Data from: Mountain Plover habitat selection and nest survival in relation to weather variability and spatial attributes of Black-tailed Prairie Dog disturbance

Habitat loss and altered disturbance regimes have led to declines in many species of grassland and sagebrush birds, including the imperiled Mountain Plover (Charadrius montanus). In certain parts of their range Mountain Plovers rely almost exclusively on Black-Tailed Prairie Dog (Cynomys ludovicianus) colonies as nesting habitat. Previous studies have examined Mountain Plover nest and brood survival on prairie dog colonies, but little is known about how colony size and shape influence these vital rates or patterns of habitat selection. We examined how 1) adult habitat utilization, 2) nest-site selection, and 3) nest success responded to a suite of local- and site-level variables on large prairie dog colony complexes in northeastern Wyoming. Abundance of adult Mountain Plovers was highest on points within older, “medium”-sized (100–500 ha) colonies with high cover of annual forbs and bare ground (5.8 birds/km2), but lower on extremely large (>2000 ha) colonies (2.1 birds/km2). Nest sites were characterized by high proportions of annual forbs and bare ground and low cactus cover and vegetation height. Nest survival was higher for older nests, and nests with lower cactus cover, and decreased with increasing temperatures. Uncertainty was high for models of daily nest survival, potentially because of two competing sources of nest failure: nest depredation and nest abandonment or inviability of eggs. Drivers of these two sources of nest failure differed, with inclement weather and higher temperatures associated with nest abandonment or egg inviability. We highlight how prairie dogs alter vegetation structure and bare ground heterogeneously across the landscape, and how this in turn influences bird abundance and nest distribution at different temporal and spatial scales. Furthermore, our work reveals how partitioning the causes of nest failure during nest survival analyses enhances understanding of survival rate covariates.

栖息地丧失与干扰格局改变已导致多种草原与蒿灌鸟类种群数量下降，其中包括濒危的山鸻（Mountain Plover, Charadrius montanus）。在其分布范围的部分区域，山鸻几乎完全依赖黑尾土拨鼠（Black-Tailed Prairie Dog, Cynomys ludovicianus）集群作为营巢栖息地。既往研究已针对土拨鼠集群中山鸻的巢与雏鸟存活率开展了相关分析，但针对集群的大小与形态如何影响这些繁殖生命率以及栖息地选择模式的认知仍较为匮乏。本研究针对怀俄明州东北部的大型土拨鼠集群复合体，探究了以下三方面内容：1）成鸟栖息地利用情况；2）巢址选择偏好；3）巢成功率对一系列局域与样地水平变量的响应。调查结果显示，山鸻成鸟种群丰度在以下样点达到最高：位于发育成熟、面积处于“中等”（100~500公顷）的集群内，且一年生杂类草盖度与裸地占比较高的区域（种群密度达5.8只/平方千米）；而在面积极大（>2000公顷）的集群内，成鸟种群丰度仅为2.1只/平方千米。山鸻的巢址选择特征为：一年生杂类草与裸地占比高，仙人掌盖度与植被高度较低。巢成功率随巢龄增加而升高，且在仙人掌盖度较低的巢中更高；同时随环境温度升高而降低。每日巢存活率模型的不确定性较高，这可能源于两类相互竞争的巢失败原因：巢捕食与巢弃巢或卵不可育。这两类巢失败的驱动因素存在差异：恶劣天气与更高温度与巢弃巢或卵不可育相关。本研究阐明了土拨鼠如何在景观尺度上异质性地改变植被结构与裸地分布，进而在不同时空尺度上影响鸟类种群丰度与巢分布格局。此外，本研究还揭示了在巢存活率分析中拆分巢失败原因，如何提升我们对存活率协变量的认知水平。