Volume 15 (2021): Issue 1 (December 2021)

The greater spotted eagle (Clanga clanga) is poorly known compared to other European eagles. We tracked an immature greater spotted eagle during 2018–2020 within the eastern European part of the species’ distribution, west of the Ural Mountains. Because so little is published about the annual movements of this species, especially from that region, tracking data from this single individual are valuable. 95% kernel density estimator (KDE) range sizes for the two complete winters in Yemen were 4,009 km² (2018), 1,889 km² (2019); 95% dynamic Brownian bridge movement models (dBBMM) encompassed 1,309 km² (2018) and 1,517 km² (2019). It returned to the same wintering area every year. During summer 2018, it settled into a small area (95% KDE = 126 km²; 95% dBBMM = 21 km²) near Birsk, eastern European Russia; in 2019 it wandered over a huge area (95% dBBMM = 66,304 km²) of western Kazakhstan and southern Russia, south west of Yekaterinburg. Spring migration 2018 was west of the Caspian Sea; during 2019 it was east of it. Mean speed of spring migration was 160±120 km/day during 2018, and 132±109 km/day during 2019. Autumn migration passed east of the Caspian in both years, and the mean speed of migration was 62 ± 78 km/day in 2018, and 84 ± 95 km/day in 2019. During both spring and autumn migrations, the eagle made stopovers, mostly lasting 1–2 days. The eastern Alborz Mountains in northeastern Iran appeared to be an important stopover locale, where autumn stopovers lasted 19 days (2018) and 27 days (2019). These and other data suggest that most greater spotted eagles that spend summers west of about 42°E, winter in southern Europe, Asian Turkey, the Levant and Africa, and those that summer to the east of that meridian winter in southern Asia, including Arabia.

The author evaluates his own data on the food of the Eurasian eagle-owl (Bubo bubo) in Slovakia using material he collected between 1975 and 2020. A total of 105,543 food items were identified in 254 samples taken at 136 localities. Mammals had the highest representation (Mammalia, 65 species, 58.4%), and the species composition of birds was diverse (Aves, minimally 140 species, 8.5%), but the common frog (Rana temporaria, 32.0%), from the lower vertebrates, is represented more abundantly. Invertebrates (Evertebrata, 0.1%) occurred in food residues only occasionally. The bulk of the samples were collected from eagle-owl nests. The samples were divided into three time periods (A–C), which differ in the manner of human land-use management: A up to the 1950s, with a smaller area of field plots and more extensive grazing in the uplands; B from the 1950s to the 1980s, during the Socialist period, with the concentration of agricultural production in large units; C the last 30 years, 1990 to 2020, with the gradual break-up of collective land management. The first period (A) is characterised by a strong dominance of frogs, particularly the European brown frog R. temporaria (44.6%), and a large share of small mammal species of the family Muridae (genera Apodemus and Mus). During the time of Socialism (B), eagle-owls adapted to hunting larger species of mammals and birds, and the share of frogs in their food fell by half (R. temporaria, 23.3%). With the decline in livestock production after 1990 (period C), the species diversity of birds increased: aquatic species and raptors in particular are on the rise. Successive overgrowth of pastures in the submontane zone is reducing the hunting territories of eagle-owls. The dominance of the common vole (Microtus arvalis) in their diet has gradually increased from period A (26.8%) to period C (37.3%). Data from eleven areas around Slovakia are evaluated separately for the three time periods. In period A, the highest proportion of frogs was in the Liptov region (R. temporaria, 68.2%), when eagle-owls nested deeper in the mountains. The proportion of frogs decreased towards lower areas, and in the Ponitrie (Nitra river basin) it was only 10.8%. At the same time, the share of M. arvalis and larger prey increased. A similar trend of increasing shares of larger prey towards lower locations also applied during the Socialist period (B). In the last 30 years (C), frogs in the higher river basins have given way to European water voles Arvicola amphibius and M. arvalis. In association with the progressive overgrowth of pastures, forest species such as the yellow-necked mouse (Apodemus flavicollis) and bank vole (Myodes glareolus) are increasingly prevalent, as are the white-breasted hedgehog (Erinaceus roumanicus) and various thrushes (Turdus sp.).

In 2020, 1296 raptors and owls (23 species) were ringed in Slovakia. The most abundant was the common kestrel (719 individuals), then the western marsh harrier (126) and saker falcon (92). The proportion of nestlings among all the ringed individuals was 76.7%. In the given period, 145 recoveries of raptors and owls (15 species) were recorded in the Bird Ringing Centre database. This number included 77 recoveries of colour-marked individuals recovered in our territory. There were 43 recoveries of birds ringed in Slovakia and resighted abroad. The last 25 recoveries were of individuals ringed abroad and recovered in Slovakia. In summary, most of the recoveries (of all types) were of red-footed falcon (69 recoveries), then common kestrel (17) and eastern imperial eagle (15). Most of the recovery circumstances were ring reading (almost 76% in total), findings of bird cadavers (6%) and recaptures (5%). Electrocutions and predations by other animals (3% each) were frequent causes of their deaths.

Table 1 in original paper (Slobodník et al. 2017, Slovak Raptor Journal 11: 83–89) was published with incorrect data. Correct version is published here.

Information on mortality rates and their causes in raptors and owls during the post-fledging dependency period (PFDP) and subsequent dispersal is essential for their more effective protection, including more efficient use of funds. Despite the importance of the above data, these data are not yet available for most birds of prey. The study aimed to provide and expand the knowledge in this field for saker falcon. We used satellite telemetry to monitor a total of six young birds since they left the nest boxes. All young birds survived the PFDP, but none survived to adulthood and died during the period of dispersal movements. The PFDP lasted 47 days (median value hereinafter), and the distance of individuals from the nest boxes during this period was 3.2 km (maximum distance 9 km). The area of the home range of the PFDP calculated by the 100% minimum convex polygon (MCP) method was 81 km². During the period of dispersal movements, the monitored individuals set up five temporary settlement areas with an area of 422 km² according to 100% MCP, where they stayed for 37 days. All individuals’ mean length of movement routes throughout the monitoring period was 3862 km. The main finding of the present study is the fact that none of the monitored individuals survived the dispersal period. At least half of them died due to human activity (electrocution, hunting), which is probably unbearable in the long term for wild populations of most animal species. This shows the need to start eliminating all types of artificial traps (e.g., electrocution, hunting, poisoning, etc.) without delay, thus helping to prevent the decline of populations of many species in the shorter or longer time horizon.