The Genesis of Bird-Song

BIRD-SONG is one of the most charming mysteries in nature; it has no counterpart in art. I have at times fancied there was some analogy between it and the art of poetry, but there is none, in fact. The genesis of poetry is intellectual and psychal; the genesis of bird-song is purely physical. Even the human voice, in song, oratory, and histrionic declamation, borrows much of its best value from the character, mental and psychal, of the individual vocalizer.

The song apparatus of the bird is, perhaps, no more a machine than that of the man ; but the controlling force, the motor, of the former is mechanical, whilst that of the latter is intellectual to a large degree. Of course I do not mean to say that birds sing involuntarily or without emotion of a certain sort, nor would I be understood as representing the song organ of any oscine to be absolutely unadjustable, which would be contrary to the first law of evolution, — the natural impulse of progression from lower to higher expression. It would seem that conscious effort to improve, such as man is capable of, works both evil and good in the way of developing the vocal organs, whilst the unconscious practice indulged by the birds never injures the voice, and if it improves it, the result comes about by the slow process of hereditary accumulation. Thus, no doubt, the wonderful voice power of our song-birds is the result of a long, steady evolutionary growth.

The theory that birds have descended from a remote reptilian ancestry has so many facts to support it that, until some convincing discoveries in palæontology shall be made to the contrary tending, we must accept it as probably true. Unfortunately, the study of comparative anatomy is both infinitely complicated and immeasurably dry to the layman, as contradistinguished from the scientist, wherefore much the greater number of even cultured people will probably always rest in ignorance of the startling details pertaining to evolution in nature. Few of us, indeed, have the time and the necessary self-devotion, even if the scarce and precious material furnished by nature were always at hand, to make the investigations necessary to a high knowledge of natural science. Large museums are far apart, scientific books are expensive, and the field of each science is as wide as the whole range of nature: consequently, none but the favored — or the self-devoted — few can afford the luxury of following, as Darwin and Huxley and Milne-Edwards and Owen and Marsh have done, the flitting spirit which beckons us back and back, over the silent, desolate grave-yards of the ages, to the beginnings of things. Still, we may all catch a light breath, so to speak, of the air from the oldest, or rather the youngest, period of organic life. Any one of us may choose a slight, narrow, but far-reaching current of inquiry, and float down it, from time to time, until at last the end is reached, away back in the chaos upon which moved the Spirit of Creation at the dawn of day.

Some years ago I was tramping and sketching in the beautiful hilly region of Western Florida. During the springtime, especially, I spent a great deal of my leisure studying the song and habits of the mocking-bird. One morning, while a fine moquer, as the Creoles call our king of song-birds, was charming me with his wonderful vocalization, the question arose in my mind : When did a mocking-bird first sing? Of course the inquiry could not be answered ; but it suggested a broad field of special research. Why not ask of Nature the general question, When did birds first sing ? or: What is the genesis of birdsong ? I lay in the shade of a widetopped live-oak and brooded over the fascinating problem, while a sweet breeze from the Gulf stirred the sprays overhead, and rippled the silvery bosom of a little lake that lapped the sand at my feet. Gradually enough I formulated a plan of investigation which I have followed, as far as my ability to profit by my own discoveries and those of others has permitted.

At first thought it may seem trivial to propose an inquiry into the origin of bird-song ; but a little reflection upon the subject will be sufficient to enlist the interest of almost any mind. All things have had a beginning, and so there was a time when no music of “ swelling throats ” filled the air of spring. Somewhere the first cat-bird sang in a brier-tangle, the first brown thrush flooded a thicket with its melody, the first mocking-bird filled the day and the night with incomparable rhapsody ; at least one imagines as much ; and then the Garden of Eden appears in the distance, some six or seven thousand years away. There it was that birds and birdsong had their beginning, just in time to welcome Adam and give Eve a brilliant wedding serenade.

Now I believe that, when they are read aright, science and revelation, so far as they pertain to material things, are mathematically equivalent to each other; they coincide in meaning, if not in form. They might be exactly superposable, were science reduced to the simplicity of revelation, that is to simple truth; but unfortunately we cannot begin at the beginning or go to the end of science. Revelation states a fact, whilst science merely collects evidence tending to establish a fact. Revelation emits simple truth ; science strives to reach this same elementary verity by a process of reconstruction.

The inspired record declares that man was given dominion, which would imply that the earth and all things upon it and in it were made for his benefit. Science may profit by this view of creation, and take the serving of man’s physical and mental needs as the end of evolution. In other words, we may assume that if the object of creation was to make a sphere for man’s dominion while in the human state, then all the lines of creature development have been drawn towards a culmination, have been led to their highest point, in the age of man’s creation ; that the Creator perfected the animal, mineral, and vegetable kingdoms before he made man. But what has all this to do with the genesis of bird-song ? you will ask. Perhaps much, perhaps little. Let us see.

Without resorting to the language of technical scientific literature, where it can be avoided, I will briefly reviewthe records of geology touching the origin of birds, and by this means we may get a clue to the origin of bird-song.

The first traces in the palæozoic rocks of anything resembling bird life are welldefined footprints ; these, however, have been attributed to certain ancient reptiles having feet approaching those of some aquatic fowls in form. Next come organic remains — fragmentary skeletons, for the most part, of strange saurians and bat-like flying animals, having membranous wings and the beak of a toothed bird. No sign of a feather was observable, however, among all the fossil records, up to the discovery of an imperfect skeleton and partial cast of a strange creature named Archæopteryx, half bird, half reptile, in the lithographic slate of Solenhofen, Bavaria. A transition state between the bat-like, birdbilled reptiles above noted and our present ornithic forms could not be better expressed than by Archæopteryx, so far as anatomy and exterior structural points are concerned. This initial bird, so to call it, appears to have possessed a very oddly arranged suit of feathers, consisting of retrices (arranged regularly on the sides of a very long, twenty-jointed tail) and wing-feathers, its body having no plumage, probably, or at best mere rudimentary, down-like feathers. As to whether this rude bird had a voice, it is useless to inquire, since the head and sternum are wanting; but I think we may safely doubt the existence of more than the obscurest development of vocal organs in birds having toothed reptile jaws and bi-concave vertebræ, as in the case of some of the Odontornithes, so ably studied and arranged by Professor Marsh. The fish-eating birds of our own time have not much voice, as a rule, — a guttural squawk, or a metallic clanging scream, being the extent of their performance. Taking the skeleton of Hesperornis regalis, as restored by Marsh, we shall see at once, considering the toothed jaws and reptilian throat, that its vocal organs were probably far inferior to those of existing loons and grebes, if it had a voice at all.

Returning to Archæopteryx, we shall become more and more convinced, the more we study its remains in the light of all that is known of comparative anatomy, that it was scarcely more ornithic than our common bat, as regards similarity to the birds of to-day, notwithstanding its feathers. Indeed, it had a sort of bat claw at the end of the wing, and its wing feathers and retrices were a very little remove from the leathery, bat vans of the flying reptiles in so far as efficiency was concerned ; but its impression in the rocks registers a definite effort of nature in the direction of evolving a true bird. Thenceforward we may look for feathered forms gradually growing toward the high type of to-day. The reptile prototype has somehow exchanged his scales for feathers ; the generation of the true bird has begun with Archæopteryx. A long, dreary blank here appears in the record of the rocks, after which we find the toothed birds of Professor Marsh, probably full-fledged, in the sense of being coated with feathers. It is to be doubted whether any of these were good flyers,— some of them certainly could not fly at all, — though they were mostly excellent swimmers, and possibly capable of living a long time under water, if not really amphibious. What Professor Marsh says of the anatomy of Archæopteryx may he applied generally to the toothed birds : “ The bones of the reptile are indeed there, but they have already received the stamp of the bird ; ” and I may add that, as regards Odontornithes collectively, the feathers are indeed there, and the stamp of the bird, but the old reptile character is still present, scarcely more than dominated by the ornithic features. I have said that it may be doubted whether any of the Odontornithes were good flyers. By good flyers I mean not merely strong flyers (like the teals), nor sailers (like the hawks and buzzards), but flyers whose movements in the air are almost instantaneous, like the highest type of oscines, say the mocking-bird, or the cardinal grosbeak, a facility of flight absolutely necessary to arboreal life, where so many thorns, spikes, branches, twigs, vines, and sprays have to be suddenly avoided in the midst of the swiftest motion. Some of the toothed birds of Marsh’s smaller group may have been as good flyers as our gulls, strong and tireless ; but they could not dodge a dozen twigs in a second, as I have seen a sparrow do in full flight.

The discovery of Palæospiza bella, a well-preserved, almost complete skeleton of a sparrow-like bird in the insectivorous shale of Colorado, has given us the nearest approach to a song-bird yet found in the old rocks; but the bill is lacking. Most probably Palæospiza was an oscine, in the ornthological sense, but I think we may well doubt whether it could sing, in the true meaning of the word. Its position in the insect-bearing shale further favors our classing it as insectivorous, another characteristic of the true song-birds; but this would not give it a song, for many of the existing oscines have no song to sing, chirp and pipe and squeak as they may.

From this slight sketch of what the old rocks tell about birds, we see that, so far as fossil remains teach anything, they teach us that the oscine form was the last to appear in the succession of structural changes in the bird’s general physique. This is as far as we can go in the direction of mere development of form, by the light of anatomy, considering fossil skeletons merely as such.

Let us turn now and take a quick glance over the evidence of voice development discoverable in the kinship between birds and reptiles.

Professor Huxley, in one of the most admirable of his great contributions to scientific taxonomy, has classed the birds and the reptiles together, or rather grouped them under one head, as constituting a primary division of the vertebrates. He has based this classification on many points in which, on one hand, birds and reptiles agree anatomically and physiologically, and on their variance from mammals in as many points on the other hand. Indeed, the kinship between birds and reptiles is still very strong, even after the immense development of the bird form and the comparatively slight modification of most reptile forms which have come about since the time of Archæopteryx and the dinosaurian animals of the triassic rocks.

We may assume, then, that the development of the vocal organs in birds has been, in some measure, apace with or dependent upon the departure of the bird form from that of the reptile.

Our present existing reptiles are almost devoid of voice proper. Some of them can make certain dismal, guttural groans or croaks, others can utter shrill, discordant sounds; but at best the reptilian vocal apparatus is rudimentary in the extreme. Hence in those days when the bird was just struggling away from the clumsiest and worst hindering characteristics of the reptile, it certainly possessed no vocal organs of any great power. It would appear doubtful whether it had any at all, since so few birds, even now, have a singing voice, and since, after all these ages of development, the reptile’s voice is scarcely a voice at best. It is a curious fact that frogs and toads, amphibians, have the best developed vocal organs of all the reptiles, and that they are not properly scale-bearing; and yet it is from the scale-bearing reptiles that our birds have sprung. Perhaps the common toad comes nearer than any known reptile to the possession of a singing voice, though the tree-frogs have a peculiar chirp or squeak not unlike certain notes of the woodpeckers. One might stop here and indulge the pretty impression that the toad in the summer grass and the treefrog among the green branches register the highest possibilities of reptilian song genius, whilst the mocking-bird, the brown thrush, and the nightingale assert the triumph of the race which long ago departed from the groove of that lower estate, by changing scales tc feathers, legs to wings, and that rudimentary vocal apparatus into the syrinx, with which to charm the poets of all time !

The crocodiles, including our alligator, have the tongue attached all round in the mouth, so that it cannot be much used, and it is at this point, so far as the power of vocalization is concerned, that song-birds have departed farthest from the scale - bearing reptiles ; for the tongues of our musical oscines are thoroughly liberated, and do good service in the complicated gymnastics of song production. The tongue of the frog is, as a rule, attached at the front of the mouth and free behind, so that, in catching insects, this organ is “ curled over itself,” and thrust out rear end foremost. Curiously enough, the “ singing ” treefrogs are the males, the females not possessing the vocal power to any great degree; thus resembling our oscines, whose males are the music - makers. Moreover, the frog, as a fossil, dates back to the time when the birds were fairly beginning to separate themselves from reptile life. Add to this the fact that there is a flying tree-frog in Borneo, and it will be seen that here is a strange, belated effort of nature to urge the scaleless reptiles up to arboreal, aerial, and song-singing life, by the side of their more fortunate avian kinsmen, who early chose a better method of development!

Turning now to rapidly sketch the really wonderful vocal organs of our oscine birds, I need not enter into any technical anatomical discussion, but, taking the mocking-bird as the highest type of singer, it will be sufficient, for the purposes of this paper, to explain the salient features of the song-producing throat in birds. First, then, all bird-song is generated in a lower larynx called the syrinx, a complicated little machine situated, in fact, at the lower end of the trachea, where it divides into two bronchial tubes, and consisting in chief of an enlargement and rearrangement of the compound lower ring of the windpipe, a bony cross-bar, or pessulus, and a membranous plate which forms a partition between the tubes, and whose upper margin is one of the vibrating vocal cords, the other cord being a membrane developed on the inside of the bronchial rings, or rather half-rings, opposite the septum or partition above mentioned. Thus a column of air passing from the lungs to escape through the trachea sets these membranes to vibrating, whilst by means of five or six pairs of delicately adjusted muscles the air space is changed with wonderful facility, the column shortened or lengthened, as is done by the flute-player, and indeed the whole lower throat becomes a generator of sweet sounds, which, passing up to the bird’s mouth, are broken into melodious bits, so to speak, and scattered to the winds; for the highest vocalization, although generated in the syrinx, is made into song, in a large degree, by the bird’s tongue, its posterior mouth walls, and the upper extremity of the trachea, all of which taken together constitute a complicated and perfectly adjusted governor of the quantity, the accent, and, in a measure, the quality of the notes.

Every observer has remarked that nearly all the superior songsters among birds have rather long and slender bills, whilst the talkers have short, stout ones. I have tried to discover, and think I have discovered, the relation that width, length, and curvature of bill have to the quality or style of voice. It is sufficient to remark here that birds having extremely short, thick beaks, like that of the cardinal grosbeak or that of the blue-jay, have not the power, apparently, of trilling, shaking, or quavering the voice (which is the distinguishing gift of the thrush and many other slender-billed birds), though the grosbeak and the jay have excellent vocal powers. Reduced to a rule, the comparison will be, The short-bills twitter and whistle, the long-bills sing. The blue-jay is the most melodious of the whistlers, whilst the quail (bob-white) and the cardinal grosbeak are the most powerful whistlers of all our birds.

It has been somewhat taken for granted by our ornithologists that all the birds belonging to the subdivision named oscines, or singers, have the vocal organs necessary to song. Even Dr. Cones remarks that the rook, though “ a corvine croaker,” has a “syrinx in good order, though he has never learned to play ” on it. Now, I have never had the opportunity of dissecting a rook’s vocal organs; but I am able to say that such corvine croakers as I have examined are not possessed of a song-making apparatus to be at all compared with that of the cat-bird, the brown thrush, or the mocking-bird. McGillivray’s figures will have to be greatly modified when applied to the best of our American songsters. Professor Müller’s researches in the comparative anatomy of vocal organs in birds, and Professor Huxley’s admirably clear description, have failed fully to recognize the office of the tongue and posterior walls of the mouth in differentiating and modifying the notes of a bird’s song. It appears to me that the oversight, or partial oversight, has arisen from taking it for granted that the bronchi-tracheal syrinx is the absolute and sole song organ in birds, instead of being merely the voice generator in songbirds. For example, the parrot has no septum in his syrinx, and but three pairs of intrinsic muscles, and yet his voice is a wonder of flexibility and elasticity. Melody is lacking, because one of the vocal cords (the septum with its membrane) is gone ; but high vocal performance is possible, because the lower mouth space and the tongue are singularly adapted to modifying and breaking up the voice into fragments surprisingly articulate, though the voice itself is inferior in timbre and range.

Long before I began my dissections, I had noted that the sweetest of the flute notes uttered by the mocking-bird and the blue-jay appeared to be blown out through a rigidly distended throat, whilst the delicately quavered passages of the mocking-bird’s song were, seemingly, manufactured at the root of the tongue. To get evidence of this, carefully watch your caged mocker when he is delivering a labored staccato combination, and you will see the convulsive shake of the mouth muscles and the peculiar management of the lower mouth space, by which he differentiates the notes. On the other hand, he will whistle, and when he has ended you can scarcely say whether or not he opened or moved his mouth at all during the performance.

There is an interesting ventriloquial effect produced by the purely syringeal or laryngeal notes of a bird’s voice. This is very pronounced in the call of the quail, and especially in the piping of young wild turkeys ; but it is most noteworthy in some of the night-cries of the mocking-bird. True song, however, has nothing of this peculiarity in it; even the careless shadow lay of the indigo-bird has its definite expression of place and distance, no matter how sketchy its outline.

From all we can gather it appears most probable that in its present form our song-bird proper — our bird with a song to sing — is not much older than man ; that he found his song just in time to gladden the ears of God’s last and greatest creation ; that he struggled through countless ages and awful changes in order to fit himself for our entertainment. Think what the avian race has endured since first Archæopteryx felt the feathers begin to bud in his arms ! What a long, slow, hesitating, faltering current of development, from a scaly amphibian of the palæozoic time, up, up, to the glorious state of the nightingale and the mocking-bird ! I never see a brown thrush flashing his brilliant song from the highest spray of a tree without letting a thought go back over the way he has come to us, and I always feel that to protect and defend the song-bird is one of man’s clearest duties. Indeed, nothing is better indicated by the records of the ages than that beautiful colors, rich fragrance, and bird-song were made especially for us. There were no flowers, properly so called, in palæozoic times. Amidst all the luxuriant vegetation of the coal measures, not a fossil blossom is found, nor do the rocks give up a single butterfly or other insect which was probably highly or delicately colored. The ancient birds (reasoning from analogy) were not gay-feathered, and, as I have shown, were not able to sing. But when man appeared the world was ready for him ; the hills and the valleys and the broad plains were covered with verdure and bloom, and the air was rich with perfume and resonant with bird-song. He might have looked around scarcely able to know whether the butterflies were winged flowers, or the flowers vegetable butterflies. All this great, riant, blooming, perfumed, music-filled world was for him and his beautiful companion. Well might it be said that they were in a garden, an Eden. Well might the gush of song from a myriad swelling throats, around, above, everywhere, suggest that the very stars of morning were singing together.

I am inclined to the belief, from my own observation, that many of our birds are still in a transition state as regards the development of their vocal organs. Take the woodpeckers, a very unmusical family, and we shall find the goldenwing giving some evidence of acquiring a song, apace with his departure from the true woodpecker habit. The woodthrush appears to lack a million years or so of practice and hereditary development to make him sing as well as the mocking-bird, though his voice is as sweet as a silver bell. The meadowlark is very nearly a singer, so is the blue-bird, whilst the blue-jay does at rare intervals render a low, mellow, incomparably pure flute passage, as if whistling a snatch from a future score of its own. The tufted tit-mouse stops just short of what one fancies would be a fine, clear lay, and the cardinal grosbeak puts on all the airs of an accomplished musician, without being quite able to find a tune. Comparative anatomy bears out these suggestions, showing that development of voice in birds runs quite along with the development of the syrinx, whilst development of song power keeps well up with and is dependent on the correlative efficiency of the syrinx and mouth arrangement. No crow, or blackbird (American), or other songless oscine is capable of learning to sing, nor can it be, until a change shall have taken place, not in its larynx or syrinx, but in the shape of the posterior part of its mouth with relation to its tongue and the opening of the trachea. In every case where a bird approaches the margin of song-making it will be found to possess a mouth arrangement superior to that of birds which have no tendency toward song. Even the mouth and tongue of the golden-winged woodpecker are verging in the direction of the true development; its bill is growing slender and weak, is taking on the songbird curve, and the posterior part of the tongue is being modified. Indeed, Colaptes auratus is much nearer the true singing bird’s estate than any rook, no matter how beautifully developed its syrinx, but it is not nearer the possession of the greatest vocal power, the power of articulate expression.

Such is a hasty glimpse of the genesis of bird-song, a subject which might well have a volume devoted to it; for so long as Keats’s ode to a nightingale and Shelley’s to a sky-lark shall exist, no one dare say that bird-song is not worthy of the highest attention.

Maurice Thompson.