The variability of song variability in wild and domesticated zebra finches Taeniopygia guttata

Birdsong is a classic example of a learned social behavior. Like many traits of interest, however, song production is also influenced by genetic factors and understanding the relative contributions of genetic and environmental influences remains a major research goal. In this study we take advantage of genetic variation among captive zebra finch populations to examine variation in a population-level song trait: song variability. We find that zebra finch populations differ in levels of song variability. Domesticated T. g. castanotis populations displayed higher song diversity than more recently wild-derived populations of both zebra finch subspecies T. g. castanotis and T. g. guttata, the Timor zebra finch. To determine whether these differences could have a genetic basis, we cross-fostered domesticated T. g. castanotis and Timor zebra finches to Bengalese finches Lonchura striata domestica. Following cross-fostering, domesticated T. g. castanotis maintained a higher level of song diversity than T. g. guttata. We suggest that the high song variability of domesticated zebra finches may be a consequence of reduced purifying selection acting on song traits. Intraspecific differences in the mechanisms underlying song variability therefore represent an untapped opportunity for probing the mechanisms of song learning and production.