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Summary 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.

Applying appropriate criteria for raptors at rehabilitation stages including release and post release determines how healthy the animal can survive in its natural habitat for any length of time. In determining release criteria, clinical examinations of animals as well as clinical data should be evaluated. In this study, plasma T3 and T4 levels of 16 Common Buzzard (Buteo buteo), 7 Long-legged Buzzard (Buteo rufinus) and 7 Golden Eagles (Aquila chrysaetos) were determined at Kafkas University/ Kafkas Wildlife Conservation, Rescue, Rehabilitation Practice and Research Center between 2016-2018. All raptors were kept at the rehabilitation center for 1-3 months in bird care rooms and flight tunnels specially arranged for each species. Rehabilitated birds blood were collected before released to wild. Plasma T3 and T4 hormone levels were analysed and determined in raptors that considered suitable for release. Although small differences were detected between T3 and T4 values as a result of the analysis, no statistical difference was found. These small differences in values may be due to the metabolic responses and environmental conditions of each raptor. As a result, these plasma thyroid hormone levels in rehabilitated raptors can be accepted as reference values.

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