One of the most important geographical bottlenecks for migrating raptors in the east African-Palearctic migration system is situated between the easternmost tip of the Black Sea and the Lesser Caucasus, just north of Batumi, in the Republic of Georgia. Since 2008, citizen scientists of the Batumi Raptor Count (BRC) have monitored the autumn raptor passage daily from mid-August until mid-October, collecting also detailed information about the age and sex of focal species. The full BRC dataset was recently made available through the Global Biodiversity Information Facility (GBIF). Here we describe how count data were collected, managed, and processed for trend analysis over the past 10 years. This dataset offers a unique baseline for monitoring the state of migrant raptor populations in the east African-Palearctic flyway in the 21st century. We discuss potential pitfalls for users and hope that the open access publication of our data will stimulate flyway-scale and continent-wide collaboration for raptor migration monitoring in the Old World.

Migration counts can offer a cost‐effective method for monitoring the state of migrant raptor populations. However, differential migration strategies between inexperienced juveniles and experienced non‐juveniles are rarely accounted for when inferring population trends from raptor migration counts. Since 2011, the Batumi Raptor Count (BRC) monitors the autumn migration of more than 1 million raptors along the eastern Black Sea coast in the Republic of Georgia. We also systematically sampled age information to assess differential migration timing between age groups and estimate age‐specific linear trends in abundance between 2011 and 2018 for eight focal species. In so doing we aimed (1) to reassess the global relevance of BRC counts for each species and the potential for monitoring abundance of juveniles and non‐juveniles, and (2) to identify demographic changes underlying recent trends in overall abundance. We found that the mean annual passage of non‐juveniles at Batumi represents at least 1% of the estimated global breeding population of five study species. As expected, counts of juveniles were more variable than counts of non‐juveniles. Yet despite our short monitoring period our models had sufficient statistical power to detect changes in abundance of 10%/year or less for at least one age group in all species except Pallid Harrier Circus macrourus. Our results indicate stable abundance and demography for half of the study species. We also found strong and significant increases in the abundance of Black Kites Milvis migrans and Short‐toed Eagles Circaetus gallicus that were primarily due to increasing numbers of non‐juveniles. By contrast, juvenile Montagu's Harriers Circus pygargus and Booted Eagles Hieraaetus pennatus significantly decreased in abundance. The first decade of BRC surveys offers an important benchmark for monitoring raptor populations using the eastern African–Palearctic flyway in the 21st century. We discuss possible causes of the observed trends and hope our work will stimulate demographic monitoring at migration count sites.

Since 2008 Batumi Raptor Count (BRC) project has been monitoring autumn migration of birds of prey in the eastern African-Palearctic flyway in southwest Georgia on the eastern coast of the Black Sea. Every autumn this flyway is used by a significant proportion of the global population of such raptor species as Honey Buzzard (Pernis apivorus), Montagu’s Harrier (Circus pygargus), Pallid Harrier (C. macrourus) and Marsh Harrier (C. aeruginosus). At least 1% of the global population of 10 raptor species migrates through the Batumi flyway. Batumi Raptor Count is of vital importance for the development of ecotourism in the region, creating an economic, political, and social foundation for raptor conservation and contributing to a reduction of widespread illegal hunting. The project also works to introduce ecology and conservation into local schools and higher education programs. This manuscript’s aim is to summarise the 13 years of the BRC. It contains a detailed description of a typical migration season in one of the most important bottlenecks for raptor migration globally. The current manuscript is loosely based on the publication in British Birds summarising the history of the BRC (Hoekstra et al., 2020). The main difference, apart from publishing it in Russian, is in taking into account the data obtained in 2021 and emphasising the importance of the autumn migration monitoring in Batumi for the conservation and research of the Russian raptor populations.