SummaryThe Inaccessible Island Rail Atlantisia rogersi, the world’s smallest extant flightless bird, is endemic to Inaccessible Island, a 14-km2 uninhabited island in the Tristan da Cunha archipelago, central South Atlantic Ocean. Rail populations are notoriously hard to survey and the rugged topography of Inaccessible Island makes a survey particularly challenging. Fortunately, Inaccessible Island Rails are very vocal, because their secretive behaviour means birds are hard to observe in the dense vegetation. We assessed the distribution of rails across Inaccessible Island using playbacks at 350 point-count sites in October–November 2018. Rail calls were heard at 98% of sites and we estimate the rail population to be in the order of 10,300 birds (95% CI 9,100–12,200), based on estimated rail densities in the six main habitats. Historic population estimates were reasonably crude and thus not suitable for inferring population trends, but the population appears to be stable and we recommend the species’ status remains as ‘Vulnerable’. The accidental introduction of alien mammals poses the greatest threat to the survival of the Inaccessible Island Rail and the removal of house mouse Mus musculus and ship rat Rattus rattus from neighbouring Tristan da Cunha Island would greatly reduce the risk of such a catastrophe.

中文翻译：

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使用回放来估计世界上最小的不会飞的鸟的分布和密度，Inaccessible Island Rail Atlantisia rogersi

摘要人迹罕至的岛屿铁路亚特兰蒂斯罗杰西是世界上现存最小的不会飞的鸟类，是长达 14 公里的无法到达岛的特有物种2位于南大西洋中部特里斯坦达库尼亚群岛的无人岛。众所周知，铁路人口难以调查，而无法进入岛崎岖的地形使调查特别具有挑战性。幸运的是，Inaccessible Island Rails 的声音非常响亮，因为它们的隐秘行为意味着在茂密的植被中很难观察到鸟类。我们在 2018 年 10 月至 11 月期间使用 350 个点数站点的回放评估了铁路在无法进入岛上的分布。98% 的站点都听到了铁路呼叫，我们估计铁路人口约为 10,300 只鸟（95% CI 9,100–12,200），基于估计的六个主要栖息地的铁路密度。历史上的人口估计相当粗略，因此不适合推断人口趋势，但种群似乎很稳定，我们建议该物种的状态保持为“脆弱”。外星哺乳动物的意外引入，对人迹罕至岛铁路的生存和家鼠的撤离构成最大威胁小家鼠和船鼠家鼠来自邻近的特里斯坦达库尼亚岛将大大降低发生此类灾难的风险。