised stock, appear to have been the Penguins, Grebes and Divers, including the extinct, giant, toothed Diver of the cretaceous epoch (p. 37), and the Petrels on the one hand; and the Anserine birds, Storks, and Accipitrine birds on the other. While these were in the making, yet a third group was developing which gave rise to types which are repre- sented to-day by the Steganopodes—Pelicans, Gannets, Cormo- rants and Darters, Frigate and Tropic-birds. Dr. Mitchell contends that it was this same Steganopodous stock which gave rise to the Penguins, the Petrels, the Stork tribe and Accipitres, but this is a matter for debate. Of the Penguins and Petrels we need say little here, the salient points in their evolution being discussed elsewhere in these pages. But of the Stork tribe it is necessary to say that this includes, besides the familiar Storks and Herons—commonly confounded with the Cranes—several less familiar and aber- rant types; the Flamingoes, Hammer-head (Scopus), Open-bill (Anastonus), Spoon-bills (Platalea), Ibises and Tantalus Storks. being among the more or less isolated ciconiine or Stork-like forms, and the Whale-headed Stork (Balenicepo) and Boat-bill (Cancroma) among the Ardeine or Heron-like forms. To return for a moment to the Steganopodous birds, it should be mentioned that it is to this group, in all probability, THE SECRETARY-BIRD PHYLOGENETIC 49 that the extinct Ichthyornis and Odontopteryx belong. The first-named, as we have already remarked (p. 37), was a bird of powerful flight, whose jaws were provided with a formidable armature of teeth, while of the Odontopteryx of the London Clay but little is known, save that the jaws were deeply serrated by a series of bony outgrowths of the edges of the jaw which were encased in horn. According to some authorities the Accipitres are descended not from’the Ciconiiformes but from a Gruiform stock, of which more presently. On the whole, however, the evidence seems to support the origin here indicated. The strange Sec- retary-bird (Serpentarius) on the one hand, and the Cathartz or New World Vultures on the other, represent the most aber- — rant and puzzling of the group, and both have preserved many proofs of their primitive character. Of the more strictly, or more specialised, Accipitrine types we have three more or less distinct groups—the typical Eagles, Buzzards, Kites and Hawks; the Vultures; and the Falcons; the last being the most highly specialised of all. The Catharte or New World Vultures probably represent a distinct branch, running parallel with the rest of the Accipi- tres, and descended from the same stock. The origin of the Anseres, as we have already remarked, is not difficult to trace; inasmuch as they are probably de- scendants, if not of the archaic Screamers—Palamedea and Chauna—at least of the stock from which these'arose. That is to say, the Screamers may either be regarded as the living re- presentatives of the actual ancestors of the Anseres, more or less modified by time, or as an offshoot of these ancestors retain- ing most of the original characters thereof. In two important characters the Screamers differ from the Anseres however. In the first place they lack the peculiar fleshy, horn-fringed tongue and the lamelle along the edges of the beak, so characteristic of the Anseres; and in the second they have an extremely emphysematous skin, a character met with again, it is to be noted, among the Steganopodes. As to absence of the horny lamelle of the beak and tongue. This is really not very important. Incipient lamella may well have been present in the earlier generations and have become eliminated later, while in the true Anseres they gradually 4 50 A HISTORY OF BIRDS gained in size in adaptation to the peculiar feeding habits of their possessors, That this is soa study of the jaws and tongues of the Anseres will show. The lamellee in question are largest in the surface-feeding-ducks, reaching their maximum develop- ment in the Shovellers. In the Geese, which are vegetivorous, the lamelle take the form of horny teeth, and these become still more tooth-like in the piscivorous Ducks. The fact, there- fore, that lamellz of the kind which obtain in the surface-feed- ing-ducks are found also along the jaws of the Flamingoes may mean, either that they have been acquired from the common ancestor of the Storks and Anseres, or that they have been in- dependently acquired. This last alternative seems to have been the case among the Petrels, some of which, as in Przon, have lamellated beaks as well developed as in many Ducks. In their pterylosis the Screamers are certainly primitive in that the apteria are but feebly developed, as in the Struthious birds, Divers, and Penguins. They furthermore resemble the Struthious birds in the convolutions of the intestines, and in the structure of the genital organs of the male. But this last char- acter, be it noted, also obtains among the Anseres but not in the Flamingoes, which, according to some, are to be reckoned, as we have seen, among the Anseres. As to the Anseres proper but little need be said here. Start- ing with the primitive Palamedea and Chauna we pass to the more typical Anseres which fall into three more or less sharply defined groups—the Swans, Geese and Ducks. Of these prob- ably the Geese are the more ancient, for in one shape or another they retain many characters which must be regarded as primitive. Thus in some genera, e.¢., Cloephaga, the nestling wears a striped mesoptyle plumage: Axseranas has only parti- ally webbed feet, and presents other characters indicative of a low position both in the skeleton and the convolutions of the intestines, though in the matter of its strangely convoluted trachea it is highly specialised. The Swans on the one hand, however, and the Ducks on the other must be regarded as offshoots of this Anserine stock. We proceed now to a survey of the second great division of the Neognathe; and commence with that branch which con- stitutes what Dr. Gadow calls the Alectoromorphine legion. First of all must come the Galliformes—Gallinaceous types— PHYLOGENETIC 51 which are divisible into two groups, according to the structure of the feet—A. Peristeropodes, B. Alectoropodes. In the first the hallux is large, and arises low down the metatarsal shaft, so that all four toes are on the same level; but besides this the skeleton displays less specialisation than is met with in group B., and this applies more especially to the sternum, shoulder and pelvic girdles, Probably the most lowly of the Peristeropod forms are the Megapodes of the Austro-Malayan region. They are generally regarded as forming a distinct Family, the Megapodiidz, while a second Family is made up of the Cracidae—the Curassows and Guans of Central and South America, comprising some four genera and fifty species in all. The group Alectoropodes embraces all the remaining Gallinaceous birds, which may well be included in a single Family divided into sub-Families, though this practice is not generally followed, the custom being to form several Families, and to divide these again into sub-Families. The more im- portant types herein embraced are the Turkeys, Guinea-fowls, Grouse, Partridges, Francolins, Quails, Pheasants and Peacocks. Anatomically the Galliformes are a very sharply defined group, and on this account it is curious that the Tinamous should so persistently be associated therewith, though this is generally done by those systematists who are guided only by superficial characters, As we have already shown, these birds should probably be regarded as Paleognathz, though this view is not accepted. by authorities of such weight as Professor Max Firbringer and Dr. Chalmers Mitchell. Two other types of doubtful affinity are commonly as- sociated with the Galliformes. These are the Turnices and the aberrant Opisthocomus of South America. The former are small, Quail-like birds occurring throughout the warmer regions of the Old World. Presenting characters in common with the Galline birds, the Sand-grouse and the Rails, these birds should perhaps be regarded as an offshoot from the Galliform stock, though there is much to be said in favour of the contention urged by Firbringer that these birds should be regarded as an aberrant type of the Charadriiformes. As touching Opisthocomus, the Hoatzin of British Guiana, the evidence is conflicting, as may be judged by the fact that 52 A HISTORY OF BIRDS this most puzzling bird has been associated during recent years with the Galli, the Rails, the Pigeons, the Musophagi (Plantain- eaters) and Cuculi, while earlier writers have made yet other attempts to indicate its place in the system. The more remarkable characteristics of this bird are else- where discussed in this work, so that here it will be necessary to say but little. Osteologically it appears to stand near to the Galli, but Dr. Mitchell, on the evidence of the intestinal convolutions, considers it more nearly akin to the Pigeons. Into the bearing of other anatomical characters we do not propose to enter, since they have not been made to reveal any material evidence either one way or another. The many-sided character of this bird is plain evidence of its isolated position, and we shall probably be near the truth if we regard it as an offshoot from the very base of the Alectoro- morphine stem: hence the many resemblances between these now more‘or less sharply differentiated forms—the Cuculi, Galli and Pigeons, for all must be regarded as descendants of the same common stock. The undifferentiated or “ generalised” stock which gave rise to the Galliformes, developing along other lines, gave rise also on the one hand to the Gruiformes and on the other to the Charadriiformes. The Gruiformes—Rails and Cranes—contain many aber- rant and extremely interesting types. The Rails must be regarded as the more ancient of the two; thereof we may cite as examples the familiar Water-rail, Land-rail, Moor-hen and Coot, while besides these there are a number of flightless forms, as the Weka-rail (Ocydromus) and the extinct Aphanapteryx and Aptornis, and Gypsornis, not to mention others. The curious South American ‘‘Courlans” (Aramus) appear to represent the half-way house between the Rails and Cranes, though on this border line we must probably also reckon such archaic forms as the South American Trumpeters (Psophia), the Kagu (Rkznochetus) of New Caledonia, the Sun-bitterns (Eurypyga) of Central and South America, and the “ Fin-foots ” (Helhornis and Podica) of South America, West Africa and India (Assam to Sumatra). More remarkable in this connec- tion is the Cariama or “Seriema” (Décholophus), inasmuch as this bird by most of the older systematists was regarded as PHYLOGENETIC 53 one of the Accipitres, and this on account of its rather close resemblance to the long-legged “ Secretary-bird ” (Serpentarius). There can be no doubt, however, as to its Gruine character, and it would seem that it is to be regarded asa near ally of the extinct giant Phororhacus, also of South America. The Bustards (Ortaide) are certainly aberrant and isolated members of the Crane tribe, though by the older Ornithologists they were regarded as giant Plovers. The true Cranes alone remain to be mentioned, and of them but little need be said here. The earlier systematists associated these stately birds with the Storks, a mistake which is commonly made to-day by those who judge merely from superficial ap- pearances, Even by external characters, however, they may be distinguished, the Cranes having a relatively shorter, less cone-shaped beak, which is deeply grooved on either side, and has the nostrils placed nearer the middle than the base. Ana- tomically the difference between Storks and Cranes is so wide that there can be no question as to the distinctness of the two types. The Charadriiformes, as has already been remarked, are close allies both of the Crane tribe (Gruiformes) and Fowl tribe (Galliformes), these three great groups being probably descendants of a common stock: though Dr. Chalmers Mitchell —the latest original contributor to this subject—prefers to regard the Gruiformes as an offshoot from the Charadriiform stem. But it must be stated, in justice to him, that this con- clusion is based only on the evidence of the intestinal con- volutions, and was never intended to be regarded as a definite decision. No one, indeed, would be less likely to allow the deductions from a single character to form the sole basis for determining so difficult a problem. But be this as it may, this group appears to present two or three more or less sharply defined grades of development, and these again present within themselves many phases of specialisa- tion. There seems to be but little doubt but that the Curlews, Dunlins, Sandpipers, Avocets and Plovers, for example, must be regarded as the final stages in the evolution of the typical Plovers. More primitive are the Thick-knees or Stone-curlews (Gdicnemide), Pratincoles and Coursers (Glareolide), Seed- 54 A HISTORY OF BIRDS plovers (Thinocoride) and Jacanas (Parride), Crab-plovers (Dromadida), “Sheath-bills” (Chionidide) and the Gulls and Auks (Laride and Alcide). With the exception of the Stone- curlews and the Gulls and Auks, these more ancient types are not generally very well known, save to the expert. The Stone-curlews, by all the older Ornithologists, were re- corded as closely allied to the Bustards, some of the smaller species of which they approach not only in size but also in their general coloration, and in the shortness of the toes. Nevertheless, there can be no question but that they are to be regarded as Plovers, in a wide sense, and not as members of the Gruiformes. The likeness which they bear to the Bustards is’ due in part to convergence, to the moulding influence of a like environment—dry heaths and wastes—and in part to their common origin. The Pratincoles are certainly not very Plover- like in their general appearance, indeed they have been as- sociated more than once with the Night-jars, and even with the Swallows! As might be supposed, they bear a superficial likeness to the Swallows on account of the length and shape of their wings; but a very cursory examination is sufficient to show their Pluvialine affinity. Nearly allied to these birds are the long-legged “ Coursers” (Cursorius) of Europe, Africa and tropical Asia, one species indeed occurring as an occasional visitant to the shores of Great Britain. The “Seed-plovers” or “Seed-snipes” of South America are no less un-plover like in their general appearance. Indeed from their general appearance they might well pass for some sombre-coloured member of the Fowl tribe, or Sand-grouse. In many of their habits indeed they also recall the Gallinaceous birds, nevertheless they are unquestionably aberrant Plovers. The “Jacanas” (Parridg) again serve as pitfalls to the unwary, inasmuch as superficially they bear a much closer resemblance to Rails; and this likeness is rendered the more striking on account of the great length of the toes, which is further exaggerated by claws of enormous length. Almost as puzzling, at first sight, are the Crab-plovers and Sheath-bills. The former are long-legged, black and white birds with a short, heavy beak. Maritime in habit they occur — commonly along the East Coast of Africa from the Red Sea to Natal, as well as along the northern and western shores of PHYLOGENETIC ci the Indian Ocean. The “ Sheath-bill” or “ Kelp-pigeon ” bears, as its name implies, a by-no-means Plover-like aspect, but rather a likeness to the Pigeons, which birds it further resembles in its flight and methods of courtship. Snow-white in plumage, it is remarkable in many ways, and especially on account of the peculiar tubular sheath which covers the base of the beak, giving the bird, in this particular, a semblance to the Petrels. Natives of the extreme south of South America, the Falklands, Crozets and Kerguelen, this Plover is essentially a bird of the seashore; it is frequently indeed found far out at sea, where it appears to be as much at ease in the water as more aquatic types, such as the Gulls for example. But this bird is further referred to elsewhere (p. 446). These aberrant types are of extreme interest, representing, as it were, Nature’s experiments at Plover-making. They are at any rate offshoots which started on their several roads to specialisation before the more typical Plovers began their evo- lution. And this also is true of the Gulls and Auks. By the older systematists, and some modern Ornithologists who judge solely by appearances, regarded as allies of the Petrels, the Gulls are nevertheless to be regarded as archaic but highly specialised Plovers, the Skuas representing the earlier and the Terns the latest phases of evolution. Just as the Gulls were, and still are by some, regarded as allies of the Petrels, so the Auk tribe were, and are, regarded as related to the Divers (Colymbi). Yet they have not the remotest relation to these birds, but are on the contrary in- tensely modified Plovers adapted for an aquatic mode of life (Pp. 450). By most authorities, and we think rightly, the Pigeons and the Sand-grouse are included in this assemblage of Plover-like birds. It is possible, however, that the older workers in this case were right who saw in these birds Gallinaceous characters. At any rate Dr. Mitchell holds that in so far as the evidence of the convolutions of the intestines is concerned the Pigeons and Sand-grouse, and that paradox the Hoatzin (Opisthoco- mus) of South America, are all derived from a common stem, running parallel with branches which gaverise to the Gallinaceous birds, Tinamous and Turnices (p. 75). We cannot, however, agree that other anatomical facts lend support to this view. 56 A HISTORY OF BIRDS The characters which the Pigeons and Sand-grouse share in common with the Plover tribe are indicative of a common descent. The several stems, in short, represent the splitting up of a common ancestral stock, indicated in the diagram by B II., 1, and this sufficiently explains the fact that the Pigeons would seem to incline more towards the Galli than towards the Plovers in the matter of intestinal convolutions. We have arrived now at a very critical point in the problem of avian descent—the question of the relationship of the “ Cora- ciiform” birds to the “Passeres,” and the position of both with regard to the rest of the Neognathine birds. As to the wider question: the weight of evidence seems to show that the members of this great group, collectively known as the Coraciomorphe, must be regarded not so much as an offshoot of any other of the groups so far considered, as an independent stem of great antiquity: a derivative of that generalised stock whose descendants represent the Neognathine types so far reviewed. Yet there seems to be some sort of affinity, though remote, between the Coraciomorphz and the Gallinaceous birds, as if the two were to be regarded as having had a common origin, such as is indicated in the diagram B II., 2. If it be admitted that this interpretation is correct, there still remains for settlement the position of the Passeres. So far the evidence seems to show that they are to be regarded as derivatives of a Caprimulgine stock. But to this point we must refer again after passing in review the principal groups of the Coraciomorphe. MAIN LINES OF EVOLUTION Before proceeding to the further sections of this work it would be well to briefly review the main lines of evolu- tion which the avian stock has undergone. The earliest bird known, it will be remembered, was of a strictly arboreal type, and we have shown that it is almost certain that this had been evolved from an arboreal reptile stock. In other words, the Class Aves began its development as a forest haunting tribe. From this environment it appears to have spread to more open country. This migration must have been followed by material changes of form in adaptation to the new environment, the avoidance of new enemies, the capture of new food, the forma- Passeres Halcyones Coli Caprimulgi Cypseh Momotus Striges Buccones Upupe Coracn Cuculi Psittaci CoLuMBLy Prerocles — Oedicnemidae Cathartes 4Falcones Alcidee Charadrii S od . CHARARADRIIF & steganopodes Fatconir \ Lori ieont! Glareoli Anseres Dromas Chionis Rhinocheetus Thino Ewryeye Psophia Otides -corys i CiconiFoR Tubinares. ‘ js GRUIFORM . Ralli eliornis Sphenisci Mesites Carta oe Grues Opisthocomus Alectoropodes Colymbi z Hesperornis GAtiFORMES Tinami Peristeropodes Rhea Apteryx giDinornis: Casuari FE pyornis Struthiones JARCHAOPTERYX 4 ‘Pro Aves ILL. 15.—-PHYLOGENETIC TREE OF DESCENT PHYLOGENETIC 59 tion of new nesting habits, and so on. But of all this we have little or no evidence, except that, in all probability, the Ostrich tribe of to-day are the most primitive survivors thereof. So far as the evidence of fossil forms goes, however, it would seem that some of these terrestrial types must have found very early that the neighbourhood of water furnished the most suitable conditions of life, since, after Archeopteryx, the earliest known fossils are of aquatic birds, and this too of a remarkably specialised, intensified type. And it is significant that aquatic and semi-aquatic types dominate to-day, for, except the Gallin- aceous and Raptorial types and the forms presently to be con- sidered, all the rest of modern birds are either waders or swimmers, in greater or less degree, though here and there are isolated exceptions—such as the Bustards among the Crane tribe on the one hand, or the curious Dippers among the Passer- ine birds on the other. The principal types of these waders and swimmers we have already cursorily outlined, and they will be dealt with later in greater detail as occasion demands. As to the Gallinaceous birds, they are still essentially forest birds, or birds which frequent thick undergrowth; while the birds of prey have adopted a roving life, they are essentially birds of the air. The Coraciomorphze, to which reference has been made, make up a very heterogeneous collection, which may be divided into Passerine and non-Passerine, derived, there seems good reason to believe, from a stock nearly akin to the Gallinaceous birds, and this stock apparently split up at a very early date, in- asmuch as their present-day descendants are for the most part separable into a number of sharply defined groups affording no very decided connecting links. Probably the oldest are the Cuculz—Cuckoos, and Plantain-eaters (Musophag?)—and the Parrots (Pstttac’). They may be safely regarded as divergent branches of a common stem, which may be assumed to have its roots in that which gave rise to the Gallinaceous birds. In common with these two branches—the Cuculine and Psittacine, there came off a third, which, splitting up, gave rise to the Upupide (Hoopoes and Hornbills), the Pici (Woodpeckers), Capitoniidz (Barbets) and the Coraciiformes, this last branching into the Coraciidz and Bucconide (Rollers, Puff-birds), the Meropidz (Bee-eaters), Momotide (Motmots) and Halcyones (Kingfishers). 60 A HISTORY OF BIRDS From the Caprimulgine stem there arose a branch which gave rise to the Striges (Owls), Cypseli (Swifts and Humming- birds), Colii (Mouse-birds) and the “ Passeres ”. The Coraciomorphine stem should probably be regarded as extremely ancient. It is highly probable indeed that we should be near the truth, as we have already hinted, in consider- ing it as arising from the same generalised stock as that which gave rise to the Pelargocolymbomorphine, and Alectoromor- phine trunks. Finally, the gradual splitting up and differentiation of this great Coraciomorphine stem has been largely due to adaptation and to the pursuit of food. And these adaptations we shall discuss in due course, at least in their more salient features. NUMERICAL STRENGTH In the matter of numbers the Class Aves far outnumbers all other vertebrates, since about 19,000 species are now known to science. It is significant to note that the Fishes approach nearest to the Birds in this matter, since between 8,000 and 9,000 living species are known. Of the Amphibia there are probably not more than 1,000 species. Of Reptiles some 3,500 have been described, and of Mammals between 2,000 and 3,000. This numerical superiority of the Birds and Fishes must be ascribed to the comparative absence. of barriers to their dis- tribution. As to their past history there is little to be said, for the records of the rocks have revealed less on this head than on any other group of'vertebrates. Such fossils as are of import- ance, however, are described later in this work. 1 CHAPTER IV (ECOLOGICAL Peculiarities of distribution. Continuous and discontinuous areas. Zoo- geographical regions. The northern and southern hemispheres and the origin of life. Some British birds and the lessons they teach in regard to the migra- tion of animal life from north to south, Factors in the formation of isolation areas. The haunts of birds. GEOGRAPHICAL DISTRIBUTION T is a matter of common knowledge that in passing from I one region of the world to another strange types of birds are sure to be met with, and it is commonly supposed that the tropics are especially rich in this respect. This, how- ever, is by no means true, nor are the differences between the various types encountered in the different regions of the world correlated with the distance which separates these several regions. Thus, as has been more than once pointed out, the birds of Great Britain and Japan bear a remarkable likeness one to another, a much greater likeness than obtains between the birds of Africa and the adjacent island of Madagascar. Yet one-fourth of the circumference of the globe separates the first two countries, while the last two are divided only by a few miles! Again, a very varied avifauna may be found within the confines of the same country; and this especially where the surface of the land is diversified by mountain and moor, forests, swamps and lakes. And when this avifauna as a whole comes to be more closely studied, it will be found to contain more or fewer types met with in no other part of the world, so that the area over which such forms are spread is to be re- garded as forming a distinct zoological province. The differences between the birds met with in any given country are due to one or other, or a combination af several ‘ 61 62 A HISTORY OF BIRDS causes—temperature, food and physical peculiarities. Thus Woodpeckers, ‘for example, will be confined to the forests, Bus- tards to the dry plains, Grebes and Divers to the lakes. In other words, any given species is to be sought for only in suit- able spots within the distributional area,and these spots are known as the “stations” of the species within that area. Thus a clear distinction is to be drawn between the area of distribution— the “locality” or “habitat” of the species—and its “station”’. This last, as we have already hinted, is more often represented by a series of discontinuous areas—or isolated stations—than by one continuous tract. Passing now to some of the more general peculiarities of distribution it is to be remarked that though, in surveying the habitat of any particular species one may expect to find that species in more or fewer numbers wherever suitable conditions occur, this expectation is by no means always realised. The curiously local distribution of birds like the Nightingale, Red- start and Stonechat, for example, among our British birds well illustrate this point, since these birds may be tolerably abundant in one place and yet appear to shun areas in the im- mediate neighbourhood which seem in every way suitable to their needs. More remarkable still are those cases where the “ stations” are not so many isolated spots dotted over a continuous area, or zoological province, but are separated by enormous distances, are scattered, in short, over one or more separate zoological provinces. These cases of “discontinuous distribution” are of peculiar interest, for they show, in the first place, that, in the majority of cases, species so isolated must have become so by the extinction of more or fewer intermediate “stations”. Such widely sundered sanctuaries, so to speak, as isolation areas, play an even more potent part in the evolution of species than do stations dotted over a continuous zoogeographical area. But of this more anon. Thus, then, it has come to pass that the Ornithologist, in studying the birds of the world—as one might study the people of the world—ignores political boundaries, and divides the surface of the earth according to the dominant and peculiar types of birds which are characteristic of such and such areas. The governing factors in this distribution are many—climate, ZOOGEOGRAPHICAL AREAS ILLUSTRATING THE DISTRIBUTION oF BIRDS By R_ BOWDLER SHARPE. 1893. On Lamberts Fputvatent \ Ks 22g : sign >. Le el. 2) 0 io 160 No ISOTHERMAL LINES | YEAR [ed 49 REFERENCE | TO ZOOGEOGRAPHICAL REGIONS, SUB-REGIONS, PROVINCES, & SUB-PROVINCES C. PALAARCTIC REGION. E. INDIAN REGION. : TIG REGION. [7 dan tie Sub-Re ton Indian Peninsular Sub-Reg. 1 ees pei jpieeliaie SS Indo. Malayan Sub-Region, ed East Siberian Province. | | Himato-Maiayan Sub-Reg. Region. \@| Manchurian Sub-Region. (84) Hémalo-Chinese Sub-Region. Mediterrance-Asia ar |) | iS =| Mediterranca eee F, AUSTRALIAN REGION. Mediterranco-Persic Prov. (75) se | Wl Mongolion Province. 1 Celebean Sub-Repion. [7 |v B |Himate-Caucasian SubReg. Nog Veluccan Sub-Region. DAD avicprce.« sonerun Sut-rree. __ D. ETHIOPIAN REGION. [| Papuan Sub-Region. B, NEOTROPICAL REGION. 54 7a" Sub Keron. eA malate ae cesar: Antilican Sub Region. L323 | West Arrican Sud Regie Central American Sub-Reg. 2 Mexican Province. ae} Isthmian Previn al _ Patagonian Sub-K 3 6) ance: Campestrian Suds 8 6 | Fiyian Sud-Region. Hawaiian Sub Region * [5] Brazilian Sub-Rei 6 CECOLOGICAL 63 temperature, rainfall, vegetation, altitude; while lastly, but by no means leastly, we must reckon with the past—the upheavals and subsidences, and changes of climate which have done so much to change the relative proportions of land and water during the last million years or so, As the history of the rocks bear testimony, land was where now an ocean heaves and swells: what are now continents have more than once been submerged areas. And these upheavals and depressions, as the sequel will show, are responsible for many of the enigmas of distribution to-day. There seems good reason to believe that birds, in common with other vertebrates, originated in the northern hemisphere and gradually travelled southwards, forming, as they moved, so many fresh centres of evolution and distribution. This hypothesis explains much that would otherwise appear inex- plicable, and furthermore is supported by the fact that the earliest known fossil birds have been unearthed either in Northern Europe or Northern America. With the formation of the existing continents migration became restricted, and new evolutionary centres came into being ; and the number of these increased as the sea, from one cause or another, cut off more or less extensive areas of these continents to form islands, or as oceanic islands came into being and afforded new areas for colonisation. And thus it is that, as a general survey of the larger groups of birds will show, certain more or less distinct ornitho-geographical areas or “regions” may be distinguished. At the present time the regions generally recognised are the :— g Palearctic. Ethiopian. . Indian. . Australian. . Nearctic. Neotropical. AunAp WN By some authorities, and with much reason, the Palearctic and Nearctic Regions are regarded as forming but one great “ Hol- arctic” Region. But be this as it may, these several regions are further divided into numerous sub-regions and provinces, the more important of which we shall now proceed to define. 64 A HISTORY OF BIRDS The Palzarctic Region embraces the whole of Europe and Northern Asia, its southern limit corresponding roughly with the 30° Parallel of N. Latitude. What may be called the typical birds of this region are the Grouse, Pheasants and Capercailzie. It is divided by Dr. Bowdler Sharpe into five sub-regions :— The Arctic Sub-region.—The first in this list comprises the inhospitable land above the Arctic Circle, with the northern islands such as Kolguev, Nova Zembla, Spitzbergen and Franz Joseph Land; while it extends southwards of the Arctic Circle to include Central Siberia and the mountain districts of Siberia. That is to say, this area is not determined merely by latitude, but by physical conditions—altitude, temperature, vegetation. Here dwell the Gyr Falcon, Steller’s Eider-duck, Bewick’s Swan, the Little Auk and Brunnich’s Guillemot, while the Knot and Curlew Sandpiper, among the waders, continue to find, in this apparently forbidding environment, a safe breeding place, spending the winter in more southerly regions; the Hawk Owl and Snowy Owl and the Snow Bunt- ing, on the other hand, are permanent residents. The Eurasian Sub-region includes the rest of Europe, most of Central Asia and Siberia to the Pacific at about Lat. 55°. No very remarkable types are characteristic of this sub-region. All the “ British” birds occur here, as well as many continental types which do not occur in these islands. In the Mediterraneo-Asiatic Sub-region are included the Mediterranean countries south of the Alps, and Carpathians, Persia, Central Asia and Thibet. As might be expected, in addition to typically Palearctic birds, such as Crows, Chats (Saxicola), Warblers, Tits, Buntings and Larks, a mingling of African, Indian and Chinese forms are met with, such as the Glossy Starling (Hagzospar tristramz) and a Sun-bird (Cinnypris osea), which are African, and the Fishing Owl (Kezupa), which is Indian. As touching the Manchurian Sub-region, Dr. Sharpe re- marks: “From the Yangtze Valley north to about 55° N. Lat. and eastwards to about Long. 100° there are found so many remarkable forms of birds that a natural sub-region must be assigned to the area they inhabit”. Not the least interesting feature of the birds herein met with is the fact that they closely CECOLOGICAL 65 resemble European birds, but yet differ sufficiently to be re- garded as distinct species. Our British Rook, for instance, has become replaced by, or shall we not say, transformed into, the Chinese Rook (7rypanocorax pastinator), and our Jackdaw into the White-necked Jackdaw (Coleus dauricus), while some forms, such as Pericrocotus and the curious Suthora, are met with in this sub-region, as also are the tropical Black-headed Kingfisher (Halcyon pileata) and the Blue Roller (Eurystomus calonyx). The Atmalo-Caucasian Sub-region is regarded by Dr. Sharpe as a well-defined sub-region of great importance. Herein he includes the Himalayas, in the higher ranges of which, above 8,000 feet, several genera are met with that occur nowhere else, such as the Snow-cocks (7e¢raogallus) and the Hill Partridge (Lerwa). Since the Snow-cocks occur also in the lofty ranges of the Altai Mountains, as well as in the mountains of Northern Persia, the Caucasus and Asia Minor, these ranges are also included in this sub-region. THE ETHIOPIAN REGION This great region includes the whole of Africa south of the Tropic of Cancer, and the islands adjacent to the Continent. The territory to the north of the Tropic of Cancer is regarded as belonging to the Palaarctic Region. Some authorities, however, contend that the Palearctic area should not be ex- tended beyond the Atlas Mountains. Quite a number of peculiar types belong to this great region, such, for example, as the Ox-peckers (Buphagide), Madagascar “Starling” (Huryceros), the Wattled Ant-thrush (PAzlepitta), Plantain-eaters (Musophagide), Kirombo (Leptosoma), Colies (Colitda), the Secretary-bird (Serpentarius), the Guinea-fowls (Numidide), and last, but not least, the Ostrich (Sz¢ruthzo). The Ostrich, indeed, is the most characteristic bird of the Ethiopian Region. Though at one time regarded as represent- ing but a single species, at the present at least three are re- cognised—Szruthio camelus, S. australis and S. molybdophanes. Some authorities further admit a fourth, S. massazcus. Since the distribution of these several species at the present day does not quite accord with the sub-regions presently to be described, they are referred to here as birds characteristic of the regions 4 66 A HISTORY OF BIRDS as a whole. “The Common or Northern Ostrich,” writes Mr. Ogilvie Grant, “is found in Northern and Western Africa, and ranges eastwards to Abyssinia, Arabia and South Palestine; ... S. massaicus is found in East Africa, S. molybdophanes in Somaliland and Central Africa, and S. australis in South Africa.” But it must be remembered that the Ostrich, though the characteristic bird of Africa to- day, was not always confined to this great Continent, since fossil remains thereof have been found in India and in Europe, a point to which we shall have occasion to refer later. As to the number of sub-regions into which the great area should: be divided opinions are divided. Dr. Sharpe recognises eight. These are :— I. The Saharan. II. Sudanese. III. West African. IV. Abyssinian. V. East African. VI. South African. VII. Cameroonian. VIII. Lemurian. Of the Saharan and Sudanese Sub-regions the ornithology ~~" practically unknown. So far we may say of the Saharan Sub- region that it is the land of peculiar desert forms, conspicuous among which are Larks and Chats. The Sudanese Sub-region includes the country to the south of the Sahara, extending northwards to Nubia below the Nile Delta and including the western and southern shores of Arabia, and the east coast thereof as far as the Straits of Ormuz. “ There is evidently,” remarks Dr. Sharpe, “a connection be- tween the avifaiina of Senegambia and that: of Abyssinia evidenced by the occurrence in both countries of such birds as the Abyssinian Roller (Coraccas abyssinica) and by certain of the Game-birds, It is a country of Francolins, Quails and Bustards. Many species of birds are peculiar to this sub-region, and here too many European migrants pass the winter. The West African Sub-region extends from the forest regions of Southern Senegambia to the Gold Coast, and after a small gap caused by the interposition of the Sudanese Sub-region at CECOLOGICAL 67 Accra, is continued practically without a break to the Cameroons, Gaboon and the Congo as far south as the river Coanza in Angola. Inland it extends to the western watershed of the Nile. The genera and species of birds ‘peculiar to this sub- region are many, and of these the most interesting are perhaps the Cuckoo-falcon (Baza cuculoides), and the curious Black and Turkey-like Guinea-fowls of the Genera Phasidus and Agelastes respectively. But beside these, in this sub-region we meet with genera both of Malayan and Indian types. Thus, of Malayan birds the curious Genus 7urdinus is represented by several species. The Ant-thrushes (P7té#d@) are eastern types, occurring in greatest plenty in the Indian peninsula and the Himalayas eastwards to China and Formosa, and throughout the Malayan Archipelago as far south as New Guinea and Australia. The Flower-peckers (Diced@) again are Indian and Malayan forms, but they also occur in West Africa. The limits of the Abyssinian Sub-region are by no means well defined, nor are the precise features of its avifauna easily demonstrated, though some 200 or more species are peculiar _. thereto. The most interesting of these is the bizarre-looking < Shoe-billed Stork (Baleniceps). But perhaps the most interest- ing feature of the birds of this area is the occurrence there, as actual residents of its mountains, of the Alpine and Cornish Choughs! birds which occur elsewhere only in the Palearctic Region. Here again is another instance of discontinuous dis- tribution, another instance of the important part played by physical conditions in avian distribution. Whether the East and South African Sub-regions will prove to be natural and well-defined areas is open to question. Time may prove that they will have to be ignored. The Cameroonian Sub-region is remarkable in many ways, and especially in that it is made up of a series of isolated areas, consisting of the elevated mountains of Central East Africa, and extending north and south from the highlands of the lake regions and across to the peaks of the Cameroons on the west coast! Some of the more remarkable forms met with in this region have already been referred to. The Lemurian Sub-region is characterised by a number of 68 A HISTORY OF BIRDS very remarkable forms, indicating a long and complete isolation for the areas here included. It is made up of the large island of Madagascar, and the adjacent Mascarene Islands—Reunion, Mauritius and Rodriguez, and the islands to the north, including Pa ILL. 16.—THE WHALE-HEADED Stork (Baleniceps) the Seychelles, Ofliving and extinct birds the islands included in this sub-region possess a richer collection of distinct and peculiar types than any other region in the world, on which CECOLOGICAL 69 account some authorities regard the Lemurian as a separate, primary region. Among extinct types may be mentioned the Giant Epyornis of Madagascar and the aberrant Giant Pigeons—the Dodo and the Solitaire of Mauritius and Rodriguez respectively. No less remarkable was the extinct Starling (fvegi/upus) of Reunion. But beside these must be mentioned an extinct crested Parrot (Lophopsittacus mauritians) of Mauritius, and a very remarkable flightless Rail (Aphanapteryx) of the same island. On Rodriguez lived a Rail closely resembling Aphanapteryx (Mtserythrus equati), a large brevipennate Heron (Ardea megacephala), a big Parrot (Necropstttacus rodertcanus) and a small but peculiar Owl (Athene murivora). Turning now to the living species, we have in Madagascar some 240 species, of which 129 are peculiar to it, and among these are no fewer than 35 peculiar genera. The so-called Madagascar Starling (Huryceros), more nearly allied to the Shrikes, the curious Pz/efitta, and the still more remarkable Mesites are found only in Madagascar. The Ground-rollers (Atelornis) and the aberrant Leptosoma also occur here. The indigenous fauna of the Mascarene Islands has been practically “wiped out” by the inroads of civilisation. Mauri- tius and Reunion, lying within sight of each other, seem to have but three species in common, and there is one genus Oxynotus which is peculiar to these two islands, each possessing its own species. Rodriguez has now left to it but three species, all peculiar, and of which the Parrot (Pal/gornis exsul) is the most noteworthy. The land birds of the Seychelles are sixteen in number, and of these fourteen are peculiar. THE INDIAN REGION Though the Indian Region embraces an enormous area, and presents extremely varied physical and climatic conditions, yet it has produced no strikingly peculiar groups. Its avifauna indeed is made up, almost entirely, of genera and species to be met with in other regions, notably the Palzarctic and Ethiop- ian. The most aberrant group which occurs here is that of the “ Broad-bills ” (Zury/emz), which represent the most primi- tive known Passeres; while the remarkable Paradorxornis, an 70 A HISTORY OF BIRDS aberrant Tit, and the strange Pink-headed Duck (Rhodonessa caryophyllacea) also belong to this region, and are met with nowhere else. Nevertheless, when the fauna is studied as a whole more or less distinctly defined zoogeographical areas can be made out, though as to their number and boundaries authorities differ. Dr. Bowdler Sharpe, for instance, recognises no less than five Sub-regions, while the late Professor Newton admitted but three—the Himalo-Chinese, the Indian (proper), and the Indo- Malayan. In the first and last, as may readily be perceived, Chinese and Malayan species respectively are conspicuous. The Himalo-Chinese Sub-region includes the southern slopes of the Himalayas, from their base to the limit of the growth of trees, and beginning with Cashmere extends through Nepal and Bhutan, thence to the coast of China. It includes all Burma as far as the middle of Tennasserim, and for the rest its southern and eastern boundaries are those of the Asiatic Continent, while to the Chinese portion belong the islands of Hainan and Formosa. This great sub-region is to be regarded as the great centre of distribution of the Pheasants, which include a number of striking though generally unfamiliar forms. For the most part strange in appearance, and often of marvellous beauty, they deserve more space than can be allotted them in these pages. It would be impossible, however, to do them justice in anything less than a monograph, and after all, this chapter is mainly concerned with the distribution of the various types of birds, and the relation which this distribution bears to the sub- ject of evolution, The number of Pheasant-like birds which occur in this region, and are confined to this region, is remark- able; and not the least noticeable fact is the conspicuous place which the Himalayas hold as a distribution centre. A large proportion of the genera now to be enumerated is to be met with here. Here, for example, are to be found the curious Blood-pheasants (/¢thagenes), and from thence they may be traced to the allied chains of mountains in North-West China. They are forest birds, living at a great altitude near the snow- line. The wonderful Horned-pheasants of the Genus Tvagopan are met with both in the Himalayas and in the hills of Assam and South-East China; while the marvellously beautiful CECOLOGICAL m1 Moonals or Impeyan-pheasants are confined to the Himalayas and the mountains of Assam and West China. The curious Fire-backed-pheasants of the Genus Acomus and Lophura are inhabitants of the mountains of the Indo-Chinese provinces and Malayan Peninsula and Islands. One of the most remarkable of all the Game-birds—the Lobed-pheasant (Lodiphasis) occurs only on the high mountains of North-West Borneo, the Lawas River, and the region of Mount Dulit. The Eared-pheasants of the Genus Crossoptilum—the sexes of which are peculiar among other things in being alike in plumage—inhabit the woods clothing the high mountains of Thibet, West China and Manchuria, living in flocks. The Silver and Kalij Pheasants inhabit the Himalayas and the hills of Assam and Burma, ranging from 1,000 to 9,000 feet. Besides these, mention must be made of the curious Koklass Pheasants (Pucrasia) and the Barred-backed-pheasant (Cal/ophasis). The former range along the Himalayan chain from Afghanistan eastwards to Thibet, and the mountain ranges of South China and Fokien and Manchuria. The latter are represented by two species only; one, C. edtot?, from the mountains of South-East China, and the other, C. ume, from the Shan States. The beautiful Golden-pheasant (Chrysolophus pictus) and the even more remarkable Amherst-pheasant (C. amhersti@) are conspicuous ornaments of this region, the Golden-pheasant inhabiting South and West China and Kokonoor, Lady Am- herst’s West China and Thibet. The wonderful Peacock- pheasants belong to the Himalayan system of mountains extending from Sikkim to Tennasserim and Cochin-China, and thence to the Malayan Peninsula, Sumatra and Borneo, affect- ing forest country up to 6,000 feet. Here is the home of the Pea-fowl which are represented by two species, the Common Peacock of India and Ceylon, and the Javan Peacock (Pavo muticus) of Indo-China and the Malay Peninsula. These are birds of the plains rather than of the mountains, which they ascend, however, occasionally. Plentiful in the plains of North-West India they will not long remain so unless some restriction is placed on their slaughter for decorative purposes. Passing now to the Indian region proper, which includes the whole of the Peninsula from the base of the Himalayas to 72 A HISTORY OF BIRDS Ceylon, little to any profit can be said, for though much has been written on the avifauna of separate districts of this great area no general summary and analysis thereof has so far been made. The Indo-Malayan Sub-region, which is made up of the Peninsula of Malacca, the great Islands of Sumatra, Java and Borneo, and the Philippine Archipelago, possesses a rich and interesting avifauna, though, it is to be noticed, it is remark- able not as the home of any peculiar groups of birds, but rather for striking species and genera, which are represented either in the Indian region proper, or in regions more or less remote therefrom. Perhaps the most remarkable ofall the birds to be met with in this sub-region are the Argus-pheasants, the Common Argus (Argusianus argus) of the Malay Peninsula ; Gray’s Argus (A. grayt) of Borneo, and A. b2-punctatus, the habitat of which so far remains a mystery. In Tonquin the allied crested Argus (Rheinhardius ocellatus) occurs, THE AUSTRALIAN REGION The Australian Region is one of peculiar interest since it is pre-eminently a region of islands, a region of isolation areas. It embraces not only the vast Continent of Australia, but all the islands of the Pacific lying between the Tropics of Cancer and. Capricorn, except those lying to the west of a line passing between Lombok and Celebes aid south of the Philippines. The narrow strait indicated by the line just referred to does not exceed twenty miles in breadth, yet it must be regarded as one of great antiquity, and this because it is of great depth: the avifauna east and west thereof presents entirely different characters. The faunas of the two areas are—east and west of this line—as distinct as those of South America and Africa. A certain amount of interchange has taken place between the land areas adjacent to the dividing strait, but this was to be expected. The avifauna to the west of the strait is Indian, that, to the east Australian, Space forbids anything like an analysis of the genera and species peculiar to the Australian Region, or even of the Sub- regions Australian, Papuan and Polynesian, which some author- CECOLOGICAL 73 ities recognise. Let it suffice to say that here is the home of the Birds of Paradise and of the Bower-birds; of the remark- able Lyre-bird, and of the Emus and Cassowaries, concerning which last we have already had something to say. Many peculiar forms of Parrots occur here, and this region is also to be regarded as the headquarters of the remarkable “ Brush Turkeys,” or Megapodes. Some of the most remarkable of known Kingfishers and Divers belong to this region, and here also occurs that aberrant Crane the Kagu (Rhinochetus)— a very strange form confined to the Island of New Caledonia— and that anomalous bird the Black Swan. THE NEW ZEALAND REGION While some choose to regard New Zealand as an Australian sub-region, others prefer to regard it as entitled to rank as an independent region, since it harbours the most remarkable and interesting of insular faunas. Here, almost within historic times, Jived the Moa; and here to-day dwells the curious and aberrant Apteryx. The re- markable and flightless Weka-rail, and the still more remark- able flightless Giant Gallinule Notornis are products of this region. The last-named was first described from fossil remains. A year or two later, to the delight and surprise of Ornitho- logists, a living example was found, and since, three others have been obtained. By some, however, the fossil remains are regarded as specifically distinct from these later captures. This determination, however, is open to question. The flight- less Parrot known as the Kakapo is another of New Zealand’s peculiar birds. This region, indeed, possesses a larger number of flightless birds than any other in the world; and this because the conditions of existence all tended to favour the development of such types, there being no carnivorous mammals to contend with, an abundance of food, and an equable climate. The Giant Moas, it must be remembered, were flightless ; indeed, so long had they thriven in this condition that the fore-limb had actually become so completely suppressed as to leave not a trace of its existence behind. And besides this, we have to record a giant flightless Goose (Cwemiornis) allied to the Cereopsts Goose of Australia. The curious Wrybill Plover (Anarhynchus) and the equally strange Huia-bird must also be 74 A HISTORY OF BIRDS mentioned here. The Kakapo or Owl Parrot, by the way, is not the only peculiar Parrot of New Zealand, for here is the home of the Kea or Kaka, a bird which has acquired an evil reputation among the flock-masters of New Zealand on account of its alleged attacks on sheep. Such, in brief, are the more striking forms of the New Zea- land regions, but there are besides a number of peculiar genera and species which bear out what has already been said as to island faunas. We pass now to the NEARCTIC REGION. The Nearctic Region, according to some authorities, as we have already remarked, should be regarded as forming, with the Palearctic Region, one great zoological area known as the Holarctic Region. For convenience sake, however, it may be well to consider the Pala- and Nearctic Regions as distinct, though the faunas thereof present a remarkable similarity. Though by some the Nearctic Region extends southwards to Mexico, by others it is regarded as terminating at about Lat. 38° N.; the area south of this line to Mexico being dis- tinguished as a separate region, or sub-region, according to fancy—the “Sonoran” Region. There are, however, no natural boundaries along the northern frontier of the Sonoran Region, and much intermingling of the faunas thereof naturally takes place, It is in short a by-no-means well-defined region. A considerable number of the Passerine birds of the Nearctic Region occur also in the Palzearctic: such, for example, are the Tits (Parus), Creepers (Certhiicle), Wrens (Anorthura), Shore- lark (Otocorys) and Wax-wing (Ampelus). But this region possesses a number of peculiar types, quite unknown in the Pale- arctic Region. Such are the Hang-nests (/cteride), Greenlets (Vireonide), American Warblers (Minotiltide) and Tanagers (Tanagride); and besides these there are others, such as Humming-birds and the “New World” Vultures, which are common to the Nearctic and Neotropical Regions, to the con- sideration of which we shall now pass. THE NEOTROPICAL REGION The Neotropical Region includes the West Indian Islands and the whole of the American Continent from Mexico south- CECOLOGICAL 75 wards. In the richness of its bird-life the Neotropical surpasses all the other regions of the world. Here are found the Ostrich-like Rheas and Tinamous, the curious Game-birds known as the Guans and Currassows, and the Hoatzin, the aberrant Goose-like birds known as the Screamers (Palamedea and Chauna), and those aberrant Cranes (Psophia and Aramus), the Seriemas and the Sun-bittern (Aury- ILL. 17. —THE Rurous Tinamou (RAynchotus rufescens) pyga). Among the Plover-like birds we find the Seed-snipe (Thinocorys) and Chionis. A host of peculiar Parrots, Cuckoos and Kingfishers occur here, and to these must be added Jaca- mars and Puff-birds, Toucans, Motmots, and a vast number of primitive Passerine types, such as the Manakins (Prprde), Chatterers (Cotingide), Plant-cutters (Phytotomide), Wood- hewers (Dendrocolaptide), Ant-birds (Formicariidg), Ant-wrens (Camopophagide) and Tapacolas (Preroptochide). But besides the foregoing we have the primitive Passerine Tyrant-birds (7yrannid@), the Humming-birds and the “New World” Vultures (p. 454), which occur also in the Nearctic Region, and a number of other peculiar types which are found 76 A HISTORY OF BIRDS also in Africa, India and the Malayan Region, the distribution of which we propose to speak of presently. Such, in brief, are the main outlines of the Zoogeographical Regions of the world. To have worked this out in fuller detail a whole volume would be required, and those who desire to acquaint themselves more fully with this subject should consult the works of such exponents of the subject as Russel Wallace, Sclater, Lydekker, Beddard, Heilprin, Sharpe and others. In the earlier part of this chapter a reference was made to the phenomena of continuous and discontinuous distribution. Let us return now to a more careful, if brief, consideration thereof. The older writers held that similar forms occupying isolated areas were to be regarded as independently created forms, but this, in the light of modern biological science, cannot be regarded as a tenable hypothesis. How, then, are we to explain the fact that certain families and genera of birds are confined to certain well-defined areas in Africa and South America, for example, on the one hand, and to Africa, India, the Indo-Malay Peninsula and Australia on the other? This question has already been discussed by other writers at various times, and many interpretations of the riddle have been offered. Space forbids anything more than a bare outline of the two most probable of the suggested explanations of this matter. Briefly, according to one hypothesis, these forms, in common with others of cosmopolitan range, originated in a great southern land area, circumpolar in extent, which, extending northwards, served during tertiary times to link together the several Continents concerned in this discussion. For this Continent Dr. H. O. Forbes—the originator of the hypothesis—suggested the name “Antarctica”. It apparently followed the 2,000 fathom line extending northwards by broad expansions to join an old New Zealand continental island (including the Antipodes, Macquaries, New Zealand and Chatham, Lord Howe, Norfolk and the Kermadec and Fiji Islands); a second to East Australia and Tasmania; a third to the Mascarene and adjacent islands; perhaps one to South Africa and finally one to South America. The Trogons, Parrots and Struthious birds were cited by CECOLOGICAL 77 Dr. Forbes as groups which supported his contentions as to the southern origin of animal life, these groups, at the present day, being still essentially southern types. Dr. Forbes’ con- tentions were, it should be remarked, not, however, based on the distribution of birds only, but of other groups of vertebrates as well. We are, however, concerned here only with the birds, and these do not support the theory of an Antarctic Continent. In the first place, so far from the Trogons, Parrots and Struthious birds being southern forms which later spread more or less northwards, there is evidence to show that they are northern forms which have spread southwards, for fossilised remains of Trogons and Parrots have been found in Oligocene beds in France, while fossil fragments of Struthious birds, allied to the existing Ostrich, have been obtained from the Pliocene of the Siwalik Hills, the: Government of Cherson,. Russia, the Lower Pliocene of Pikermi, Greece, and from that of the Island of Samos in the Turkish Archipelago. The Secretary-bird (Sevpentarius), now confined to South Africa, is represented by remains from the Miocene of Allies. More than this, the earliest known bird, the Jurassic Archeopteryx, was obtained from the Solenhofen States of Bavaria, while the only other remains of toothed birds have come from the cretaceous formations of North America, eg., Hesperornis and Ichthyornis, and the Enaliornis from the Cambridge Green- sand (Upper Cretaceous) of England. Besides these we have the curious Odontopteryx—a bird with strongly serrated jaws —apparently related to the Gannet and Cormorant, from the London Clay (Lower Eocene) of Sheppey, Kent, and fragments of apparently Ostrich-like birds, Gastornis, from the Lower Eocene of Western Europe; Dasornis, from the London Clay of Sheppey and Diatryma from the Eocene of New Mexico. All these facts go to show that the northern hemisphere from remote times has been inhabited by a very rich and varied bird-fauna. And thence, in all probability, this fauna gradually spread southwards. The Penguins seem to be the only group of importance which has had a southern origin, and no species appear ever to have wandered north of the Equator. That Africa and South America were at one period joined by a land bridge there is but little room for doubt, but this connection was probably between the westernmost portion of 78 A HISTORY OF BIRDS North Africa and the easternmost extremity of South America. Into the evidence for this, however, there is no need to enter here, as this evidence is supplied by the facts of mammalian distribution, and will be dealt with in the volume dealing with this group. The peculiarities of avian distribution with which we are here concerned can be explained without the aid of a Southern Antarctic Continent. There are some significant facts, furnished by existing species, which support this contention, and these are provided by some of our commonest British birds. The Nuthatches, for example, represented in Great Britain by the Common Nut- hatch (Sz#ta costa), ranges throughout Europe, North Asia, North America, India, China, Indo-Malaya and Australia. The Gold-crests (Regulide), represented by two species in Great Britain, range throughout Europe, North Asia and North and Central America. The Wax-wings in Europe and Asia— essentially northern types—pass into North America and then southwards into Central America. The Dippers (Cznclide) range throughout Europe and Asia, and crossing into North America—vza North Asia—pass into South America. Now it is significant to note that there are certain Families which occur in Southern Europe which range into Africa and India, pass by the Indo-Malay Peninsula into Australia, but which do not occur in America, as for example, the Bee-eaters (Meropida), and others, as the Bulbuls, Hornbills and Trogons, which are met with only in Africa, India and the Indo-Malay Peninsula. These possibly originated in southern latitudes, and hence did not find their way into America, as did those which originated in Northern Europe. But there are some Families, such as the Barbets (Capiztones) and Jacanas (Parre) which are found in Africa, India, the Indo-Malay Peninsula and Australia, and South America. The occurrence of these birds in South America may be due to the land bridge between Africa and South America referred to already. Into the details of the distribution of these Families it is not the province of this chapter to enter, nor into the several species and sub-species, or geographical races, by which these Families are represented: our aim being to account for the discontinuous CECOLOGICAL 79 distribution which they present. The factors which caused the breaks in the continuity are naturally impossible to trace with any certainty, though occasional glimpses may be caught which may some day be turned to account. A very potent influence in the formation of isolation areas is undoubtedly to be ascribed to changes in the plant world, caused in turn by river systems, and changes in the level of the earth’s surface and consequent alteration in the condition of temperature, moisture and so on. Both insectivorous and vegetivorous birds are naturally vitally affected thereby, more particularly those which perform but limited migrations, or are non-migratory. The study of the haunts of birds is the study of geographical distribution on a minute scale. Just as we look for Humming- birds and Toucans only in America, Secretary-birds and Ostriches in Africa, and Lyre-birds and Emus in Australia, so we look for Petrels and Auks only in the immediate neighbour- hood of the sea, Grebes and Water-hens in fresh waters, Grouse on moors, and so on. And we know that while some birds may vary their haunts according to the season, others appear unable to affect any change whatever, and are consequently the more endangered in times of stress. Little then can with profit be said with regard to the haunts of birds, for the theme is too discursive. But one point is certainly worth considering, and this relates to the bird-life of large woods and forests. One would expect that such areas would teem with bird-life, yet such is not usually the case. Forests of deciduous trees such as are to be met with only in temperate climates are notoriously poor in bird-life, only the outer fringe being at all thickly populated. But here the tree-dwellers are free to scour the surrounding open country in search of food, for within the gloomy interior of such forests insect-life is scarce, and edible fruits are rare. Coniferous forests harbour a few highly special- ised species, such as Nutcrackers, Cross-bills and Wood-peckers. Tropical forests, from their more luxuriant growth, and the abundance of trailing, flower-bearing creepers, support a far larger and more varied avian population; but these dwell oz the forest, rather than zm it, as we shall show, CHAPTER V SEASONAL LIFE. RELATIONS TO MOISTURE, TEMPERATURE, ETC., AND TO PERIODIC CHANGES IN THE COSMOSPHERE. The bleaching effect of light. Desert forms. The effects of a saturated atmosphere. “Arctic conditions. Size and latitude. Storms and drought. LTHOUGH much valuable information has been ac- cumulated as to the effect of light, moisture and temperature on the lower invertebrate animals, but little in the way of close observation or experiment has been carried out with regard to the higher animals, and to birds in particular. In the following short account an attempt is made to bring together some of the more important facts which have been collected on this subject. These do not refer, however, to periodic, seasonal, climatic conditions, which will be discussed in another chapter. As to the direct effect of the action of light, and weathering, on the feathers of living birds little seems to be known. It would appear, however, to have a decidedly destructive influence, not only destroying the colour, but also bringing about the dis- integration of the horny tissue of the feather. This is well seen in the large quill or flight feathers of birds, such as those of the Plover tribe, which spend much time in exposed situations. These feathers, in the first place, if examined just before the annual moult takes place, will be found to have faded in just those areas which are left uncovered when the wings are closed, each feather, when the wing is extended, showing a silhouette of the feather next above it, a dark area representing the portion covered, and a distal light area representing the part subjected to “weathering”. Disintegration seems to accompany this fading, and to take place most rapidly in those parts of the feather which are unpigmented. Thus, in many waders, as in the Curlew, where the darkly pigmented areas of the feathers 80 SEASONAL LIFE 81 have deeply incised margins filled in with white, the latter dis- appears, leaving a dull rusty brown feather with a serrated edge as is shown in I]. 18. But Mr. Beebe, of the New York Zoological Gardens, made some experiments which seem to show, on the other hand, that strong light, in itself, may have the effect of intensifying colour. “T transferred,” he says, “a male Purple Finch, which had for several years moulted yellow, from a dark cage to one which was exposed to bright sunlight, and in one moult the bird assumed his original normal . colour”. But this may have been due rather to the more vigorous health of the bird, following on the improved conditions of captivity. Loss of colour certainly cannot invariably be set down to the action of light, for it is well known that many brilliantly coloured birds become more or less pallid in captivity. This is especi- ally noticeable in the case of Flamin- goes which lose their wonderful rose colour and become almost white in Zoological Gardens. The curiously bleached appear- ance of desert forms may possibly prove to be the result of intense light, or more probably light and a dry atmosphere accompanied by a high ILL, 18.—A WING FEATHER OF A CuRLEW SHOWING THE INITIAL STAGES IN THE Dts- INTEGRATION OF THE WHITE PaRTS: AND A PoRTION OF THE QuILL FEATHER OF A GuLL SHOWING THE SAME PROCESS Note the imperfect tip of the feather, and the worn inner edge of the white portion, and contrast w th the unworn black area, temperature, since the most pallid forms appear always to occur where the temperature is very high, and the air free from mois- ture. And it is well known that a sandy desert heats the atmo- sphere above it much more than a fertile tract or a watery expanse. As to the bleaching and the opposite effect of intensification, Mr. J. S. Whitaker, in describing, the various races of crested Larks met with in Tunisia, remarks: “In their coloration and mark- ing they vary according to the particular district inhabited ; thus, 6 82 A HISTORY OF BIRDS roughly speaking, the birds frequenting the mountainous and more humid regions of the north are dark in colour, those found in the lower lying and drier central districts, paler, while those inhabiting the arid desert country of the south are isabelline or sand-coloured.” Captain Boyd .Alexander, on his return in 1907 from his remarkable journey across Africa, showed me a particularly interesting case of bleaching. This was furnished by a Night- jar (Caprimulgus claudi) which presented two phases—a light anda dark phase. The former is found only in open country away from the forest region—by Lake Albert—on ironstone rocks. The birds which exhibit this pallid hue are never found among grass or other vegetation, but pass their whole lives amid the rocks, which they so closely resemble in colour that they are invisible until approached within a couple of feet or less. The darker phase of this bird occurs towards the Gold Coast, on the borders of the forest, where there is a heavy rainfall. Since desert conditions beget bleached forms it is not sur- prising to find that the opposite—a moist atmosphere—should produce dark-coloured types. A case in point we have just referred to, in the Night-jar. White-throated Sparrows and Wood-thrushes are said by Mr. Beebe to become “almost like Blackbirds in colour when confined in a bird-house where the air was constantly moist”. ‘A South American Pipit,” he continues, “the individuals of which passed their lives on very circumscribed plots of earth, exhibit two colour forms entirely different, and thought to be due solely to the amount of moisture in the ground on which it lives. Very dark coloured and very pale individuals live within a few hundred yards of each other, in dry and swampy stations respectively, each, it is said, keeping entirely to its own little beat!” Mr. Whitaker has drawn attention to the fact that the Skylark (Alauda arvensis), which is found in the marshy Roman Campagna, is exceedingly dark in colour, so much so as to form a distinct race. Similarly in the Galapagos Islands, where the climate is damp, the birds are remarkable for their dark coloration. That this is due to the humidity of the climate is clearly demon- strated in the case of two species—a Short-eared Owl (Asio galapagoensis) and a Night-heron (Vyctcorax pauper), inasmuch SEASONAL LIFE 83 as the former is, save for its darker hue, indistinguishable from the Common Short-eared Owl (Asio brachyotus), a bird which ranges over well-nigh the whole world, and is known in Great Britain as the Woodcock Owl, while the Night-heron is similarly only distinguished from the South American Violaceus Night-heron (VV. violaceus). Mr. J. A. Allen has brought to light some extremely interesting facts with regard to the relation between changes of colour and meteorological conditions. An intensity of pigmentation occurs, he points out, with regard to American animals, from North to South, coinciding with the intensity of the sun’s rays and the increase of humidity. The increase in colour observed in birds on passing from East to West points to the same factors, “the darker representatives of any species occurring where the annual rainfall is greatest, and palest where it is least”. In Europe the same phenomena obtain. Birds from the Scandinavian coast are much darker than in Central Europe, where the rainfall is only half as great. And similarly, British races of birds are darker than the Continental forms. Wallace, among others, has contended that light, heat and moisture have no influence on the coloration of animals. Without in this place entering further into the reasons he advances in support of his views, we may remark that the evidence is overwhelmingly against him. That wherever in- dividuals of a widely distributed species settle down and become more or less sedentary, there that species takes on the characters of “local” or “geographical” races, paler or darker, than the parent form, according as they settle in a desert or a marshy area, There is no need here to add to the number of cases which could be cited to show the importance of the action of light and dry heat, and of the effects of a deficiency of sunlight and excess of moisture on coloration. We have chosen the Galapagos to serve as an illustration for other reasons which will be apparent later. It is generally believed that the bleached appearance of desert forms is the result of the action of natural selection, whereby all dark coloured, and therefore conspicuous forms, have become weeded out by predatory foes, while those indi- viduals which tended towards the development of light plumage survived, in proportion as they harmonised with their surround- 84 A HISTORY OF BIRDS ings. To this we shall return in a later chapter. But here we would remark that the evidence seems rather to show that the action of natural selection followed another line—the physiological reaction of the organism to heat and a dry atmo- sphere, which seem, in some way, inimical to the production of pigment, except in a dilute form such as would give rise to pale coloration. How much is due to the direct action of the sun’s . rays on the ceratin which forms so large a portion of thé superficial part of the feather remains to be discovered. But it would seem that this is a factor to be seriously considered. That there is a direct relation between high temperature and a dry atmosphere on the one hand, and weak pigmentation on the other, seems certain. To suppose that the phenomenon of bleaching as here set forth is a concession to Lamarckism would be to fall into a grievous error. The reduction of colour is due either to the selection of individuals with reduced powers of pigment secre- tion which may be correlated with other qualities necessary for- such an environment, and therefore be of blastogenetic origin ; or it may be somatogenic, that is to say, a purely physiological phenomenon, impressed anew upon each generation ; in other words this coloration is not transmissible. Let us pass now to a review of the evidence as to the opposite relation between extreme cold and pigmentation. As is well known, the birds of Alpine and Arctic Regions are commonly white, at least during the winter months, while during the rest of the year they may wear a plumage quite richly coloured. The Ptarmigan and Willow-grouse are cases in point. These birds, at the approach of winter, gradually discard their richly mottled plumage and assume a dress of pure white, though it has been stated that this white dress is assumed, not by a moult, but by the ingestion of the pigment of the feathers by phagocytes. This, however, does not appear to be supported by fact, for in the first place the moulting has been watched repeatedly, and in the second it seems improbable that phagocytes would be able to make their way up the tissue ofa feather. That this whiteness is the direct result of a nicely sensitive reaction to cold is shown by the fact that the change varies in completeness according to the intensity of the stimulus. But since it does not manifest itself in all Alpine and Arctic SEASONAL LIFE 85 birds there must be some other governing cause at work demanding this change, but this so far has eluded dis- covery. The naturalist Allen, to whom we have already referred, showed that in the birds of North America there is increase in size from the southern towards the northern regions, where, in the northern forms, this increase is correlated with an appreci- able decrease in colour. This increase in size from the south northwards appears to be true not only of individuals of the same species, but also, as a rule, the largest species of each genus are to be met with inthe north. But there are some exceptional cases, however, in which the increase in size is in the opposite direction. This apparent contradiction Allen suggests may be explained by assuming that the largest forms are found in the area from which the species took its origin— that is, if the species arise in the north then the northern forms will be largest, if in the south then the reverse is the case. The increase in size northward is, however, less common than in the opposite direction. In species whose breeding area covers a wide range of latitude the northern birds are not only smaller, but have a different coloration, as in the Common Quail, Meadow Lark, Purple Crackle, Red-winged Blackbird, Blue Jay, Crow, Titmouse, and numerous species of Finches, Warblers and Thrushes, the variation amounting to as much as from 10 to 15 per cent. of the average size of the species. Possibly this decline in size as the species wanders further from its area of origin is due to the fact that the new conditions encountered during the migration grow less favourable as the distance between the ancestral home is increased. That is to say, those which remain in the area of origin have become so completely adapted to their environment that an increased size has .become possible. And the huge bulk attained by certain island forms which have become largely freed from the struggle for existence seems to support this view. But Allen further contends that in birds the peripheral parts—the beak, claws and tail—also increase towards the south. That in passing from New England to Florida the beak in slender-billed forms becomes larger, longer, more at- tenuated and more decurved; while in short-beaked forms the southern individuals have larger and thicker beaks, although 86 A HISTORY OF BIRDS the birds themselves are smaller. This increase, however, is not so much due surely to climatic conditions as to adaptation to feeding and other inevitable changes in the environment. In supporting this view we may cite an instance of this kind given by Mr. J. S. Whitaker. Writing in his Birds of Tunisia, he says of one of the crested Larks (Galerida cristata macror- hyncha) it ‘shows considerable variation in its colouring, ac- cording to the particular district it inhabits. To a certain extent it varies in other ways as well, notably in the size and shape of its bill, the modification of which is presumably brought about by the nature of the soil in which the bird finds its subsistence, a soft sandy soil calling for a long, fine-pointed bill, while a hard gravel or rocky soil requires a shorter and blunter bill” He further points out that the small-beaked group of crested Larks shows a greater variability generally than the large-beaked group. And this he says ‘‘is no doubt due to the fact of the former having a wider and more extended range in the Regency (Tunisia) than the latter. The small- billed crested Larks are to be found universally throughout the country, and frequent the hills and high plateaux, as well as the lower ground, whereas the larger-billed birds are confined to certain districts, and are, asa rule, only to be met with in the plains.” The foregoing facts seem to leave but little room for doubt but that birds are directly affected by climatic conditions, that they react to the stimuli of temperature and moisture, for- example, when long continued. Moreover, it seems clear that similar stimuli produce similar results in widely different species, when, be it noted, these are sedentary species, though all are not affected to the same degree. But the climatic conditions here referred to are such as are uniform and long-sustained. Climatic conditions, however, are nowhere absolutely stable. Periodic or seasonal changes and sporadic, meteorological periods of inclemency occur every- where, and these two factors exercise a very important part on avian life the world over. They play an important part in the geographical distribution of species; and they further serve to eliminate all but the most perfectly developed individuals, all but those which are exceptionally well adjusted to their en- vironment, or those which can contrive to tide over times of SEASONAL LIFE 87 stress by superior cunning or intelligence; or by sensibly re- ducing the number of a species which in other ways affect the balance of nature. A few illustrations relative to this aspect of the effect of natural conditions will contribute more towards indicating what is meant by the influence of climate and weather than a long dissertation. After great storms along our coasts great numbers, some- times thousands, of Razor-bills, Puffins, Guillemots and Little Auks are picked up along the shore, or are found floating at sea. These victims succumbed either to the buffeting of the wind and waves when fishing, or to their inability to procure any food at all. Only the very strongest birds survive such visitations ; while young birds of the year are especially notice- able among these dead. During the winter months great numbers of Starlings cross over from Great Britain into Ireland, and should severe weather—frost and snow—set in, these numbers are enor- mously increased. As the cold wave moves westwards the birds flee before it. ‘All day long,” remarks Mr. Ussher in his Birds of Ireland, ‘‘the race for life has been watched streaming towards Kerry, whose peninsulas and islands enjoy that freedom from frost which makes them the last resort of the refugees. After the snowstorm of February, 1895, the Rev. W. S. Green, on visiting the cliffs of Moher, in Clare, found cartloads of dead Starlings, chiefly on the landward side of the fence that ran along the top of the cliff . . . but the strangest observations made at this, the most western island of Donegal, and at Eagle Island and Blackrock, west of Mayo, are of flocks flying west, as though to perish in the Atlantic.” Periods of drought are no less disastrous; and the same is true of volcanic eruptions, though these last are happily ex- tremely rare. Nevertheless, within the last few years several species of birds are known to have been exterminated from this cause only. Thus, the eruption of Mount Pelée on Mar- tinique and La Soufriére on St. Vincent have exterminated the Thrushes (Myadestes stbilans) of St. Vincent, Myadestes gent- barbis of Martinique, Cinclocerthia cutturalis and Rhamphocin- clus brachyurus of Martinique, as well as the magnificent Parrot (Chrysotis guilding?) of St. Vincent. 88 A HISTORY OF BIRDS Storms and droughts, and cataclysmal disturbance, how- ever, though they very materially affect bird-life, do so for the most part only indirectly. That is to say, the shifting from one area to another, and the mortality to which reference has been made, are not so much due to these adversities as to the lack of food or the inability to procure it. Since birds neither zstivate nor hybernate—though the older naturalists were convinced that the Swallows and some other birds really did hybernate—such species as cannot obtain a sufficiency must wander till they find this. With some species such wanderings are limited to a relatively small area, but with others vast distances are annually traversed on this account: though there are many cases, to which reference will be made in due course, which seem to be prompted by some other motive. These periodic movements constitute the study of migration. CHAPTER VI MIGRATION _ ,Kinds of migration. Routes. The. height at which birds fly. Speed. Lighthouses and their influence. Erratic migration. Causes of migration. Meaning of migration. : ; N whatever part of the world the Ornithologist may live there. he will find birds: and further that the birds of any -given area may be divided into two more or less well-defined classes—the resident and the migratory. That is to say, that the ranks of the resident population are constantly receiving new-comers, either in the shape of stragglers which appear suddenly and as suddenly vanish, or of large bodies of more or fewer species whose appearance and disappearance is periodic and apparently governed by the seasons. Of these larger bodies of wanderers, some may stay but a short time, others may remain for months. And thus there will inevitably arise the question—What governs the movements of these migrants ? To this at present no really satisfactory answer is forthcoming, we must perforce remain content with speculation. For reasons more or less obvious, it will be best, in con- sidering this difficult subject, to confine our remarks, in the main at any rate, to observations on this theme made on the birds of the British Islands: they may safely be regarded asa guide to what ‘obtains in more remote regions of the world. . First of all as to.casual vagrants. The ever-increasing list of birds new to the British list shows that these are fairly numerous. With the largely increased army of keen observers the number of species of birds new to Great Britain is not only steadily increasing, but the number of records for each of these “new species” seems to be increasing also. The spring and autumn, it is to be noticed, are the seasons when these vagrants most generally. make their appearance, and it is further to be 89 90 A HISTORY OF: BIRDS noticed that immature birds occur the most frequently. Such wanderers would appear to have been blown out of their course while journeying towards some distant goal. They may re- present species common in parts ef Europe in close proximity to our own shores, or individuals from the far distant North America. These latter, as the late Professor: Newton has re- marked, are of species which breed in somewhat high northern latitudes. “On their way thence to their winter-quarters, some are driven out to sea by violent westerly gales—the strongest winds, be it remembered, that prevail in the North Atlantic, and thus strike the coast of Norway. . . . Such storm-beaten wanderers there consort with the allied species to be found at that season in abundance on its shores, and in their company pursue the same southerly course. With them they cross to the east of Great Britain, and once arrived here are speedily picked out and secured by the practised gunner. But should they even escape his notice, they with their comrades follow the shore-line, where they obtain the best supply of food, until passing round the South Coast they find themselves at the western extremity of England—the district of the Land’s End in which, next to Norfolk and Suffolk, the greatest number of these Transatlantic stragglers have been obtained. This sug- gestion may serve to show what most likely goes on in other parts of the world, though the materials for establishing its general truth are not forthcoming.” Time may prove the truth of this suggestion. But even so there will remain a greater mystery to be explained, a problem which seems at the present day well-nigh insoluble. And this refers to the regular and orderly movements of a large number of totally unrelated species whereof every member partici- pates—movements which compel the attention of even the most unobservant, while at the same time it excites the wonder of those who find in the study of Nature a never-ending delight. As the late Professor Newton eloquently puts it: “The Hawk that stretches her wings towards the south is as familiar ta the latest Nile-boat traveller or dweller in the Bosphorus as of old to the author of the book of Job. The autumnal thronging of the myriads of Water-fowl by the rivers of Asia is witnessed by the modern sportsman as it was of old by Homer. Anacreon welcomed the returning Swallow in numbers which his imitators MIGRATION gI of the colder north, to whom the associations connected with it are doubly strong, have tried in vain to excel. The Indian of the Fur-Countries in forming his rude calendar names the re- curring moons after the Birds-of-passage whose arrival is coinci- dent with their changes. But there is no need to multiply instances. The flow and ebb of the feathered tide has been sung by poets and discussed by philosophers, has given rise to proverbs and entered into popular superstitions, and yet we must say of it still that ‘our ignorance is immense’.” The wandering hordes to which reference is here made are all bent on the same errand. In the spring they seek their breeding quarters, in the autumn they are hastening away to more congenial climes wherein they may pass the winter. Great Britain harbours large numbers of such migrants, which find here a suitable breeding ground, or come to us in the autumn to tide over the winter; while some species merely pass through on their way to other lands. Thus, from March to May, while the birds that wintered with us silently steal away for more northern latitudes, others crowd in to take their place. In the autumn these movements are reversed. Before we endeavour to analyse the possible meaning and origin of these movements, let us trace, so far as may be, the extent of the journeys which some of these wanderers take. Than the Swallow it would be difficult to find a more in- structive example. The species known in Great Britain as the Common Swallow (Hzrundo rustica) occurs also all over Europe, Northern Asia and North America, but presenting in each of these great areas characters sufficiently distinct to warrant re- cognition as sub-specific, or geographical races, though some prefer to regard them as true species. Be this as it may, these birds in their seasonal wanderings all agree, as do migrants in general for that matter, in taking a course due north and south. Thus then the Swallows of these several regions keep each to the land areas lying more or less directly north and south of their range. That is to say, their latitudinal range is relatively limited. The Swallows of Northern Europe go south to Africa, those of Northern Asia (7. gutturalis and H.. tytler?) to India and Burma, and even farther southwards, occasionally reaching Australia and New Zealand, while those of North 92 A HISTORY OF BIRDS America (7. ce ak extend their wanderings to Southern Brazil. - Out of these bread facts an sitemipe has been made to trace the wanderings of the Common Swallow (Hzrundo rustica) in more detail. ‘And it is found that while some go to West Africa, as far south as the Gold Coast, others extend down the whole of the eastern portion of that continent as far as the Cape. Now Dr. Bowdler Sharpe, in discussing these facts, assumes that the migrant hosts wintering in these two areas are made up indiscriminately of British-bred birds, as well as of birds bred on the Continent of Europe. But this assumption, we venture to suggest, is possibly incorrect. However, let this pass for the moment. With this interpretation before him he proceeds to ask by what routes do these two main bodies— West and South African—travel. Do those making for West Africa go across the Mediterranean direct or by the short cut to Gibraltar, or from Italy to Malta, and so to Algeria and across the Sahara? Or do they follow the coast-line and so come to Liberia and the Gold Coast? Asa yet further alternative he suggests that the whole migratory army may travel together to the Nile Valley when it breaks up into two great bodies, one making for the West Coast, and the other continuing its southern journey which ends in the Transvaal and the Cape. | Bearing in mind the evidence as to the tendency to travel as far as possible due north and south it seems probable, we venture to think, that we shall. eventually prove,t@ be right in assuming that the Swallows which winter on the Gold Coast of Africa are those which make their breeding quarters in Great Britain, France and Spain, and that they reach their winter resort by the shortest and most direct route possible. This being so, we may assume that those which reach the Transvaal and the Cape have been bred in leastenn and South-Eastern Europe. » A i acess of hes summer migrants to Great Batata, even the frail Warblers and Chats, winter in Africa. Our Common Night-jar (Caprimulgus europeus) goes to East Africa by way of the Great’ Lakes. But nearly ‘allied species which may occur together in their breeding quarters often adopt very different winter quarters. This is true of two European Shrikes —the Red-backed Shrike (Lanius collurio) and the Woodchat MIGRATION 93 Shrike (Z. pomeranus), The former “ extends its winter range,” says Dr. Sharpe, “to the Cape Colony. Not so the Woodchat, which goes to North-Eastern Africa and to Somaliland, but then reappears in West Africa. Failing information that it crosses the Sahara direct, we can only imagine that it turns westward from the Nile Valley, skirts the Sahara . . . and re- appears in West Africa.” The most ambitious attempt to map out the migration routes of European birds is that made by Professor Palmen. These are nine in number. The first leaving the Siberian shores of the Polar Sea, Nova Zembla and the north of Russia, passes down the West Coast of Norway to the North Sea and the British Islands. The second, proceeding from Spitzbergen and the neighbouring islands, follows much the same course, but is prolonged past France, Spain and Portugal to the West Coast of Africa. The third starts from Northern Russia, and, threading the White Sea and the Great Lakes of Onega and Ladoga, skirts the Gulf of Finland and the southern part of the Baltic to Holstein, and so to Holland, where it divides—one branch uniting with the second main route, while the other, running up the valley of the Rhine and crossing to that of the Rhone, splits up on reaching the Mediterranean, where one path passes down the Western Coast of Italy and Sicily, a second takes the line by Corsica and Sardinia, and a third follows the South Coast of France and Eastern Coast of Spain —all three paths ending in North Africa. The fourth, fifth and sixth main routes depart from the extreme north of Siberia. The fourth ascending the river Obi, branches out near Tobolsk —one track, diverging to the Volga, descends that river and so passes to the Sea of Azov, the Black Sea, and thence, by the Bosphorus and A®gean to Egypt; another track makes for the Caspian by way of the Ural River and so leads to the Persian Gulf,.while two more are lost sight of on the Steppes. The fifth mounts the Yennesei to Lake Baikal and so passes into Mongolia. The sixth ascends the Lena and striking the Upper Amoor reaches the Sea of Japan, where it coalesces with the seventh and eighth, which run from the eastern portion of Siberia and Kamschatka. Besides these the ninth, starting from Green- land and Iceland, passes by the Faroes to the British Islands, and so joining the second and third runs down the French coast. 94 A HISTORY OF BIRDS These are Professor Palmen’s main routes, the minor channels of these vast streams being formed by river-courses. The great migration routes, as we have already remarked, run north and south, but there are cases where an exceptionally wide easterly or westerly trend is to be noted. These, it is significant to notice, occur mainly where the migrants are com- pelled to follow a shelving coast-line, where a course due north or south, as the case may be, would carry them out into trackless wastes of ocean. Tytler’s Swallow, for example, nests in Kams- chatka and winters in Burma. “In New Zealand,” wrote Professor Newton, “there are two Cuckoos which are annual visitors; one, a species of Chrysococcyx, probably has its winter quarters in New Guinea, though commonly supposed to come from Australia, the other, Eudynamys taitensis, is widely spread throughout Polynesia. . ..” Here are two nearly allied forms which take opposite directions—east and west—yet each follow- ing land routes, and the objective of each, be it noted, being ' °° north or south as the season may determine. More remarkable is the case of the Red-footed Kestrel (Erythropus amurensis) of Eastern Siberia, which winters in Eastern South Africa, more especially, apparently, in the Zambesi region. So far as can be made out at present this enormous journey is not made westward through Arabia and by way of the Nile Valley and the Great Lakes, but across the Indian Ocean. This conclusion has been arrived at, because so far no specimens of this species have yet been taken on the route just referred to, but examples have been taken in the Indian Peninsula, in Cachar and in Canada. This is the more inexplicable because the nearly allied European Red-footed Kestrel (Erythropus vespertinus)—which differs from its Siberian relative only in having the under wing coverts grey instead of white—nests in South-Eastern Europe and winters in South- Western Africa, though the two species are occasionally found together in their winter quarters. Time may show that the Siberian bird after all follows an overland route, but eastwards by the Nile and the Great Lakes, while those birds found in the Indian Peninsula stray no farther southwards. But on the whole it seems clear that though an east to west course, and wice-versd, is followed by some species when on migration, the ultimate goal of all is always north and south, ¥ MIGRATION 95 Although the migratory movements such as we have just described take place, asa rule, ona stupendous scale they attract comparatively little attention. A few stragglers tell us that the arrival of our guests is at hand, or remind us that they have departed, but the main body of these wandering hordes is seen but by a few privileged ones. And this largely because, as a rule, they come in rushes, and come, very commonly, by night, leaving in a like manner. This, however, is largely determined by the conditions of the weather. But whether they travel by day or night, as a rule they appear to prefer to perform their journeys at high altitudes, perhaps because less wearisome. Often they betray their presence only by their whistling, though it would appear that as a rule they travel in silence, save only on dark, foggy nights, when their constant cries serve to keep the troop together. American naturalists have made some interesting observa- tions by directing a telescope against the sky. Thus Mr. Frank Chapman, by turning his instrument towards the full moon, has seen birds passing at night at an altitude, according to his computation, of five miles, while Mr. W. E. D. Scott saw, through an astronomical telescope at Princeton, in New Jersey, great numbers of birds passing across the face of the moon. Most of these were the smaller land birds, among which he recognised Warblers, Finches, Woodpeckers and Icteride (Quiscalus purpureus). These, it is computed, were travelling at heights varying from one to two miles. Mr. Chapman again, on another occasion, when in New Jersey, during three hours saw no less than 262 birds pass over the field of the telescope at a height of from 1,500 to 15,100 feet ; and the most remark- able thing of all was the fact that the lowest birds were flying upward, as if they had risen from the immediate neighbour- hood and were seeking the proper elevation at which to continue their flight. Mr.S. Tennant has recorded the fact that through a telescope turned towards the sun, at Roorkee, he saw birds, apparently Kites, frequently pass over its face, some of which were in focus with the sun itself and must therefore have been several miles high, while the nearest must have been quite a mile above the earth’s surface. These birds, it should be re- marked, were soaring in search of prey, and not migrating. More than once doubt has been expressed as to whether 96 A HISTORY OF BIRDS birds can maintain themselves at an altitude of five miles, or whether indeed they can attain this height, and this partly on account of the low temperature which would be there en- countered, and partly because the rarefied air would not serve to sustain flight. This last is perhaps the more serious objection, for cold would scarcely be felt by birds engaged in such violent exercise as flight, while the clothing of feathers would be a further protection. Birds on migration do not always, however, travel at a great height, fcr there are occasions indeed when the exact opposite isthe case. Mr. W. Eagle Clarke, one of our greatest authorities on all that pertains to these mysterious wanderings, has recorded more than one occasion when enormous numbers of Larks, Starlings, Thrushes and other small birds were crossing the North Sea flying so low that they barely topped the crests of the waves. On one such occasion when on the Kentish Knock Lighthouse, during a gale accompanied by a downpour of rain, the birds were scudding along after this fashion, apparently to escape, so far as was possible, the force of the wind. And this continued throughout the day, thousands and thousands passing during this time. Estimates as to the height at which birds migrate sometimes make large demands upon our faith, and this is no less true of calculations as to the speed attained during their journeys. Thus the late Herr Gatke, of Heligoland, one of the pioneers of the study of migration, believed that the little Arctic Blue-throat (Cyanecula suecica) could leave Africa at dusk one evening and arrive in Heligoland nine hours later, having travelled 1,600 geographical miles in a single night at the astounding velocity of 180 miles per hour! According to another estimate of his, Curlews, Godwits and Plovers crossed from Heligoland, to the oyster-beds lying to the eastwards, a known distance of rather more than four English miles, in one minute, or at a rate of over 240 miles an hour! Against such extravagant estimates it is hardly necessary to attempt to bring rebutting evidence, but if any be demanded this may be furnished by the Carrier Pigeon, which has been known to maintain a speed of fifty-five miles for four hours in succession; and it is extremely unlikely that this is much, if at all exceeded by wild species during long-distance flights. MIGRATION 97 Not until the erection of lighthouses along our coasts did we gain an opportunity of realising the magnitude of migratory movements, and of the astounding numbers of the birds which participate therein. But by a strange irony these beacons of safety to the human race have become veritable death-traps to the birds, for the lanterns, when sending forth their beams for the guidance of those who go down to the sea in ships, exert at the same time a fascination for the winged wanderers which seems to be absolutely irresistible. In thousands they dash themselves against the blinding light, and in thousands they fall stunned on to the rocks below, or into the surging sea, so making an annual death-roll which is positively appalling. On clear and moonlit nights such tragedies are largely, if not en- tirely averted, but cloudy skies and a mist-like rain are fatal, for the light reflected on the latter gains a peculiar brilliancy which appears to exert a dazzling effect which these birds can- not escape. Two of many instances given by Gatke show the extent of these visitations. From ten o'clock on the night of the 28th of October, 1882, to the next morning, Goldcrests eddied thick as flakes in a heavy snowfall round the lighthouse on the little island of Heligoland; on the morrow they literally swarmed over every square foot of the island; and twelve months later Hawks in myriads thronged to its bright beams for four nights in succession, accompanied by Starlings in hardly fewer numbers, But “these great hosts,” remarks Professor Newton, ° ‘consist usually of many kinds of birds congruous only in their congress—Larks and Lapwings, Starlings and Sandpipers, Fieldfares and Curlews, Golden-crested Wrens and Golden Plovers, Oyster-catchers and Owls—while the air is filled with their cries, among which are several that are wholly unrecognisable, for it would seem that some birds have a lan- guage that they use only when migrating. Otherwise is it with the return of the wanderers in spring, when the exciting scenes of autumn are seldom if ever presented, yet under a moonless and clouded sky the wakeful ear may often catch positive evi- dence of what is going on aloft, though owing to the smaller numbers (for at that season it is only the birds which are about to breed that pass) and the shorter nights, the movements at- tract far less attention. Generally troop after troop of the travellers succeeds in orderly, and what has been called 7 98 A ‘HISTORY OF BIRDS ‘wave-like’ fashion, varying indeed in rapidity according to the species, but taken as a whole in comparatively little else.” Only where the lighthouses show a red light do the migrants pass unharmed, the ruddy beams failing to exert any influence over them. One cannot help expressing a wish that the lighthouses which lie in the more frequented routes of these tired travellers could accordingly exchange their white for red lights, could this be done without diminishing their value as guides to mariners. Reference has already been made in this chapter to casual migrants to our shores, vagrants swept hither by adverse winds. But at times such visitants make their appearance not in twos and threes, or as solitary individuals, but in large flocks. Among the most remarkable of such visitations are to be reckoned the sporadic irruptions of Pallas’s Sand-grouse (Syr- rhaptes paradoxus). These birds, natives of the vast Gobi deserts, occasionally make their appearance in Europe in enormous numbers and for reasons which as yet are absolutely inexplic- able. During the last forty years three separate invasions of this handsome spécies have occurred in Great Britain. The first of these took place in 1863, the last in 1888, when both previous records were totally eclipsed, vast hordes making their way across Europe, following on the routes taken by their predeces- sors ; of these, thousands finally reached Great Britain only to be speedily exterminated by the “Collector”. The Wax-wing and the Nutcracker, similarly, at rare intervals, sally forth in their thousands apparently in search of fields and pastures new. “ The inroads of the Wax-wing” (Ampelis garrulus), wrote Pro- fessor Newton, “have been the subject of interest for more than 300 years, and by persons prone to superstitious auguries were regarded as the forerunners of dire calamity. Sometimes years have passed without its being seen at all in Central, Western or Southern Europe, and then, perhaps for two or three seasons in succession vast flocks have suddenly appeared. Later ob- servation has shown that this species is as inconstant in the choice of its summer as of its winter quarters . . ., ” the cause, he suggests, of this irregularity may possibly be due to lack of food; and this also may have been the inciting cause of the invasion of Western and Central Europe in the autumn of 1844 MIGRATION 99 by a great band of Nutcrackers (Nucifraga caryocatactes), But nothing whatever on this head is known. And this brings us to the question—Why do birds migrate ? To attempt an answer to this question is, at present, to attempt a very difficult task. But before proceeding to make the en- deavour it would be well to draw attention to one or two further mysteries of migration which have long excited the comments of Ornithologists but as yet defy all attempts at solution. Why, for example, in so many species do males usually arrive in advance of females? This is true of the Warblers, for example, males of which reach their breeding quarters some days in advance of the females. More extraordinary still in a large number of species, the adults leave before the young birds, while with the Swallow the young leave first, undertaking their stupendous journey without guides. That is to say, birds which have but recently left the nest are left to find their way, ap- parently unaided, to the winter quarters in Africa! The young Cuckoo, for example, accomplishes this feat, and so also, ap- parently, do the young of the Red-backed Shrike. Yet another remarkable feature of our annual migrants is the wonderful regularity with which they make their appearance and disappearance. Thus of the Puffin (/vatercula arctica) Professor Newton wrote: “ Foul weather or fair, heat or cold, the Puffins repair to some of their stations punctually on a given day as if their movements were regulated by clockwork, Whether they have come from far or from near we know not, but other birds certainly come from a great distance, and yet make their appearance with scarcely less exactness.” Such, in brief outline, are the main features of the migration of birds. In the space of a single chapter no room can be found to describe the laborious work that has been expended on this subject by workers abroad, nor of the splendid work of Barring- ton and Eagle Clarke and others in Great Britain. During the last year or so some most valuable work has been done by a committee of the British Ornithologists Union, the aim being to gain an insight into the lines of migration and dispersal in Great Britain; and it is certain that if this work is carried on most important results will follow. But we are yet as far off as ever with regard to the crux of the whole matter--Why do birds migrate? 100 A HISTORY OF BIRDS On this theme much has already been written, but little to any purpose. An American writer of good repute would have us believe that when Professor Newton wrote that on this theme “our ignorance is immense” he was really making mystery where no mystery was. The whole matter, he assures us, is simply one of securing suitable breeding sites; and adduced in evidence the migration of the shad and the salmon, which for this purpose, and none other, leave the sea and ascend the rivers, there to lay their eggs, just as the fresh-water eel for a like purpose leaves the rivers to perform the duties of re- production in the sea. Even so, what impels the one to seek the fresh and the other the salt water? When they start on their perilous journeys have they any fixed ideas as to the relative merits of fresh or salt water as repositories for their eggs? The fresh-water eel and the species of salmon of which he wrote perform these journeys but once. Reproduction over, they die—every one, like Pharaoh's host, perishes. He further seems to commit the very grave mistake of supposing that what may be true of fishes is true of all other migrants. The veteran Darwinian, Alfred Russel Wallace, took a more serious view of the matter. He says—in reference to birds— (Nature, x., p. 459): “It appears to me probable that here, as in so many other cases, ‘ survival of the fittest’ will be found to have had a powerful influence. Jet us suppose that in any species of migratory bird breeding can as a rule be safely accomplished only in a given area; and further, that during a great part of the rest of the year sufficient food cannot be obtained in that area. It will follow that those birds which do not leave the breeding area at the proper season will suffer, and ultimately become extinct; which will also be the fate of those which do not leave the feeding area at the proper time. Now, if we suppose that the two areas were (for some remote ancestor of the existing species) coincident, but by geological and climatic changes gradually diverged from each other, we can easily understand how the habit of incipient and partial migration at the proper seasons would at last become hereditary, and so fixed as to be what we term an instinct. It will prob- ably be found that every gradation still exists in various parts of the world, from a complete coincidence to a complete separation of the breeding and the subsistence areas ; and that MIGRATION IOI when the Natural History of a sufficient number of species is thoroughly worked out, we may find every link between species which never leave a restricted area in which they breed and live the whole year round, to those other, cases in which the two areas are absolutely separated.” That migration among birds is, and has been, largely if not entirely connected with the problem of food supply would seem to be highly probable. A strong point in favour of such an interpretation is the fact that birds which have a sufficient and constant food supply do not migrate. Whole groups of birds, it must be remembered, either do not migrate at all, or confine their wanderings to small areas. The majority of tropical and sub-tropical species, for example, do not migrate ; while of typically migratory species not a few will be found which have become stationary in some part of their range throughout the year, having found an abundant and unfailing food supply. There is no more typically migratory bird than the Common Swallow (Hirundo rustica), yet a closely allied species, differing only in a few slight particulars (A. saviguiz) is resident in Egypt. The tropical and sub-tropical species to which reference has just been made, are, be it noted, relatively far less numerous in individuals than are such migratory species as Warblers and Swallows. And this because they have be- come adapted to live on a peculiar kind of diet to be met with only in their own particular neighbourhood. For such species migration would be suicide: thus the numerical strength of such species is determined by the food supply; a shortage spells famine, and the consequent reduction of the species to limits which the area can support. Migration is possible only so far from the original centre of dispersal as food is obtainable. And it would seem that migratory species follow their food more than is supposed. So far as is possible, overland routes appear to be followed just because of the need of food all along the route. “It is well known,” writes Dr. Sharpe, “ that in certain parts of Africa, during the northern winter, vast flocks of birds of prey are observed. They consist of Kites, Eagles, Hobbies, Kestrels, etc., and they follow the swarms of locusts, or appear in numbers where grass-fires take place.” Migratory birds, in short, have acquired this power to shift from place to place, and the consequent advantage to the species, just because 102 A HISTORY OF BIRDS they have not become too highly specialised in the matter of food, and so can avail themselves of supplies that in some form or another are universal. That these migratory birds are the descendants of a line of forebears of similar habits extending far back in time none can doubt, extending back indeed to a time when the physical geography of the world, in the matter of the distribution of land and water, differed materially to what obtains at the present day. This is a fact which is not only commonly recognised by students of bird migration, but which is also made to play what to some must seem rather too imaginary a part. Thus it has been contended that many present-day migration routes are taken irrespective of present areas of land and water, and in conformity with the route followed by their ancestors when these areas were otherwise than now. That is to say, they cross such and such areas of water not because they afford short cuts, but because these areas were traversed ages ago when what is now a sea was then dry land. And just as submerged areas are now traversed purely for traditional motives, so it is held certain land areas are now skirted rather than crossed because they represent areas once covered by sea. Thus Dr. Sharpe, in describing the route of the Woodchat Shrike on its way to its winter quarters in Africa, remarks that it “skirts the Saharaas if it were still asea .. .”; yet he shows that the Willow Warbler, on the other hand, “winters in the oases of the Northern Sahara,’ whence it appears some individuals perform a further flight to Senegambia, this species being found during the winter months both in West and South Africa. The inference seems rather to be that while the Willow Warbler can safely enter the Sahara, being sure of food, the Woodchat cannot. Of course it is open to argument that the Willow Warbler is the more recent species, and therefore entertains no hereditary prejudices against this region, but of this there is no evidence. Ancient and now submerged land surfaces, however, are undoubtedly to be reckoned with in considering the subject of migratory birds, for these submerged areas would seem to act as barriers of a hitherto unsuspected kind. But before this hypothesis can be profitably developed it will be necessary to say a few words anent what has been called the “homing MIGRATION 103 instinct” in migrants. This theme has been most admirably yet briefly handled by the late Professor Newton. By way of illustration he cited the case of a “pair of Stone Curlews (Gadicnemus crepttans)—a very migratory species, affecting almost exclusively the most open country—which were in the habit of breeding for many years in the same spot, though its character had undergone a complete change. It had been part of an extensive and barren rabbit-warren, and was now become the centre of a large and flourishing plantation.” Two other in- stances quoted by Newton are scarcely less remarkable. Of these oneconcerned “the nest of a Falcon (Falco peregrinus) on Avasaxa —ahillin Finland . . .—is mentioned by the French astronomer Maupertuis as having been observed by him in 1736. In 1799 the nest was discovered by Skjoldebrand and Ascerbi. In 1853 Wolley found it tenanted, and from inquiries he made of the neighbours it was evident that such had yearly been the case so far as any one could remember, and so it was in 1855, as I myself can testify.” Continuing, he remarks: “In 1779 ac- cording to one account, in 1785 according to another, a pair of the Blue Titmouse (Parus ceruleus) built their nest in a large earthenware bottle placed in the branches of a tree in a garden at Oxbridge, near Stockton-on-Tees. With two exceptions only, this bottle, or a second which had been placed close to it, was tenanted by a pair of birds of this species from the year it was first occupied until 1873, when I saw it; ... but I regret to add that I learnt through Canon Tristram in 1892 that the occupancy had ceased for four years.” Bearing these facts in mind, and applying them to British birds, it seems to the writer of these pages that our annual migratory visitants may be regarded with a tolerable degree of probability as the direct descendants of the migrating hosts which made their way to these islands when they formed part of the mainland of Europe. The invading sea made its way by slow imperceptible inroads. Though with the cycle of the seasons the successive generations of these ancestral migrants saw more and more water stretched across their path to the summer breeding-home they heeded not, because the change was so slow that none took note of it. By such gradual stages was the barrier thrown across that no confidence was shaken. The birds passed on, sure of what was beyond: and for this 104 A HISTORY OF BIRDS reason their descendants continue in the same unshaken faith. In other words, our summer migrants are so many British races of their species, though indistinguishable from their con- tinental relatives. Now for the sequel to this. As, by human interference—drainage, agriculture, persecution at the hands of game-preservers and collectors—these British races become reduced, their numbers are not replaced. The Bittern, Avocet, Ruff, Spoon-bill, Harriers, Ospreys, and the dozen or so more of our vanishing native avifauna that turn up year by year among us are the last survivors of these old races. When they are gone their places will be taken only by occasional, accidental stragglers blown out of their course by adverse winds. Their place will not be taken by annual visitants because the repre- sentatives of these species on the mainland of Europe have similarly become “local” races—using this term in the wide sense—which therefore return year by year to their accustomed breeding spots, and as their ranks in turn become depleted so will they too become rare, then vanish. The intimate relation between migration and food supply is demonstrated annually within the confines of the British Islands during such visitations of “hard” weather as occur during the winter months: and on this head both Barrington and Eagle Clarke, our foremost authorities, have furnished some remarkable evidence. Though we must still regard the origin and survival of the migratory habit as a problem never likely to be certainly solved, we may yet find some satisfaction in hypothesis. Thus then it is to be noticed that migratory species, individually, vastly outnumber sedentary species, and _ this because of the enormous breeding areas which this wandering habit secures. But migration is only possible where a sufficient supply of food is to be secured, both on the journey and at its terminus—and this is true even where great distances can be covered without food, Very well. We may assume that the migratory species owe their origin to the matter of food supply. Composed of individuals subsisting on a food of universal range, but limited in supply, they were enabled’to roam farther afield as their numbers strained this supply in their immediate neighbourhood. Annually, however, a check was placed on further extensions of range by the cares of breeding and by MIGRATION 105 the diminution of food at the end of the breeding season— whether caused by climate or otherwise—while behind them the supply was increasing. Thus they were drawn back towards their starting-point. Again threatened by famine, they once more turned outwards, finding the earlier depleted area restocked. These movements, in short, were doubtless then, as now, periodic, and determined largely, if not entirely, by seasonal changes. Such species increasing numerically with their increase in range were naturally automatically compelled to still further extend this to obtain the means of sustenance. That each individual would return by the route he came by is but a natural inference, and the same is true of the offspring of each pair—hence the “homing instinct” and the formation of British—or other races—of migrating species. The range of a migratory species, “in fact, would seem to increase of necessity—so long as no severe check is placed on the annual increase in numbers of that species, and this because the younger generations have to stake out new claims for territory, so to speak: since the older birds will return to the breeding spots annexed by them previously, and will drive away any younger would-be settlers, which must therefore settle outside the range of the earlier occupiers of these sites. Thus is explained the fact that the Common Swallow (Hirundo rustica), for example, is found breeding throughout the whole of its range from Southern Europe northwards, those breeding farthest north having been forced thither by the settle- ment of the earlier migrants: and thus is explained the general rule that species which go farthest north in summer go farthest south in winter. CHAPTER VII RELATIONS TO THE ANIMATE ENVIRONMENT Relation to plants. Birds and pollination. Birds and spread of seeds. Birds in relation to other animals. The perils of nestling birds. Birds and “ civilisation ’’. HE fact that birds in any way modify their animate environment is generally, if at all, but vaguely real- ised; whereby it is plain that this influence is too subtle, or too small, to make itself felt. Nevertheless, careful observation will show that though the part they play may be a small one, birds do indeed leave their mark upon the organic world, though it be but a ripple-mark on the surface of the great ocean of life. In the plant world such forms as the Sun-birds and the Humming-birds play the part of insects in the pollination of flowers. But since it does not appear that these flowers are ab- solutely dependent upon the birds for pollination— | that is to say, these same flowers are probably more commonly visited by in- sects which perform the ILL. 19.—HummMinc-BirD FERTILISING work of pollination quite as Flowers oF MarcGRaviaA NEPENTH- ores. (After Wallace) effectually —we may turn with more profit to the facts which have been collected with regard to the part played by birds in the dispersal of seeds. Here there can be no doubt but that, in a large number of 106 RELATIONS TO ANIMATE ENVIRONMENT 107 cases, the evolution of many plants has been very materially affected, in so far as the fruit and its dispersal are concerned, by the agency of birds. The eminent botanist Kerner carried out a series of inter- esting experiments designed to test the vitality of seeds after having been swallowed by birds. Asa result he found that birds are in this respect divisible into three groups. The first - group includes those which grind up even the hardest fruits and seeds in their muscular gizzards by the aid of small stones and grit. Amongst these some strip the fruits and seeds when they first lay hold of them, and thereby condemn them to destruction. Such were, he found in his experiments, the Turkey, Common Fowl, Pigeon, Duck, Cross-bill, Bullfinch, Goldfinch, Siskin, Serin-finch, Nutcracker and Titmouse. No seed, under ordinary conditions, was found capable of germina- tion in the excrement of these birds. The seeds used were those of Avrenaria serpyllifolia, Papaver rheas, Sisymbrium sophia, Ribes rubum, Ligustrum vulgare, Fragrare indica and some other species. Ravens and Jackdaws form a second group, wherein the stones of the drupes and hard-coated seeds of the berries which they ate passed uninjured through the intestine, whilst soft-coated seeds and fruits were all destroyed. Kerner draws particular attention to the fact that after these birds had been fed with cherries their excrements contained cherry-stones 15 mm. in diameter, every one of which was able to germinate. The Blackbird, Song-thrush, Rock-thrush and Robin formed a third group. Of these the Blackbird proved to be the least fastidious about its food. It even swallowed the fruits of the yew without afterwards relieving its crop of the stony seeds, and it never rejected a single fruit that was mixed with its food. The Song-thrush rejected all dry fruits of 5 mm. diameter or more, even when they were mixed with the finely chopped meat with which the bird was fed. They also avoided such strong-smelling fruits as those of the yarrow. On the other hand, the aromatic fruits of umbelli- ferae were eaten with great avidity. The seeds of the tobacco plant, henbane and foxglove mixed with the food were not rejected and caused no ill effects, neither did the berries of the deadly nightshade which were greedily devoured. On the other hand, however, a Song-thrush sickened after eating 108 A HISTORY OF BIRDS berries of Phytolacca. One species of this genus, ?. decandra, a native of North America, is used as a source of colouring matter in the making of wine, and for other purposes. When fleshy fruits with seeds of a diameter exceeding 5 mm., such as those of Berberis, Ligustrum, Opuntia and Viburnum, were introduced into the crop, the pulp passed into the gizzard, but all the seeds were thrown up. And the seeds of fleshy fruits which were greedily devoured were thrown up if the stones which they enclosed measured as much as 3 mm. In some cases seeds, as those of Lychnis flos-Jovis, were carefully re- moved from the rest of the food with which they had been mixed. , The interval of time between ingestion and evacuation in the birds of this third group (Thrushes) was very short. A Thrush fed with Rides petreum at 8 A.M. excreted numbers of seeds after the lapse of three-quarters of an hour, and seeds of Sambucus nigra passed through the alimentary canal in half an hour; but the majority of seeds took from one and a half to three hours to perform this journey; though, curiously enough, the small seeds of Myosotis sylvatica and Panicum diffusum were retained for the longer period. Of the fruits and seeds which passed through the intestine of one or other of these birds 75 per cent. germinated in the case of the Blackbird, 85 per cent. in the Thrush, 88 per cent. from the Rock-thrush, and 80 per cent. with the Robin. But the germinating power of these seeds seems, as a rule, to suffer a check—in from 74 to 79 per cent. of the cases examined by Kerner—though the ultimate vitality of the seed does not appear to suffer in any way. This point was established by ,control experiments, the seeds of similar fruits, and we presume from the same plant, which were sown directly germinating quicker than those which had been swallowed. In a few cases, how- ever, as in the case of a few berries, e,¢., Rébes, Berberts, Lont- cera, germination was hastened by this ingestion; while the seeds of such plants as grow on richly manured soil, eg., Am- aranthus, Polygonum, Urtica, after passing through the in- testines of birds actually produced stronger seedlings than did those which were cultivated without having passed this test. Thus then we may assume that the brightly coloured fruits which distinguish so many plants have been evolved by the RELATIONS TO ANIMATE ENVIRONMENT tog agency of birds. That is to say, these bright colours are, so to speak, a device on the part of the plants to secure the dissemin- ation of their seeds. Thereby intraspecific competition is re- duced, and an extended range and continuance of the species is secured. Some plants, indeed, appear to owe their very exist- ence to the agency of birds; as, for example, in the case of the mistletoe. The part played by Thrushes in this distribution is well known, as witness the name “ Mistle-thrush”. But it is generally believed that the seeds of these viscous berries are deposited in the crannies of the bark of trees by the bird’s beak. To this it is supposed they become attached as they escape from the sticky pulp when this is squeezed. And to rid itself of the annoyance the bird is said to rub the beak vigorously across the bough until successful in transferring the offending particle to the bark. As a matter of fact, however, the berry is swallowed whole and the seed escapes when the faeces are expelled. In sup- port of this one has only to note that only occasionally do mistletoe plants spring from the upper surface of a bough. As a rule they start off from the side, or hang down from the under surface thereof. And this because the fzecal matter being semi- fluid, it runs some little way across the bough until stopped by some flake of bark. Here the seed is deposited; occasion- ally the fluid excreta may run on until it forms a drop beneath the bough. The nutmeg again appears to be largely dependent on fruit Pigeons to carry on the work distributing its seeds. The fruit is yellow, in shape resembles a peach, but is firm and not edible. When quite ripe it splits open and exposes the seed, which is of a glossy black colour, partly concealed by a bright scarlet laciniated sheath or “arillus,’ known commercially as ‘‘ mace”. The fruit Pigeons greedily seek out these seeds and swallow them entire for the sake of the mace. Later the nutmeg is said to be expelled with the faeces, and thus wild nutmegs have been spread over New Guinea and the surrounding islands. More probably, however, the mace is removed while in the crop, and the nutmeg is then thrown up, as other birds eject pellets. Nutcrackers, Jays, Magpies, Rooks and Woodpeckers, which keep stores of food in hiding-places—which they appear very 110 A HISTORY OF BIRDS frequently to forget—do much towards distributing the nuts of such trees as beeches, oaks and hazels. Some valuable evidence as to the important part birds play in the dispersal of seeds has been brought together by Mr. H. N. Ridley, who found that in the Malay Archipelago the principal carriers were Bulbuls, the dark-blue Starling (Cadornis chalybea), the Minah (Mainatus savatus), and the Horn-bills (Buceros, Anthracoceros, etc.), the latter being especially fond of the nutmeg. The Parrots of the Genus Palgornis also aided in this work. The granivorous Finches of the Genus Muna he found aided considerably in the dispersal of adhesive seeds which were carried about by the feathers and finally dropped. He states that, on the authority of Mr. G. Clunies Ross, on Cocos Islands ‘‘when Boobies are not nesting, and have con. sequently left, the Frigate-birds (Tachypetes aguila) are unable to procure their ordinary food, which consists of fish taken from the Boobies, and that they then swallow seeds of Guzlandina and beans which they find floating on the sea, and on flying to the land vomit them up again, apparently merely using them to fill up temporarily empty crops!” He further shows that while the bulk of the seeds dispersed by birds are highly coloured, dull-coloured seeds are dispersed by nocturnal mammals who seek their food by smell and not by sight. The mud adhering to the feet of birds furnishes another source of seed dispersal, for seed becomes embedded therein and may be transported over vast distances, though this, probably, plays no very important part in the distribution of plants. Not infrequently, perhaps, small seeds are carried inthe plumage. ~ Instances of the latter kind rest, however, rather upon circum- stantial evidence than upon established cases, The granivorous birds are supposed to act as seed distributors in this fashion. Certainly, small Finches and Gallinaceous birds which love to dust themselves in dry earth, may well enclose small seeds between the feathers during this operation. | Migrant waders, it has been suggested, carry seeds of marsh plants about in this manner, and one observer—Mr. H. N. Ridley—has re- corded the fact that a number of plants of Rhynchosposa aurea suddenly appeared in a stone tank in the Botanic Gardens at Singapore after the visit of a small Sandpiper. The evidence as to seed borne in mud adherent to the feet RELATIONS TO ANIMATE ENVIRONMENT 111 of birds is much more satisfactory. We may begin with the now historic case, cited by Darwin, of the leg of a Red-legged Partridge which was found encased ina ball of earth, asa result of injury to the foot. This foot was submitted to Darwin by Professor Newton, who suggested that it might afford some in- teresting facts in the matter of the relation of birds to seed dis- persal. And this proved to be the case, for, as is recorded in the Origin of Species, this ball of earth, which weighed six ounces, and had been kept for no less than three years, “when broken, watered, and placed under a bell-glass, [produced] no less than eighty-two plants. ..: these consisted of twelve monocotyledons, including the common oat, and at least one kind of grass, and of seventy dicotyledons, which consisted, judging from the young leaves, of at least three distinct species”. This, of course, was a quite abnormal case; but Darwin had already collected much evidence on this point. Thus he in one case removed sixty- one grains, and in another twenty-two grains of dry argillaceous earth from the foot of a Partridge. And again, from the shank of a Woodcock, he removed a little cake of earth, weighing only nine grains, and this contained a seed of the toad-rush (Juncus bufonis) which germinated and flowered. The botantist Kerner has since brought to light additional evidence on this subject. He remarks: “The extraordinary oc- currence on the edges of ponds in Southern Bohemia of the tiny Coleanthus subtilis, which is indigenous to India, and the sudden appearance of the same species of grass in the West of France about twenty years ago, may be unhesitatingly attributed to the mode of dispersion in question; as may also the occur- rence of the tropical Sccrpus atropurpureus on the shores of the Lake of Geneva, and that of the southern native Anagallis tenella on the shores of the Schwarzsee at Kitzbiithel in North Tyrol.” He also gives an instance of the case of a Little Owl (Athene noctua), which in catching mice brushed against worm- wood-bushes (Artemisia), and when it flew away was all be- smeared with the fruits which had been rendered sticky by a previous shower of rain. A similar case is recorded by Dr. H. O. Forbes in his Wanderings in the Eastern Archipelago, where two species of Heron (Herodias nigripes) and Demiegretta sacva breeding in “West Island”—Cocos Keeling Group Is- lands—nest on high Pisonia trees, and often, in consequence, 112 A HISTORY OF BIRDS died from the number of the glutinous seeds which clogged their feathers. Again, Dr. C. W. Andrews, of the British Museum, has shown that Pisonia seeds are constantly being dis- tributed over Christmas Island (Indian Ocean) by sea-birds whose feathers become so clogged thereby that flight is consider- ably impeded. Birds of prey aid in this work of seed dispersal in another way. Vegetivorous fishes, when eaten by piscivorous birds— Hawks, Owls, Kingfishers and so on—frequently contain seeds in the stomach. These are either torn from the body of the victim on the margin of the stream, or are ingested by the bird with the prey; but in either case many germinate, sometimes being deposited far from the place whence they were taken, and from the habits of the bird, the chances that they will be set free in a favourable spot are considerable. Similarly, when granivorous birds are eaten by Hawks and Owls, the seeds contained in the victim’s crop are either scattered over the ground at once, or are sown in the excreta of the slayer. Thus, then, it is clear that the influence of birds on the plant world, though not perhaps very great, is by no means a negligible quantity. But some plants, such as the mistletoe and its allies, are dependent for their very existence to the agency of birds, and it seems certain that the brightly coloured fruits of our hedgerows have come into existence through the same cause. That is to say, they have been developed to serve as allurements to bring about seed dispersal and the spread of the species. More correctly, perhaps, the factors which brought about the initial stages in the development of this fruit —whether mutation or the cumulative action of definite varia- tion—secured to these plants material advantages in the struggle for existence; and hence the increasing perfection in the device, if device it may be called. On the other hand, the birds have also profited, for fruit-eating birds certainly owe their existence to this evolution of fruit-bearing plants. In distributing the seeds of these they are sowing for their future use, as much as when men sow acorn-field. In favour of the mutation theory we may remark that, whatever may have originally served as the inducement to birds to swallow the seeds of these plants, served at the same time, in all probability, to encourage muta- tion, inasmuch as it has been shown that, as a rule, the growth RELATIONS TO ANIMATE ENVIRONMENT 113 of ingested seeds is retarded, and this fact, as De Vries has shown, tends to produce mutation. While, in considering the relation of birds to their animate environment, it is easy to show that they undoubtedly exert a modifying influence upon the plant world, it is by no means so easy to demonstrate the fact that they play a similar part with regard to the animal world, including their influence on one another. Yet such is the case, though from the nature of the evidence this influence rests largely rather on deduction than on an array of stereotyped facts. That many groups of invertebrates with enormous powers of multiplication are kept in check by birds, there can be no doubt, and nowhere is this more certain than in the case of the Insecta, for a vast number of species of birds subsist entirely on an insect diet ; and to these must be added a number of species which during the breeding season at least become insect de- stroyers. No less important is the part played by birds in keeping down the numbers of such prolific Mammalia as the rodents. How real is this check may be seen during times, when, gener- ally from man’s stupid interference in killing off these police of nature, these mammals increase till they become a veritable plague. The recurrent vole plagues in Great Britain may serve as acase in point. In the last of these, which occurred in the South of Scotland and North of England during 1890-92, the common field-vole (Microtus agrestis) multiplied to such an appalling extent as to threaten the farmers of the infested districts with ruin. And by far the most powerful agent in the final suppression of these invaders was the work of birds of prey, especially of Kestrels and Short-eared Owls. The latter in- deed developed a remarkable fecundity under the stimulus of this plenty. Normally laying from four to eight eggs, clutches of thirteen now appeared. And before the end of the plague it was estimated that no less than 400 pairs of Short-eared Owls alone were finding sustenance in the stricken area. Further, it is said that not only were clutches of eggs enormously increased in size, but that at least two broods were produced by each female during this time. But for the work of these birds the whole face of the country round might well have been changed. 8 114 A HISTORY OF BIRDS Incidentally this remarkable case serves also to illustrate the fact that the numerical level of a species is dependent largely upon the supply of food. And-that this is so we may point out, on the authority of Mr. W. H. Hudson, that the Caracaras or Carrion Hawks of South America have largely increased in numbers sincé the introduction of large herds of cattle into the plains of this vast cattle-raising region. They find abundant food in the offal from the carcasses of the cattle slain for European markets. By way of further illustration of the influence of birds on their animal environment, take such a case as that cited by Darwin, of the absence of feral cattle, horses and dogs in Para- guay owing to the abundance of a certain fly which lays its eggs in the navels of these animals as soon as they are born and so destroys them. Darwin contended that these flies must be held in check by insectivorous birds, and that these were in turn kept down by Hawks; but for which, he argues, the insectiv- orous birds might increase sufficiently to hold the pestiferous flies in check, and so render existence possible for these per- secuted mammals. It may well! be, indeed, that the navel- breeding insects owe their amazing abundance to this chain of circumstances. But, be this as it may, the main point—the inability for these mammals to maintain a hold on life in this region—remains the same, and this materially affects, as he shows, the whole face of the country in so far as its vegetation is concerned. A similar case affecting sheep in New Zealand is furnished by the Kea Parrot, if all accounts are true. This bird, originally vegetivorous, has taken to a carnivorous diet, feeding on the backs of the huge flocks of sheep kept by the colonists. The Parrot is said to tear away the wool, and burrow down through the flesh for the sake of devouring the kidneys, though this part of the story savours of the ridiculous, since the bird would certainly never succeed in obtaining these morsels. Neverthe- less, if, as the flock-owners avow, these birds actually devour any part of the flesh of the back, death would certainly ensue. And after such fashion birds may well have played an import- ant part in the past in determining or controlling the mam- malian life in different parts of the world. Before man took it upon himself to regulate the balance of RELATIONS TO ANIMATE ENVIRONMENT 11s nature, birds must have played no inappreciable part in keeping in check the prodigious fecundity of gregarious fishes, both fresh and salt water ; and blundering-efforts made to-day by certain ill-informed would-be legislators to keep down fish-eating birds, on the ground that they lessen our food supply, fail of their purpose. For should they succeed in appreciably reducing the numbers of these birds, they will but give a fresh impetus to the shoals of predaceous fishes which would profit by the increased abundance, and over these they have no control whatever. The Secretary-bird, the New-World Vultures, and certain species of Kingfishers may serve as examples of birds which contribute more or less effectually to keep in check the undue increase of reptiles. The Secretary-bird (Serpentarius reptilivorus) of S. Africa, from its fondness for poisonous snakes, has during the last few years been carefully protected by law. Standing nearly four feet in height and of powerful build, this remarkable bird—an aberrant member of the Hawk tribe—displays no small skill and caution in attacking its venomous prey, shielding itself by means of the wings, and kicking violently with both feet until its victim is vanquished. The “ Turkey-buzzard” of the Genus Cathartes—more commonly known as the Turkey-buzzard or Turkey-vulture—like the Secretary-bird is an aberrant member of the Accipitres. By preference a Carrion-feeder, this bird, however, confers yet other benefits by its fondness for the eggs of the alligator. In this it displays great cunning, watching the process of deposition, and pouncing down upon the prize so soon as the unsuspecting reptile has taken to the water. We have been considering birds in relation to their animate environment only in so far as they directly influence this, in so far-as they may be regarded as affecting the balance of organisms other than birds. But we may turn now to another aspect of the picture, or rather, to the complementary picture, which shows us how this animate environment reacts upon the birds. This reaction appears to obtain only between the birds and their animal environment, and different groups of birds on one another. And instances of this phase of bird-life will only be cited where this reaction is exhibited in what may be called a measurable quantity. 116 A HISTORY OF BIRDS The keenness of the struggle for existence between differ- ent organisms occupying the same area is, and can only be, appreciated by us in part; we get but occasional glimpses of | what is going on in this direction. And thus it seems as though the conflict between birds and their animal neighbours is con- fined mainly to the brooding parents and their offspring. During the breeding season birds are subjected to a very heavy toll. Snakes and lizards and rats devour their eggs. Squirrels and prowling carnivores destroy their young, while the sitting bird is always in danger of being surprised and seized when brooding, though the mortality from this last source is trifling compared with that which overtakes the eggs and young. When the critical period of reproduction is passed in the neighbourhood of human communities, the destruction, especially with regard to eggs, is appalling, and it appears to attain its highest intensity where civilisation is most advanced. This is largely due to the ravages made for economic purposes. The young birds, from the moment they leave the egg till the time they have learned to fly, run the gauntlet of a host of enemies, even invertebrates taking part in the carnage. For Dr. Alcock has recorded in his charming book, A Naturalist in Indian Seas, how when landing on Pitti Island, in the Laccadive Sea, he found “every foot of the ground above high water-mark literally carpeted with young Terns of two species, many living and nearly full-fledged, many dead and rotting, and many reduced to clean-picked skeletons with only the quill feathers still sticking to the wing-bones. . . . We soon discovered that one great cause of the wholesale destruction of young birds was the voracity of swarms of large hermit crabs (Cenobita), for again and again we found recently killed birds in all the beauty of their first speckled plumage being torn to pieces by a writhing pack of these ghostly crustaceans. There were plenty of large ocypode crabs too (O. ceratophthalmus) aiding in the carnage.” And he continues: “ Moseley, in his Notes of a Naturalist on the Challenger, made mention of a grapsus crab that he saw on St. Paul’s Rocks carrying off a newly hatched Tern, but such an accident does not shock one’s feelings nearly so much as does the thought of full-grown young birds, nearly ready to fly out into the world and to exercise their intelligence, being overpowered by force of numbers (SASNANAG SAQISINTHAS) SNINONYd Ad vO RELATIONS TO ANIMATE ENVIRONMENT 117 and slowly eaten alive by animals so far inferior in the scale.” Strangely enough, the nestlings of the Booby (Szla leucog- aster) and of the Noddies (Anous stolidus and A. melanogenys) which Moseley found on St. Paul’s Rocks, defended themselves vigorously and successfully from the similar attacks of this crab (Grapsus strigosus). It may here be noted that while many birds appear to suffer the spoliation of their nests and the slaughter of their young by their more rapacious neighbours, if not with indiffer- ence, at least with but a feeble show of resistance, others profiting by experience have adopted measures whereby they may escape these unwelcome attentions. Thus Moseley on his visit to Inaccessible Island found that feral pigs had nearly exterminated a Penguin rookery on the south side of the island, but a few Penguins remained which had saved themselves by building in holes under stones where the pigs could not reach them. Similarly, the Barn Owl (Strzx flammea) in Texas and in India, and the Short-eared Owl in the Aleutian Islands, breed in fairly deep burrows, though the causes which have led to this appear to be unknown. But besides enemies from without, a very heavy infant mortality is inflicted by ravages from within, by the depreda- tions of predatory birds, which contrive to support themselves and their families by preying upon the eggs and nestlings of their more helpless neighbours. An instance of this is furnished by the great breeding colonies of Penguins and Cormorants on Dassen Island, off the Cape of Good Hope. Mr. M. J. Nicoll, a naturalist who visited this island in 1906, found in addition to vast hordes of Jackass Penguins (Spheniscus demersus) ;— it was estimated that about nine millions of these birds were breeding here, laying their eggs in holes—an enormous colony of Cormorants, and con- siderable numbers of Sacred Ibises and Gulls. The Gulls and Ibises seem to subsist, during the breeding season, on the eggs and young of the Cormorants. The Gulls displayed a most extraordinary watchfulness over the sitting Cormorants, seizing the eggs with a devilish dexterity if for a moment they were left unguarded: later they took the young. The Ibises appear 118 A HISTORY OF BIRDS to content themselves with preying upon the young only, which they seized for the sustenance of their own offspring, feeding them upon the entrails of their victims. Wherever large breeding colonies of marine species are to be found the larger Gulls and Skuas are sure to be met with, these living almost entirely on the eggs and young of their more helpless neighbours. Of the depredations caused by Skuas among the Penguin colonies of the Antarctic, Dr. E. A. Wilson, one of the naturalists of the Déscovery expedition, tells some lurid stories. Writing of McCormick’s Skua and the colonies of the Adélie Penguin he says: “ Hanging round the rookery, with the unmistakable look of a thief, the Skua will run up to a chicken almost as big as himself, drag it by degrees away from the more crowded part of the rookery, and then gradu- ally worry it to death. . . . The Penguin chick pipes his loudest, but the old birds standing round take very little notice. Oc- casionally one in passing will make a run at the Skua, drive him off for a moment, but the chick is separated from the rest, and the old Penguin has no mind to stop and shelter him, so back the Skua comes to complete his work. Literally, in a rookery such as that of Cape Crozier, one cannot walk ten yards without coming on a dead Penguin chick. Many of these ... are dried and flattened mummies, trodden down and flattened into the stones and guano that cover the ground. But an enormous proportion are seen to be fresh victims, if one visits a rookery in January, when the Skuas have not only themselves but their young to feed.” “ But,” he also remarks, “the Skua even robs its own kind, and in a nesting colony of some twenty or thirty birds, the numbers that have apparently * lost their eggs, or one at least, by robbery is always fairly large.” This fact, coupled with the pugnacity of the young (p. 320), tends to keep down the numbers of these predaceous birds, which otherwise would long since have exterminated the Penguins. The foregoing illustrations of the severity of the struggle for existence deals only with a struggle sustained by species which yet contrive to maintain a hold on life. But we must pass now to another aspect of this theme—to an aspect which shows how the extermination and extinction of species is brought about as soon as such species become too highly specialised to respond to changes in their environment. RELATIONS TO ANIMATE ENVIRONMENT 119 Unfortunately, Great Britain furnishes us with many in- stances of this process of extermination, which is the first step to extinction. The recital of this history makes a melancholy story which has been told at length, and with uncommon force and weight by Professor Newton, than whom none have ever excelled in all that pertains to the history of birds. From his account the following instances are for the most part selected. First of all we have the Crane, which was described by Turner as breeding in our fens in 1544, but soon after this date this magnificent bird seems to have forsaken its breeding haunts and to have been met with only as a winter visitant. Though we have no record of the fact, this must be inferred from an observation of Sir Thomas Browne, who speaks of it, in 1682, as being found in the open parts of Norfolk in wzder, the county in which it formerly bred in considerable numbers. In 1678 Willoughby was still able to say : “ They come to us often in England, and in the fen-counties, Lincolnshire and Cam- bridgeshire, there are great flocks of them; but whether or no they breed in England I cannot determine. .. .” Their disap- pearance is to be attributed to the drainage of the marshes, the increase of the population, and the use of firearms. With the dying out of the original breeding stock the number of annual visitants slowly declined, till now it occurs only sporadically —a single bird being seen and generally killed at once—every ten years or so. The same is true of the Spoon-bill (P/atalea leucorodia), and of its near relative the Glossy Ibis (/é7s falcan- ellus). And to these we must add the Great Bustard (Ozzs tarda), the Ruff (Machetes pugnax), the Avocet (Avocetia recurvi- vostra) and the Capercailzie, which has been successfully rein- troduced, while others, such as the Bearded Tit (Panurus biarmicus) and the Great Skua, are fast disappearing. Among birds of prey the havoc has been even more striking, and this is owing to the zeal of game-preservers who, in their slaughter of so-called “ vermin,” have exhibited a combination of greed and ignorance such as cannot be described in temperate language. The insane vanity of women has brought about a desperate condition of things with regard to birds in other lands. The ends of the earth have been searched to provide birds of beauti- ful plumage for the trade of the milliner; and this traffic has 120 A HISTORY OF BIRDS led to the perpetration of atrocious barbarities. The total ex- tinction of some species, such as Birds of Paradise, Egrets and Humming-birds, will surely come to pass unless legislation steps into the breach, while the reduction of others has already reached such a pass that their doom is sealed. A distinction has been drawn, it will be noticed, between extermination and extinction. The former term is here used to indicate species which have been extirpated over large geo- graphical areas, but still survive elsewhere; extinction marks the final disappearance of that particular species throughout the world, though in most cases extinction has befallen only such species whose range was limited—for the most part island forms. The most familiar instance of the extinction of a bird en- joying a fairly wide distribution is that of the Great Auk or Gare-fowl, nearly allied to and closely resembling the Razor- bill, still common along the British coasts. This bird ranged from our shores eastwards as far as Denmark and northwards and westwards to Iceland, Greenland and Newfoundland. Yet it had absolutely lost the power of flight. As large as a Goose—measuring about two feet eight inches in length—its wings were actually smaller than those of the Razor-bill which does not exceed seventeen inches from the tip of its beak to the tip of its tail, Entirely aquatic in its habits, and free from enemies at sea; the wings slowly degenerated, and it is possible that they would in course of time have completely disappeared, as in the case of the wingless fossil Hesperonis, of the cretaceous epoch. When, however, man appeared upon the scene, and discovered that Great Auks were at least palatable, the fate of this bird was sealed. This war of destruction appears to have been chiefly waged in the neighbourhood of Newfound- land, which was apparently the headquarters of this bird, inas- much as it occurred here in great numbers, as may be gathered from the narratives of the early travellers, according to whom it was much sought after by French fishermen, who victu- alled themselves with, and salted down, the wretched victims. Mr. Howard Saunders records that in A Discourse and Dis- covery of Newfoundland written by Captaine Richard Whit- bourne of Exmouth, in the county of Devon, published in 1620, it is stated that among the Water-fow]l, which are very plenti- ful, are “Penguins” which “are as big as Geese and flye not, RELATIONS TO ANIMATE ENVIRONMENT 121 for they have but a little short wing, and they multiply so in- finitely upon a certain flat Iland, that men drive them from thence upon a boord, into their boates by hundreds at a time, as if God had made the innocency of so poore a creature, to become such an admirable instrument for the sustentation of man”. “How long,” Mr. Saunders remarks, “this slaughter continued it is impossible to say, but Auspach, writing in 1819, speaks of ‘the Penguin’ as exterminated in that quarter.” On Funk Island these birds were discovered in 1534, and could then be reckoned by thousands. For more than 200 years they were subjected to a ceaseless persecution, till at last they were exter- minated. On this island, it is said, it was the custom for the crews of several vessels to spend the summer for the sole pur- pose of killing “Gare-fowl” for the sake of théir feathers. Stone pens were erected into which the birds were driven like sheep, to be slain by millions and their bodies left to rot where they lay. As a British bird it appears to have been nowhere plentiful during the two or three centuries of its existence. Earlier, however, it must have been commonly used for food, inasmuch as its bones occur in the kitchen-middens of Caithness and Oronsay, and ina cave near Durham. Similarly, its bones occur in kitchen-middens in Denmark. Hence we may suppose that the cause of its extermination in this part of the world was the same as that which culminated in extinction some hundreds of years later in Newfoundland. The last Great Auk in Britain was taken alive in Waterford Harbour in 1834. The Islands of Mauritius and Rodriguez furnish us with two further illustrations of the work of extermination due to man’s handiwork. Mauritius was the home of a gigantic Pigeon—the Dodo, a bird as large as a small swan, but absolutely in- capable of flight. This combination of great stature with flightlessness was the outcome of an abundance of food, and the freedom from all necessity of procuring this food by flight, or by resorting to the use of the wings for the purpose of avoid- ing enemies. The atrophy of the wing had proceeded so far when man entered into this paradise that it had become so reduced as to be inferior in size to that of our common Rock Pigeon. Thus pinioned, it was at the mercy of the invader; who, however, accomplished the work of destruction unwittingly, 122 A HISTORY OF BIRDS and this by the introduction of pigs which devoured the eggs and young. The sister island of Rodriguez harboured another Pigeon scarcely inferior in size to the Dodo. This was known as the Solitaire; but somehow or other the fame of this bird has been quite eclipsed by that of its relative the Dodo, yet, in many respects it was the more interesting bird of the two. Most of our knowledge of this bird we owe to the traveller Leguat, who published an account of his wanderings in 1708, Indiscriminate slaughter, under the pretext of killing for food, has wiped out many other species, of which not more than one or two can be mentioned here. First of all we may take the case of the Labrador or Pied- duck (Somateria labradoria), which occurred in plenty, in summer, about the mouth of the St. Lawrence and the coast of Labrador, migrating in winter to the shores of Nova Scotia, New Brunswick and New England. This bird, which closely resembled the Eider-duck, was at one time as commonly dis- played in American markets as Mallard or Wigeon are in England. Suddenly the supply ceased, and inquiry soon showed that it had ceased for ever. Those who had so long found its capture profitable had not wit enough to see that the policy pursued of plundering the nests and mercilessly shooting the birds, must soon end in putting an end to this source of income, the wretched victims being flightless, and therefore restricted as to their breeding area. About thirty-eight specimens are all that are known to exist in museums. A similar case is that of the largest known species of Cor- morant (Phalacrocorax perspicillatus), which, according to Dr. Steijneger, became extinct about the middle of the nineteenth century. This bird was formerly abundant in Behring Island in the North Pacific, but was exterminated by incessant slaughter for the purposes of food, though one would hardly have supposed that Cormorant, in any shape, would prove a sufficiently palatable dish to bring about the extinction of the bird. Only four skins and a tew bones are all that remain of this bird. Finally let us take the case of the giant flightless Moa of New Zealand. “Although Moas were still numerous,” says Mr. F. A. Lucas, the distinguished American Ornithologist, “when man made his appearance in this part of the world, the RELATIONS TO ANIMATE ENVIRONMENT 123 large deposits of their bones indicate that they were on the wane, and that natural causes had already reduced the feathered population of these islands. A glacial period is believed to have wrought their destruction, and in one great morass, abounding in springs, their bones occur in such enormous numbers, layer upon layer, that it is thought the birds sought the place where the flowing springs might afford their feet at least some respite from the biting cold, and there perished miserably by thousands, “What Nature spared man finished, and legends of Moa hunts and Moa feasts still lingered among the Maoris when the white man came and began the extermination of the Maori.” That these gigantic birds—the largest species being far larger than an Ostrich—owe their final extinction to man there can be no doubt; for masses of charred bones and egg-shells show that they were hunted for the purposes of food. Further illustrations of this work of extermination and extinction could be shown, but enough has surely been quoted for the purpose of this chapter, since our aim is more especially to show that birds, by close adaptation to any particular environ- ment, become too highly specialised to respond to any further changes therein, and consequently must die out. Nowhere is this fact more strikingly illustrated than in the case of flightless birds. Here, from an abundance of food procurable on the ground, and freedom from enemies, flight becomes unnecessary. As a consequence, in the course of a few generations the wings have so decreased that flight has become impossible. Should these times of abundance and peace continue, the wings, as in the case of the Moa, vanish completely. The introduction of carnivorous animals now introduces‘a new factor into this Edenic environment, to which it is impossible to respond further. Return to flight is impossible, and before any devices for avoid- ing or meeting the new conditions can be developed, extinction has overwhelmed the victims. CHAPTER VIII PECULIAR INTERRELATIONS Ostriches and Zebras. Rheas and Guanacos. Oxpecker and big Game. Egrets and Elephants. Bee-eaters and Bustards. Penguins, Albatrosses and Petrels. Osprey and small birds. Chaffinch and Missel-thrush. Burrowing Owl and Prairie-dogs. Petrels and “ Tuatera Lizard’’. Puffins and Rabbits. Skuas and Gulls. Frigate-birds and Gannets. Cuckoos and their dupes. The causes of parasitism. HE subject of the last chapter leads us insensibly up to the consideration of those remarkable interrelation- ships which exist between different species of birds, or more commonly, between different species of birds and of other animals, though the part these interrelationships play in evolu- tion is not very obvious. For example, it is not easy to see why the Ostrich in Africa and the Rhea in South America should commonly associate with herds of the larger ungulates of their respective countries. Thus the Ostrich commonly consorts in troops of from thirty to forty with herds of Zebras or the larger Antelopes; while the Common Rhea similarly associates with herds of Deer, and the smaller Darwin’s Rhea with herds of Guanacos (Lama huanacos). In this association there is no apparent advantage to be gained, but there are many similar cases which are less Gace: See Take, for example, the case of the Oxpecker or Rhinoteros-bird (Buphaga Africanus), a native of South Africa, and generally regarded as a species of Starling. This bird is commonly found in intimate association with basking herds of cattle and big game, running about all over the bodies of these creatures in their search for the ticks and other parasites which harbour there. Lately, however, this bird has fallen into disgrace, since it has extended its attentions to the horses and cattle of the colonists with any- thing but happy results. It would seem that in removing ticks 124 SLAY GNV SLNVHd WI BEE-EATERS AND BUSTARD FROM ‘‘ ELEPHANT HUNTING IN EQUATORIAL AFRICA” PECULIAR INTERRELATIONS 125 from the more tender hides of these animals the birds caused wounds, and at the same time gained a taste for blood, with the result that, where horses and cattle are at all numerous, they become severely persecuted by these birds, who now seek, not so much to prey upon the ticks as the hosts thereof, which suffer considerably in consequence. Thus we see how easily long-rooted habits may become changed, and how an originally useful instinct may become depraved. The tough hide of the rhinoceros was proof against the beaks of these birds, and consequently nothing but good resulted from their presence, but, as we have shown, a very different state of things began when the hides of the imported domesticated animals became subjected to a similar inspection. On account of the damage they do the restrictions imposed by Government for their protection have now been removed, but the Oxpecker will doubtless long contrive to hold his own in this vast country. The work of the Rhinoceros-bird in England is performed by the Common Starling, and so far no harm to cattle has been done by reason of injuries inflicted on the hides. Similarly, in East Africa, Egrets swarm over the bodies of elephants when they approach the neighbourhood of water, apparently, as it has been suggested, for the sake of capturing the various kinds of insects put up by the elephants as they move about. In like manner the Rosy Bee-eater (Merops nubicus) in East Africa is described by Mr. Arthur Neumann as habitually riding about “on the back of the large crested Bustard or ‘Pauw’ (Eupodotis kor’) which is common about the north- east extremity of Bassu. It sits far back on the rump of its mount, as a boy rides a donkey. The Pauw does not seem to resent this liberty, but stalks majestically along, while its bril- liantly clad little jockey keeps a lookout, sitting sideways, and now and again flies up after an insect it has espied, returning again after the chase to ‘its camel’ as Juma [his native servant] not inaptly called it. . . . I have also noticed this pretty little bird sitting on the backs of goats, sheep and antelopes, but the Pauw seems its favourite steed. I imagine it gets more flights in this way at game put up by its bearer, which also affords it a point of vantage whence to sight and pursue its prey in a country where suitable sticks to perch on are few.” Much more curious are the associations formed by birds 126 A HISTORY OF BIRDS during the breeding season. In the case of aquatic birds which have perforce to congregate in great numbers on a small area of land, this phase is presented in a very striking manner. Moseley cites a case of this kind, where, when visiting Night- ingale Island—one of the Tristan Da Cunha group—he found vast numbers of Penguins (Catarrhactes chrysocome) and Yellow- billed Albatrosses (Diomedea culminata) breeding together on the open ground, and with these were many nestling pairs of Skuas (Stercorarius antarcticus), while the soil beneath was riddled with holes burrowed by various species of Petrels. Similarly, the huge nests of large birds of prey, such as those of the Secretary-bird (Serpentarius) and of the Osprey (Pandion\, invariably lodge within their walls numbers of nests of small Passerine birds—and even Night-herons in the case of the Osprey—these nests being built into the outer walls, much as birds build nests in the thatched roofs of houses. This peculiar site is chosen, however, not so much for convenience as for the sake of freedom from molestation which they gain by thus seeking the protection of their powerful neighbours. Similarly, in France the Chaffinch is said to build its nest, whenever possible, as near as may be to that of the Missel- thrush, a bird which is exceedingly pugnacious and intolerant of the presence of Magpies which have rather a fondness for the eggs of small birds. But instances of this kind could be multiplied with ease. Let as pass on to stranger associations. One of the most familiar examples of the kind to which we refer is that afforded by the Burrowing Owl (Speotyto) of America. In North America this bird shares the burrows of “ prairie-dogs,” rats, ground-squirrels or badgers, and in South America those of the Viscacha, Patagonian hare, and, it is said, even of armadillos and large lizards, constructing therein a nest of grass and feathers, Where ready-made burrows are not to be had, however, they will dig for themselves. Similarly, various species of Petrels in New Zealand share the burrows of the “Tuatera Lizard” (Sphenodon). The Petrel seems generally to live on the left, the Tuatera on the right side of the burrow ! The amicable terms which these birds seem to have es- tablished with the occupants of these burrows is the more striking because the British Puffin which, whenever possible, PECULIAR INTERRELATIONS 127 selects rabbit burrows for its nursery, will not tolerate the presence of the rightful owners of the burrow. Without doubt the most interesting and most puzzling of all the interrelationships displayed by birds relate to the phenomena of parasitism which is manifested in two distinct ways. The first of these is illustrated by birds which waylay others for the sake of robbing them of their food, and among these the Skua-gulls and the Frigate-birds hold perhaps the foremost place. “Woe to the Gull or other sea-bird,” says Brehm, “ which seizes its prey within sight ofa Skua! With arrow-like swiftness he follows the fortunate possessor uttering barking cries, dances, as if playfully, round him on all sides, cunningly prevents any attempts at flight, resists all defence, and untiringly and ceaselessly teases him till he gives up his prize, even though it has to be regurgitated from his crop.” It is this habit of catching the food of the persecuted bird which has given the Skua the unenviable name of dung-eater, the common notion being that the bird in its fright voided ex- crement! The Frigate-bird is a no less persistent robber. Dr. C. W. Andrews, during his exploration of Christmas Island (Indian Ocean) had plenty of opportunities of watching these birds. They “by no means depend for food,” he says, “on the fish they catch themselves, but systematically rob the Gannets which feed in great numbers on the island. Towards sunset many Frigate-birds may be seen sailing along the coast, watching for the return of the Gannets full-fed from the fishing grounds. The birds being well aware of what is in store for them, and knowing that if they can reach the shelter of the trees they are safe, approach the island at a great speed, flying as low down as possible. Usually, while they are still at some distance, two or three Frigate-birds give chase, and hunt the Gannet back- wards and forwards, continually trying to get beneath it and to cut off its retreat to the trees. The chase may last several minutes, but at length the exhausted bird disgorges some of the fish it had swallowed, and this is immediately caught in mid-air by one of the pursuers.” Before proceeding further it would be well to point out that neither in the cases which have been cited, nor in those which are to follow on the subject of parasitism, are these inter- 128 A HISTORY OF BIRDS relationships so close as is the case with the lower animals. Commensalism and symbiosis are unknown among the birds, while the parasitism of which instances have been given, and of which we are presently to speak, is of a very different kind\to that which obtains among invertebrates. As may have been surmised, the parasitism of the Cuckoos and some other birds is now to be discussed. In this form of parasitism the female has adopted the practice of depositing her eggs in the nests of other birds and there leaving them, without further care, to be hatched by her dupes, who, un- conscious of the trick which has been played, perform the duties the immoral parent has contrived to_ shirk. First of all as to the Cuckoos. Though the broad facts of the case, as illustrated by the Common Cuckoo (Cuculus canorus), are well known, they will be repeated here for the sake of the bearing they have on less widely known facts which have been brought to light during recent years, facts which are of the highest importance. This bird then, which reaches the shores of Great Britain in the month of April, deposits its eggs, singly, in the nests of the smaller Passerines, though occasionally, by an error of judg- ment, other species are selected. No less than eighty-four different species of birds are known to have been victimised in this way—including Eider-ducks and Grebes !—but the majority of such eggs are distributed among Robins, Hedge-sparrows, Wagtails, Meadow-pipits, Tree-pipitse Warblers, Thrushes and Red-backed Shrikes. The egg is duly brooded by the dupe with her own eggs, and in due time is hatched. Within an hour or so of this event a gruesome domestic tragedy is invariably enacted ; for, prompted perchance by the overmastering instinct of self- preservation, the foundling proceeds to eject from the nest the offspring of its foster-parents, as though conscious that they would be utterly unable to provide sufficient food to satisfy its insatiable appetite while these competitors remained alive. Accordingly, with a most diabolical persistence and ingenuity, this blind and naked hooligan proceeds to the work of eviction, one after another being pitched over the edge of the nest. This feat is performed by burrowing under the victim until the body thereof rests upon the middle of the little murderer’s back, PECULIAR INTERRELATIONS 129 when, raising the wings to keep its burden in position, it climbs up the nest backwards. Little by little, with widely spread legs, and the use of the beak as a lever, the journey to the top of the nest is made, when, with a supreme effort the helpless little Robin or Hedge-sparrow, as the case may be, is sent sprawl- ing, todie very shortly after of exposure. Not until the last is ejected does this extraordinary little criminal relax its efforts; but so soon as all is over it settles down contentedly to enjoy life, developing a most ravenous appetite, and making the most exacting demands upon its foster-parents. Without for the present discussing the factors which have resulted in this most successful fraud on the part of the Cuckoo, we may refer next to another very remarkable phase of this life-history, and this concerns the coloration of the Cuckoo's egg, which, as a rule, bears a very close resemblance to those of the nest in which it is laid. In other words, the eggs of the Cuckoo show a very remarkable range of variation, or rather of colora- tion, corresponding, roughly, with the number of species which are used as dupes. Evidence has now accumulated to show, however, that this range of colours becomes manifest only when the eggs of a large series of Cuckoos are examined. In other words, the eggs of any particular Cuckoo are all of the same type, both in colour and markings; and this is true when all the eggs laid by a single female throughout each season for a number of years are examined—and such series have been found, by reason of certain peculiarities of colour and pattern. Further, it is now almost conclusively established that the colour and pattern of any given egg bears a more or less close resemblance to the eggs of the host in whose nest they are placed. Where this rule is broken it is more than probable that the disparity is due to untoward circumstances, to the fact that the Cuckoo at the time she deposited her egg was unable to find a suitable nest, and so dropped the egg into the nearest likely nest available to take its chance. How this curious resemblance came about it is not easy to see at first; for it is certain that the bird cannot in any way voluntarily influence the colour of her egg, nor can we suppose that she carries her egg in her mouth while she makes the round of nests in the neighbourhood for the purpose of selecting that as a nursery which contains eggs most 9 130 A HISTORY OF BIRDS like her own. The most probablé explanation is that which has been formulated by the late Professor Newton—though he does not claim the discovery as wholly his own—who suggests that the Cuckoo has split up intoa number of distinct “gens”. Thus he recognises Robin Cuckoos, Meadow-pipit Cuckoos, Wagtail Cuckoos, Reed-warbler Cuckoos, and so on—Cuckoo-types whose eggs resemble the several species just enumerated. This formation of Cuckoo “ gens” has, he suggests, been brought about by selection. When the Cuckoo first began to shirk the duties of incubation by dropping its eggs into the nests of other birds, only those were hatched which sufficiently matched those of the dupe, the others being ejected from the nests by the owners thereof. A further process of selection took place, moreover, if, on hatching, the food of the dupe proved unsuitable to the needs of the foundling. Thus, it would come about that female Cuckoos reared in Robins or Wagtails’ nests would seek the nests of these birds in which, in turn, to lay their own eggs. The probability of this explanation of the evolution of the resemblance between the eggs of the Cuckoo and those of its host has recently been exhaustively investigated by Mr. Oswald Latter, and though he at first felt sceptical about the matter, he has come to the conclusion, after examining many hundreds of eggs, that the theory is well founded. A most serious objection, however, it has been urged, to the stability of this theory is the certainty that female “ Robin Cuckoos” must frequently mate with male “ Wagtail Cuckoos,” and so on, and that this being so we must assume that the inherited habits and characters of every female Cuckoo must follow only the female line of descent. But this objection is based on a confusion of the facts of the case. It appears to be forgotten that these “ Robin Cuckoos” and “ Wagtail Cuckoos” are not hybrids between the foster-parent and the Cuckoo, What the female Cuckoo has inherited is the instinct to seek out, whenever possible, nests of birds of the species by which it was reared, And there is nothing more wonderful in this than in the remarkable inherited instincts of many female insects which make peculiar provisions for their offspring: in the case of the Cuckoo we are dealing with inherited instinct prompted by memory. That the Cuckoo must keep a careful watch on birds likely PECULIAR INTERRELATIONS 131 to prove suitable victims is evident from the position of many of the nests which are found to contain young Cuckoos. Asa case in point mention may be made of an instance where a young Cuckoo was found in the nest of a Pied Wagtail which had built in a flower-pot containing a plant trained over an intricate trellis-work, leaving but small interspaces just big enough to allow the passage of so small a bird, and this flower- pot, it is to be noted, was placed in a greenhouse. Thus then the Cuckoo must have noticed the Wagtails collecting nesting materials, and have watched their destination. Then, having deposited its egg on the ground somewhere in the vicinity, it must have picked it up and gone straight to the flower-pot, thrust in its head and dropped the egg into the nest. The Common Cuckoo (Cuculus canorus) is not the only species of the Cuckoo tribe which is addicted to parasitism. Thus, the great Spotted Cuckoo (Coccystes glandarius)—-a rare visitor to Great Britain, but common in Southern Spain and North Africa—foists its eggs upon various species of the Crow tribe. In Spain, its choice falls upon the Magpie, in Egypt the Hooded Crow, and in Algeria the Moorish Magpie. In this restriction to birds of the Crow tribe this Cuckoo differs re- markably from the Common Cuckoo, which levies service on a large number of species of widely different families. It is further peculiar in that at least two eggs are laid in each nest— sometimes as many as four—while the newly hatched birds live amicably with the rightful occupants of the nest. So closely, it may be remarked, do the eggs of this Cuckoo resemble those of the Crows in whose nests they are placed, that even oologists have been deceived by the resemblance. Many other species of Cuckoos have also become parasitic, and so far as the evidence goes, it would appear that, like the Great Spotted Cuckoo, the young have not developed the re- markable, one might almost say criminal, instincts displayed by the Common Cuckoo. The Cuckoos of the Genus Exdynamys are parasitic. Thus the Koel of Palawan (&. orzentalis) victim- ises a Mynah (Eulabes javanicus), while the Indian Koel (£. honorata) chooses Crows for this purpose. Similarly, the New Caledonian Cuckoo (Caccomantts bronzinus) lays its eggs in the nest of a Flycatcher (Pseudogerygone flavilateralis). The case of the Drongo Cuckoo (Surniculus lugubris) of India is still 132 A HISTORY OF BIRDS more remarkable, since this bird lays its eggs in the nest of the Black-drongo (Buchanga atra),a feat which it apparently could not accomplish but for the fact that it has acquired a most extraordinary resemblance to this bird, thereby enabling it to evade the notice of the owners of the nest when about to thrust upon them the doubtful privilege of incubating its eggs. But of this particulars will be given elsewhere in these pages (p. 327). In Java, however, it appears to dupe the Bulbul (Pycnonotus aurigaster), at any rate two eggs in the British Museum were obtained from the nests of this bird. Though Cuckoos all over the world, and of widely different genera, have acquired parasitic habits, some species build nests and incubate their eggs in normal fashion, though, as a rule, these nests are but indifferently constructed. This does not apply, however, to the Lark-heeled Cuckoos of the Genus Centropus, which build a large globular nest, generally with an entrance at the side. One or two species at least, though commonly parasitic, appear occasionally to build a nest and incubate. This is the case, for example, with the Hawk Cuckoo (Azerococcyx spar- verotdes) of the Himalayas and East Asia, which appears to be normally parasitic, but in the Nilgiris to build a nest and rear its young. This strange aberration of the parental instinct is, however, not confined to the Cuckoos, since it is met with also among the South American “Hangnests,” birds belonging to a widely different group—being true Passeres, Thus one species (Cassidix oryzivorus) in Pard appears always to leave the in- cubation of its eggs and care of its young to an allied species, C. persicus, while farther south it victimises others of about its own size, such as the Crested Cassique (Ostiniops decumanus) or the Yellow Cassique (Cassicus hemorrhous). The nearly allied polyandrous “Cow-birds,” belonging to the Genus Molobrus, are yet more interesting from this point of view, inasmuch as this parasitism appears to have brought about a state of disorganisation of the parental instinct which threatens all the species concerned with extinction, Only one species, Molobrus badius, appears to have retained the normal re- productive instincts. The rest seem to share in common the habit of dropping a considerable number of their eggs in empty PECULIAR INTERRELATIONS 133 nests, or abandoning them by the wayside. But a few are laid in the nests of other birds, by them to be hatched. The only care they appear to take to secure any degree of safety for their offspring is when they pick holes in some, at least, of the eggs they find in the nests they visit for their nefarious pur- poses. Should any of these eggs succeed in hatching, the young Cow-bird quickly seals the fate at any rate of most of the callow-young, by sitting on them until they are smothered, when the dead bodies appear to be thrown out by the Cow- birds’ foster-parents. Even when these strange birds exhibit sense enough to deposit their eggs in nests where incubation is going on they not seldom exhibit a curious lack of discernment, since several.females will deposit their eggs in the same nest, or they will stupidly stab and break their own egg while destroy- ing those of their dupes! The only respectable member of the family, Molobrus badius, is victimised by its near ally J. rufoaxillaris, though strangely enough another species, J/. bonariensts, which is found in this same region—Buenos Ayres— is always detected and repulsed when it similarly attempts to rid itself of the ties of parentage. While among the Cuckoos the majority appear to be para- sitic some at least retain their normal parental instincts, while in others, aberration has taken another course, which, in some ways, recalls features which obtain among the Cow- birds. Thus certain New World Cuckoos, known as the White Ani (Guzra) and the Black Ani (Crotophaga), the former repre- sented by only a single species (Gucra piririqua), the latter by at least three species (Cvotophaga ant, C. major and C. sulct- rostris), exhibit a most remarkable prolificness in the number of eggs produced, as many apparently, or more, being dropped about promiscuously as are deposited in nests. But these Cuckoos are not parasitic. Instead they perform their maternal duties on the co-operative system. A number of females combine to build a large nest of twigs which is placed in a tree, and lined with moss and green leaves. Herein each deposits about five eggs, to the number of twenty or more, and upon these, according to some accounts, all proceed to sit, huddled together, until the eggs are hatched, when the company of mothers proceed to the work of feeding. So flimsily are these nests constructed, however, that not seldom the eggs fall through the nest as they are laid, while 134 A HISTORY OF BIRDS many other eggs appear to be carelessly dropped outside the nest. According to another version, these eggs are arranged in layers, with leaves between each layer, and are then aban- doned, incubation taking place from the fermentation of the decaying vegetable matter aided by the sun. Be this as it may it would seem that the Ani Cuckoos, like their parasitic neighbours and relatives, owe the decadence of their parental instincts to the fact that they are polyandrous, and this because the males largely outnumber the females. But for the fact that the parasitic types have succeeded in producing eggs which, for the most part, are sufficiently like those of their dupes to pass muster, they would have become extinct. There seems to be no doubt about this mimicry of the eggs—to which reference will be made again—and in this connection it is of importance to note that the European Cuckoo (Cuculus canorus) in India, chooses birds of European types as its victims. That parasitism is due to polyandry—and to a less extent to polygamy—we believe is almost certain. And this because such a sexual relationship tends inevitably to lower the parental instincts, just as monogamy tends to strengthen them. Among the polygamous Game-birds there are not wanting signs of degeneracy in the parental instinct. Thus the males commonly leave the care of their offspring entirely to the female, which, indeed, often have to guard them against the violence of the paternal jealousy: while two females will frequently share a common nest, a custom which offers an easy means of shelving responsibility altogether, as in the case of parasitic species. CHAPTER IX PHASES OF SOCIAL LIFE Gregarious birds. Curious sleeping habits. Pelicans fishing. Woodpeckers and food stores. Significance of gregarious habits. HILE the facts related in the previous chapters with regard to the relationships of birds one to another are well known, they are facts which can only be verified by close and careful observation. But the most casual observer needs not to be reminded that many birds are gregari- ous. What advantages may accrue from this relationship, and what modifications thereof have been evolved are, however, by no means so obvious, and it will be the purpose of this chapter to trace these, at any rate in outline. No better example of a gregarious bird could be found than that of the Rook, which the year round herds together in larger or smaller bands. The Limicoline birds afford another good example. But though they commonly keep together to breed in colonies, sometimes of enormous size, in many cases they elect to perform their parental duties in seclusion. Herons breed in colonies but are otherwise extremely solitary birds. While commonly birds of gregarious habits associate in small parties, they may, in the case of some species, as in Flamingoes, the Rice-bird (Dolichonyx oryzivorus) and Starlings, roam in huge flocks, But these numbers are never so great as in the vast assemblages of birds which gather together during the breeding season. ‘This is especially true of Penguins, Alba- trosses and Terns, which may number millions of birds. Among land birds the only parallel is, or rather was, that afforded by the Passenger Pigeon (Ectopistes migratorius). A breeding colony of this species was discovered in 1876 by the naturalist - Brewster. It began near Petosky and extended north-east, past Crooked Lake for twenty-eight miles, averaging three or 135 136 A HISTORY OF BIRDS four miles wide. The birds arrived in two separate bodies, one directly from the south by land, the other following the east coast of Wisconsin, and crossing Manitou Island, the latter body forming an army at least five miles long and one mile broad. The birds at once began the work of nest-building, and in a very short time this colony extended for a distance of about twenty-eight miles of forest, every tree having one or more nests, and some being filled therewith ! It is clear that large assemblages of the same species are only possible when there is an abundance of food for all, and the gregariousness of some birds is probably due to this fact alone, as in the case of Gannets and Guillemots, for example, or the large gatherings of birds of prey, as when following the hordes of migrating Lemmings. It does not seem that such assemblages are bound by any ties of mutual affection or for desire of protection, though these several inducements cannot by any means be sharply divided. Parrots, for example, appear to roam in bands for the mere pleasure of company; while Rooks find in association security against surprise while engrossed in feeding, since one or other of the flock is constantly performing the réle of sentinel. The vagrant bands of the Long-tailed Titmouse, which lend such a charm to our woods during the autumn and winter months, are held together very largely at any rate by their common needs. The discovery of insect food at this time is an arduous task, and if undertaken individually many would starve. As Professor Newton remarks: “A single Titmouse searching alone might hunt for a whole day without meeting with a sufficiency, while if a dozen are united by the same motive, it is hardly possible for the place in which the food is lodged to escape their detection, and when discovered a few call-notes from the lucky finder are enough to assemble the whole company to share the feast... . One tree after another is visited by the active little rovers, and its branches examined: if nothing be forthcoming, away goes the explorer to the next that presents itself, merely giving utterance to the usual twitter that serves to keep the body together. But if the object of the search be found, another kind of chirp is emitted, and the next moment the several members of the kand are flitting in succession to the tree, and eagerly engaged with the spoil.” PHASES OF SOCIAL LIFE 137 That the gregarious habit is formed originally not so much by community of interests as by the common attraction of an abundance of food is, as we have already hinted, indisputable. Thus it is that birds of prey are rarely gregarious. An ex- ception is found in the case of the little Red-footed Falcon (falco vespertinus)—a summer visitor to Europe—which just before migration assembles in immense flocks, reuniting in autumn previous to departure for its African winter quarters. But it also forms small breeding communities, and further assembles together in some number to roost. This is possible because the food of this species consists almost entirely of insects, such as dragon-flies, large moths, beetles and grass- hoppers, varied by lizards, shrews and field-mice. The Osprey again breeds in enormous colonies wherever the food supply admits. As many as three hundred pairs are described as nesting together in North America, and large colonies are formed in parts of Europe, as in Pomerania. Thus we see, in the case of the Red-footed Falcon, how a species, assembling at first merely because drawn by a bountiful food supply, may later develop more social instincts. While among some birds the gregarious instinct is deeply rooted, in others it forms but the slenderest of ties. Some species, for example, appear to associate during migration and disperse immediately on their arrival at their destination. With most gregarious species the flocks are made up of birds of both sexes, but in some cases the males and females, during a part of the year at least, form separate companies. This is true, for instance, of the Chaffinch, which, in some localities at any rate, passes the winter after this fashion. Speaking generally, it would appear that gregarious species hold their own best in the struggle for existence, and this is most noticeable where the development of the social instinct is highest. Such species are certainly numerically stronger than solitary species. Thus Rooks and Jackdaws are far more abundant than Ravens, though the last species has been mercilessly persecuted by many and so further reduced. Swifts are more numerous than Night-jars, Plovers than Rails. Nut- hatches and Titmice are nearly allied, yet the latter are more numerous than the former, which is a solitary bird. This difference is certainly not due to the relative abundance of food 138 A HISTORY OF BIRDS demanded by these several species, for in those between which these comparisons are made the food is practically the same. Nor can it be attributed to relative differences in fertility, the shy and retiring Rail, for example, having a far larger progeny than the Plovers. It would seem then, that on the whole the evidence favours the superiority of gregarious over solitary habits, Among gregarious species some display a much more in- timate association than others—are more social in their relation- ships. And this is shown very clearly in the devices which some species have adopted for their mutual. protection during sleep. The Common Partridge, as is well known, lives in small companies, or “coveys,” which scatter only while feeding, and then not far enough to be beyond call, Late in the day, as soon “as the beetles begin to buzz,” says Professor Newton, the whole move away together to some spot where they jug, as it is called—that is, squat and nestle close together for the night; and from the appearance of the mutings, or droppings, which are generally deposited in a circle of only a few inches in diameter, it would appear that the birds arrange themselves also in a circle, of which their tails form the centre, all the heads being outwards—a disposition which instinct has suggested as the best for observing the approach of any of their numerous enemies, whatever may be the direction, and thus increase their security by enabling them to avoid a surprise. Ducks similarly take special precautions to secure safety during sleep, when this must be taken in exposed situations, as when, for example, they desire to doze between the intervals of feeding during the night, which they pass afloat. At such times they keep close together, and to avoid drifting ashore keep one leg slowly paddling and thus drive themselves round in circles. More remarkable still are those cases where a number of birds crowd together in ball-like masses during sleep. Our British Long-tailed Titmouse furnishes an example of this strange habit. Similarly, the Crested Tree-swift of India roosts in this fashion, forming feathery balls. The Wood-swallows (Artamide) have also adopted this practice. But the Australian species seem to have carried it a stage further, inasmuch as instead of forming a ball on the upper side of the bough, they are said to cling together suspended from the under side. If this be so, one can PHASES OF SOCIAL LIFE 139 only wonder how those clinging to the bough manage to sustain the weight of their fellows for so long a time. By way of corroboration we may remark that the Mouse-birds or Colies also sleep after this fashion. This reversed position during sleep, by the way, is still more marked in the little Hanging Parrots. Numbering some twenty species, and ranging from India and the Philippine Islands, through the Malayan region as far east as Duke of York Island, these little birds, which do not exceed five inches in length, all share the habit of sleeping suspended by their feet from the under surface of the bough, hanging for hours at a time head downwards, after the fashion of bats. Not only during sleep, however, do they thus hang, for in confinement they will so hang crowding together and caressing one another after the fashion so common among Parrots. The good comradeship displayed in these curious sleeping communities is exhibited in other directions among birds, and especially in the co-operation many display in the capture of agile prey. Thus the Golden Eagle (Aguzla chrysetos) will some- times at any rate hunt in concert for game. On such occasions one bird glides over the ground beating the bushes and under- growth with its wings, while the other remains on the lookout at a slight elevation, pouncing at once upon whatever game is driven out, and sharing with its companion. Similarly, Pelicans, when fishing in a lake or bay, combine to form a semicircular cordon, driving a shoal of fish before them to the bank. As soonas they have succeeded in getting their victims sufficiently massed they set about reaping the fruits of their shepherding, filling their large pouches as one might fill a landing-net. Cormorants are said, occasionally at any rate, to adopt ‘similar methods of hunting. Gregarious habits are, as we have seen, fostered and devel- oped where the food supply is unlimited; but wherever a suf- ficiency is obtainable only by strenuous hunting, segregation and competition result. These factors, however, are not so obvious, and cannot be seen at work as the opposite to this picture can be seen. Flocks of birds feeding in harmony impress us: those that lead solitary lives escape our attention, and the fact that this isolation is more or less enforced does not easily admit of demonstration. Asa tule, probably, it is taken for granted that 140 A HISTORY OF BIRDS the pugnacity which species which lead solitary lives cunningly exhibit, is due to an inherent moroseness of disposition. Asa matter of fact it is rather begotten by stern necessity. An area which would provide an abundance for a pair of birds would spell famine if occupied by a flock, and hence the instinct of self-preservation develops pugnacity. Competition for whatever is to be had results, and the most aggressive species will pre- vail. Yet all this is to be gathered rather by inference than by observation, for this struggle between individuals of the same species, or between two or more allied species of similar habits, is carried on decently, as it were: there is no parade by the con- querors before the public. Consequently, we only realise what has taken place by inference, as a rule. That one gregarious species will invade the territory of another nearly related species and more or less totally supplant it, is shown, for instance, in the case of the Lesser Kestrel, which since 1877 has annually in- vaded the district of Orenberg, Russia, in thousands, displacing the Red-footed Falcon, which has retreated to the northern pro- vinces of Russia. Although earlier in this chapter it was suggested that gre- garious species, on the whole, hold their own best, inasmuch as they are numerically stronger than species which lead solitary lives, it may well be that this is not really the correct interpreta- tion of the facts. That is to say, this numerical superiority may be the result of a uniformly abundant food supply, so that the formation of large colonies may be not so much the consequence of the evolution of a sense of comradeship, or of a more or less intelligent sense of the many advantages gained thereby, as of a lessened mortality due to the lightening of the struggle for food. Birds, as a rule, do not lay up stores of food for use during times of scarcity, and, strangely enough, the only exceptions to this rule appear to be made in the case of certain Woodpeckers which band together for this purpose. Thus the Californian Woodpecker (Melanerpes formicivorus) is said to band together in considerable numbers, and, selecting an oak-tree suitable to the purpose, proceed to riddle the bark with holes. This done they set to work to collect acorns which are then thrust each into a separate hole. For some unknown reason only one tree in an area of several miles is selected, and having been duly stocked is left for some considerable time. At irregular intervals PHASES OF SOCIAL LIFE 141 stragglers of the original party return to inspect the store, and disperse again. Finally, at a time apparently agreed upon, all return to feast upon the hoard. But whether these nuts are stored till they ripen, or for the sake of attracting and harbouring insect grubs, is not known. No less interesting are the accounts given of the Red-headed Woodpecker, which is abundant in Indiana only when beech- nuts are plentiful. From the time these begin to ripen the Woodpeckers are constantly at work in storing nuts, which they Ue Q! yy oOg ILL. 20.—DeEvices TO SECURE A PERMANENT Foop SuppLy The right-hand figure is that of the Sapsucker or Yellow-bellied Wood- pecker; the left-hand the Californian Woodpecker, deposit in every conceivable situation—the cavities of decayed trees, clefts in gateposts, and even into the thatches of houses! The felling of a tree in such a neighbourhood is always sure to disclose several pints of these small nuts. In one instance where they had been dropped into a crevice, pieces of bark and wood had been driven into the aperture to conceal the treasure from poachers! These birds have also formed a habit of stor- ing grasshoppers in the way that the Californian Woodpecker 142 A HISTORY OF BIRDS stores nuts, These insects are captured with as little injury as possible, borne to some old oak post or tree, and there wedged in between the crevices of the bark and left struggling vainly to get free. As many as a hundred grasshoppers have been found so wedged at one time. Later the birds return to devour their victims. This record loses something of its importance at present, since it does not appear to have been ascertained whether the stores referred to are made by individuals or by a number of birds banded together for a common purpose. In this connection mention may be made of the case of the American Yellow-bellied Woodpecker (Sphyrapicus varius) which has developed a great fondness for the sap of trees, to obtain which it pierces a system of more or less symmetrically disposed holes through the bark so as to tap the source of the sap. This soon collects in the holes prepared for its reception, and, inci- dentally, attracts large numbers of insects which are also devoured by the Woodpecker. There is no record to show whether this species also works in concert with its neighbours, after the fashion of the Californian Woodpecker just referred to. The taste for sap is probably an acquired one, possibly gained in the first instance when this was tapped in searching for insects. The fact that insects became attracted to the sweet juice issuing from these originally more or less accidental wounds in the tree made by the bird, would soon, it may be imagined, be as- sociated by the bird with the fact that only certain trees—apple and maple, and one or two others—yielded this exudation, and the consequent fly-decoy, as a result of vigorous hammering. At any rate only profitable trees are so punctured, and hence this bird in orchards is not much welcomed ! CHAPTER X THE RELATIONS OF THE SEXES The division of labour in nest-building. Manifestations of sexual activity. Forms of this activity. Plumage displays. ‘Sdcaleli.” Wind-bags and display. Tournaments. Weapons and their uses. Dancing. ‘Gardening.” Song. Instrumental music. Where the sex réle is reversed. HE high degree of individuality which birds, in common with the rest of the higher animals, have attained, has rendered them independent of one another to a very large extent. Combinations of individuals each with a limited réle to play, such as is met with among the lower and less intelligent animals, have passed away, and individualism with its greater responsi- bilities and greater possibilities has asserted itself. But in studying the relations of the sexes it will be found that the principle of division of labour has to a limited extent been revived. Thus in the work of nest-building, of the incuba- tion of the eggs, and of the feeding of the young, the two sexes often take equal shares, though in a very large number of in- stances the whole of these labours are undertaken entirely by the female, and in a few striking exceptions by the male alone. This phase of bird-life, however, will be dealt with in the next chapter. Here it is proposed to review a very different aspect of this matter of the relations of the sexes. In short, we shall survey, as briefly as may be, some of the more remarkable of the facts which have been collected relating to that stormy period of life during which the fateful choice of mates takes place. In some species this choice is accompanied by most extra- ordinary behaviour, and in all peculiarities of conduct are to be remarked, which for the rest of the year are dormant. The mass of facts which have been accumulated on this theme is bewildering, the more so since the most conflicting theories 143 144 A HISTORY OF BIRDS have been built up by way of interpreting the significance of what has been observed. Ignoring, for the moment, these interpretations, let us take a brief survey of the more striking facts which have been recorded on this head. In the first place, sexual activity in birds manifests itself in many ways, sometimes indeed in a complex of emotions not easy of analysis. But roughly we may divide the phenomena into (1) periodic outbursts of ecstatic frenzy, during which strange postures are assumed, generally in the presence of the opposite sex; (2) outbursts of jealous rage which vents itself in fighting all possible rivals who may appear upon the scene. Such con- flicts are often severe, one or other of the combatants often being badly mauled, or left dead upon the field ; and (3) in vocal or instrumental music, often of great beauty. But the living bird defies systematic definitions; many, for example, contrive to combine all three of these phases. Asa rule, in the vast majority of cases indeed, the males alone are the performers, but in a few species the tables are turned, the réle of the male being played by the female. Considerations of space forbid anything like an exhaustive analysis of this aspect of bird-life ; indeed little more than a very brief survey thereof is possible. And this shall commence with an indication of the nature of displays of the kind indicated in Section I. I. PLUMAGE DISPLAYS Of these no more familiar example could be found than that furnished by the ridiculous antics of the common House- sparrow, which are generally preceded by unseemly brawls, such as are, however, quite in harmony with the life of this street arab among birds, The grotesque manner in which he struts with drooping wings and outspread, upraised tail, around his chosen mate are, however, but feeble performances compared with what many of his betters indulge in; though these last have contrived to mask the grotesque element by the splendour of their plumage. The Turkey and the Peacock may serve us as examples of this. The gorgeous dress of the latter bird is so familiar that any description thereof is unnecessary, but it may be well to remark AVTdSIG NI AOOOVYd AHL THE RELATIONS OF THE SEXES 145 that the wonderful “train,” which is the Peacock’s crowning glory, is composed partly of the feathers of the back and partly of the coverts of the tail feathers, which latter are used as a support to the train. The long ocellated feathers, by the way, are the covert feathers. This magnificent appendage, this marvellous train, is made to play a most important part in the Peacock’s courtship, though whether he is as conscious of its beauty as some imagine is a debatable point. If he be carefully watched it will be seen that he first places himself more or less in front of her, but at some distance off; then watching his opportunity, turns round, and in turning effectually conceals the beauties which it is his desire at the right moment should overcome her! Walking rapidly. back- wards and going faster and faster, and faster still, till, arrived within a foot of her, he suddenly, like a flash, swings round and displays to the full his truly gorgeous vestments. This turning movement is accompanied by a violent shaking of the train, the quills of which rattle like the pattering of rain upon leaves, Often this movement is followed by a loud scream. But the curious part of it is that the female, for whom all this elaborate display is made, appears to remain supremely in- different, and offers him no encouragement whatever. In some ways the display of the Argus Pheasant (Argusz- anus argus) is even more remarkable. This bird, a native of the Indo-Malay mainland and Sumatra, has the secondary quill feathers of the wings enormously elongated and of great breadth, while they are furthermore remarkable for the great beauty of their coloration. This consists of a number of large eye-like spots, so coloured that when the feathers are held with their free ends upwards, the ocelli appear like so many balls lying each within a cup or socket. But, further- more, the primary quills are also extremely beautiful, being of a soft brown tint sprinkled with small dark spots, while the shaft of the quill is dark blue. Running along the outer mar- gin of this blue shaft is a band ofa paler colour than the-rest of the vane, and this is thickly spotted with minute white points. It is this band which gives the final touch of perfection to the whole. feather. Lastly, the tail of this bird is like the wing feathers, of enormous length, and also possesses.a rare beauty of coloration. 10 146 A HISTORY OF BIRDS While the bird is at rest there is little or no evidence of this beauty ; it appears to be remarkable only on account of the great length of the wing and tail feathers. But during the courting season the utmost seems to be made of this wonderful livery. A great deal, however, is yet to be discovered with regard to the habits of this bird at this time. It would seem, from the observations of the late Mr. W. R. Davidson, that the Argus Pheasant leads a very solitary life, the sexes living apart. During the breeding season the male appears to choose some open, level spot in the depths of the forests—which this bird never leaves—from which he clears all the dead leaves and weeds for a space of some six or eight yards square, until nothing but the bare clean earth remains, and thereafter he keeps this area scrupulously clean, removing every dead leaf and twig that may drop from the trees above. Here, in solitary state, this gorgeous creature spends his days, calling at short intervals ‘‘ how-how, how, how, how,” and this note is repeated some ten or a dozen times. It is an intensely penetrating call, and is repeated apparently until answered by the female who calls ‘“howowoo, how-owoo,” the last syllable much prolonged. This call, as in the case of the male, is repeated many times, ending in a series of “owoos” run together! But in this way the sexes discover the whereabouts of one another; and the female apparently comes to the call of the male, and ultimately enters his “ parlour,” as the cleared space is called. Once in, it would seem, she is entertained by a very remarkable perform- ance, which has been graphically described by Darwin. Having obtained an audience, it appears the bird erects his tail and expands his huge wing feathers “into a great, almost upright, circular fan or shield, which is carried in front of the body. The neck and head are held on one side so that they are concealed by the fan; but the bird, in order to see the female before whom he is displaying himself, sometimes pushes his head between two of the long wing feathers . . . and then presents a grotesque appearance. This must be a frequent habit with the bird in a state of nature, for . . . on examining some perfect’ skins sent from the East, [there was] found a place between two of the feathers which was much frayed, as if the head had here frequently been pushed through.” A STAGE IN THE DISPLAY OF THE LESSER BIRD OF PARADISE THE RELATIONS OF THE SEXES 147 By way of contrast with the several displays just described it would be hard to find a more striking illustration than that afforded by the great Bird of Paradise (Paradisea apoda), inas- much as here the display is associated with rivalry between a number of individuals. For much of our knowledge on this matter we have to depend upon the descriptions of natives, collected on the spot by Mr. Alfred Russel Wallace, but happily this has now been supplemented by observations made by Mr. Ogilvie Grant on a captive in the Gardens of the Zoological Society of London. It appears then, that during the period of courtship these birds at frequent intervals gather together, up to the number of twenty, on certain of the forest trees of the Aru Islands, selected apparently on account of the fact that they have an immense head of spreading branches, and large but scattered leaves, thus affording plenty of space for the revels, which take the form of “Sacaleli,” or dancing parties. By the time the ball opens the birds appear to have worked themselves up to a state of great excitement, and each com- mences his performance with quivering wings and a loud cry— “waa! waa! waa! waa!” Then the wings are suddenly held out in a semi-vertical position on either side of the body, the tail is bent forward under the branch, and with a quick shuffle of the plumage, the side plumes are erected, forming an arched cascade over the back, meeting one another in the middle line. With every muscle tense the bird will remain in this attitude from ten to twenty seconds, slightly quivering his wings, and from time to time hitching up his long plumes, which are raised somewhat above the level of the top of the head. Then a second stage commences. Each bird, seemingly gone mad, commences to dance and hop wildly backwards and forwards along the bough, and with head bent down, wings fully extended horizontally, and side plumes erected to their utmost, he utters loud harsh cries—“ca! ca! ca! ca!” For some seconds he remains in a sort of ecstasy, rubbing his beak on the bough, and occasionally glancing backwards below his feet with the back fully arched. Then, the climax passed, he reverts once more to the first and more erect stage of the display, when the paroxysm either gradually subsides, or is renewed, and ‘after an interval of about half a minute again 148 A HISTORY OF BIRDS reaches an acute stage and the wild dance is in full swing once more! Although in the earlier part of the chapter it was implied that the strange antics of which examples have just been cited were performed in the presence of the opposite sex, this appears by no means to be a general rule. It does not seem to be known, for example, whether the females of the Paradise-birds are witnesses, at a respectful distance, of the strange dances in which their respective lords engage, or whether these are in- dulged in by the males alone for their own delight. But with some species at any rate, as will be shown presently, the presence of the female seems to be all-important. Since, in the light of modern discovery, all birds appear to indulge in antics more or less remarkable during the season of courtship, it is obviously impossible to do more than select some of the more important of such displays, and the further accom- paniments which in a large number of instances are to be met with. So far we have cited cases where this accompaniment takes the form of brilliant and highly specialised plumage, using the Sparrow as a foil, so to speak, inasmuch as here, though the antics are grotesque enough, the plumage presents no striking features. But there are a number of species which at this critical period develop special organs, or for the nonce make temporary use of existing organs, apparently for the sole purpose of en- hancing their suit with the opposite sex. Anatomical changes, in short, of a more or less complex character, make their ap- pearance at this time, and disappear, or at any rate remain dormant, for the rest of the year. The most remarkable of these organs are those which take the form of wind-bags, or inflatable sacs, and they are used solely in displays of a peace- able character. But there are some species which, during the season of courtship, become extremely pugnacious, and among these many are provided with formidable weapons of offence, weapons which, unlike the antlers of the stag, are permanent. On the other hand, there are a few species which become more markedly social and indulge in the most curious dances. These several phases will now be discussed. The displays which depend on the use of wind-bags shall be taken first. And of such displays the most familiar is that NAH-AIMIVad AHL JO FAONVA ‘IVIIGON FHL THE RELATIONS OF THE SEXES 149 of many of the Pigeon tribe. Herein the bird inflates the gullet, and more especially the crop, and this done, proceeds to pay his vows of everlasting constancy to his mate by keeping up an incessant “cooing” accompanied by a succession of most courtly bows. The great Australian Bustard (Eupodotis australis) similarly inflates its gullet. “The premonitory symptoms,” says Dr. Murie, “observable when [this] Bustard is about to exhibit himself in the pride of lust ... is a slight swelling of the infra-mandibular portion of the throat, while the head is thrown upwards. Immediately afterwards the neck swells, and the feathers of the lower parts concomitantly bulge out and descend gradually downwards in the form of a bag; oftentimes nearly reaching the ground. “If the paroxysm is a strong one, then the tail is shot up- wards and forwards over the back, the rectrices coming almost in contact with the neck. “In this peculiar attitude, with bloated neck, hanging, baggy chest, elevated tail, and stiff, stilt-like legs, the creature struts about in a somewhat waddling manner, the elongated pouch swaying to and fro. The feathers of the throat start out on end, those of the depending sac are also raised but less upright. While all this has taken place the bird seems to have gulped in air, or rather, with partly opened gape, to have taken a long, deep and forced inspiration. “The acme of inspiratory effort and strange attitude at- tained, the Bustard begins to snap the mandibles together in a loud manner and utter a series of cooing sounds for a short interval of time. Usually and more frequently he struts towards the female Bustards in a most dignified manner. . . .” No less remarkable are the displays of the American Ruffed- grouse (Zympanuchus americanus) and the Frigate-bird. In the case of the Ruffed-grouse the inflatable sac appears to be formed by specially modified air-sacs running up the neck. But the effect is heightened by the fact that the featherless spaces which normally occur on each side of the neck are deeply pigmented with bright yellow, so that, when the sacs are distended with air the bare yellow skin is thrust out in the form of a pair of globular swellings, which have been compared to oranges. Above these sacs have been developed a frill of long narrow feathers which during the time that the sacs are 150 A HISTORY OF BIRDS in use stand out like a ruff just below the head, while, as if in sympathy, the whole of the body feathers are set on end, and the wings are dropped, as in the Turkey and Peacock. The displays appear to take place early in the morning, when parties of from a dozen to fifty of both sexes assemble on some high dry knolls where the grass is short. Having gathered together, the more eager males immediately begin to set themselves in order for the morning’s revels, the first part of the performance apparently consisting in the passive display— the inflation of the sacs and erection of the feathers. Next, some “ proud cock, in order to complete his triumph, will rush forward at his best speed for two or three rods through the midst of the love-sick damsels, pouring out as he goes a booming noise, almost a hoarse roar, only more subdued, which may be heard for at least two miles in the still morning air. This heavy booming sound is by no means harsh or unpleasant, on the contrary, it is soft and even harmonious. When stand- ing in the open prairie at early dawn listening to hundreds of different voices pitched on different keys, coming from every direction and from various distances, the listener is rather soothed than excited. “Every few minutes this display is repeated. I have seen not only one, but more than twenty cocks going through this funny operation at once, but then they seem careful not to run against each other, for they have not yet got to the fighting point. After a little while the lady-birds begin to show an interest in the proceedings by moving about quickly, a few yards at a time, and then standing still a short time. “The party breaks up when the sun is half an hour high to be repeated the next morning and every morning for a week or two before all make satisfactory matches. It is toward the latter part of the love-season that the fighting takes place among the cocks, probably by two who have fallen in love with the same sweetheart whose modesty prevents her from selecting between them.” The display of the Frigate-bird, though of a very different kind, is no less remarkable. And we owe to Dr. C. W. Andrews the best account of this which has yet been published. His descriptions are based on observations made upon Fregata SS = ILL. 21.—Poucn oF GREAT BustTarD, DissEcTED TO SHOW ITS RELATION TO THE GULLET AND WINDPIPE P.= Pouch. (.= Cisophagus. T.= Trachea. H.=Hyoid. V.= Vascular tissue. Ibu. 22.—TuHe Dispray oF THE Great Bustarp (Otis tarda) The upper figure shows one of the preparatory stages of the display. THE RELATIONS OF THE SEXES 155 aguila during the time that he was engaged in the exploration of Christmas Island (Indian Ocean). “ About the beginning of January,” he remarks, ‘ the adult males begin to acquire [a] remarkable pouch of scarlet skin beneath their throat. This they can inflate till it is nearly as large as the rest of the body, and a dozen or more of these birds sitting on a tree with outstretched drooping wings and this great scarlet bladder under their heads are a most remark- able sight. When a hen-bird approaches the tree the males utter a peculiar cry, a sort of ‘wow-wow-wow-wow’ and clatter their beaks like castanets, at the same time shaking the wings. When they take to flight the air is allowed to escape from the pouch, but occasionally they might be seen flying with it partly inflated.” This pouch, it should be remarked, is not formed by inflating the gullet, but, as in the case of the Ruffed-grouse, by certain enlarged air-sacs of the cervical system. Two other instances of inflatable pouches and the réle they play in courtship must suffice for the purposes of this chapter. The first of these is that furnished by the Great Bustard (Otis tarda), a bird at one time common on the heaths of England. The pouch in this bird is a quite remarkable structure, being formed by a long sac running down the front of the neck just beneath the skin, and opening above by a narrow slit just beneath the free end of the tongue. Its walls are extremely delicate, and just between the furcula are constricted, as may be seen in Jll. 21. How it is filled is not yet known, but the performance of the bird after the work of inflation is completed is remarkable. The neck is then drawn downwards and backwards so as to rest on the back, while the tail is raised and drawn forwards. Unlike so many of the displays already described, that of the Great Bustard is apparently addressed very directly to the female. Approaching her with a mincing gait and rustling wings, he draws the neck backwards and downwards till it rests upon the back, while the tail is raised and drawn forwards and downwards, and is there held in place by the aid of the tips of the long quill feathers of the wings. Simul- taneously the scapular feathers are set on end, and with these 156 A HISTORY OF BIRDS the long white inner secondary quill feathers. The head, meanwhile, is drawn down on to the pouch, while the long, spike-like feathers which normally project backwards on either side of the head now stand erect like a row of slender palisades on each side of the partly hidden beak. Behind the head is a great billowy mass of white feathers formed by the under-tail coverts, and brought into view by the overturning of the tail feathers. The feathered contortionist having completed this complex series of movements, now stands solemnly facing his mate, uttering now and again a low grunt like “oak, oak, oak!” and then slowly returns to his normal shape again. Of the display of the Adjutant Stork there appears to be no record. But this bird is provided with a pouch in some respects more peculiar than that of the Bustards, inasmuch as it can be filled and emptied with remarkable rapidity. Deflated it is hardly visible, but may be detected in the shape of a conical swelling of bare skin in front of the neck. Suddenly it shoots out, or rather downwards, in the form of a large, naked wind-bag of considerable size, and again disappears with magical rapidity. This sac is filled through the naso-pharyngeal system, that is, from air-sacs opening into the nose. How that of the Great Bustard is filled is, by the way, unknown. II. TOURNAMENTS During the time that birds are under the stimulus of sexual excitement mutual jealousies, leading to more or less vio- lent encounters between rivals, are common among all species. But there are some species which, of set purpose, appear to gather together for the purpose of “sparring,” apparently by way of displaying their prowess in the presence of the females, but without any desire to come to actual blows, though this oc- casionally happens. These fight unarmed. On the other hand, there are several species, especially among the Game- birds, the Plover tribe and the Anatidz, which have developed formidable weapons of offence, and these are used in deadly earnest on every possible opportunity, at any rate during the period now under discussion. There is, however, no hard and fast line between these harmless encounters and duels to the death, as we shall presently show. ANNOUWD-ONIAVId WIFHL NO MO000-MOVIE <= A Aone THE RELATIONS OF THE SEXES 157 There is, in fact, no better illustration of this than is furnished by the “gathering of the clans,” so to speak, described so graphically and so vividly by Mr. J. G. Millais, anent Black game in Scotland. Their arrival at the tourney-ground, he remarks, which begins soon after daybreak, is preceded by the almost con- tinuous whirring calls of the cocks, calls which he likens to the sounds produced by a luggage train passing over loose metals at a distance, and which are audible at two miles. This call rouses the Grey hens. Soon after, one or two Black cocks put in an appearance on the field, and at once begin to attack one another. Both birds simultaneously lower their heads and arch their tails, the beautiful curled feathers almost touching the ground, while the primary feathers are trailed. This posture may be assumed when the birds are as far as thirty yards apart, when they advance till separated only by a few ‘feet. “Then the actual fighting, if there is to be any, begins. It, however, often happens that, as with our bombastic race, it is all ‘gas, and the two, after skirmishing up to one another with every apparent gesture of rage and fury, by the time that close quarters are arrived at have come to the conclusion that another occasion will do just as well as the present for fighting it out. . . . More often they stand and fence, after the manner of bantams, until one, by superior tact and rapidity, suddenly seizes his adversary by the ‘scruff’ of the neck, and gives him a right good dusting, handling him in no gentle manner with his strong bill, whilst he beats him over the head with both his wings, the latter making a loud noise. When he who hath come off second best eventually gets clear, he has generally had about enough for the time being, and is either chased igno- miniously off the ground to hide his diminished head in some quiet corner, or wings it off altogether to the nearest wood. This is only temporary, however, for he does not consider that he is altogether vanquished till he has made at least another attempt to display his prowess. The victor gives his plumage a shake, and calmly proceeds to select for himself a position of vantage in the shape of a grassy mound, the possession of which he is now prepared to contest with any opponent who may be bold enough to tackle him; and if the birds are at all numerous he is not long in having his wish gratified. He seats 158 A HISTORY OF BIRDS himself composedly on his little hillock and again commences his song of war, at which some wandering knight, who has yet his laurels to win, soon takes offence, and at once challenges him. Now in preparation for this coming battle the victor of the former strife entirely alters his tactics, and his attitude is one purely of a defensive nature; for after rising to his feet, he simply watches the advance of his adversary with lowered head, allowing the latter to waste his energies in futile attempts at getting above or behind his guard, till the process of fencing | wearies him, when, with one quick movement, he repeats the lesson he gave his former antagonist. “ At intervals during each separate fight, Black cocks emit a curious call; it is a hoarse screech, resembling the noise too painfully familiar to us, namely, that of cats on house-tops, supplemented by the said animals being afflicted with sore throats. The sound is both wild and un-musical in the extreme. “We will suppose that the observer has come early on the scene, before the Grey hens have made their appearance. The approach of one of the latter is the signal for an immedi- ate cessation of hostilities on all sides, and intense excitement prevails amongst the assembled Black cocks, Her approach has been observed by a single bird, who has been sharper than the rest in detecting the lady afar off . . . [he will] suddenly draw himself up to a rigid position of attention, till he is sure she is really coming. Having settled this in his mind to his own satisfaction, he throws himself into the air and flutters up a few feet, uttering the while hoarse notes with all the power and effect he can muster. This is, of course, done to impress the lady in his favour, and arouse in her breast a proper sense of admiration which he considers his due. His example is immediately followed by all the others, who on alighting dance about in the most absurd manner, each one trying to see who can screech the loudest and be the most ridiculous in his antics. “When a hen has alighted on the playing-ground, the male that is nearest to her pairs with her and fights off any other that disputes his possession. She then meanwhile walks sedately round her lord and master, picking about the grass coquettishly and pretending to be feeding. Each hen on THE RELATIONS OF THE SEXES 159 arrival causes the same general excitement, and is appropriated by one or other of the successful cocks, till the harems are filled up, one cock having at times as many as six or seven hens. As the season advances, after the first few mornings of the hens coming to the ground, they resort to the same spot each day, and stay with the same cock who has previously trodden them, and are not interfered with afterwards by other cocks, who acknowledge the superior claims of the male to whom they rightfully belong.” The tournaments of the Ruffs may serve as our second illustration of these weaponless duels, The term “ Ruff” is more particularly applied to the males of a species of Sandpiper (Pavoncella pugnar), the females being distinguished as “Reeves”. The male bird derives its name from the fact that during the spring it develops a very remarkable nuptial dress, the most conspicuous feature of which is formed by a large frill of feathers which, encircling the upper part of the neck, can be erected or depressed at will. But besides these, certain feathers from the occipital region of the head become greatly elongated, forming a pair of tufts known asthe“ ears”. This frill, which, as we have elsewhere remarked, presents a most wonderful variety in its coloration, is made to play a very important part in the critical work of courtship. During this time the Ruffs select such eminences as the fen- lands afford whereon to assemble and display their finery. At the break of day, as in the case of the Black game, the per- formers assemble at the favoured spot and commence at once to disport themselves, now sparring one with another, and now standing one in front of another with outspread frill and head bent down till the beak rests upon the ground, immovable, only to commence again to spar. Now and again some display of temper is shown, one bird endeavouring to seize another by the beak and administer a rain of blows with its wings; or the two will rise in the air and strike at each other with their feet. The more vigorous appear to take possession of certain definite areas and to hold these against all comers. Sooner or later the females appear upon the scene, when they are courted vigorously by the males, who display their frills assiduously. And, so far as can be made out, it would seem that the more active, excitable and strikingly coloured 160 A HISTORY OF BIRDS birds are generally the favoured ones in securing mates. Poly- gamy, as might be supposed, is here the rule, but the females appear to be allowed, or to insist on, a very considerable amount of liberty in their choice of a mate. They may be said to abandon themselves to, rather than be taken possession of by, the master males of the community. III]. WEAPONS AND THEIR USES The males of all birds, during the period covering the time of courtship and the helplessness of the young, are more or less pugnacious towards other males of the same species, furious battles being the result; and these not seldom result in the death of one or other of the combatants. With some species this pugnacity exhausts itself in contests for the possession of the females, while with others it appears to be reserved for the defence of the sitting hen and young. The ‘‘dove of peace” at this time of the year appears in a new and not always pleasing light, for not only will he fight his neighbours, but he does not always show that gentleness towards his wife which tradition has credited him with. The tiny Humming-bird would seem to be as little capable of fight- ing as a bird could be, yet few birds are more pugnacious., Robins and Titmice, too, fight savagely. And certain species of Quails, and a Rail (Gadlcrex cristatus), nearly related to the Moor-hen, are commonly kept by the natives for the sake of setting them to fight one another. In all these cases, however, no special weapons are used, the birds seizing one another by the beak, and buffeting with the wings, or striking with the feet. Such as have stout beaks endeavour to beat out their opponents’ brains, and in this they are frequently successful. A considerable number of species, however, notably among the Game-birds, have developed powerful weapons in the shape of long, pointed spurs upon the legs, some, such as Pheasants and Jungle-fowl, having but a single pair, others, as in Francolins, having several pairs. And these birds are notorious for the ferocity of their encounters. It is said that in the Indian Swamp Francolin (Francolinus gularis) nearly every individual is marked by scars and wounds received in such combats. These battles appear to be fought in defence of, or rather, perhaps, THE RELATIONS OF THE SEXES 161 for the retention of, their females. But there is some evidence to show that they not seldom occur as the outcome of displays at preconcerted meeting-places such as have already been described in these pages as occurring among Grouse and Ruffs for example. Certain members of the Plover tribe, and certain Anserine birds have, however, developed spurs of a very formidable character on the wings. Among the Plover tribe the best example is that furnished by the Egyptian Spur-winged Plover (Hoplopterus). These birds fight, after the manner of our common English Lapwing, by turning suddenly in the air and striking with the wings. In the case of the formidably armed Egyptian bird the result is often fatal. In our own birds a fatal result is rarely the case, since slightly swollen knobs take the place of spurs. In Hoplopterus and in the Jacana this spur arises from the base of the thumb, but in the Spur-winged Goose (Plectropterus) it is borne by the radial carpal bone, while in the Screamers (Palamedea and Chauna) there are two spurs on each wing, one at each end of the metacarpus. That these formidable weapons have been developed for the purposes of offence and defence there can be no doubt, but there are no detailed records as to the frequency of such encounters. No less remarkable is the form of the weapon which has been developed by another Plover, one of the Jacanas (J/edo- pidius). In this bird the radius has been broadened out from its middle onwards, in the form of a flat plate, or blade, but the manner in which this is used seems to be unknown. The dearth of facts with regard to the time and place of the use of these weapons is deplorable; but this is partly to be explained by the fact that these birds live in regions little visited by observing naturalists, and when encountered by collectors are promptly shot, life-histories having for them no interest. We may pass now to a brief outline of the more important facts which have been recorded with regard to the peaceful arts of dancing and music among birds. As touching dancing among birds. This curious exercise is practised by many different birds belonging to widely different groups, and in parts of the world remote from one another. One of the Manakins—small South American birds belonging to the Family Pipridee—and perhaps others, isan expert dancer, Il ny 162 A HISTORY OF BIRDS practising the art, apparently, as a means of winning the favour of the females. “The natives call this bird the ‘bailidor’ or ‘dancer, ” says Mr. Nutting, “but it was not until I had been in the region for some time that I understood why it was called by that name. One day, when hunting through the dense forest, the profound silence was suddenly broken by the regularly repeated note of ‘EI Bailidor, and softly making my way to the spot I witnessed one of the most remarkable performances it has ever been my lot to see. Upon a bare twig which over- hung the trail at a distance of about four feet from the ground two male ‘bailidors’ were engaged in a ‘song and dance’ act that simply astonished me. The two birds were about a foot and a half apart, and were alternately jumping about two feet in the air, and alighting exactly upon the spot whence they jumped, The tune was as regular as clockwork, one bird jumping up the instant the other alighted, each bird accompany- ing himself to the tune of ‘to-lé-do—to-lé-do—to-lé-do’ sounding the syllable ‘to’ as he crouched to spring, ‘lé’ while in the air, and ‘do’ as he alighted. This performance was kept up without intermission for more than a minute, when the birds suddenly discovered that they had an audience, and made off,” The stately Albatross even indulges in dancing when over- wrought with excitement! The Hon. Walter Rothschild, in his Avifauna of Laysan gives a vivid word-picture of the antics of this bird: “First they stand face to face, then they begin nodding and bowing vigorously, then rub their bills together with a whistling cry. After this they begin shaking their heads and snapping their bills with marvellous rapidity, oc- casionally lifting one wing, straightening themselves out and blowing out their breasts; then they put their bill under the wing or toss it in the air with a groaning scream, and walk round each other, often for fifteen minutes at a time.” Even more remarkable are the performances of Cranes. Mr. Nelson, in his Birds of Alaska, gives a striking illustration of this: “On 18th May I lay in a hunting blind and was much amused by the performances of two Cranes which alighted near by. The first-comer remained alone but a short time, when a second bird came along, uttering his loud note at short intervals, until he espied the bird on the ground, when he made THE RELATIONS OF THE SEXES 163 a slight circuit, and dropped close by. Both birds then joined in a series of loud rolling cries in quick succession. Suddenly the new-comer, which appeared to be a male, wheeled his back towards the female and made a low bow, his head nearly touch- ing the ground, and ending by a quick leap into the air. An- other pirouette brought him facing his charmer, whom he greeted with a still deeper bow, his wings meanwhile hanging loosely by his side. She replied by an answering bow and hop, and then each tried to outdo the other in a series of spasmodic hops and starts, mixed with a set of comically grave and ceremonious bows. The pair stood for some moments bowing right and left, when their legs appeared to become envious of the large share taken in the performance by the neck, and then would ensue a series of skilled hops and skips, which are more like the steps of a burlesque minuet than any- thing else I can think of. Frequently others join, and the dance keeps up until all are exhausted.” Similarly, according to Mr. W. H. Hudson, the South American Cayenne Lapwing indulges in dances of an elabor- ate description, These birds, which are known in the Pampas by the name of “teru-teru,” generally live in pairs. “Any one watching a pair,’ says Mr. Hudson, “will see an individual from another pair rise and fly to them. Advancing to receive their visitor, the pair place themselves behind it; then, all three keeping step, begin a rapid march uttering resonant drumming notes in time with their movements, the notes of the pair behind being emitted in a stream like a drum-roll, while the leader utters loud single notes at regular intervals. The march ceases, the leader elevates his wings and stands erect and motionless, still uttering loud notes; while the other two, with puffed-out plumage and standing exactly abreast, stoop forward and downward, until the tips of their beaks touch the ground, and sinking their rhythmical voices to a low murmur, remain for some time in this posture, The perform- ance is then over, and the visitor goes back to his own ground and mate to receive a visitor himself later on.” Another South American species of Spur-winged Plover, which indulges in dances of this kind is the Jacana, a bird remarkable for the enormous length of the toe-nails. Herein both sexes participate. These birds go about in pairs, but 164 A HISTORY OF BIRDS “ occasionally,” says Mr. Hudson, “in response to a note of invitation, they all in a moment leave off feeding and fly to one spot, and, forming a close cluster, and emitting a short, excited, rapidly repeated note, display their wings, like beautiful flags grouped loosely together; some hold the wings up ver- tically and motionless ; others half open and vibrating rapidly, while still others wave them up and down with a slow, measured motion.” Such, then, are a few of the more striking cases of dances among birds. But there remains yet to be described another form of play connected with the period of sexual activity which must be briefly referred to here. This concerns the remark- able performances of the “ Bower-birds” of Australia, of which there are several species, all displaying similar habits; con- sequently space can be found here only fora single detailed illustration. This shall be furnished by the “ Gardener Bower- bird” (Amblyornis inornatus). This species builds at the foot of a small tree a kind of hut or cabin, some two feet in height, roofed with orchid stems that slope to the ground, regularly radiating from the central support, which is covered with a conical mass of moss sheltering a gallery round it. One side of this hut is left open, and in front of it is arranged a bed of verdant moss, bedecked with blossoms and berries of the brightest colour. As the ornaments wither they are removed to a heap behind the hut, and replaced by others that are fresh. The hut is circular and some three feet in diameter, and the mossy lawn in front of it is nearly twice that expanse. Each hut and garden are believed to be the work of a single pair of birds. The use of the hut, it appears, is solely to serve the purpose of a playing-ground, or as a place wherein to pay court to the female, since it, like the bowers built by its near relatives, are built long before the nest is begun, this, by the way, being placed in a tree. The less elaborate ‘“‘bower” of the Satin-bower bird (Ptilonorhynchus holosericus) indicates an earlier stage in the evolution of this remarkable custom. Herein a long gallery or avenue is constructed of fine twigs placed on end, and roof- less. The entrance to this is decorated with snail shells, bleached bones and bright feathers, When complete the male uses the bower, as we have indicated, as a courting-ground. In THE RELATIONS OF THE SEXES 165 his moments of ecstasy he seizes a leaf or other object in his beak, and with feathers on end and quivering wings chases his mate in and out of the bower till both are tired! The Spotted Bower-birds provide a roof to this avenue, which may be of considerable length, and confine their decorations almost entirely to shells, which are often collected on the sea-shore some miles away from the site of the bower. This, by the way, appears to be almost entirely constructed by the males, though in all cases the females are believed to assist. IV. SONG AND INSTRUMENTAL MUSIC It will scarcely be necessary in this place to dilate upon the marvellous perfection to which some birds have attained in the matter of song, The exquisite performances of the Skylark, Nightingale, Blackcap, Thrush and Blackbird, and a dozen others, must be known to all who will read these pages. Rather, we are concerned here with the nature and purpose of song among birds. . It is commonly supposed that Passerine birds alone sing; and further, that among these only those of sober-coloured plumage are so gifted. Both these suppositions, however, have no foundation in fact, though it is true the more brilliantly coloured birds are rarely good songsters. But it is equally true that a large proportion of dull-plumaged birds, even among the Passerines, have no song, or at least can give forth but a short musical refrain. No bird is absolutely mute, but some species are extraordinarily silent, and at most give forth but mono- syllabic sounds, No hard and fast line can be drawn between call-notes, uttered to keep individuals or flocks together, or to give warning of the approach of danger, and true song. Nor can any hard and fast line be drawn between the times and occasions when song is practised. In many cases it would seem to play a very important part in courtship, the male seeking this means whereby to gain a mate: but long after this important event has been accomplished, singing is continued, apparently in sheer exuberance of spirits. Some birds, on the other hand, sing but little after the courtship is over. That song plays an important part in the task of 166 A HISTORY OF BIRDS procuring mates is shown in the case of the British Warblers, where the males arrive before the females, and take up their posi- tion for the summer. This done, the females on their arrival are attracted to the chosen sites by the sound of the familiar song, probably electing to alight within the area of the troubadour which pleases most. That the song of any given species varies with the geo- graphical range of that species has often been denied ; but never- theless it would seem to be true. Although it is commonly supposed that true song-birds sing only when extremely happy, only when possessed by some spasm of exaltation, so to speak, this is by no means altogether the case, The most famous singer of all, for example, the Night- ingale, will sing when alarmed, or under the emotion of a great shock, as when its nest and eggs are destroyed, or when roused from sleep by some sudden alarm, V. INSTRUMENTAL MUSIC Though by no means generally known, it is nevertheless a fact that many birds possess the power of making sounds by mechanical means: sounds which may not be musical to cultiv- ated ears, but which are nevertheless at least as worthy of this designation as the music of savage peoples. We can distinguish wind-instruments and instruments of percussion, And while in some cases the males alone play, in others both sexes appear to be equally skilled performers. Among wind-instruments one of the most remarkable is that of the Emu. In both sexes of this bird the outer wall of the windpipe is pierced near the middle of its length for a space of several inches ; and through this aperture the inner lining of the windpipe escapes to form a large inflatable sac lying immedi- ately under the skin. Therewith these birds make a very re- markable sound which resembles the “rolling” of a big drum. But whether this noise is made only during the courting season, as a kind of music, or whether it is used as a call-note at all seasons, does not appear to be known. In many species of Cranes and Swans the windpipe has undergone a no less remarkable modification. Herein it has greatly increased in length, the additional inches being stowed away in a long chamber formed by the keel of the breast-bone, Wy —*i Y Y .—TypPEs oF WINDPIPES 23 LL. I B, Spoonbill. D, Manucodia keraudrent. Manucodia. Cc A, Crane. THE RELATIONS OF THE SEXES 169 after the fashion shown in Ill. 23. Confined to the males alone, this lengthening of the tube seems to have been acquired for the sake of increasing the resonance of the voice. Though it is undoubtedly remarkable that in two such completely distinct groups the same structural modification should have taken place, we meet with an exact parallel in another fashion of disposing of an elongated windpipe. Herein the increased length is disposed of in a series of coils lying between the breast muscles and the skin! This obtains in certain Passerine birds—related to the Birds of Paradise, many Game-birds, ¢.g., Curassows, the curious Goose Anseranas, and the Sandpipers known as “Painted Snipes” (Rhynchea). The nature of these coils are shown in Ills, 23. Though we must assume that in all these modifications in- creased resonance of the voice has been secured, either to en- hance the performer in the eyes of its mate during the courting season, or for the more prosaic purpose of indicating the whereabouts of individuals which have got separated, there is but little concrete evidence obtainable at present bearing on the problem. That such elaborate devices should have come about is somewhat puzzling, since many birds continue to make exceedingly powerful and penetrating sounds though possessed of no special sound-producing apparatus whatever. The Ostrich and the Cassowary may serve as striking examples of this, for in both the windpipe and voice organ generally is of a most primitive character. We must pass now to a brief review of what we may call instruments of percussion whose purpose is the production of sound. Some of these, however, scarcely come within this category, since the sounds they give forth are due to vibrations set up by their rapid motion through the air. The simplest form of percussion music is perhaps that produced by the White Stork. Throwing the head backwards till the point of the beak almost touches the back, the jaws are set rapidly in motion, clashing one against another and produc- ing a curious rattling sound, which has been compared to castanets. As the sound is being produced the head is slowly turned into its normal position; but not until the beak has described a half-circle and rests almost on the ground does the music cease. This sound, so far as can be made out, 170 A HISTORY OF BIRDS appears to be made at all times of the year, and by both sexes, but especially during the courting season, when two or more birds join together keeping the most perfect tune. Pigeons and Night-jars when on the wing can produce at will a curious snapping sound by bringing the wings together smartly over the back; and this appears to be most frequently indulged in during the period of courtship. Similarly, certain small South American Passerine birds, known as Manakins, have the shafts of the secondary quill feathers curiously thickened to an extraordinary degree, so as to form solid, horny lumps. Therewith, by bringing the two wings sharply together over the back, a peculiar noise, not unlike the crack of a whip, is produced. One of the Game- birds—the Black Penelope (Penelope nigrina) of Guatemala— while on the wing will occasionally pitch suddenly earthwards with outstretched wings, and at such times a crashing, rushing, sound is produced, which has been likened to the sound of a falling tree. This is peculiar inasmuch as there seems to be no modification of the wing feathers which would account for such a noise, while, on the other hand, certain relatives of this bird have the three outermost primary quills curiously excised along their inner webs, yet, as far as is known, they produce no peculiar sounds. Better known, and more easily verified, is the strange “ drum- ming” or “bleating” practised by various species of Snipe, and especially the Common Snipe (Gallinago media), during the courting season. It is now known that these remarkable sounds are produced by both sexes, and by means of the tail feathers. Mounting to a great height, these birds suddenly turn and descend with prodigious speed, meanwhile holding the tail fully expanded. The outermost pair of feathers are, how- ever, specially modified, so that, in the first place, during this descent, they stand at right angles to the long axis of the body, and well away from all the rest of the tail feathers. This alone, however, would not produce the sound, which is due to the fact that the shafts of the feathers are somewhat thickened and peculiarly curved, while the vane or web of the inner side of the feather is of great width, and structurally differs from the vanes of the other feathers. This difference consists in a greater number of hooklets, and in the larger size of those THE RELATIONS OF THE SEXES 171 belonging to the barbs of this region of the feather, whereby the vane becomes more resistant to the rush of air caused by the wings during the descent. The fact that this curious musical instrument occurs in both sexes makes its interpretation the more difficult; for there is little difference in the performance of the two sexes, though that of the male is said to be the more resonant. The tail of the best performer of all, the Common Snipe, is, it is to be noticed, superficially, but little or not at all modified either in shape or size for the production of this sound. But there are other species of Snipe, ¢.g., G. stenura, which have greatly increased the number of the tail feathers, and at the same time has reduced the vanes or webs of these to the vanish- ing-point. Yet these birds are unable to produce any sounds appreciable to human ears. IV. WHERE THE SEXUAL ROLE IS REVERSED Before bringing this chapter to a close it is necessary briefly to refer to a most remarkable collection of facts, which show that, in several widely different and unrelated species of birds, the position of the sexes with regard to courtship, the brooding of the eggs, and the care of the young is entirely re- versed, the female playing ‘the part of the male in all these particulars. In consonance with this fundamental reversal of the sexual relations, the females are in every case the more brightly coloured! Nature has few other such striking illustra- tions of hen-pecked males among the vertebrates! The Quail-like Hemipodes, the Tinamous, ithe Painted Snipe (Rhynchea) and the Phalaropes, afford the best-known examples of this, though other instances are on record. All these birds appear to be polyandrous, indeed there is little room for doubt in the matter. A recent writer, Mr. D. Seth-Smith, has added much to our knowledge of this matter from his observation on captive species of the Australian Hemipode (Zurnzx varia). The court- ing of the female recalls that of the male of the Common Pigeon, the crop being inflated with air, the while the proud suitor bows and “coos” to her chosen mate. He describes the court- ing thus: ... “The male squats upon the ground amongst short grass, and the female runs round him in a circle with tail 172 A HISTORY OF BIRDS more or less erected, and crop puffed out. She then stops and faces him, and commences ‘booming’ or ‘cooing’ to him... the while stamping and scratching on the ground with her feet. The male meanwhile answers her with low crooning notes. “ At this time the female would very frequently pick up a dainty morsel, such as a grub or grain of seed, and holding it at the tip of her bill, would call her mate and present it to him.” So soon as all the eggs were laid the cock commenced to sit, and the hen took no more notice of him, but commenced to boom as if to call another. mate. The Tinamous, similarly, have been kept in confinement, and from this it has-been found that the female, after laying clutches for two different cocks to brood, seeks yet a third husband, and in a wild state probably more. Of Wilson’s Phalarope, an American writer, Dr. D, G. Elliott, remarks: “The female is the larger and altogether the hand- somer bird, the male having very little of the brilliant tints which render his mate so attractive when arrayed in her full summer dress. Upon him too devolves the duty of incubation, . . . the female amusing herself upon or near the water. Like the other species of Phalarope, she makes all the advances at pairing season, and sometimes more than one female fixes her attention on the same male, who thereupon has but little peace, as he is pursued from place to place by rival suitors.” From the nature of the case there would seem to be some error of interpretation here, since rival females would almost certainly fight. Instead, the choice, according to this author, seems to be left to the male. If he pairs with both hens it is obvious that one clutch of eggs at least would be wasted. CHAPTER XI REPRODUCTION—NIDIFICATION The first nest-builder. Origin of nests. Primitive nests. Burrowing. Simple nests. The nest of the Thrush tribe. Complex nests. Pensile nests. Mud nests. The remarkable nests of Tree-swifts. Colonies. Variability in nesting sites. Strange nesting sites, Nest-building and instinct, HOUGH some birds are content to deposit their eggs on the bare ground, the majority construct a receptacle of some kind in which to lay them, displaying in this work every imaginable degree of skill; for while some contrive to manage with the merest apology for a nursery, others exhibit the most: marvellous ingenuity in its architecture. At no time perhaps, except just before and during this time of nest-building, are the inherent peculiarities of birds more evident. And inno phase of their life-history do they show their racial character- istics more strikingly. Species at other times social enough now steal away in pairs to work out in seclusion the command laid on them by Nature, to increase and multiply; while on the other hand, birds usually of solitary habits combine to form huge communities, where, as is usual in communities, robbery, battle and murder, and sudden death, are hourly occurrences. Only at this time having any really fixed dwelling-place, idio- syncrasies in the choice of the site thereof are not rare; and so too we meet at this time with curious departures in this matter on the part of some species from the common traditions of the tribe; departures the more puzzling and the more instructive, because they appear, as a rule, to be prompted rather by a love of eccentricity than by motives of expediency. This phase of bird-life, the prelude to the crowning work of every living thing—reproduction—is by no means to be re- garded as the measure of the birds’ parental affection. We do not find in short that those birds which build no nests prove but indifferent parents, and that the parental instinct grows 173 174 A HISTORY OF BIRDS with the increasing perfection of their procreant cradles. As the following facts will show, nidification, in its broad outlines at least, is determined by environment, though there can be no doubt but that other factors are at work, some of which perhaps we can at least indicate while others yet remain to be discovered. That the earliest birds were arboreal there can be little room for doubt, and we may assume that they brooded their eggs . either in the holes of trees or on the stumps of decaying tree- ferns, or amid the crowns of evergreen oaks, and similar trees which had, with the appearance of the first bird —Archzopteryx —already come into existence. It may be objected how- ever, that the long and peculiarly formed tail of Archzopteryx was but ill-suited to the cramped quarters of a hollow tree-trunk —though the long-tailed modern Hornbills contrive to overcome the difficulty—and that the work of hatching was carried on in the open. But be this as it may, with the gradual spread of the race some became denizens of the open country, and these would probably at first have deposited their eggs on the bare ground without making any special preparations for their safety or protection. Two new selective factors would now come into operation, one tending to eliminate all eggs which were not protectively coloured (p. 206), and on the other, all such as suffered from contact with cold or moist earth. It is not diffi- cult to imagine that sooner or later more or fewer of the birds nesting in such sites would hit upon the plan of collecting bits of grass and stick or small stones into a small heap whereon to lay their eggs, prompted not so much by any conscious desire to protect the eggs from injury as to keep warm and dry when sitting where the ground was damp. Only those birds which had sufficient intelligence to adopt this expedient would rear offspring, and this offspring would probably inherit the same instinct. Thus were the first nests built. The habit of building a nest once fixed, wherever the eggs were laid, some receptacle would be first constructed, and thus the way was prepared for those birds which, to avoid enemies, took to laying their eggs amid the branches of shrubs and trees. The possibility that the earliest nesting sites were holes in trees receives some little support from the fact that many birds still retain this habit, and lay white eggs (p. 208). As the primitive, arboreal bird left the forest regions some sought the REPRODUCTION—NIDIFICATION 175 dark recesses of caves or the deserted burrows of other animals. Not finding these in all cases sufficiently roomy, they naturally enlarged the end of the burrow which was to form the brooding chamber, and thus they acquired the first lessons in excavation, to be turned to account when no ready-made burrows were to be found. A survey of the various types of living birds will show that in nearly every group some select either burrows or caves for the work of incubation. Thus one of the “ Rock-hopper” Pen- guins (Catarrhactes chrysocome) in Kerguelen’s Land nests in caves, though in Prince Edward Island it must be remarked they breed in the open, laying a single egg on a small heap of stones. The Magellan “Jackass” Penguin (Spheniscus magellanicus) digs large and deep burrows in the peat banks by the sea, often constructing one large chamber to serve for several pairs of birds; and similarly the little Blue Penguins of the Genus Exdy- ptula breeds in dark recesses of caves. All the Petrels, save the Albatrossesand the Giant Petrels (Osszfiagagigantéea), build either in deep crevices or in burrows, though but the merest apology for a nest is ever made, and this may be wanting. The Tropic- birds (Phethon) nests in holes in cliffs, e.g., P. rubricauda, or, when these are wanting, in holes in trees, eg., P. fulus. Among the