Department of Psychology, University of British Columbia, Vancouver BC, Canada.
Horm Behav. 2012 Sep;62(4):455-63. doi: 10.1016/j.yhbeh.2012.08.002. Epub 2012 Aug 10.
It is well known that songbirds produce high amplitude songs ("broadcast songs"). Songbirds also produce low amplitude songs ("soft songs") during courtship or territorial aggression in the breeding season. Soft songs are important social signals but have been studied far less than broadcast songs. To date, no studies have examined seasonal changes in soft song or its endocrine regulation. Here, in male song sparrows, we examined soft songs during a simulated territorial intrusion in the breeding season and non-breeding season. We also measured plasma testosterone and dehydroepiandrosterone (DHEA) levels in subjects immediately after the aggressive encounter. The total number of songs produced (broadcast+soft songs) did not vary between seasons. However, there was a dramatic increase in the percentage of soft song in the non-breeding season. Further, the percentage of soft song was negatively correlated with plasma testosterone levels in the non-breeding season. There were seasonal differences in the acoustic structure of two major elements of soft song, trills and buzzes. The minimum frequency of trills was lower in the non-breeding season, and the element repetition rate of buzzes was lower in the non-breeding season. To our knowledge, this is the first study to (1) examine soft songs outside of the breeding season and (2) to identify endocrine correlates of soft songs, which are important social signals in songbirds.
众所周知，鸣禽会发出高振幅的歌曲（“广播歌曲”）。在繁殖季节的求偶或领地侵略期间，鸣禽也会发出低振幅的歌曲（“柔和歌曲”）。柔和歌曲是重要的社交信号，但研究却远少于广播歌曲。迄今为止，尚无研究探讨过柔和歌曲的季节性变化或其内分泌调节。在这里，我们在雄性歌雀中研究了繁殖季节和非繁殖季节模拟领地入侵时的柔和歌曲。我们还在攻击性相遇后立即测量了受试者的血浆睾丸酮和去氢表雄酮（DHEA）水平。两个季节产生的歌曲总数（广播+柔和歌曲）没有差异。但是，在非繁殖季节，柔和歌曲的比例却急剧增加。此外，在非繁殖季节，柔和歌曲的比例与血浆睾丸酮水平呈负相关。柔和歌曲的两个主要元素——颤音和嗡嗡声的声学结构也存在季节性差异。非繁殖季节的颤音最小频率较低，而嗡嗡声的元素重复率在非繁殖季节较低。据我们所知，这是首次（1）在繁殖季节之外研究柔和歌曲，以及（2）确定柔和歌曲的内分泌相关性的研究，柔和歌曲是鸣禽中重要的社交信号。
