Data from: Male risk-taking is related to number of mates in a polygynous bird.

Evolutionary theory predicts that when intrasexual competition is intense, risky behaviors can evolve if they enhance reproductive success. Here we tested the idea that polygynous males exhibit predictable variation in risk-taking during intense competition for mates. We conducted an observational study of a village weaverbird (Ploceus cucullatus) breeding colony, and video recorded synchronous fleeing events, a common predator avoidance behavior. Males adjusted their flight from the colony according to the amplitude (loudness) and Wiener entropy (harshness) of conspecific alarm calls during a perceived threat. Males also varied in how often they fled the colony. Specifically, in line with predictions based on the value of a male’s territory, males with more nesting females were less likely to flee, and returned sooner if they did flee, compared to males with fewer nesting females. Males with a nest under construction also returned to their nests sooner than males without constructions in progress, consistent with predictions based on nest sabotage by conspecifics. These results suggest that male weavers perform a cost-benefit analysis in real time in order to decide how to respond to a perceived threat, with self-protection trading off with the security of one’s territory and mates.

进化论预测，当同性竞争（intrasexual competition）激烈时，若风险行为可提升繁殖成功率，此类行为便可能演化形成。本研究针对"一夫多妻制雄性在激烈的配偶竞争中，其冒险行为存在可预测的变异"这一假说开展了验证。我们对斑织雀（Ploceus cucullatus）的一个繁殖群进行了野外观测，并对同步逃逸事件——一种常见的反捕食行为——进行了录像记录。在感知到威胁时，雄性个体将根据同种警报叫声的振幅（响度）与维纳熵（Wiener entropy，即声音粗糙程度），调整其从繁殖群的逃逸行为。此外，雄性个体的逃逸频率也存在个体差异。具体而言，结合雄性领地价值的理论预测：与拥有较少筑巢雌鸟的雄性相比，拥有更多筑巢雌鸟的雄性逃逸概率更低，且即便发生逃逸也会更快返回巢区；正在营建巢穴的雄性，其返回巢区的速度也快于未处于营建阶段的雄性，这一结果与同种个体破坏巢穴的相关理论预测相符。上述结果表明，雄性斑织雀会实时开展成本收益分析，以决定如何应对感知到的威胁，此时自我保护与领地及配偶的安全之间存在权衡。