Data from: Male receiver bias for red agonistic signaling in a yellow-signaling widowbird: a field experiment

Receiver bias models of signal evolution are typically regarded as alternatives or complements to ornament evolution due to coevolving mate choice, whereas sexually or socially selected agonistic signals are rarely studied with respect to receiver psychology. Against the background of convergent evolution of red agonistic signals from yellow ancestors in the genus Euplectes (widowbirds and bishops), we experimentally test the function of a yellow signal in the montane marsh widowbird (E. psammocromius), as well as a hypothesized receiver bias for redder (longer wavelength) hues. In a field experiment in southern Tanzania, males that had their yellow wing patches blackened lost their territories or lost territorial contests more often than controls or reddened males, which together with a longer wavelength hue in territory holders, indicates an agonistic signal function. Males painted a novel red hue, matching that of red-signalling congeners, retained their territories and won contests more often than controls. To our knowledge, this is the first demonstration of a receiver bias driving agonistic signal evolution. Although the sensory or cognitive origin of this bias is yet unknown, it strengthens our view that genetically constrained signal production (i.e. carotenoid metabolism), rather than differential selection, explains the carotenoid colour diversification in Euplectes.信号演化的接收者偏好模型（receiver bias models of signal evolution）通常被视作协同演化配偶选择背景下，装饰性特征演化的替代或补充理论，而针对性选择或社会选择介导的对抗性信号的研究，却极少涉及接收者心理维度。针对寡妇鸟属（Euplectes，寡妇鸟与主教雀）中由黄色祖先趋同演化出红色对抗性信号的研究背景，本研究以山地沼泽寡妇鸟（E. psammocromius）为实验对象，对其黄色信号的功能，以及针对更偏红（更长波长）色调的推测性接收者偏好进行了实验验证。在坦桑尼亚南部开展的野外实验中，相较于对照组或被染为红色的雄鸟，那些被涂黑黄色翅斑的雄鸟更易丢失领地或在领地竞争中落败；结合领地持有者具有更长波长色调的观测结果，这表明该黄色信号具备对抗性信号的功能。被涂抹为与发出红色信号的同属物种一致的全新红色调的雄鸟，相较于对照组，更易保留领地并赢得竞争。据我们所知，本研究首次证实了接收者偏好可驱动对抗性信号的演化。尽管该偏好的感官或认知起源尚不明晰，但该结果进一步支撑了我们的核心观点：寡妇鸟属的类胡萝卜素色彩多样性，是由受遗传约束的信号产生机制（即类胡萝卜素代谢）而非差异化选择所塑造的。