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 shorebirds. 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 exclosures for the nesting success of this species and confirm that chronic stress levels are not a detrimental side effect of their use.为提升种群数量下降的地面筑巢鸻鹬类的孵化成功率，巢周防捕食者围栏（predator exclosures，又称"巢笼"）的应用日益广泛。然而此类围栏存在争议，有研究指出其可能对目标保护物种产生不利影响。本研究旨在探究围栏是否会提升孵卵鸟类的生理应激（physiological stress）水平——这是此前未被认知且未得到验证的围栏潜在弊端。针对红顶鸻（Charadrius ruficapillus）的研究显示，筑有围栏的巢的孵化成功率较无围栏巢（6.8%）显著提升至96.2%，二者差异悬殊。以血液异嗜性粒细胞/淋巴细胞（heterophil/lymphocyte, H/L）比值作为检测指标，亲鸟的慢性生理应激水平在有围栏与无围栏的巢之间，以及雌雄个体间均无显著差异。但巢址缺乏植被覆盖与H/L比值升高62.7%相关，这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。本研究结果证实了围栏对该物种筑巢成功率的关键作用，并确认使用围栏不会带来慢性应激水平升高这一不利副作用。