Dialect Discrimination by White-Crowned Sparrows: Reactions to Near and Distant Dialects

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Abstract
In Marin County, California, the dialect populations of Zonotrichia leucophrys nuttalli are contiguous, and there is little dialect mixing. The possible importance of male-male interactions in preventing dialect mixing was tested with song-playback experiments. Males of the Limantour dialect were presented the Limantour dialect, Drake or Buzzy dialects (neighboring), or Clear dialect (distant). From previous work, we predicted that Limantour males would respond with equal or more aggression to songs of immediately neighboring dialects in comparison with their own dialect but would respond at lower levels to a distant dialect. Instead, we found that Limantour males sang significantly more songs in response to the Limantour dialect than to either neighboring or distant dialects, although the response decreased with distance, as expected. These results led us to hypothesize that responses to an alien dialect may be influenced by (1) opportunity to habituate to the alien dialect, (2) recency of divergence of the two dialects, (3) recency of contact of the two dialects, and (4) sounds common in aggressive vocalizations in other contexts being also present in some song dialects but not others.