The extent to which geographical features like coastlines and mountain ranges funnel migrating birds depends on the seasonal context and direction of migration. Near Batumi, in the Republic of Georgia, the eastern Black Sea coast and Lesser Caucasus funnel over one million raptors through a 10-20 km wide coastal strip every autumn. The funnelling effect of the Lesser Caucasus appears much less evident for northbound migrants. Yet historical data suggest tens of thousands of raptors pass through the region in spring. To elucidate the composition and timing of spring raptor migration we conducted full-season migration surveys near Batumi in 2019, 2020 and 2022. In total, we recorded 33 species and, on average, counted 542,161 raptors (range: 455,799-618,848) annually. The bulk of the spring passage consisted of Black Kite Milvus migrans (239,649 +/- 22,547 SD) and Steppe Buzzard Buteo buteo vulpinus (194,029 +/- 102,702). The most diverse and intense spring migration occurred from late March through mid-April when the median passage date of 12 of 15 common species (>100 individuals/year) occurred. Species with longer autumn migration periods tended to have longer spring migration periods, and most species had a longer migration period in spring than in autumn, likely due to larger age differences in timing during spring. Species' abundance was up to an order of magnitude lower in spring than in autumn, consistent with a weaker bottleneck-effect in spring. Nevertheless, our results confirm the eastern Black Sea coast as a principal spring flyway and help redraw the map of East African-Eurasian migration for several Palearctic raptors. Our data provides a baseline for detecting changes in raptor migration through short-term surveys and can help plan migration-based conservation and research at Batumi in spring.

The energy transition intensifies spatial conflicts between energy infrastructure (EI) and migratory birds, fueling public resistance, litigation and permitting delays. These conflicts are often addressed only at the project level, after EI sites are chosen, leaving little room for proactive impact avoidance. We present a globally scalable method using existing weather radar infrastructure and open data to map nocturnal bird migration at high spatial resolution across large areas, demonstrating its application in the Netherlands. We find that around 50% of migration occurs at altitudes of EI. Contrary to assumed homogeneous distributions or discrete routes, our maps reveal that migration intensity varies over distances relevant for spatial planning. We demonstrate how such maps can inform selection of wind energy sites with considerable variation in migration and wind potential. Our method facilitates early-stage impact avoidance through strategic EI siting, targeted mitigation and faster permitting, offering a low-cost, scalable path toward a more nature-inclusive energy transition.

Weather radars detect more than weather, they also continuously register the movements of billions of animals aloft in the lower atmosphere. This makes archived, unfiltered weather radar data a goldmine for biological monitoring purposes, providing coverage of the aerial habitat in a way no other method can. Here we present two datasets of biological data extracted from European weather radar data, obtained through a collaboration with the Operational Programme for the Exchange of Weather Radar Information (OPERA) and three national meteorological services. The datasets were created by processing weather radar data with methods optimized for extracting bird targets, resulting in vertical profiles of biological targets. The datasets collectively cover 141 radar stations in 18 countries, from 2008 to 2023. Data quality and coverage differs between years, countries, and radar stations, so care must be taken when evaluating data for each specific use case. Despite these challenges the datasets are currently the most comprehensive of their kind in Europe and open new avenues in understanding continental scale movements of aerial animals.

Fireworks are important elements of celebrations globally, but little is known about their effects on wildlife. The synchronized and extraordinary use of fireworks on New Year's Eve triggers strong flight responses in birds. We used weather radar and systematic bird counts to quantify how flight responses differed across habitats and corresponding bird communities, and determined the distance-dependence of this relationship. On average, approximately 1000 times as many birds were in flight on New Year's Eve than on other nights. We found that fireworks-related disturbance decreased with distance, most strongly in the first five kilometers, but overall flight activity remained elevated tenfold at distances up to about 10 km. Communities of large-bodied species displayed a stronger response than communities of small-bodied species. Given the pervasive nature of this disturbance, the establishment of large fireworks-free zones or centralizing fireworks within urban centers could help to mitigate their effects on birds. Conservation action should prioritize avian communities with the most disturbance-prone, large-bodied bird species.

One of the most important autumn migration bottlenecks for birds of prey in the Western Palearctic is situated in South-Western Georgia, between the east coast of the Black Sea and the range of Lesser Caucasus. Every year from mid-August till October at least 1% of the world’s population of 10 raptor species passes through this corridor. Specifically, over one million raptors are recorded annually, including on average 528467 Honey Buzzards (Pernis apivorus), on average 163985 Black Kites (Milvus migrans), 304819 Steppe Buzzards (Buteo buteo vulpinus), and around 8000 Lesser Spotted Eagles (Aquila [Clanga] pomarina). The specifics of the landscape and relief makes the foothills of the Lesser Caucasus to the north of Batumi an ideal spot for counting raptor migration, and since 2008, an international team of volunteers, the Batumi Raptor Count, has monitored autumn raptor migration from two strategic vantage points. The count effort is focused on 7 priority species, including Honey Buzzard, Black Kite, Lesser Spotted Eagle, Booted Eagle (Hieraaetus pennatus), Marsh, Montagu’s and Pallid Harriers (Circus aeruginosus, C. pygargus, C. macrourus, respectively). In addition, 13 other diurnal raptor species and 10 non-raptor bird species are monitored at the BRC. Using the trektellen-app, BRC is able to record all data digitally in the field, and to provide daily updates of migration counts on its website. At the end of each season, the data is cleaned and made available through the Global Biodiversity Information Facility (GBIF). Protocols were developed to standardize count effort across years, thus allowing an accurate assessment of population trends in the priority species. Importantly, the BRC systematically records data on the age and sex of raptors, allowing to infer trends separately for different demographic groups. The standardized data collected from 2011 till 2019 revealed rather stable numbers for most priority species, but also a significant annual decrease in numbers of juvenile Montagu’s Harriers; a strong ongoing increase in numbers of both juvenile and adult Black Kites; and increase in numbers of adult Booted Eagles accompanied by a decrease in juvenile birds of this species. Based on GPS-tracking studies on a variety of species, it appears that the western border of the breeding area for the populations counted by BRC is most probably not too far away from the western border of Russia. At least in case of Spotted Eagles, individuals breeding in the Baltic States, Finland, and Germany tend to use the migration routes to the West from the Black Sea, and this is also the case for birds from Western Ukraine and Belarus. There is insufficient data available to define the eastern border for the populations migrating through Batumi. We do know that raptors tracked from the south of Siberia tend to migrate to the east from the Caspian Sea, although some Pallid Harriers tracked from Russia and Kazakhstan do migrate over the Caucasus. All considered, we assume that the vast majority of raptors observed in Batumi during autumn migration breed in Central European Russia up to the Ural Mountains. A comparison of Batumi counts with the breeding population size estimates in Russia and neighbouring countries suggests that a significant proportion of the Russian population of the Lesser Spotted Eagle and Honey Buzzard is passing through the Batumi bottleneck on migration. Trends in migration counts at Batumi are probably representative of changes in raptor breeding populations from European Russia and Western Kazakhstan. In addition to collecting the data on migration, the BRC supports the development of ecotourism in the area and combats the widespread poaching of migrating raptors in Georgia by implementing various educational programs in schools and higher education institutions in Georgia. The BRC would like to build stronger links with professional ornithologists and amateur birdwatchers from the breeding areas of the raptors that pass through Batumi each year, and cordially invites everyone to participate in its migration counts.

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.

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.

© British Birds 113 • August 2020 • 439–460 Abstract Since 2008, the Batumi Raptor Count project has monitored the autumn migration of raptors at Batumi, on the eastern shore of the Black Sea in southwest Georgia. What started as an expedition by young birders has become an invaluable project for monitoring raptor populations in the little-studied east African– Palearctic flyway. Autumn raptor migration through the Batumi bottleneck is notable for globally important concentrations of Honey-buzzards Pernis apivorus, Montagu’s Circus pygargus, Pallid C. macrourus and Marsh Harriers C. aeruginosus and accounts for at least 1% of the global breeding population of ten raptor species. By stimulating migration-based ecotourism, the project has had a significant economic impact on the communities where the count stations are located, which has increased societal and political support to reduce the widespread illegal raptor shooting in the region; it has also developed an important educational role for schoolchildren and older students. This paper summarises the 12-year history of the Batumi Raptor Count, and provides a detailed description of a typical autumn migration season. The project aims to expand its education and conservation remit while continuing to monitor one of the world’s biggest raptor migration bottlenecks.

Interactions between landscape and atmosphere result in a dynamic flight habitat which birds may use opportunistically to save energy during flight. However, their ability to utilise these dynamic landscapes and its influence on shaping movement paths is not well understood. We investigate the degree to which gulls utilise fine scale orographic lift created by wind deflected upwards over landscape features in a virtually flat landscape. Using accelerometer measurements and GPS tracking, soaring flight is identified and analysed with respect to orographic lift, modelled using high-resolution digital elevation models and wind measurements. The relationship between orographic lift and flight routes suggests gulls have advanced knowledge of their aerial surroundings and the benefits to be gained from them, even regarding small features such as tree lines. We show that in a landscape constantly influenced by anthropogenic change, the structure of our landscape has an aerial impact on flight route connectivity and costs.