Songs and Sexual Responses of Female White-Crowned Sparrows (Zonotrichia Leucophrys) From a Mixed-Dialect Population

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Abstract
Some researchers have suggested that female songbirds mate with males singing local song types in preference to males singing dialects from more distant populations. Such behaviour might promote genetic isolation among dialect populations. We studied captive female white-crowned sparrows (Zonotrichia leucophrys) from a population in which two song types were equally common, as a model for behaviour at dialect boundaries. Subjects were captured as adults, and the song type of the mate of each was known. Treated with estradiol, females gave sexual displays in response to playback of conspecific male song. As a group, they solicited no more strongly to either local song type, suggesting that males singing either local song type should be able to attract mates. Individuals solicited no more strongly to their mate's song type than to the other local song type. This suggests that strength of response of captive females to song playback may not accurately reflect the behaviour of free-living individuals. Subjects were also treated with testosterone to induce singing. Individuals sang their mates' song type more often than expected by chance. Given that female white-crowned sparrows in this population do not consistently choose mates of one song type, we develop the argument that females learn, for performance, the song type of their first mate. However, the type of song learned for performance appears unlikely to restrict their subsequent mate choice decisions. Our results suggest that female white-crowned sparrows do not base their choice of mates on dialectal variation in male song, and that it is unlikely that mate choice decisions based on song dialect promote the genetic isolation of dialect populations.

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