ABSTRACT Sexual displays that require extreme feats of physiological performance have the potential to reliably indicate the signaller’s skill or motivation. We tested for evidence of performance constraints in Adelaide’s warblers (Setophaga adelaidae) songs. At the note level, we identified three trade-offs with well-defined limits. At the song level, we identified two trade-offs, but their limits were less well-defined than the note-level limits. Trade-offs at both levels suggest that song structure is constrained by limits to the speed of both frequency modulation (while vocalising and between notes) and respiration. Performance metrics derived from the observed limits to performance varied moderately among individuals and strongly among song types. Note-level performance metrics were positively skewed, as predicted by the hypothesis that performance is constrained. We conclude that physiological limits on frequency modulation and respiration constrain song structure in male Adelaide’s warblers. Further work is needed to determine whether receivers respond to natural levels of variation in performance, and whether performance correlates with singer quality or motivation.

中文翻译：

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音符和歌曲级别的鸟类声乐表现分析

摘要 需要极端生理表现的性展示有可能可靠地表明信号员的技能或动机。我们测试了阿德莱德莺 (Setophaga adelaidae) 歌曲中表现受限的证据。在音符级别，我们确定了三个具有明确限制的权衡。在歌曲级别，我们确定了两个权衡，但它们的限制不如音符级别限制那么明确。两个级别的权衡表明歌曲结构受到频率调制（在发声时和音符之间）和呼吸速度的限制。从观察到的性能限制得出的性能指标在个人之间适度变化，在歌曲类型之间变化很大。笔记级别的绩效指标呈正偏差，正如性能受限的假设所预测的那样。我们得出结论，频率调制和呼吸的生理限制限制了雄性阿德莱德莺的歌曲结构。需要进一步的工作来确定接收者是否对表演的自然变化水平做出反应，以及表演是否与歌手的素质或动机相关。