Data from: Experimental tests of the function and flexibility of song consistency in a wild bird

Measures of bird song that capture aspects of motor performance, such as consistency, have become a major focus in understanding sexual selection on song. Despite accumulating evidence that consistency is related to reproductive success in many species, the relative importance of male–male interactions and female–male interactions is still unclear. We studied the function and flexibility of song consistency and song rate in common yellowthroat warblers (Geothlypis trichas). A previous study of this population found that song consistency—measured as the amount of variability within a bout of songs—was positively correlated with the likelihood of siring extrapair young. In this study, we conducted two experiments aimed at testing (1) the role of song consistency and rate in mediating male–male and male–female interactions and (2) whether song effort is flexibly adjusted to changes in social context. In the first experiment, we simulated a male territorial intrusion with song playbacks that varied in consistency and rate; focal males responded aggressively to playbacks, but their response did not differ with playback consistency or rate. In the second experiment, we presented focal males with a taxidermic female mount and female vocalizations; focal males approached the speaker, but continued to sing and did not perform the aggressive rattle vocalization observed during male encounters. Immediately after the simulated female encounter, focal males increased in song consistency. Taken together, our results are most consistent with the hypothesis that song consistency in common yellowthroats is primarily a female-directed signal that is actively adjusted in response to rapidly changing social conditions.能够捕捉鸣唱运动表现维度（如一致性）的鸟类鸣唱量化指标，已成为理解鸣唱相关性选择机制的核心研究方向。尽管已有越来越多实证研究表明，鸣唱一致性与诸多鸟类的繁殖成功率存在关联，但雄-雄互动与雌-雄互动二者的相对重要性仍未明确。本研究以普通黄喉地莺（Geothlypis trichas）为研究对象，探讨其鸣唱一致性与鸣唱速率的功能及可塑性。此前针对该种群的研究显示，以单串鸣唱内的变异程度衡量的鸣唱一致性（song consistency），与雄性产生婚外子代（extrapair young）的概率呈显著正相关。本研究设计了两项实验，旨在验证两个核心问题：其一，鸣唱一致性与速率在调控雄-雄及雌-雄互动中发挥的作用；其二，鸣唱投入是否会随社会环境变化进行可塑性调整。第一项实验中，我们通过播放一致性与速率均存在差异的鸣唱录音，模拟雄性领地入侵事件；实验雄性个体对回放鸣唱表现出攻击性反应，但该反应强度并未随回放鸣唱的一致性或速率产生显著差异。第二项实验中，我们向实验雄性个体展示雌性剥制标本并同步播放雌性鸣唱录音；实验雄性个体向扬声器靠近，同时持续鸣唱，但并未表现出雄-雄互动中常见的攻击性颤鸣发声行为。模拟雌性互动结束后，实验雄性的鸣唱一致性随即显著提升。综合来看，本研究结果最支持以下假说：普通黄喉地莺的鸣唱一致性本质上是指向雌性的信号，且会主动响应快速变化的社会环境进行调整。