Naguib Marc, Diehl Joris, van Oers Kees, Snijders Lysanne
1Behavioural Ecology Group, Wageningen University & Research, Wageningen, De Elst 1, 6708WD, Wageningen, The Netherlands.
2Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
Front Zool. 2019 Jul 9;16:27. doi: 10.1186/s12983-019-0328-7. eCollection 2019.
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 () 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.
鸟鸣作为动物交流研究中的一个关键模型，一直是深入研究的焦点。鸣声特征通常被认为反映了个体或领地质量的差异。然而，很少有研究对个体间与个体内鸣声特征的变异性（即可重复性）进行量化，因此也未确定某些鸣声特征是否确实能提供可靠的个体特异性信息。在此，我们研究了雄性大山雀的晨鸣，以确定关键鸣声特征在多天以及不同繁殖阶段是否具有可重复性。此外，我们还研究了可重复性是否与探索行为（一种相关的个性特征）有关。最后，我们测试了鸣声特征的变异是否可以用繁殖阶段、最低夜间温度和探索行为来解释。
我们发现，个体晨鸣的开始时间在繁殖阶段内和不同繁殖阶段之间确实具有可重复性，并且在配偶产卵阶段之前比产卵阶段更具可重复性。前一晚温度较低时，雄性开始鸣叫的时间较晚。每日曲目数量具有可重复性，尽管程度低于鸣声开始时间，且不同繁殖阶段之间未观察到差异。我们没有发现探索行为与晨鸣特征变异之间存在关联的证据。曲目组成，特别是起始鸣声类型，在不同日期有所变化，但差异程度往往小于随机预期。
我们的研究结果表明个体在关键鸣声特征上存在持续差异，这有助于更好地理解信息接收者在对不同雄性的鸣声进行采样时能够获得的信息。令人惊讶的是，尽管开始时间受到高度可变的环境因素影响，但它似乎比曲目数量更能可靠地反映个体差异。与预期相反，雄性在配偶产卵阶段之前比产卵阶段更具可重复性，可能是因为在产卵前，雌性在无保护状态下活动的限制较少，因此可能已经对不同雄性的鸣声进行了采样（并进行了比较）。将重复的晨鸣录音与空间追踪相结合，可以揭示信息接收者的采样策略是否确实是鸣声特征可重复性的重要驱动因素。这种互补方法将进一步加深我们对动物信号系统动态和进化的理解。
