Cultural divergence within novel song in the Black-capped Chickadee (Poecile atricapillus)

摘要

Geographic variation in learned vocalizations is commonly attributed, in part, to imperfect song learning, but rarely has this been documented. Additionally, we know little about how spatial structure of populations affects geographic divergence in song. Using novel fee-bee song in Black-capped Chickadees (Poecile atricapillus) in Fort Collins, Colorado, we investigated both of those concepts by recording songs from juveniles at the time of natal dispersal and from adults at study sites along a continuous riparian corridor and in small isolated populations north of Fort Collins. Acoustic differences within juveniles' songs corresponded to acoustic differences distinguishing the songs of adults from separate study sites. We also found more acoustic divergence among the small isolated populations than among the continuously distributed riparian populations, and we found that the song-type grouping most similar in acoustic structure to the stereotyped continental fee-bee diverged the least. These findings suggest that song variants introduced by developing juveniles can indeed account for geographic variation and that song diverges more in small isolated populations.