The role of male vs male interactions in maintaining population dialect structure

Summary

Nonmigratory populations of Whitecrowned Sparrows in coastal California exhibit dialects in territorial male songs that are stable in space and time. By field playback experiments, we tested a prediction from the hypothesis that male aggressive interactions prohibit mixing of song dialects. Playback of the home dialect ‘Clear’ song to territorial males singing the ‘Clear’ dialect resulted in less response than that given to playback of the neighboring ‘Buzzy’ dialect. Response to both ‘Buzzy’ and ‘Clear’ dialect songs by target ‘Clear’ males, however, was greater than that given to the ‘Bodega’ dialect recorded 55 km away (Figs. 2 and 3). We conclude that these results are consistent with the hypothesis that male-male aggressive interactions play an important role in reducing dialect mixing.