Comparisons of song perception in male and female songbirds utilizing cardiac responses

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In most songbirds, males sing to defend territories and to attract females, and females evaluate the quality of males based on songs. This should lead to differences in song perception between the sexes, but it has been difficult to devise an assay that can evaluate song perception without introducing motivational bias. For example, the copulation solicitation assay is useful for evaluating female perception of songs, but this assay cannot be utilized for males. We found that birds react to a sound of interest by increasing the heart rate, and this response was used to compare song perception in Bengalese and zebra finches. We used conspecific and hetero-specific songs as stimuli and these were presented in a planned order. In Bengalese finches, only females responded to the changes in conspecific song repertoire. In zebra finches, both males and females reacted to such changes. Bengalese finches are a domesticated species and males do not establish breeding territories. Conversely, male zebra finches establish a small territory when breeding. In both species, songs are an important trait by which females select males. These ecological differences concur with the species and sex differences in the cardiac response. [Work supported by JSPS and JST.]