But avoiding "genealogies and contentions," and taking up the question with which we began, we may safely say that birds sing, sometimes to gratify an innate love for sweet sounds; sometimes to win a mate, or to tell their love to a mate already won; sometimes as practice, with a view to self-improvement; and sometimes for no better reason than the poet's,—"I do but sing because I must." In general, they sing for joy; and their joy, of course, has various causes.
For one thing, they are very sensitive to the weather. With them, as with us, sunlight and a genial warmth go to produce serenity. A bright summer-like day, late in October, or even in November, will set the smaller birds to singing, and the grouse to drumming. I heard a robin venturing a little song on the 25th of last December; but that, for aught I know, was a Christmas carol. No matter what the season, you will not hear a great deal of bird music during a high wind; and if you are caught in the woods by a sudden shower in May or June, and are not too much taken up with thoughts of your own condition, you will hardly fail to notice the instant silence which falls upon the woods with the rain. Birds, however, are more or less inconsistent (that is, a part of their likeness to us), and sometimes sing most freely when the sky is overcast.
But their highest joys are by no means dependent upon the moods of the weather. A comfortable state of mind is not to be contemned, but beings who are capable of deep and passionate affection recognize a difference between comfort and ecstasy. And the peculiar glory of birds is just here, in the all-consuming fervor of their love. It would be commonplace to call them models of conjugal and parental faithfulness. With a few exceptions (and these, it is a pleasure to add, not singers), the very least of them is literally faithful unto death. Here and there, in the notes of some collector, we are told of a difficulty he has had in securing a coveted specimen: the tiny creature, whose mate had been already "collected," would persist in hovering so closely about the invader's head that it was impossible to shoot him without spoiling him for the cabinet by blowing him to pieces!
Need there be any mystery about the singing of such a lover? Is it surprising if at times he is so enraptured that he can no longer sit tamely on the branch, but must dart into the air, and go circling round and round, caroling as he flies?
So far as song is the voice of emotion, it will of necessity vary with the emotion; and every one who has ears must have heard once in a while bird music of quite unusual fervor. For example, I have often seen the least flycatcher (a very unromantic-looking body, surely) when he was almost beside himself; flying in a circle, and repeating breathlessly his emphatic chebec. And once I found a wood pewee in a somewhat similar mood. He was more quiet than the least flycatcher; but he too sang on the wing, and I have never heard notes which seemed more expressive of happiness. Many of them were entirely new and strange, although the familiar pewee was introduced among the rest. As I listened, I felt it to be an occasion for thankfulness that the delighted creature had never studied anatomy, and did not know that the structure of his throat made it improper for him to sing. In this connection, also, I recall a cardinal grosbeak, whom I heard several years ago, on the bank of the Potomac River. An old soldier had taken me to visit the Great Falls, and as we were clambering over the rocks this grosbeak began to sing; and soon, without any hint from me, and without knowing who the invisible musician was, my companion remarked upon the uncommon beauty of the song. The cardinal is always a great singer, having a voice which, as European writers say, is almost equal to the nightingale's; but in this case the more stirring, martial quality of the strain had given place to an exquisite mellowness, as if it were, what I have no doubt it was, a song of love.
Every kind of bird has notes of its own, so that a thoroughly practiced ear would be able to discriminate the different species with nearly as much certainty as Professor Baird would feel after an examination of the anatomy and plumage. Still this strong specific resemblance is far from being a dead uniformity. Aside from the fact, already mentioned, that the characteristic strain is sometimes given with extraordinary sweetness and emphasis, there are often to be detected variations of a more formal character. This is noticeably true of robins. It may almost be said that no two of them sing alike; while now and then their vagaries are conspicuous enough to attract general attention. One who was my neighbor last year interjected into his song a series of four or five most exact imitations of the peep of a chicken. When I first heard this performance, I was in company with two friends, both of whom noticed and laughed at it; and some days afterwards I visited the spot again, and found the bird still rehearsing the same ridiculous medley. I conjectured that he had been brought up near a hen-coop, and, moreover, had been so unfortunate as to lose his father before his notes had become thoroughly fixed; and then, being compelled to finish his musical education by himself, had taken a fancy to practice these chicken calls. This guess may not have been correct. All I can affirm is that he sang exactly as he might have been expected to do, on that supposition; but certainly the resemblance seemed too close to be accidental.
The variations of the wood thrush are fully as striking as those of the robin, and sometimes it is impossible not to feel that the artist is making a deliberate effort to do something out of the ordinary course, something better than he has ever done before. Now and then he prefaces his proper song with many disconnected, extremely staccato notes, following each other at very distant and unexpected intervals of pitch. It is this, I conclude, which is meant by some writer (who it is I cannot now remember) when he criticises the wood thrush for spending too much time in tuning his instrument. But the fault is the critic's, I think; to my ear these preliminaries sound rather like the recitative which goes before the grand aria.
Still another musician who delights to take liberties with his score is the towhee bunting, or chewink. Indeed, he carries the matter so far that sometimes it seems almost as if he suspected the proximity of some self-conceited ornithologist, and were determined, if possible, to make a fool of him. And for my part, being neither self conceited nor an ornithologist, I am willing to confess that I have once or twice been so badly deceived that now the mere sight of this Pipilo is, so to speak, a means of grace to me.
One more of these innovators (these heretics, as they are most likely called by their more conservative brethren) is the field sparrow, better known as Spizella pusilla. His usual song consists of a simple line of notes, beginning leisurely, but growing shorter and more rapid to the close. The voice is so smooth and sweet, and the acceleration so well managed, that, although the whole is commonly a strict monotone, the effect is not in the least monotonous. This song I once heard rendered in reverse order, with a result so strange that I did not suspect the identity of the author till I had crept up within sight of him. Another of these sparrows, who has passed the last two seasons in my neighborhood, habitually doubles the measure; going through it in the usual way, and then, just as you expect him to conclude, catching it up again, Da capo.
But birds like these are quite outdone by such species as the song sparrow, the white-eyed vireo, and the Western meadow-lark,—species of which we may say that each individual bird has a whole repertory of songs at his command. The song sparrow, who is the best known of the three, will repeat one melody perhaps a dozen times, then change it for a second, and in turn leave that for a third; as if he were singing hymns of twelve or fifteen stanzas each, and set each hymn to its appropriate tune. It is something well worth listening to, common though it is, and may easily suggest a number of questions about the origin and meaning of bird music.