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.

为提升种群衰退的地面筑巢滨鸟的孵化成功率，巢周捕食者防护围栏（predator exclosures，俗称“巢笼”）的应用日益广泛。然而这类防护围栏存在争议，有观点认为其可能对目标保护物种产生不利影响。本研究旨在探究防护围栏是否会提升孵卵亲鸟的生理应激水平——这是此前未被认知且未经过验证的围栏潜在弊端。针对红顶鸻（Charadrius ruficapillus）的研究显示，安装防护围栏的巢的孵化成功率发生根本性改变：围栏组孵化成功率达96.2%，显著高于无围栏组的6.8%。亲鸟的慢性生理应激水平（以血液中异嗜性粒细胞与淋巴细胞比值（heterophil/lymphocyte [H/L] ratio）衡量）在有围栏与无围栏的巢之间，以及雌雄个体之间均无显著差异。但巢址缺乏植被覆盖与H/L比值升高62.7%相关，这表明将巢筑于开阔地带的孵卵亲鸟会承受更高水平的慢性应激。本研究结果证明了捕食者防护围栏对该物种筑巢成功率的至关重要性，并证实慢性应激水平并非使用该围栏所带来的不利副作用。