Data from: Nest predation risk and growth strategies of passerine species: grow fast or develop traits to escape risk?

Different body components are thought to trade off in their growth and development rates, but the causes for relative prioritization of any trait remains a critical question. Offspring of species at higher risk of predation might prioritize development of locomotor traits that facilitate escaping risky environments over growth of mass. We tested this possibility in 12 altricial passerine species that differed in their risk of nest predation. We found that rates of growth and development of mass, wings, and endothermy increased with nest predation risk across species. In particular, species with higher nest predation risk exhibited relatively faster growth of wings than of mass, fledged with relatively larger wing sizes and smaller mass, and developed endothermy earlier at relatively smaller mass. This differential development can facilitate both escape from predators and survival outside of the nest environment. Tarsus growth was not differentially prioritized with respect to nest predation risk, and instead all species achieved adult tarsus size by age of fledging. We also tested whether different foraging modes (aerial, arboreal, and ground foragers) might explain the variation of differential growth of locomotor modules, but we found that little residual variation was explained. Our results suggest that differences in nest predation risk among species are associated with relative prioritization of body components to facilitate escape from the risky nest environment.

学界普遍认为，生物体各组成部分的生长与发育速率存在权衡关系，但为何某一性状会获得相对发育优先级，其背后的成因仍是一个关键科学问题。面临较高捕食风险的物种种群，其幼体可能会优先发育运动相关性状以助力逃离危险环境，而非单纯增加体质量。我们针对12种巢捕食风险（nest predation risk）存在差异的晚成性雀形目鸟类（altricial passerine），对这一假说进行了验证。研究发现，随着物种种群巢捕食风险的升高，其体质量、翼部以及恒温性（endothermy）的生长与发育速率均随之提升。具体而言，巢捕食风险更高的物种，其翼部生长速率相对体质量更快，出飞时翼展更大但体质量更小，且在体质量相对更小的阶段便提前发育出恒温性。这种差异化的发育模式，既能帮助幼体逃离捕食者，也能提升其出巢后的生存能力。而跗跖骨（tarsus）的生长并未因巢捕食风险的差异出现发育优先级的分化，所有物种均在出飞时便达到了成体跗跖骨的尺寸。我们还测试了不同觅食模式（foraging modes，包括空中觅食者、树栖觅食者与地面觅食者）能否解释运动模块差异化生长的变异，但结果显示其所能解释的剩余变异极少。本研究结果表明，物种种群间的巢捕食风险差异，与生物体各组成部分的相对发育优先级存在关联，以此助力幼体逃离充满风险的巢环境。