Ręk Paweł, Osiejuk Tomasz S
Department of Behavioural Ecology, Institute of Environmental Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
Behav Processes. 2011 Mar;86(3):323-8. doi: 10.1016/j.beproc.2011.01.011. Epub 2011 Feb 1.
Individually specific acoustic signals in birds are used in territorial defence. These signals enable a reduction of energy expenditure due to individual recognition between rivals and the associated threat levels. Mechanisms and acoustic cues used for individual recognition seem to be versatile among birds. However, most studies so far have been conducted on oscine species. Few studies have focused on exactly how the potential for individual recognition changes with distance between the signaller and receiver. We studied a nocturnally active rail species, the corncrake, which utters a seemingly simple disyllabic call. The inner call structure, however, is quite complex and expressed as intervals between maximal amplitude peaks, called pulse-to-pulse durations (PPD). The inner call is characterized by very low within-individual variation and high between-individuals difference. These variations and differences enable recognition of individuals. We conducted our propagation experiments in a natural corncrake habitat. We found that PPD was not affected by transmission. Correct individual identification was possible regardless of the distance and position of the microphone which was above the ground. The results for sounds from the extreme distance propagated through the vegetation compared to those transmitted above the vegetation were even better. These results support the idea that PPD structure has evolved under selection favouring individual recognition in a species signalling at night, in a dense environment and close to the ground.
鸟类个体特有的声学信号用于领地防御。这些信号能够减少能量消耗，因为对手之间可以通过个体识别以及相关的威胁程度来实现。用于个体识别的机制和声学线索在鸟类中似乎具有多样性。然而，迄今为止大多数研究都是针对鸣禽物种进行的。很少有研究关注个体识别的潜力究竟如何随信号发出者与接收者之间的距离而变化。我们研究了一种夜间活动的秧鸡物种——长脚秧鸡，它发出一种看似简单的双音节叫声。然而，其内部叫声结构相当复杂，表现为最大振幅峰值之间的间隔，称为脉冲到脉冲持续时间（PPD）。内部叫声的特点是个体内部变化非常小，个体之间差异很大。这些变化和差异使得能够识别个体。我们在长脚秧鸡的自然栖息地进行了传播实验。我们发现PPD不受传播影响。无论高于地面的麦克风的距离和位置如何，都有可能正确识别个体。与在植被上方传播的声音相比，通过植被传播的极远距离声音的识别结果甚至更好。这些结果支持了这样一种观点，即PPD结构是在有利于夜间在密集环境且靠近地面发出信号的物种进行个体识别的选择下进化而来的。
