Abstract Most of our knowledge about the function, evolution, neurobiology and ontogeny of complex vocalizations in birds comes from previous work on male song. However, the recent increase in focus on female bird song over the last few decades has helped bridge that gap in our knowledge and has vastly changed our understanding of the function, phylogeny and evolution of bird song. Here we present evidence that female song may be modifiable based on signal function. Eastern bluebirds primarily use female song for within-pair communication with their social mate. We examined the female songs of eastern bluebirds sung during within-pair communication and compared the acoustic structure to female songs used in other contexts. Within-pair communication songs differed significantly from other female songs that we measured by six of the eight acoustic variables we measured. Additionally, we examined the song structure of within-pair communication songs at variable distances between mates and between neighbour females. Song structure did not vary over distance. However, we found significant differences between neighbouring females and the number of syllables and frequency modulations each female included in her within-pair communication songs. We propose that female songs have the potential to indicate individual identity, through acoustic structure modification. Our findings further highlight the need for additional study of female song and functional acoustic plasticity in bird song. Significance statement Animal signals may be stereotyped to convey honest information, they may be functionally plastic to convey additional information, or elements of a signal may fall in both categories. Historically, bird song has been primarily studied as a stereotyped male trait. Whereas male bird song may have variable acoustic structure in some instances, such as extreme aggression, the functional plasticity of female song is largely unknown. We examined female song plasticity for within-pair communication songs of female eastern bluebirds. We present some of the first evidence that female song structure may be variable between functional contexts and that females may alter their song structure to encode additional information, such as individual identity. Our results inform future work on the function and ontogeny of female bird song. Additionally, our findings support the need for further study on female bird song and the functional plasticity of complex acoustic signals.

中文翻译：

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东方蓝鸟的雌性歌曲在声学结构上因社会环境而异

摘要我们关于鸟类复杂发声的功能、进化、神经生物学和个体发育的大部分知识都来自以前对雄性歌曲的研究。然而，最近几十年来对雌性鸟鸣的关注度增加有助于弥合我们知识上的差距，并极大地改变了我们对鸟鸣的功能、系统发育和进化的理解。在这里，我们提供了证据，表明女性歌曲可以根据信号功能进行修改。东方蓝鸟主要使用雌性歌曲与社交伴侣进行配对交流。我们检查了成对交流中东方蓝鸟的雌性歌曲，并将声学结构与其他环境中使用的雌性歌曲进行了比较。对内交流歌曲与我们测量的八个声学变量中的六个测量的其他女性歌曲显着不同。此外，我们检查了配偶之间和相邻雌性之间不同距离的配对内交流歌曲的歌曲结构。歌曲结构不随距离变化。然而，我们发现相邻雌性之间的显着差异以及每个雌性在她的配对交流歌曲中包含的音节和频率调制的数量。我们建议女性歌曲有可能通过声学结构修改来表明个人身份。我们的研究结果进一步强调了对鸟鸣中的女性鸣叫和功能性声学可塑性进行额外研究的必要性。意义声明 动物信号可能被刻板印象以传达真实信息，它们可能在功能上是可塑性的，以传达附加信息，或者信号的元素可能同时属于这两个类别。从历史上看，鸟鸣主要被研究为一种刻板的男性特征。虽然雄鸟鸣声在某些情况下可能具有可变的声学结构，例如极端攻击性，但雌鸟鸣声的功能可塑性在很大程度上是未知的。我们研究了雌性东部蓝鸟的成对交流歌曲的雌性歌曲可塑性。我们提出了一些初步证据，表明女性歌曲结构可能在功能上下文之间变化，并且女性可能会改变她们的歌曲结构来编码额外的信息，例如个人身份。我们的结果为未来关于雌鸟鸣叫的功能和个体发育的工作提供了信息。此外，