Seasonal species richness of birds on the world’s islands and its geographical correlates

Migratory birds occur on islands during different seasons of the year, which results in seasonal variation in species richness. These patterns and their geographical correlates have not been examined. We used 20 years of bird observations on 690 islands to examine how seasonal species richness estimates vary as a function of island area, isolation, and latitude. Species richness was highest on islands within the mid-latitudes of the Northern Hemisphere during migration and on islands within tropical latitudes during the non-breeding season. Area defined positive, non-linear relationships with species richness across seasons, with the steepest slopes occurring with islands >1,100 km2. Distance to mainland defined negative, non-linear relationships with species richness across seasons, with the strongest slopes occurring with islands located >150 km from the mainland. Species-area relationships were weakest for the most remote islands and strongest for islands at intermediate distan...候鸟会在一年中的不同时节造访各类岛屿，这使得岛屿的物种丰富度呈现季节性变化。这类分布模式及其地理关联影响因子尚未得到系统研究。本研究基于690座岛屿长达20年的鸟类观测数据，探究了季节性物种丰富度估算值如何随岛屿面积、隔离度与纬度发生变化。在迁徙季，北半球中纬度岛屿的物种丰富度最高；而非繁殖季，热带纬度岛屿的物种丰富度则居于首位。各季节中，岛屿面积均与物种丰富度呈正向非线性相关关系，其中面积大于1100平方千米的岛屿，其物种丰富度随面积增长的斜率最为陡峭。各季节中，岛屿与大陆的距离均与物种丰富度呈负向非线性相关关系，其中与大陆距离超过150千米的岛屿，其物种丰富度随距离增加的斜率最为显著。物种-面积相关关系在最偏远的岛屿中表现最弱，而在中等距离的岛屿中则最为显著……