Data from: Effects of land use and climate on the distribution of the Jungle Nightjar Caprimulgus indicus in Hokkaido, northern Japan

Although the relative importance of land use and climate to large-scale bird distributions has received great attention, it is difficult to separate the effects of land use and climate, and there are few studies on bird abundance distributions on a large scale. Here, we examined the effects of land use and climate on the abundance of the nocturnal Jungle Nightjar Caprimulgus indicus in Hokkaido, northern Japan. We chose 125 sampling sites with low correlations (|r| < 0.58) between land use and climate, and combined a playback method with a hierarchical model (N-mixture model). We thereby accounted for the possibility that we could not detect all individuals during the field survey. Results show that Jungle Nightjar abundance was greater at sites within a 4-km radius of moderate forest cover (~75%) and with high average temperatures during the breeding season. Moreover, the effects of land-use were greater than those of climate. Mapping predictions of Jungle Nightjar abundance indicated that suitable areas are distributed in southern and central Hokkaido and around the margins of montane zones. Factoring in the covariation of land use and climate, land use may be the most important driver of the distribution of the Jungle Nightjar in Hokkaido.

尽管土地利用与气候对大尺度鸟类分布的相对重要性已受到广泛关注，但区分二者的影响却颇具挑战，且针对大尺度下鸟类丰度分布的研究仍较为匮乏。本研究以日本北部北海道地区的夜行性普通夜鹰（Jungle Nightjar，*Caprimulgus indicus*）为研究对象，探讨土地利用与气候因子对其种群丰度的影响。我们筛选出125个土地利用与气候因子相关性较低（|r| < 0.58）的样地，并结合鸣声回放法与层级模型（N混合模型，N-mixture model）开展研究，以此校正野外调查中可能存在的个体检测遗漏问题。研究结果显示，普通夜鹰的种群丰度在周边4公里半径范围内森林覆盖率适中（约75%）、繁殖季平均气温较高的样地中更高。此外，土地利用因子对其丰度的影响程度大于气候因子。普通夜鹰种群丰度的预测分布图表明，适宜生境主要分布于北海道南部、中部以及山地带周边区域。综合考虑土地利用与气候因子的协变关系，土地利用可能是北海道地区普通夜鹰分布的最关键驱动因子。