Playback of predator calls inhibits and delays dawn singing in a songbird community

Recent studies have demonstrated that experimental increases in perceived predation risk can substantially impair breeding behavior and reduce reproductive success. Perceived predation risk may also occur in the context of sexual signaling, with potential consequences for sexual selection. In songbirds, singing at dawn is an important sexual signal, but may also attract predators. Here, we report on two experiments designed to test whether perceived predation risk affects the occurrence and timing of dawn singing in a songbird community. In a pilot experiment, we broadcast predator playbacks intermittently across half a forest plot and non-predator playbacks across the other half throughout early spring. In the second experiment, we repeated the treatments in 16 independent, but smaller plots (8 with predator calls, 8 with non-predator calls). In the predator treatment, most species were less likely to sing at dawn (small, non-significant effects) and to start later if they did sing (significant for 2 species). Meta-analyses combining the data from both experiments showed an overall significant effect of the treatment on both the likelihood and timing of singing. Species that were less likely to sing also sang later if they did sing, corroborating that an increase in perceived predation risk was the common cause of the effects on both measures.

现有研究表明，通过实验提升感知捕食风险（perceived predation risk），可显著损害繁殖行为并降低繁殖成功率。感知捕食风险也可能出现在性信号传递场景中，并对性选择产生潜在影响。鸣禽（songbird）的黎明鸣唱（dawn singing）是重要的性信号，但同时也可能吸引捕食者。本研究通过两项实验，旨在探究感知捕食风险是否会影响鸣禽群落的黎明鸣唱发生概率与鸣唱时间。预实验中，我们在早春时节，于一片林地的一半区域间歇性播放捕食者鸣声回放（predator playbacks），另一半区域则播放非捕食者鸣声回放（non-predator playbacks）。第二项实验中，我们在16个独立但面积更小的样地中重复了上述处理（8个样地播放捕食者鸣声，8个播放非捕食者鸣声）。在捕食者鸣声回放处理组中，多数物种的黎明鸣唱概率降低（效应量较小且无统计学显著性），若鸣唱则起始时间更晚（其中2个物种的效应具有统计学显著性）。整合两项实验数据的元分析（meta-analyses）结果显示，该处理对鸣唱概率与鸣唱时间均存在整体显著影响。鸣唱概率更低的物种，若鸣唱其起始时间也更晚，这证实感知捕食风险的提升是上述两项指标受影响的共同诱因。