The singing-birds, with reference to their songs, may be divided into four classes. First, the Rapid Singers, whose song is uninterrupted, of considerable length, and uttered with fervor, and in apparent ecstasy. Second, the Moderate Singers, whose notes are slowly modulated, but without pauses or rests between their different strains. Third, the Interrupted Singers, who seldom modulate their notes with rapidity, and make decided pauses between their several strains, of which there are in general from five to eight or nine. Fourth, the Warblers, whose notes consist of only one or two strains, not combined into a song.
The canary, among foreign birds, and the linnet and bobolink, among American birds, are familiar examples of the first class; the common robin and the veery of the second; the wood-thrush, the cat-bird, and the mocking-bird, of the third; and the blue-bird, the pewee, and the purple martin, of the fourth class. It may be added, that some birds are nearly periodical in their habits of singing, preferring the morning and evening, and occasional periods in other parts of the day, while others sing almost indifferently at all hours. The greater number of species, however, are more tuneful in the early morning than at any other hour.
June, in this part of the world, is the most vocal month of the year. Many of our principal songsters do not arrive until near the middle of May; and all, whether they come early or late, continue in song throughout the month of June. The bobolink, which is one of the first to become silent, continues vocal until the second week in July. So nearly simultaneous is the discontinuance of the songs of this species, that it might seem as if their silence were preconcerted, and that by a vote they had, on a certain day, adjourned over to another year. If an unusually genial day occurs about the seventh of July, we may hear multitudes of them singing merrily on that occasion. Should this time be followed by two or three successive days of chilly and rainy weather, their tunefulness is so generally brought to a close during this period, that we may not hear another musical note from a single individual after the seventh. The songs of birds are discontinued as soon as their amorous dalliances and the care of their offspring have ceased. Hence those birds that raise but one brood of young during the season, like the bobolink, are the first to become silent.
No one of the New England birds is an autumnal warbler; though the song-sparrow often greets the fine mornings in October with his lays, and the shore-lark, after spending the summer in Labrador and about the shores of Hudson's Bay, is sometimes heard in autumn, soaring and singing at the dawn of day, while on his passage to the South. The bobolink, the veery, or Wilson's thrush, the red thrush, and the golden robin, are silent after the middle of July; the wood-thrush, the cat-bird, and the common robin, not until a month later; but the song-sparrow alone continues to sing throughout the summer. The tuneful season of the year, in New England, embraces a period of about four months, from the middle of April to the middle of August.
There are certain times of the day, as well as certain seasons of the year, when the birds are most musical. The grand concert of the feathered tribe takes place during the hour between dawn and sunrise. During the remainder of the day they sing less in concert, though many species are very musical at noonday, and seem, like the nocturnal birds, to prefer the hour when others are silent. At sunset there is an apparent attempt to unite once more in chorus, but this is far from being so loud or so general as in the morning. The little birds which I have classed in the fourth division are a very important accompaniment to the anthem of dawn, their notes, though short, serving agreeably to fill up the pauses made by the other musicians. Thus, the hair-bird (Fringilla Socialis) has a sharp and trilling note, without any modulation, and not at all melodious, when heard alone; but in the morning it is the chief harmonizer of the whole chorus, and serves, more than any other voice, to give unity and symphony to the multitude of miscellaneous parts.
There are not many birds whose notes could be accurately described upon the gamut. The nearest approach we can make to accuracy is to give some general idea of their time and modulation. Their musical intervals can be distinguished but with difficulty, on account of the rapidity of their utterance. I have often attempted to transcribe some of their notes upon the musical scale, but I am persuaded that such sketches can be only approximations to literal correctness. As different individuals of the same species sing very differently, the notes, as transcribed from the song of one individual, will never exactly represent the song of another. If we listen attentively, however, to a number of songs, we shall detect in all of them a theme, as it is termed by musicians, of which the different individuals of the species warble their respective variations. Every song is, technically speaking, a fantasia constructed upon this theme, from which none of the species ever departs.
It is very generally believed that the singing-birds are confined to temperate latitudes, and that the tropical birds have not the gift of song. That this is an error is apparent from the testimony of travellers, who speak of the birds in the Sandwich Islands and New Zealand as singing delightfully, and some fine songsters are occasionally imported in cages from tropical climates. The origin of this notion may be explained in several ways. It is worthy of notice that within the tropics the singing season of different species of birds does not occur at the same time. One species may be musical in the spring, another in summer, and others in autumn and winter. When one species, therefore, has begun to sing, another has ceased, so that, at whatever time of the year the traveller stops, he hears but few birds engaged in song.
In the temperate latitudes, on the contrary, as soon as the birds arrive, they commence building their nests, and become musical at the same time. If a stranger from a tropical climate should arrive in this country in the spring, and remain here during the months of May and June, he would hear more birds singing together than he ever heard at once in his own clime; but were he to arrive about the middle of July, when the greater number of our birds have discontinued their songs, he would probably, if he knew the reputation of the Northern birds, marvel a little at their silence. If there are as many birds singing at one time during the whole year, in the hot climates, as we hear in this country in the latter half of summer, the greater average would appear to be on the side of the former.
It may also be remarked, that the singing-birds of the tropics are not so well known as those of temperate latitudes which are inhabited by civilized men. The savages and barbarians, who are the principal inhabitants of hot countries, are seldom observant of the habits or the voices of the singing-birds. A musician of the feathered race, as well as a harpist or violinist, must have an appreciating audience, or his powers can never be made known to the world. But even with the same audience, the tropical singing-birds would probably be less esteemed than songsters of equal merit in the temperate latitudes; for, amid the stridulous and deafening sounds made by the insects in warm climates, the notes of birds would be scarcely audible.
We are still inclined to believe, however, that there is a larger proportion of musical birds in the temperate than in the torrid zone, because in the former region there are more of those species that build low and live among the grass and shrubbery, and it is well known that the singing-birds are mostly of the latter description. In warm climates the vegetation consists chiefly of trees and tall vines, forming together an umbrageous canopy overhead, with but a scanty undergrowth. In temperate latitudes the shrubbery predominates, especially in the most northerly parts. Moreover, the grasses that furnish by their seeds a great proportion of the food of the smaller birds are almost entirely wanting in the torrid zone.