Congruence among multiple indices of habitat preference for species facing human-induced rapid environmental change: A case study using the Brewer’s sparrow

Accurate evaluations of habitat preference are key to understanding optimal conditions for wildlife survival and reproduction. Habitat selection, however, usually is evaluated using a single index of preference, and congruence among multiple, relevant indices of preference is examined rarely. We assessed the concordance between patterns of habitat preference using three different indices of breeding site preference in a migratory songbird. Specifically, we compared the chronology of territorial establishment, pair formation, and reproductive initiation of the Brewer’s sparrow (Spizella breweri) along a gradient of surface disturbance associated with natural gas development in Wyoming, USA during 2019. We expected all three indices to demonstrate a preference for breeding sites with less surface disturbance, where reproductive success typically is higher. By contrast, all indices suggested suboptimal preference with respect to surface disturbance, with some discrepancy among them. The chronology of settlement and pairing did not vary across the disturbance gradient, whereas nest initiation tended to occur earlier at sites with more disturbance. If the pattern of suboptimal selection of breeding sites that we identified is generalizable across other populations of migratory birds affected by energy development, the resultant lower fitness in those areas may exacerbate population declines. Our results suggest that traditional, single-index approaches to the study of habitat selection, if chosen carefully, may provide adequate inference on habitat preferences. Different metrics, however, can lead to at least subtle differences in patterns of habitat selection. The simultaneous examination of multiple indices of preference across a diversity of systems would help clarify the contexts under which preference metrics can become decoupled.对栖息地偏好的精准评估，是阐明野生动物生存与繁殖最优条件的关键所在。然而当前的栖息地选择评估通常仅采用单一偏好指数，极少对多个相关偏好指数间的一致性进行检验。本研究以美国怀俄明州一处存在天然气开发相关地表干扰梯度的区域为研究对象，于2019年针对迁徙鸣禽布氏麻雀（Brewer’s sparrow，学名Spizella breweri），利用3种繁殖位点偏好指数评估了其栖息地偏好模式间的一致性。具体而言，我们比较了该物种在不同干扰梯度下的领域建立、配对形成以及繁殖启动时序。我们曾推测，三种指数均会表现出对地表干扰更低的繁殖位点的偏好——这类位点的繁殖成功率通常更高。但与之相反，所有指数均显示出繁殖位点选择对地表干扰存在次优偏好，且不同指数间存在一定差异。领域建立与配对的时序并未随干扰梯度发生变化，而筑巢启动时间往往在干扰程度更高的位点更早出现。若本次研究发现的繁殖位点次优选择模式可推广至其他受能源开发影响的迁徙鸟类种群，那么这些区域内更低的适合度可能会加剧种群数量下降。本研究结果表明，若经过审慎选择，传统的单一指数栖息地选择研究方法或可对栖息地偏好做出足够可靠的推断。但不同的度量指标，至少会在栖息地选择模式上产生细微差异。同时对多个研究系统中的多种偏好指数进行考察，将有助于明确偏好度量指标出现脱节的具体情境。