Data from: Rodent-avoidance, topography and forest structure shape territory selection of a forest bird

Background - Understanding the factors underlying habitat selection is important in ecological and evolutionary contexts, and crucial for developing targeted conservation action in threatened species. However, the key factors associated to habitat selection often remain poorly known. We evaluated hypotheses related to abiotic and biotic factors thought to affect territory selection of the wood warbler Phylloscopus sibilatrix, a passerine living in an unpredictable environment owing to irregular rodent outbreaks and showing long-term declines particularly in Western Europe. Results - Comparing breeding territories to unoccupied areas located close-by revealed that territory occupancy in north-western Switzerland was positively related to slope steepness (topographic hypothesis supported) as well as to numbers of tussocks and trees, respectively, while it showed a unimodal relationship to cover of herb layer (forest structure hypothesis supported). Furthermore, a strong negative correlation between breeding territory occupancy and rodent numbers was found, suggesting that wood warblers avoid areas with high rodent densities (rodent-avoidance hypothesis supported). Comparing breeding territories to abandoned territories showed that breeding territories were located on steeper slopes (topography hypothesis supported), at larger distance from the forest edge (anthropogenic disturbance hypothesis supported) and harboured more trees (forest structure hypothesis supported) than abandoned territories. Conclusions - Aside from structural and topographic features of the habitat, wood warblers are affected by rodent numbers when settling, making habitat selection unpredictable from year to year. Forestry practices promoting relatively high tree densities, few bushes and an intermediate low-growing ground vegetation cover would enhance habitat quality for this declining passerine. In contrast, forestry practices aiming at increasing light in forests (selective thinning, group-felling) or keeping forest stands permanently covered with shrubs, bushes and trees of various sizes (continuous cover forestry) do not benefit the wood warbler.

**背景**：阐明生境选择（habitat selection）背后的驱动因子，在生态与进化研究范畴中具有重要意义，同时对受威胁物种（threatened species）制定针对性保护行动至关重要。然而，与生境选择相关的核心因子往往仍未得到充分认知。本研究针对林柳莺（wood warbler，*Phylloscopus sibilatrix*）——一种因啮齿动物周期性暴发而生存环境波动不定、且种群（尤其在西欧地区）出现长期下降的雀形目鸟类——的领域选择（territory selection），对被认为影响其领域选择的非生物与生物因子（abiotic and biotic factors）相关假说开展了验证。**结果**：将繁殖领域与邻近的未占据区域进行对比后发现，瑞士西北部的领域占有率与坡度（slope steepness）、草丘数量及树木数量均呈显著正相关（支持地形假说，topographic hypothesis），同时与草本层覆盖度呈单峰关系（支持森林结构假说，forest structure hypothesis）。此外，研究发现繁殖领域占有率与啮齿动物种群数量间存在极强的负相关，表明林柳莺会回避啮齿动物密度较高的区域（支持避啮假说，rodent-avoidance hypothesis）。将繁殖领域与弃用领域对比后可知，相较于弃用领域，繁殖领域所处坡度更陡（支持地形假说，topographic hypothesis）、距林缘距离更远（支持人为干扰假说，anthropogenic disturbance hypothesis），且树木数量更多（支持森林结构假说，forest structure hypothesis）。**结论**：除生境的结构与地形特征外，林柳莺在繁殖定居阶段还会受到啮齿动物种群数量的影响，这使得其生境选择每年都难以预测。能够维持较高树木密度、较少灌丛以及中等高度地面植被覆盖度的林业经营措施，可提升该种群下降的雀形目鸟类的生境质量。与之相反，旨在提升林内光照的林业措施（如选择性疏伐（selective thinning）、块状皆伐（group-felling）），或永久维持林分由不同大小灌木、灌丛与树木覆盖的经营方式（恒续林经营（continuous cover forestry）），则无法为林柳莺带来益处。