Vegetation phenology and nest survival: diagnosing heterogeneous effects through time

Birds should select nest sites that minimize predation risk, but understanding the influence of vegetation on nest survival has proven problematic. Specifically, the common practice of measuring vegetation on nest fate date can overestimate its effect on survival, simply because vegetation at hatched nests grows for a longer period of time than vegetation at nests that were depredated. Here, we sampled the literature to determine the prevalence of this bias in studies of duck breeding ecology. We then used survival data collected from ~2,800 duck nests to empirically evaluate evidence of bias in four different vegetation metrics: vegetation density measured when the nest was found, density when the nest was fated, and date-corrected regression residuals of these two. We also diagnosed the magnitude of vegetation effects on nest survival by restricting analysis to only nests which were fated contemporaneously (thereby removing potential bias in the timing of measurement). Finally, w...鸟类理应选择可最小化捕食风险的巢址，但要阐明植被对巢存活率的影响却始终颇具挑战。具体而言，常规研究中会在巢结局判定当日对周边植被进行测量，这一操作可能会高估植被对巢存活率的效应——究其原因，成功孵化的巢周边植被的生长时长要长于被捕食巢周边的植被。本研究通过文献抽样分析，旨在明确该偏差在鸭类繁殖生态学研究中的普遍程度。随后，我们利用从约2800个鸭类巢中收集的巢存活数据，对四类不同植被指标中的偏差证据开展实证评估：这四类指标分别为发现巢时测量的植被密度、确定巢结局时测量的植被密度，以及基于上述两项指标经日期校正得到的回归残差。此外，我们通过将分析范围限定于同期判定结局的巢（以此消除测量时序带来的潜在偏差），以此量化植被对巢存活率的影响强度。最后，