The Great Bustard Otis tarda is a globally threatened species with populations inhabiting the steppe zones of Turkey. In recent decades, its populations in Turkey have suffered severe declines in range and size. Although the remaining populations are in urgent need of protection, there has been no national-scale study on the species since 2009, and huge information gaps remain concerning its range, abundance, and movements in the country. Here, we combined data from five years of fieldwork together with all available sight and literature records to present up-to-date estimates of distribution and population size in Turkey, to better understand its movement patterns, to reveal its recent and historical population changes, and to assess its national extinction risk and threats. We find that the species’ breeding population has shrunk by 20–29% over the last five years, and there are only 559–780 breeding Great Bustards in Turkey distributed in two discrete subpopulations. Comparison with historical records shows that the species’ range has shrunk by at least 60% since the beginning of the 20th century. We suggest possible migratory routes within and through Turkey and that Turkey might have a higher regional importance for the species than previously thought. Illegal hunting, agricultural intensification, shift to irrigated crops, overgrazing, collision with powerlines, and disturbance are the most severe threats to the species in Turkey. Our national Red List assessment yields an Endangered categorisation. Further studies are needed to understand the metapopulation structure and movements of the species and to conserve its remaining populations in Turkey.

大鸨Otis tarda是一种全球受威胁的物种，其种群居住在土耳其的草原地带。近几十年来，其在土耳其的种群范围和规模严重下降。尽管剩余种群急需保护，但自 2009 年以来一直没有对该物种进行全国范围的研究，关于其分布范围、数量和在该国的活动，仍然存在巨大的信息差距。在这里，我们将五年实地调查的数据与所有可用的视觉和文献记录相结合，以提供对土耳其分布和人口规模的最新估计，以更好地了解其运动模式，揭示其近期和历史人口变化，并评估其国家灭绝风险和威胁。我们发现该物种的繁殖种群在过去五年中减少了 20-29%，土耳其只有 559-780 只繁殖大鸨分布在两个离散的亚群中。与历史记录的比较表明，自 20 世纪初以来，该物种的分布范围至少缩小了 60%。我们建议可能在土耳其境内和通过土耳其的迁徙路线，并且土耳其对该物种的区域重要性可能比以前认为的要高。非法狩猎、农业集约化、转向灌溉作物、过度放牧、与电力线碰撞和干扰是土耳其物种面临的最严重威胁。我们的国家红色名录评估产生了濒危类别。需要进一步研究以了解该物种的集合种群结构和运动，并保护其在土耳其的剩余种群。