fcais5z ' SMITHSONIANSCIENTIFIC SERIES, Editor-in-chiefCHARLES GREELEY ABBOT, D.Sc.Secretary of theSmithsonian Institution Published bySMITHSONIAN INSTITUTION SERIES. Inc.NEW YORK. Wilson's phalarope {Steganopus tricolor), of America, a species in which the female (above)is larger and more brilliantly colored than the male (below) w v-3CdLS WARM-BLOODEDVERTEBRATESPart IBIRDSByAlexander WetmoreAssistant Secretary, Smithsonian Institution Part IIMAMMALSByGerrit S. Miller, Jr.Curator, Division of MammalsUnited States National MuseumandJames W. GidleyAssistant Curator of Mammalian FossilsUnited States National Museum VOLUME NINEOF THESMITHSONIAN SCIENTIFIC SERIES Copyright i 931, bySMITHSONIAN INSTITUTION SERIES, Inc.[Printed in the United States of America]All rights reserved Copyright Under the Articles of the Copyright Conventionof the Pan-American Republics and theUnited States, August II, 1910 CONTENTSPart IBIRDSI. Birds in Relation to Man .II. Adaptations for Progression by FlyingIII. Color and its ArrangementIV. Ancestors and Ancestry .V. Migration and its Study .VI. Homes and their LocationVII. Eggs and their Care .VIII. Something about Young BirdsIX. Voice and other Sounds .X. Studies Afield and in the LaboratoryXL Food and Economic RelationsXII. The Kinds of Birds in Brief Review 1325395o68799 1103114126H3Part IIMAMMALSI. Personal Experiences with FossilMammals 171II. How History is Read from the FossilRecord 188III. How Existing Mammals are Collected 207IV. Mammals in the Museum 218V. How Mammalogy Began and Grew . . 228VI. Some Simple Shop Talk 242VII. Museum Comedy 260VIII. The Most Ancient Known Mammals . 267IX. Egg-laying Mammals 269X. Pouched Mammals 280XL Ordinary Mammals 311Bibliography 376Index 381 ILLUSTRATIONS LIST OF PLATESPart IWilson's phalarope FrontispieceI. Figure of domestic cock from tomb of Tut-ankh-Amen. . 2i. Page from De Avibus 33. Study skins of birds 84. Form of wing in herring gull 145. Form of wing in upland plover 156. Form of wing in kingbird 167. Feathers magnified to show structure 188. Feathers magnified to show structure 199. Green-winged teal 2410. Snow buntings 3011. Killdeer on nest 3112. Flicker at nesting hole 3213. Ferruginous rough-legged hawk 3414. Whippoorwill 3615. Screech owl simulating bark of tree 3716. Skeleton of Hesperorni s 4417. Restoration of Hesperornis 451 8. Skeleton of Diatryma 4619. Restoration of Diatryma 4720. Skeleton of Ichthyornis, partially restored 4821. Nighthawk 5622. A chickadee family 6423. Mourning dove, nest, and eggs 6524. Caspian terns and young 7025. Lark sparrow, nest, and young 7026. Ruffed grouse on nest 7027. Eggs of black skimmer 7128. Costa Rican tanager and lovely cotinga 7229. Wedge-tailed shearwaters at nesting burrow .... 7430. Little blue heron, nest, and young 74 31. Least bittern simulating background of reeds .... 7432. Blue-headed vireo on nest 7533. Nest of osprey on schoolhouse 7634. North American ovenbird and nest 7635. Nests of South American ovenbird 7636. Pied-billed grebe, nest, and eggs 7737. Loon on nest 8038. Long-billed marsh wren and nest 8139. Kingbird on nest 8240. Nest and eggs of eider duck 8341. Fijian lory and orange dove 8442. Blue-faced booby, nest, and eggs 8843. Virginia rail, nest, and eggs 8944. Herring gull, nest, eggs, and young 9445. Marsh hawk and young 9546. Young belted kingfishers 9647. Laysan albatrosses 9748. Brown pelicans, nests, and young 9849. Brown thrasher, nest, and young 9950. Bobwhite no51. Ruffed grouse drumming in52. Rufous and Anna's humming birds 11253. Feeding shelves to attract birds 11654. Great brown kingfisher of Australia 11755. A country store in the Argentine Chaco 12056. Work quarters in the field, Argentina 12157. Nest mound of the mallee fowl 12458. Nest mound of the mallee fowl partly opened . . . . 12559. Eggs of the mallee fowl 13260. Florida burrowing owl 14061. Decoy duck made by prehistoric Indians 14162. Frigate bird, nest, and young 14463. Canvasback duck 14564. Canvasback ducks swimming 15265. Virginia rail 15366. Lesser yellowlegs 16067. Blue jay 16168. Bronzed grackle, or crow blackbird 16469. Young rose-breasted cockatoos 165Part II70. Pair of gibbons 16871. Restoration of a mastodon 17672. The Badlands 17773. A typical Badlands landscape 184 74- Skeleton and restoration of a titanothere 18575. Restoration of Entelodon 19276. Restorations of Hoplophoneus and Hyracodon . . . . 19377. Restoration of Mesohippus 19678. Restoration of Agriochoerus 19779. Skeleton of Stenomylus in matrix 20080. Skeleton of Teleoceras 20181. Restoration of Hyaenodon 20482. Restoration of Protoceras 20583. Cow and calf elk 20884. Mole, one of the common shrews, and jumping shrew . 21685. Malayan fruit bat 21786. Pacific walrus 22087. Giraffe and okapi 22188. Striped hyena 22489. African lions 22590. Restoration of a ground sloth 24091. American bisons 24192. Armadillo and pangolin 24493. Kangaroo rat 24594. Tropical squirrels 24895. Skeletons of horse and man 25296. Head of sperm whale 25397. Polar bears 26498. Coyotes 26599. Echidna 272100. Duckbill and nest 2731 01. Kangaroo's pouch with young 282102. Honey-mice and wombat 288103. Koalas 296104. Mandrill 3 12105. Flying-lemur 3 l &106. Marten and squirrel 3*7107. Fur seals 32?108. Lemur and spider monkey 3ai109. Horse-tailed monkeys 324no. Gorilla 3 2 S111. Lemming and harvest mice 3 2^112. Capybara and African porcupine 329113. Restoration of an extinct rodent with horns 332114. Pika and common hare 333115. Dassie 33&116. African rhinoceroses 337117. Rocky Mountain goats 344 1 1 8. Restorations of Alticamelus and Dromomeryx .... 345119. Caribou 352120. Skeletons of giant deer and mule deer 353121. Three-toed sloth 360122. Aard-vark and great anteater 361123. Skeleton and carapace of Glyptotherium 368124. Manatee, porpoise, and whale 369LIST OF TEXT FIGURESPart I1. Prehistoric figures of birds 32. Bird carved from stag horn in prehistoric times .... 43. Feather tracts in the gartered trogon 214. Pigment areas in the domestic pigeon 235. Head of crow blackbird 131Part II6. Skull of modern and horns of extinct bison 2337. Cyclone trap 2388. Skull fragments difficult to identify 2619. Tree kangaroo 28610. Rabbit bandicoot 28811. Numbat 29112. Skull of Thylacoleo 29313. Pygmy flying phalanger 29714. Spotted-tailed dasyure 29915. Thylacine 30016. Tasmanian devil 30117. Common phalanger 30318. Brush-tailed phascogale 30519. Jerboa pouched-mouse 30720. Feet of pig-footed bandicoot 30821. Marsupial-mole 30922. Skull of vampire bat 31823. Skin ornamentation on bats' heads 31924. Color patterns of hair on monkeys' heads 32825. Four stages in the evolution of the horse 355 PARTIBIRDSByAlexander WetmoreAssistant Secretary, Smithsonian Institution CHAPTER IBIRDS IN RELATION TO MANWe have only to consider the great ostrich, with its two-toed feet and flightless wings, and the tiny hummingbirds (some of which are smaller than the larger insects),with bodies highly specialized for flight, to realize some-thing of the complexity of that class of animals called birds.Yet in spite of the diversity indicated by these two ex-tremes, the various birds betray remarkable uniformity intheir structure and have many characters in common.They all have, for example, a body covering of feathers,a characteristic which instantly differentiates them fromall other vertebrated animals. Though feathers may varyfrom soft, fluffy downs and graceful plumes to stiffenedquills that give to wings the supporting surface essentialto flight, yet as a body covering they are so characteristicthat we can always identify them and so assign the mostpeculiar of birds to its proper class. For practical pur-poses, therefore, it is sufficient to define birds as warm-blooded animals with a body covering of feathers.Birds as a group have attained almost universal distri-bution over the earth, thanks to their ability to fly and totheir many specializations of form, which permit them tomaintain a continuous existence over or on both land andwater. As a result of these adaptations to varied environ-ment some type of bird may be found at some season ofthe year everywhere in the world, with the possible ex-ception of the central part of the vast Antarctic continent,which is not yet thoroughly explored. Even the broadareas of ocean furnish a home to peculiar avian species at[i] BIRDS certain seasons. Some sections of the open seas may bebirdless for months at a time when the species that fre-quent them seek the land to breed; but at the close of theirreproductive season the birds come again to these ap-parently trackless wastes of water, either as travelersmigrating over them or, if conditions are suitable for theirexistence, as sojourners. The seas and lands of the Arcticregions are as friendly to species of birds adapted to themas one noted explorer has observed they may be to manunder suitable circumstances. Land birds, like the ravenand snow bunting, nest far to the north on the coasts ofGreenland, and in summer gulls and other aquatic speciestraverse the vast spaces of the north polar sea. Deserts aswell have their feathered inhabitants.As individuals birds may abound in many temperateregions, but it is within the Tropics that the greatestvariety of species or forms occurs. And, as might be ex-pected, where the topography of the land varies extensivelywithin a comparatively small number of miles from moun-tain highland to humid, tropical lowland, there we find thegreatest concentration of species. The record for suchconcentration for a limited area is held at present by theRepublic of Ecuador: there, according to Dr. Frank M.Chapman, within an area of approximately seventy-fivethousand square miles, 1,508 distinct avian forms are atpresent known, and the list is not yet complete. To under-stand what these figures signify, contrast them with thelist of known forms for the State of California, which hastwice the land area and a highly varied topography andenvironment but which, according to the latest figures(March, 1925) of Dr. Joseph Grinnell, supports only 594forms of birds. The influence of the Tropics on bird lifeis indeed favorable.As to the relation of birds to mankind, we may be surethat well back in the prehistoric past they began to playan important role in human economy. The domestica-tion of the barnyard fowl, goose, duck, and pigeon is[2] PLATE 2De Onocrotalo.A. Lib. III. 605*fufctrs,pars fupina alba,maculis aliquot afpcrfa cinereis. partem etiam fub Cauda albcre puto. Ion.giores alarum pennar nigricant.roftrum longiufculum modice inflerJtitur. Scd cum de occulcaiicKne eius nilul cognorimjOenanthen e(Te non atTero. Speciem eius in prsccedente pagma adiet imus.DE ONOCROTALO. Icon hie orwaotik rfl,cjptt in Hr/urlu m ktu profc Tugim,qucm ipfi inf^rximm. 4? Cwsi rotiU ai>ut,j fichrc (jm.lm ofrm no&K commam^ j.Tus. Onoctotdt figure r* (jf-u/j Irf trn ? r? fe?K<" a n c auem a Latinis truonem appcllari Verrius Tlaccus fcripfit : unde Caccilius Comi?i cus(ut citat I-eftus)irndcns quendam ob nafi magmtudincm dixerit : Proh drj immorca. I les.undc luc prorepCt truo? Kaath Hebraicam uoce, ns^, interpretantur all) cticulum,! alq onocrotaluxnjpckcanum^erguluiTijupupamiut diximus fupra in hiltoru Akrgi inEe jPage from De Avibus, a hook on birds by Conrad Gesner, publishedin 1555 BIRDS IN RELATION TO MANhidden in antiquity. The fowl may have been domesti-cated in Burma or India, as these countries are withinthe range of its wild form, and the Chinese have a tradi-tion that the fowl came to them from Burma about1400 B.C. The Code of Manu, most authoritative of Hindulaw books, whose origin has been placed at varying datesbetween 1200 b.c and 200 a.d., forbids the eating of thetame fowl though it permits the eating of the wild form.Aristophanes calls the fowl the "Persian bird," indicatingthat it came to Greece fromPersia (Plate 1). Accordingto Canon Tristram, an Eng-lish writer of the lastcentury, knowledge of thedomestic pigeon in Egyptgoes back to the fifthdynasty, about 3000 b.c;while existing records of adate only shortly later in-dicate the use of pigeons asmessage carriers betweendistant points.The earliest human rec-ords relating to birds goback to the period followingthe Ice Age, when thatbranch of the prehistorichuman family known asAurignacian man lived inwhat is now France and Spain. This primitive peoplepainted or engraved animal figures, including those ofbirds, on the walls of caves and carved them on bits ofhorn, bone, or stone. The birds represented in that re-mote human art which have been identified so far includeamong others the crane, duck, goose, grouse, owl, par-tridge, and swan. The drawings date back many, manythousands of years. We find representations of birds in[3] Fig. 1. Figures of birds, probablybustards, traced in the early post-glacial period (Aurignacian orSolutrean) on the walls of thecave of El Pendo, northern Spain.After del Rio, Breuil, and Sierra BIRDS Paleolithic cultures later than the Aurignacian (Fig. 2),but not until Neolithic times, long after the close of theIce Age, do they become at all common. In the cavern atTajo Segura, in Spain, Colonel Willoughby Verner hasfound figures of the great bustard, crane, duck, goose,raven, spoonbill, flamingo, purple gallinule, glossy ibis,stork, eagle, and marsh hawk. These indicate consider-able familiarity with bird life on thepart of a people that lived, accordingto the present estimates of archeolo-gists, from six thousand to eightthousand years ago. It is probablethat most of the species included fur-nished food for these ancient people.In any Indian village in the wilderparts of South America today thetraveler may see birds of various kindswhich have been taken captive whileyoung and which, through chance orchoice on the part of their captors,have escaped being killed for food.We may fairly assume a comparableFig 2 Bird phenomenon to have been the firstcarved from stag steP m the domestication of ourhorn, from post- various domestic birds. As aestheticglacial deposits sensibilities awakened in the develop-ing brain of man he began to keepbirds captive for their beauty, odd-ity, or pleasant song, a customwhich has grown in our day to apoint where it has assumed some importance in trade.Ctesias, a Greek author, writing before 400 b.c, men-tions parrots as birds that speak the language of man? a fact which indicates that parrots were then kept captive,since they must have been brought from a distance, prob-ably from Africa, and since they develop an imitativehabit only in captivity. The Romans, at a little later[4] of Andernach,Germany. AfterR. R. Schmidt BIRDS IN RELATION TO MANperiod, are said to have confined parrots in silver-wiredcages with frames of tortoise shell and ivory. The com-mon canary was known in a domesticated state as earlyas the close of the fourteenth century but seems to havebeen rare as late as the year 1555, if we may judge froma statement of Conrad Gesner, who was deeply inter-ested in birds of all kinds (Plate 2), to the effect that hehad heard of these birds but had never seen one. Theoriginal canary stock is reputed to have come from theCanary Islands, where the wild form (Serinus serinuscanarius) still is common. The wild form has mixed gray,olive-green, and yellowish plumage, the sides and flanksbeing streaked v/ith a dusky shade?a pattern at timesreproduced wholly or in part in domestic birds?but bythe close of the seventeenth century pure-yellow and pure-white canaries were known.Another group of birds that came early into semi-domestication were hawks and falcons, which weretrained for hunting. The earliest references to the domes-tication of falcons for hunting winged and four-footedgame are Chinese, but of indefinite date. The use offalcons in hunting is recorded from Persia as early as 1700B.C. and is believed to have existed in Europe in 300 B.C.Hunters went afield carrying on their wrists these fiercebirds, with eyes hooded, tethered by a short leash. Whengame was sighted the hawks were released in its pursuit.The birds were trained to return to their masters at thesound of a whistle. For a long period, until, in fact, gun-powder and firearms came into general use, falconry re-mained the accepted method for hunting small game, andthere are extended references in literature to the sport.In some sections of central Asia today golden eagles aretrained to hunt gazelles and other game.The study of birds as a branch of natural history, thatis, the science of ornithology, follows two general meth-ods: First, observation of the living individual and itsreactions to the varying conditions that it encounters;[5] BIRDS second, examination of the dead body. Observations ofthe living bird enjoy the greater popular interest and havethe larger following, particularly among those for whomornithology is an avocation. Birds are easily observed,both because they are the most conspicuous of vertebrateanimals in a wild state and because they abound nearlyeverywhere. In addition, when given the slightest en-couragement they come readily about our homes, unlessthese happen to be in such unfavorable locations as thecenters of great cities.Primitive peoples everywhere have noted the move-ments of birds as portents of the weather and of sea-sonal or other natural phenomena. I have had huntersamong the Toba Indians in the Pilcomayo jungles ofnorthern Argentina recount at my camp fire as part of thenews of the day the sighting of rheas (flightless runningbirds remotely related to the ostrich) on certain openplains and of wild ducks or screamers on the lagoons, or thefinding of the nest of the yacu, a pheasantlike bird thatlives in trees. The passage of migratory birds figuredfrequently in the omens by which the priests of ancientGreece and Rome attempted to forecast future events.From unrecorded times men have used the flights ofmigratory birds as omens; savage peoples have namedcalendar periods for migrants that appeared regularly inthe course of the seasons; and the migrant flights of ducksand geese still supply the countryman with importantnews.The study of dead birds is likewise nothing new, sinceit began in a primitive way with the first preparation, inany manner, of the bodies of birds for human food andthe utilization of feathers and skins for ornament or dress,of tendons for sewing, or of bones for tools. Though mod-ern studies of the dead bird include dissections of speci-mens preserved in alcohol or other fluid and the examina-tion of skeletons, the majority of ornithologists working inmuseums devote their attention to specimens prepared in a[6] BIRDS IN RELATION TO MAN special manner. This special preparation consists ofskinning the bird in such a way that the feathers, bill,and feet are kept intact, after which the skin is filled withcotton, tow, or excelsior and arranged in compact formto appear like a complete bird. Such specimens, knownas study skins (Plate 3), are readily prepared by expertnaturalists during their travels; and in the museum theyrequire little space, as they rest in sliding trays in speciallybuilt cabinets provided with tight-fitting doors to preventthe entrance of skin-destroying insects. Examples ofinteresting species are mounted for public exhibit, butthese are only a small proportion of the great collectionsof bird specimens possessed by the larger museums, sinceto exhibit too many would only confuse the public.It may appear on casual inspection that our study col-lections include too many duplicates?too many speci-mens of the same species of bird. But only by extensivesets of specimens can we learn the differences in color orsize, great or small, that may exist in male, female, andyoung at different seasons of the year or in different partsof the geographic range, the manner of molt and featherrenewal, and many other items of value and interest. Insome cases fifty or more individuals of one kind of birdmay be needed to exhibit properly these and other points.Furthermore, the ardent conservationist need feel noalarm at the size of the bird collections in our largermuseums. In many of our States a sportsman is permittedby law to kill fifteen ducks in any day of the open season,which means that the number of ducks shot for sporteach year throughout our country runs literally into mil-lions. Compare these numbers with the series of twenty-five or, rarely, fifty skins of a species found in each of afew museums and it will be seen that the individualspreserved for science amount to practically nothing inthe annual slaughter. The great majority of small birds,of course, are not hunted as game and so escape the sports-man. The comparatively few killed annually for science[7] BIRDShave small bearing on the continuance of most species,though certain forms of very restricted range and others,like the whooping crane and ivory-billed woodpecker,which are near extinction, need careful protection if theyare to endure.It is also worthy of mention that hundreds of birdskilled by accident come to museum collections for preser-vation as specimens. The National Museum constantlyreceives bodies of birds which have met their death bystriking against wires while in flight or which have beenkilled by cats, automobiles, or other agencies. A maleflicker is killed in fight with a rival and is brought in for thecollection by a museum messenger who chances to witnessthe battle; a guard on night duty at the WashingtonMonument brings in a dozen migrant warblers that havemet death by striking the great shaft of stone during thehours of darkness. Lighthouses have sent in hundreds ofspecimens accidentally killed, and on one occasion theNational Museum received nearly one hundred birdskilled by flying against the Statue of Liberty in New Yorkharbor. It has been my good fortune to preserve forscientific study many hundreds of ducks and other waterbirds which had succumbed to alkali poisoning in thevicinity of lakes in the Great Basin region, and to securedozens of valuable specimens from dead birds washed upon sea beaches in various parts of the world.As a final comment on this matter I may add that thefirst collections made for what is now the United StatesNational Museum were secured about ninety years ago,while a few specimens in its cases date back to the year1 8 17. In other words its collections have been accumu-lating during more than a century, a sufficient length oftime to assure any one that the number taken has notthreatened the existence of any species of bird.The art of preserving the bodies of birds more or lesspermanently is older than history; probably it began withthe preservation of such single feathers, partial or entire[8] PLATE 3 5.0 - J BIRDS IN RELATION TO MAN skins with the feathers attached, and dried or smokedheads and feet as we find used for ornaments by primi-tive peoples of today. The mummification of birds waspracticed in Egypt in the fourth century b.c. and fur-nishes us with the earliest known instances of theirpreservation. The mummies, which include kites, eagles,falcons, ibises, and numerous other birds, were entombedwith human bodies; and so well have they endured thatwe can still identify them by their bones and feathers.Thirty-five species or more have been recognized in thesemummies.Aristotle, the father of recorded natural history, livingfrom 385 to 322 B.C., is said to have had at his disposal,thanks to the patronage of Alexander the Great, severalthousand persons who hunted and fished and otherwisegathered information for his work on the natural historyof animals. He mentions many birds and must have hadat least partial specimens of some of them, though of thisthere is no actual statement. To reach authentic recordsof the possession of preserved specimens we have to skipmany hundreds of years. Between 1415 and 1440, Nicolodi Conti secured in Java preserved skins of birds of para-dise, which came as articles of trade from New Guineaand the near-by islands. These were prepared by nativesand were the forerunners of the bird skins prepared forscientific study today.Early naturalists in their travels depended largely onsketches or descriptions for information about strangebirds. William Turner, writing in 1544, asked his readersto send him notes on any birds they might secure thatwere not already described in his published work. Butactual specimens were also used, and we know that birdsor fragments of birds were brought back to Europe aboutthis time from the New World. Pierre Belon in 1555 men-tions dried skins of birds brought by mariners for sale,describing from this source what he called the "merle debresil," which is a species of tanager (Ramphocelus[9] BIRDSbrasilius) of bright plumage. He outlines methods ofpreserving birds by removing the intestines, placing saltin the body cavity and throat, and hanging the body up bythe legs to dry; or by removing the entire skin and pre-serving it in salt. John Tradescant writes, during a voyageto Archangel in 1618, that "on Monday the 13 of Julythere wer many small bird come abord the shepe beingsume 3 leags from the shore. I have thre of ther skinswhiche wer caut by myself and the rest of the company."James Petiver, a London apothecary, in 1698 instructs usthat "smaller birds are easily preserved Entire, by openingtheir Bodies which is best done by cutting them under theWing, and take out their Entrals, and then stuff themwith Ockam or Tow mixt with Pitch or Tar." Birds werealso preserved entire in spirits by numerous travelers.After the middle of the eighteenth century, however,naturalists began to make study skins, and by the firstof the nineteenth century this had become the standardmethod and has led to the accumulation of our present-day collections.Among the oldest bird skins of which the approximateage is known are those found in a curious book preservedin the Emma Shearer Wood Library of Ornithology atMcGill University in Montreal. This book contains il-lustrations made by cutting off the skin of one side of abird and pasting it on the page in lifelike attitude, withlong feathers arranged to indicate the wing, and the billand ! feet glued in place. The considerable number ofspecies thus illustrated includes an American parrot. Ac-cording to the title-page this work was prepared in 161 8 by Dionisio Minaggio, an official of the court at Milan.The museum at Upsala, Sweden, is said to possess half adozen bird skins known to have been in existence in 1747,while the University of Parma has a few specimens her-metically sealed in glass bottles by Jean Fourcault, whodied in 1775. Finally, in the museum at the University ofOxford there are the head and foot of a dodo which John[10] BIRDS IN RELATION TO MANTradescant preserved in 1656 and which came to Oxfordfrom Sir Elias Ashmole in 1669. The head of anotherdodo, a species which was last recorded alive in 168 1, isalso preserved at Copenhagen. In addition to theseearly-preserved specimens we still have the Egyptianmummies already mentioned and feathers found inancient Indian dwellings in America. Ravages of feather-eating insects have, however, destroyed the greater partof the earlier specimens, a destruction that began to bechecked successfully only about 1740 with the employ-ment of arsenic to poison the skins. Today we must lookto museum collections to examine the great auk, the pas-senger pigeon, the Labrador duck, and scores of otherbirds that man has exterminated. Meanwhile the exten-sion of human civilization to the remotest sections of theglobe tends yearly to crowd out of existence thousandsupon thousands of other species. Only a relatively smallnumber of birds find the new physical environment createdby man favorable to their continuance. The rest succumb,and the next fifty years are sure to witness a tremendousdiminution in the number of birds and other wild crea-tures. For this reason museum collections increase inimportance yearly, and we need to take care that speci-mens of birds threatened with extinction are preserved.In concluding this chapter it may be said that themuseum investigator, absorbed in his trays of skins orbones or in his jars of alcoholic specimens, and the ob-server watching living birds in the open air are workingtoward a common end. Each is dependent on the other,and the work of both is necessary to complete our knowl-edge. The manuals on which the observer depends toidentify species come almost entirely from the indoorscientist, as does our knowledge of the limits of familiesand their relationships, of ancestry through fossil records,and of the physical composition of their feathers andbodies. The outdoor observer contributes to our knowl-edge of the psychology, manner of life, nesting, and haunts[11] BIRDS of birds, and furnishes the laboratory student with speci-mens. A modern development that in a way combinesthe methods of the two schools is the use of living birds incontrolled captivity for the study of various phases oftheir reactions to environment, their development, andtheir psychology. [12] CHAPTER IIADAPTATIONS FOR PROGRESSION BYFLYINGFlight has been a powerful factor in controlling the bodilyform of birds, maintaining it within the boundaries of avery definite pattern, and allowing only such variation asdoes not interfere with a flying existence. It is true that anumber of species of living birds, like the ostriches,penguins, and numerous rails, as well as various peculiarfossil forms (see Plates 17 and 19), do not, or did not, fly.Some authorities have gone so far as to argue that theostriches and penguins have always been flightless, andthat they have not descended from the same ancestor ashave the flying birds. I hold, however, with many others,that the form of the wing in ostriches and penguins, withthe fused bones of the hand and other peculiarities, indi-cates definitely that these groups have come from flyingancestors and have lost the power of flight as they becamespecialized for their own peculiar habits of life. Nodefinite basis seems to exist for the suggestion that birdshave originated from two distinct and separate lines ofancestors.The adaptations of birds for flight, though presenting anumber of departures from those found in other flyinganimals, are relatively simple. We find the most strikingmodification in the forelimb, which has become a wingwith feathers projecting from its posterior margin. Thewings form a strong supporting plane which maintains thebird in the air, provided it has a certain forward momen-tum, and at the same time can be flexed easily. Thus as[13] BIRDSthe wings are moved up and down the form of the surfacechanges first to provide the power for driving the entirebody forward and then to return with the least amount ofretarding friction to position for another driving stroke.The wing performs the functions of the plane in theaircraft and is far more efficient because it is in threeseparate sections?the humeral part, corresponding to ourupper arm, the forearm, and the hand. This makes itpossible for the bird to adjust its wings readily to changingstresses and conditions, and when it alights to fold theminstantly to fit the curves of the body and thus permitfreedom of movement. (For illustrations of the form ofthe wing in living birds, see Plates 4, 5, and 6.)The bones of the hand in the bird's wing, which bearmuch of the stress of flight, are stiffened and fused sothat they do not have the pliability found, for example,in the hands of lizards and squirrels, which are used forgrasping. To hold or draw objects to itself, the birdmust employ the foot assisted by the bill or, as do thesparrows, must depend upon the bill entirely for that pur-pose. The stiffened hand, however, forms a perfect sup-port for the outer feathers of the wing, which are of primeimportance in flight.The driving force in avian flight is the muscles of thebreast, which in flying birds are developed to great size;they are attached to a broad breastbone which has a highcentral keel. Long tendons transmit the driving power tothe wing bones. The muscles found on the wing itself aresmall, their purpose being to hold the wing rigid when it isextended, to control change in the shape of the wing dur-ing flight, and to hold the wing securely against the bodywhen it is folded. The bulking of the flight muscles onthe lower surface of the body results in a low center ofgravity, which is advantageous in affording stabilityduring flight.Two adaptations reinforce the skeleton of flying birds:Thin, narrow plates of bone, called the uncinate processes,[14] ?r J4 .5 o 3 6 ? 3C OO -C H c3 ^