The causes and consequences of interspecific variation in sex-specific contributions to animal parental care are relatively well understood during pregnancy or incubation and during offspring provisioning, but comparative patterns of sex-biased investment during nest-, den-, or other shelter-building have been almost completely overlooked. This is surprising because birthing shelters’ protective properties have important fitness consequences for both parents and offspring. Here, we address this gap in our knowledge by testing predictions concerning sex-specific contributions to avian nest building in more than 500 species of Western Palearctic birds in relation to the time available to breed and sex-specific reproductive effort, while also examining correlates with nesting site and nest structure. Using multivariate phylogenetic comparative and path analysis approaches, we found that, opposite to what had been predicted, species in which females build nests alone have shorter breeding seasons and breed at higher latitudes. In addition, species in which females lay larger clutch sizes and incubate eggs alone are more likely to have nests built by females alone, again countering predictions that reproductive contributions are not traded-off between the sexes. Finally, however, sex-specific nest building contributions were predictably related to nest site and structure, as species in which females built nests alone were more likely to have open cup nests relative to enclosed, domed nests of species in which both parents build. Our study provides important new insights, and generates several new questions for experimental research into the adaptive dynamics of sex-specific contributions prior or at the onset of parental care.

中文翻译：

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性别对鸟类筑巢的贡献

在怀孕或孵化期间以及在后代供应期间，对动物父母照顾的性别贡献的种间差异的原因和后果相对较好，但在巢穴、巢穴或其他庇护所建设期间的性别偏见投资的比较模式已经几乎完全被忽视了。这是令人惊讶的，因为分娩庇护所的保护特性对父母和后代都有重要的健康影响。在这里，我们通过测试关于 500 多种西古北冰洋鸟类的性别特定贡献对鸟类筑巢的预测与可用于繁殖的时间和特定性别的繁殖努力相关的预测来解决我们知识上的这一差距，同时还检查了与筑巢地点和巢结构。使用多元系统发育比较和路径分析方法，我们发现与预测相反，雌性单独筑巢的物种繁殖季节较短，并且在较高纬度地区繁殖。此外，雌性产卵较大并单独孵化卵的物种更有可能单独由雌性建造巢穴，这再次反驳了生殖贡献不会在两性之间进行权衡的预测。最后，然而，可以预见的是，特定性别的筑巢贡献与筑巢地点和结构有关，因为雌性单独筑巢的物种相对于父母双方筑巢的封闭、圆顶巢穴更可能拥有敞开的杯形巢穴。我们的研究提供了重要的新见解，