Zebra finches go wild! Experimental cultural evolution of birdsong.

Vocal learning in songbirds is guided by experience and experience-independent factors. Previously, lineages of zebra finches founded by isolate-reared tutors showed cultural evolution to wild-type song features. This suggests that biases lead to selective imitation even in the absence of wild-type song. We hypothesized that cultural evolution of song depends on both experience-independent biases and the tutor songs available. We predicted that songs more distant from wild-type would take longer to culturally evolve toward wild-type features. We bred zebra finches in three groups of lineages in which offspring of each generation served as tutors for the next. Lineages were founded with males singing wild-type song, isolate song, or heterospecific song. The two experimental lineages exhibited rapid cultural evolution of song with many features converging to wild-type within two generations. However the rate of change differed depending on song features measured, and took longer for lineages founded with heterospecific song.