Data from: Predictably philandering females prompt poor paternal provisioning

One predicted cost of female infidelity in socially monogamous species is that cuckolded males should provide less parental care. This relationship is robust across species, but evidence is ambiguous within species. We do not know whether individual males reduce their care when paired with cheating females compared with when paired with faithful females (within-male adjustment) or, alternatively, if the males that pair with cheating females are the same males that provide less parental care in general (between-male effect). Our exceptionally extensive long-term data set of repeated observations of a wild passerine allows us to disentangle paternal care adjustment within males—within pairs and between males—while accounting for environmental variables. We found a within-male adjustment of paternal provisioning, but not incubation effort, relative to the cuckoldry in their nest. This effect was mainly driven by females differing consistently in their fidelity. There was no evidence that this within-male adjustment also took place across broods with the same female, and we found no between-male effect. Interestingly, males that gained more extrapair paternity provided less care. Data from a cross-foster experiment suggested that males did not use kin recognition to assess paternity. Our results provide insight into the role of individual variation in parental care and mating systems.在社会一夫一妻制物种中，雌性不忠行为的一项预测性代价是，被出轨的雄性亲本会降低抚育投入。该关联在跨物种层面表现稳健，但在物种内部的相关证据却模棱两可。目前我们仍无法明确：与忠贞雌性交配的雄性个体相比，与出轨雌性交配的雄性是否会主动减少抚育投入（即个体内调整效应）；或是，那些与出轨雌性交配的雄性，本身就是整体上抚育投入更低的雄性个体（即个体间效应）。我们针对一种野生雀形目鸟类收集的大规模长期重复观测数据集，使得我们能够在控制环境变量的前提下，区分雄性亲本抚育的个体内调整（包括配对间与个体间）效应。我们发现，相较于巢内的出轨情况（即额外配对父权），雄性在育雏投喂行为上存在个体内调整，但在孵化投入上并无此类调整。这一效应主要源于雌性在忠贞度上的固有差异。未有证据表明，这种个体内调整也会出现在与同一雌性交配的多窝雏鸟中，同时我们也未观测到显著的个体间效应。值得注意的是，获得额外配对父权越多的雄性，其亲本抚育投入越少。交叉抚育实验的数据表明，雄性并未通过亲属识别来评估父权归属。我们的研究结果为理解个体变异在亲本抚育与交配系统中的作用提供了新的理论视角。