Vocal learning in White-crowned Sparrows: sensitive phase and song dialects

Abstract

In a laboratory song tutoring experiment, eight male White-crowned Sparrows learned their natal song dialect, presented to them at 10 to 50 days of age, in preference to an alien dialect, presented to them from 51 to 90 days of age; two males learned the alien dialect, one developed a hybrid song, and one a simple song lacking structural detail (Fig. 3). Three other males developed aberrant songs (Fig. 5). Excepting these three aberrant songs, the song patterns of the males were similar to, though not close copies of, the tutor songs. The songs of all males remained consistent through two photoperiodically induced breeding ‘seasons’ (November–January and April–May; Fig. 4). During these ‘season’, females were induced to sing by administration of testosterone. Six females sang during the first season, eight sang during the scond season, with five singing in both seasons. Unlike those of the males, the song patterns of all females (with the exception of F9), were not similar to the tutor models. The songs of those five females that sang during both seasons remained consistent through both seasons (Fig. 6). We conclude that because the sensitive phase for song learning generally coincides with natal philopatry, White-crowned Sparrows are predisposed to learn their natal dialect which they retain through life. This result may be an important factor in the maintenance of populations structured by geographic systems of dialects.