A new assay for vocal learning

Fledgling sparrows, hand-reared in the laboratory, can recognize their own species' song with little or no prior experience with adult song when first presented with it in playback tests. Males and females give more "chirp" calls to playback of white-crowned sparrow songs than to the songs of other species. We have recently extended this test by tutoring males and females for five 10-day-long periods, and then conducting playback tests after each period. Males called more to tutor songs than to novel playback songs after the first 3 periods, but females did so only after the first 2 periods. Neither sex discriminated between novel and tutor songs presented in the winter, outside of the normal sensitive period for song learning. Males called more to tutor songs they subsequently imitated the next spring when they came into song. Thus, the pattern of calling when young predicted which songs were held in long-term memory for song production. This work is in press in Animal Behaviour.

Future studies using this assay will explore how songs are represented in memory during the 6 month storage interval that intervenes between when songs are memorized during the sensitive phase and when they are subsequently reproduced. Also, females hand-reared in the laboratory do not sing (usually), and so do not inform us whether they have learned song. We hope to use an alternative bioassay for song learning in adult females, the copulation solicitation assay, to establish whether the juvenile preferences for tutor songs displayed by chirp calls correlates with preferences for songs in adult females.