Data from: Cover, not caging, influences chronic physiological stress in a ground-nesting bird

Predator exclosures (‘nest cages’) around nests are increasingly used to enhance hatching success of declining ground-nesting birds. However, such exclosures are contentious and have been suggested to have detrimental effects on the species which they aim to protect. This study examines whether exclosures increase physiological stress of incubating birds, a hitherto unrecognised and untested potential drawback of exclosures. Red-capped plover Charadrius ruficapillus hatching success was radically altered and significantly higher for nests with exclosures (96.2%) compared with those without (6.8%). Chronic physiological stress in parents (as measured by the heterophil/lymphocyte [H/L] ratio in blood) did not vary between nests with and without exclosures, or between the sexes. However the absence of vegetative cover at the nest site was associated with a 62.7% elevation in H/L ratio, indicating that incubating birds which place their nests in the open are subject to increased levels of chronic stress. The results from this study demonstrate the fundamental importance of predation for the nesting success of this species and confirm that chronic stress levels are not a detrimental side effect of exclosure use.为提升种群衰退的地面筑巢鸟类的孵化成功率，巢周防捕食者围笼（predator exclosures，亦称巢笼（nest cages））的应用日益广泛。然而此类围笼存在争议，有研究指出其可能对目标保护物种产生不利影响。本研究旨在探究防捕食者围笼是否会提升孵卵鸟类的生理应激水平——这是此前未被认知、未被验证的围笼潜在弊端。本研究以红顶鸻（Charadrius ruficapillus）为研究对象，结果显示，加装围笼的巢穴孵化成功率达96.2%，显著高于未加装围笼的巢穴（6.8%），二者差异悬殊。亲鸟的慢性生理应激水平（以血液异嗜性粒细胞/淋巴细胞比值（heterophil/lymphocyte [H/L] ratio）衡量）在加装与未加装围笼的巢穴间，以及雌雄个体间均无显著差异；但巢址缺乏植被覆盖会使H/L比值升高62.7%，表明将巢建于开阔地带的孵卵鸟类会面临更高水平的慢性应激。本研究结果证实了捕食压力对该物种筑巢成功率的核心影响，并确认围笼使用不会带来慢性应激水平升高这一有害副作用。