THE VOICE-REGISTERS OF BIRDS.
Musicians have distinguished several ranges of tone in human voices, and, with the object of rendering vocalization even and harmonious, teachers of singing have always laboured to smooth out these breaks or cracks in the voice. Although some teachers deny that these breaks are natural, and contend that they are due to a vitiated style of singing, the breaks are very noticeable in the passionate crying of a baby, and therefore must be considered as quite natural. The most distinct breaks in adult voices are to be found in basses and contraltos, whose deep song notes are widely different from their alto and soprano notes. The jodelling with which lads in the street sometimes amuse themselves very clearly illustrates this subject.
My present purpose is to draw attention to a seemingly analogous break in the voices of many birds. The subject is difficult to discuss, but not, I believe, devoid of scientific value. Perhaps the most obvious break in a bird-voice occurs in the Goose, whose discordant cries strongly suggest the first attempt of a person to play a clarionet. In man the upper register is merely the survival of the child's voice, but it is very difficult to determine whether the same survival of the infantile voice occurs in birds' songs, for half-grown birds rarely sing. It must at the same time be observed that the first songs of young Blackbirds and Thrushes are much like the high squeaky notes to which the voices of the adults often change abruptly from the full song.
In some birds we hear what may be termed the "chest voice" (corresponding, say, to our contralto and bass), and a "head voice" (analogous to our alto and soprano). The Blackbird affords the commonest instance. Its song consists of a few full whistled notes (the number increases as the season advances), never slurred from one to the other; and these, in every successive phrase, are immediately succeeded by some harsh squealing
