MACDOUGALL-SHACKLETON, E.A.; MACDOUGALL-SHACKLETON, S.A.; SMITH, A.W.; HAHN, T.P.; University of Western Ontario; University of Western Ontario; Princeton University; University of California, Davis: Sierra Nevada mountain white-crowned sparrows do not discriminate among within-mountain-range song dialect types

Song dialects have been the subject of much theoretical and experimental research. Many hypotheses have been proposed to explain the widespread existence of this form of geographic variation in a culturally transmitted trait. Mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) in the Sierra Nevada of California exhibit long-term stable song dialects. It has been shown recently that there is a small but significant reduction in gene flow among these dialect populations. Furthermore, males singing non-local dialect have reduced reproductive success. A potential mechanism for these population effects is that males and/or females behaviorally discriminate against males singing songs of neighboring dialect regions. In this study we tested whether male and female mountain white-crowned sparrows in the Sierra Nevada respond differentially to songs of their local dialect, songs from an adjacent dialect, and songs from a distant dialect (but within the Sierra Nevada). Females gave similar numbers of solicitation displays to playback of all three types of songs. Males responded aggressively and non-differentially to playback of all three types of songs. These null effects do not appear to be due to a lack of statistical power. Thus, song dialects in this mountain range and subspecies do not appear to be maintained by female mate choice or by male competitive exclusion. Although song dialects are associated with reduced gene flow and differential reproductive success in this subspecies, this study suggests that behavioral discrimination based on song dialect is not the cause of these population level effects.