Jakubowska Aleksandra, Osiejuk Tomasz S
Department of Behavioural Ecology, Institute of Environmental Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
Department of Behavioural Ecology, Institute of Environmental Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
Behav Processes. 2018 Dec;157:244-249. doi: 10.1016/j.beproc.2018.10.012. Epub 2018 Oct 23.
Low-amplitude soft songs have been described in many birds, but in most species, research has addressed only broadcast songs. Soft songs may have a similar or distinctive structure in comparison to broadcast songs produced in order to defend a territory and attract females. In some species, such soft songs were found to be produced in an aggressive context and were the best predictors of conflict escalation and later physical attack. However, such observations are not consistent across all species studied. Several hypotheses have been put forward to explain the function(s) of soft songs and why they are so quiet. Studies on the ortolan bunting (Emberiza hortulana) show that males produce soft songs similar in structure to broadcast songs during close interactions with conspecific intruders. However, experiments with the playback of loud and soft songs as well as taxidermic mount presentation revealed that soft song in this species does not fulfil aggressive signal criteria. Here we performed an experiment with two loudspeakers simulating movements of the intruder in order to test whether the soft songs are used to evoking a response from a nearby but not localised rival. We found that males responded with similar strength to songs played back from single and double speaker systems. Simultaneously, males produced more soft songs during and just after the phase of the experiment in which we simulated short flights of the intruder. Our results indicate that soft songs might be used during close interactions with rivals without being an aggressive signal and are used as short-range signals to check if the rival is still around. Our results also provide an alternative explanation of soft song behaviour in comparison to the hypotheses of eavesdropping avoidance and readiness to fight.
许多鸟类都有低振幅的轻柔歌声，但在大多数物种中，研究仅涉及广播歌声。与为保卫领地和吸引雌鸟而发出的广播歌声相比，轻柔歌声可能具有相似或独特的结构。在一些物种中，人们发现这种轻柔歌声是在具有攻击性的情境中发出的，并且是冲突升级和随后身体攻击的最佳预测指标。然而，这些观察结果在所有研究的物种中并不一致。已经提出了几种假设来解释轻柔歌声的功能以及它们为何如此安静。对圃鹀（Emberiza hortulana）的研究表明，雄性在与同种入侵者近距离互动时会发出结构与广播歌声相似的轻柔歌声。然而，对大声和轻柔歌声回放以及标本展示的实验表明，该物种的轻柔歌声不符合攻击性信号标准。在这里，我们进行了一项实验，用两个扬声器模拟入侵者的移动，以测试轻柔歌声是否用于唤起附近但未定位的对手的反应。我们发现，雄性对从单扬声器和双扬声器系统回放的歌声反应强度相似。同时，在我们模拟入侵者短距离飞行的实验阶段期间和之后，雄性发出了更多的轻柔歌声。我们的结果表明，轻柔歌声可能在与对手的近距离互动中被用作短距离信号，以检查对手是否仍在附近，而不是作为一种攻击性信号。与避免窃听和准备战斗的假设相比，我们的结果也为轻柔歌声行为提供了另一种解释。
