The Songs and Calls of the Wood Thrush

Abstract

THE song of the Wood Thrush (Hylocichla mustelina) is longcontinued, and made up of phrases with comparatively long pauses between them. Each of these phrases is composed of up to three parts, differing from each other in quality and loudness. The parts are the introductory phrase, the main central phrase, and the termination. A bird may sing a phrase containing all three of these parts or omitting any one or two of them. The one most commonly omitted is the introductory phrase. The phrase most rarely omitted is the central phrase. This central phrase is the loudest, clearest, and most musical part, and from a distance often the only phrase heard. While I consider this song a long-continued one, the matter may have a different interpretation. In a recent publication (Borror and Reese, 1956) each phrase is considered to be a distinct song, and an individual bird is credited with 10 different songs, five of them being what I consider to be central phrases. If there are those who do not understand the diagrams used in illustrations, these have been explained. The first explanation is in Saunders (1915), and a more detailed one is in Saunders (1929). The song (Figure 1) is a difficult one to illustrate just as it is, because of rather long pauses between the phrases, that would require a large amount of space. The illustration shows a bird singing at a rate of about 10 phrases in 24 seconds, somewhat faster than the average song of nearly 10 phrases in 38 to 40 seconds. Some birds are very irregular, and slower than this, especially toward the end of the singing season. In illustrations other than Figure 1, I have not attempted to show the actual time, for altogether too much space would be required. In singing, the Wood Thrush uses different combinations of introductory notes and terminations. For example, one bird (Figure 2) sings four different central phrases, and combines these with two introductory phrases and eight different terminations. Thus the singing of 24 phrases is recorded, and there are, in that time, 15 different combinations. I have labelled the diagrams (Figure 2) with capital letters for introductory notes, numbers for the central phrases, and small letters for the terminations. This record shows how the bird may sing occasional central phrases that stand alone, without either introductions or terminations. The introductory notes are simple, but the terminations are exceedingly complex. To the ear they are quite perfectly pitched,