Smith Joseph T, Tack Jason D, Doherty Kevin E, Allred Brady W, Maestas Jeremy D, Berkeley Lorelle I, Dettenmaier Seth J, Messmer Terry A, Naugle David E
Wildlife Biology Program University of Montana Missoula MT USA.
US Fish & Wildlife Service, Habitat and Population Evaluation Team Missoula MT USA.
Ecol Evol. 2017 Nov 28;8(1):356-364. doi: 10.1002/ece3.3679. eCollection 2018 Jan.
Much interest lies in the identification of manageable habitat variables that affect key vital rates for species of concern. For ground-nesting birds, vegetation surrounding the nest may play an important role in mediating nest success by providing concealment from predators. Height of grasses surrounding the nest is thought to be a driver of nest survival in greater sage-grouse (; sage-grouse), a species that has experienced widespread population declines throughout their range. However, a growing body of the literature has found that widely used field methods can produce misleading inference on the relationship between grass height and nest success. Specifically, it has been demonstrated that measuring concealment following nest fate (failure or hatch) introduces a temporal bias whereby successful nests are measured later in the season, on average, than failed nests. This sampling bias can produce inference suggesting a positive effect of grass height on nest survival, though the relationship arises due to the confounding effect of plant phenology, not an effect on predation risk. To test the generality of this finding for sage-grouse, we reanalyzed existing datasets comprising >800 sage-grouse nests from three independent studies across the range where there was a positive relationship found between grass height and nest survival, including two using methods now known to be biased. Correcting for phenology produced equivocal relationships between grass height and sage-grouse nest survival. Viewed in total, evidence for a ubiquitous biological effect of grass height on sage-grouse nest success across time and space is lacking. In light of these findings, a reevaluation of land management guidelines emphasizing specific grass height targets to promote nest success may be merited.
人们对识别可管理的栖息地变量非常感兴趣，这些变量会影响相关物种的关键生命率。对于地面筑巢的鸟类来说，巢穴周围的植被可能通过为巢穴提供躲避捕食者的隐蔽处，在调节巢穴成功率方面发挥重要作用。巢穴周围草丛的高度被认为是影响艾草松鸡（艾草松鸡）巢穴存活率的一个因素，艾草松鸡是一种在其分布范围内种群数量普遍下降的物种。然而，越来越多的文献发现，广泛使用的野外方法可能会对草高与巢穴成功率之间的关系产生误导性推断。具体来说，已经证明在巢穴命运（失败或孵化）之后测量隐蔽度会引入时间偏差，即成功的巢穴平均比失败的巢穴在季节后期被测量。这种抽样偏差可能会产生一种推断，表明草高对巢穴存活率有积极影响，尽管这种关系是由于植物物候的混杂效应而产生的，而不是对捕食风险的影响。为了测试这一发现对艾草松鸡的普遍性，我们重新分析了现有数据集，这些数据集包含来自三项独立研究的800多个艾草松鸡巢穴，这些研究在草高与巢穴存活率之间发现了正相关关系，其中两项研究使用的方法现在已知存在偏差。校正物候后，草高与艾草松鸡巢穴存活率之间的关系不明确。总体来看，缺乏证据表明草高在时空上对艾草松鸡巢穴成功率具有普遍的生物学影响。鉴于这些发现，可能有必要重新评估强调特定草高目标以提高巢穴成功率的土地管理指南。
