Variation in White-Throated Sparrow Songs

Abstract

This paper is based on a study, by means of a sound spectrograph, of the recorded songs of 433 birds and field observations of 278 additional birds; these 711 birds were in 8 states of the United States and 6 provinces of Canada. White-throated sparrow songs consist of s series of clear, whistled notes, and usually end in triplets. The songs studied contained 9 types of notes, and were classified in 15 patterns on the basis of note character and pitch changes through the song. The songs of each pattern varied in several ways; each type of variation was found in the songs of a given bird, but some types were more pronounced in songs of different birds. Four of the 15 song patterns were sung by 96.5% of the birds studied. The most common pattern, sung by 62.5%, had the 1st note low, the 2nd higher, the 3rd about the same pitch as the 2nd, and the remaining notes at the same pitch as the 3rd or slightly lower; the most common variation of this pattern, sung by 197 birds, might be paraphrased "tooooo tititi tweee tititi tititi tititi." Only 3 of the 711 birds sang songs consisting of 2 long, steady notes followed by triplets, the pattern suggested by the common descriptions of this species'' song in the literature. The range in pitch in the songs studied was 2,150 to 6,500 cps; the range of pitch in individual songs varied from 0.2 to 12.7 musical intervals. The amount of change in pitch through the song varied in a given pattern, principally in songs of different birds, sometimes as much as 5 intervals. The 1st note of the song varied in length from 0.27 to 1.17 seconds, and the entire song from 1.24 to 6.06 seconds. The songs of each pattern followed a definite sequence of notes, but ended at various points; most songs ended in triplets (up to a maximum of 7), but 6 birds had songs ending in two-parted notes. Of the 711 birds, 15 sang songs of 2 patterns; the others sang songs of a single pattern. Of the 433 recorded birds, 30 showed variations in the types of notes in the song; the 2nd note varied most often. Most birds showed variations, usually less than an interval, in the pitch of the 1st note of the song and in the amount of pitch change through the song. The songs of migrants were more variable than those of nesting birds. Two of the 4 most common song patterns were widely distributed; one was primarily eastern, the other was most common in the midwest. The differences in songs of a given pattern from different areas were rarely significant. There are relatively few patterns in the song of the white-throated sparrow, and these are generally recognizable in the field. Since each bird usually sings songs of a single pattern, it is often possible to recognize individual birds; this is of value in censusing breeding birds and mapping territories. Since this species sings in spring migration, songs of migrants suggest their destination. A white-throat''s song pattern is probably learned from other birds; occasionally a bird develops an inaccurate copy of another song, resulting in an unusual pattern; 11 such patterns were found, in 27 of the 711 birds.