Birdsong, a key model in animal communication studies, has been the focus of intensive research. Song traits are commonly considered to reflect differences in individual or territory quality. Yet, few studies have quantified the variability of song traits between versus within individuals (i.e. repeatability), and thus whether certain song traits indeed provide reliable individual-specific information. Here, we studied the dawn chorus of male great tits (Parus major) to determine if key song traits are repeatable over multiple days and during different breeding stages. Additionally, we examined whether repeatability was associated with exploration behaviour, a relevant personality trait. Finally, we tested if variation in song traits could be explained by breeding stage, lowest night temperature, and exploration behaviour. We show that the start time of an individual’s dawn song was indeed repeatable within and across breeding stages, and was more repeatable before, than during, their mate’s egg laying stage. Males started singing later when the preceding night was colder. Daily repertoire size was repeatable, though to a lesser extent than song start time, and no differences were observed between breeding stages. We did not find evidence for an association between exploration behaviour and variation in dawn song traits. Repertoire composition, and specifically the start song type, varied across days, but tended to differ less than expected by chance. Our findings that individuals consistently differ in key song traits provides a better understanding of the information receivers can obtain when sampling songs of different males. Surprisingly, start time, despite being influenced by a highly variable environmental factor, appeared to be a more reliable signal of individual differences than repertoire size. Against expectation, singers were more repeatable before than during their mate’s egg laying stage, possibly because before egg laying, females are less constrained to move around unguarded and thus may then already sample (and compare) different singers. Combining repeated dawn song recordings with spatial tracking could reveal if the sampling strategies of receivers are indeed important drivers of repeatability of song traits. Such a complementary approach will further advance our insights into the dynamics and evolution of animal signalling systems.

中文翻译：

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鸟类黎明合唱中信号特征的可重复性

鸟鸣是动物交流研究的关键模型，一直是深入研究的重点。歌曲特征通常被认为反映了个体或地区质量的差异。然而，很少有研究量化歌曲特征在个体之间与个体内部的变异性（即可重复性），从而确定某些歌曲特征是否确实提供了可靠的个体特定信息。在这里，我们研究了雄性大山雀（Parus major）的黎明合唱，以确定关键的歌曲特征是否可以在多天和不同的繁殖阶段重复。此外，我们检查了可重复性是否与探索行为相关，这是一种相关的人格特征。最后，我们测试了是否可以通过繁殖阶段、最低夜间温度和探索行为来解释歌曲性状的变化。我们表明，一个人的黎明歌曲的开始时间在繁殖阶段内和整个繁殖阶段确实是可重复的，并且在其配偶的产卵阶段之前比在其产卵阶段更可重复。当前一天晚上更冷时，男性开始唱歌。每日曲目大小是可重复的，尽管程度低于歌曲开始时间，并且在繁殖阶段之间没有观察到差异。我们没有找到证据表明探索行为与黎明歌曲特征的变化之间存在关联。曲目组成，特别是起始歌曲类型，随着时间的推移而变化，但往往差异小于偶然预期。我们的研究结果表明，个体在关键歌曲特征上始终存在差异，这有助于更好地理解接收者在对不同男性的歌曲进行采样时可以获得的信息。令人惊讶的是，开始时间，尽管受到高度可变的环境因素的影响，但似乎是比曲目大小更可靠的个体差异信号。出乎意料的是，歌手在之前比在其配偶的产卵阶段更容易重复，这可能是因为在产卵之前，雌性在无人看管的情况下四处走动的限制较少，因此可能已经对不同的歌手进行了采样（和比较）。将重复的黎明歌曲录音与空间跟踪相结合可以揭示接收器的采样策略是否确实是歌曲特征可重复性的重要驱动因素。这种互补的方法将进一步推动我们对动物信号系统的动态和进化的见解。出乎意料的是，歌手在之前比在其配偶的产卵阶段更容易重复，这可能是因为在产卵之前，雌性在无人看管的情况下四处走动的限制较少，因此可能已经对不同的歌手进行了采样（和比较）。将重复的黎明歌曲录音与空间跟踪相结合可以揭示接收器的采样策略是否确实是歌曲特征可重复性的重要驱动因素。这种互补的方法将进一步推动我们对动物信号系统的动态和进化的见解。出乎意料的是，歌手在之前比在其配偶的产卵阶段更容易重复，这可能是因为在产卵之前，雌性在无人看管的情况下四处走动的限制较少，因此可能已经对不同的歌手进行了采样（和比较）。将重复的黎明歌曲录音与空间跟踪相结合可以揭示接收器的采样策略是否确实是歌曲特征可重复性的重要驱动因素。这种互补的方法将进一步推动我们对动物信号系统的动态和进化的见解。将重复的黎明歌曲录音与空间跟踪相结合可以揭示接收器的采样策略是否确实是歌曲特征可重复性的重要驱动因素。这种互补的方法将进一步推动我们对动物信号系统的动态和进化的见解。将重复的黎明歌曲录音与空间跟踪相结合可以揭示接收器的采样策略是否确实是歌曲特征可重复性的重要驱动因素。这种互补的方法将进一步推动我们对动物信号系统的动态和进化的见解。