Eggs and nests are two critical traits for the ecological success of birds. Their functional interactions, however, remain unclear. Here, we examined the functional connections between egg stiffness and nest attachment, site and structure for 1350 avian species. We revealed high eggshell stiffness for eggs in nests with a pensile attachment, located on non-tree vegetation or having a domed shape, suggesting that birds produce stiffer eggs in response to higher egg-collision risk in unstable or enclosed nests. Interdependence models suggested that the evolution of eggshell stiffness was more likely to be driven by than drive that of nest characters. Our results implied a trade-off between investment in competing for established nesting niches and producing stiff eggs to explore novel niches with high collision risk, possibly mediated by predation or thermoregulation. This study highlights an overlooked connection between nests and eggshells that may have broadened the ecological niches of birds.

中文翻译：

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通过巢中蛋碰撞的风险，鸟蛋壳刚度和巢特征之间的功能联系

鸡蛋和巢穴是鸟类生态成功的两个关键特征。然而，它们的功能相互作用仍不清楚。在这里，我们检查了 1350 种鸟类的蛋硬度和巢附着、位置和结构之间的功能联系。我们发现巢中的蛋具有较高的蛋壳硬度，具有悬挂附件、位于非树木植被上或具有圆顶形状，这表明鸟类在不稳定或封闭的巢中产生更高的蛋碰撞风险时会产生较硬的蛋。相互依赖模型表明，蛋壳硬度的演变更可能是由巢特征驱动而不是驱动。我们的结果暗示了在竞争已建立的筑巢生态位和生产硬蛋以探索具有高碰撞风险的新生态位之间的权衡，可能由捕食或体温调节介导。这项研究强调了巢和蛋壳之间被忽视的联系，这可能扩大了鸟类的生态位。