Migratory birds face numerous challenges as they travel to and from their wintering grounds. Their ability to overcome these obstacles depends on their physical fitness, energy reserves and migration strategy. During migration, birds often need flight interruptions in vegetated areas which play a crucial role for migrants heading to wintering quarters or flying back to breeding areas. For the migratory raptor, the Western Marsh Harrier Circus aeruginosus a particularly difficult challenge is crossing the Sahara Desert. In this region, the birds encounter areas with lack of vegetation and harsh atmospheric conditions. To understand their behaviour in such an unfavourable environment, we studied the migratory patterns of Marsh Harriers in the Sahara Desert using GPS/GSM telemetry from 2019 to 2023. We examined flight interruptions within an hourly resolution and unique stop sites in hyper-arid areas of the Sahara Desert and enhanced the dataset with Normalised Difference Vegetation Index (NDVI), land cover data, U (velocity of the east-west) and V (velocity of the north-south) wind components and sunrise and sunset times. We explored the timing of the daytime flight interruptions used by Marsh Harriers and described the selection of sites with emphasis on the NDVI. Marsh Harriers preferred areas with higher NDVI and increased distance between unique stop sites. We also found increased density of flight interruptions during late afternoon and tendency for flight interruptions in the vicinity of consecutive night roost. Flight interruptions were also affected by wind conditions. Our study, made possible by advanced GPS/GSM technology and remote sensing data, provides new insights into the use of unique stop sites by Marsh Harriers during migration over the Sahara Desert. It underlines the importance of scarce vegetation during the Sahara crossing for the Marsh Harrier and helps to explain the selection of areas within a harsh environment used for breaks of a short duration. Our findings open the door for further investigation of Marsh Harrier behaviour during migration through harsh environments.

Designation and management of protected areas (PAs) can mitigate detrimental anthropogenic impacts on biodiversity. Across Europe, an extensive network of PAs exist to protect wildlife and habitats. These sites aim to provide important refugia for species of conservation interest, which include the Red Kite (Milvus milvus; hereafter "kites"). Currently, kites are classified as globally Least Concern but in danger of extinction in parts of their range such as Spain. However, it remains unclear to what extent kite ranges overlap with PAs with fundamental knowledge gaps persisting for the species during winter. Using data for 103 kites tagged with GPS-GSM telemetry loggers over 180 winters between 2013-2022, we modelled proportional overlap between kite winter ranges and both European Natura 2000 sites and Important Bird and Biodiversity Areas (IBAs). We also explored the effects of various demographic, geographic and environmental predictors of PA overlap in tagged kites. Overall, 24.5 ± 28.1% (± SD) of kite winter core areas and 26.6 ± 20.5% of winter home ranges overlapped with European PAs. Kites that wintered in areas with greater agricultural land cover had lower overlap with PAs. Kites that wintered in Iberia (Spain and Portugal) and the Pyrenees (France and into northern Spain) had lower overlap with PAs than conspecifics wintering in Central Europe. Wildlife that rely on traditional agricultural landscapes during winter may thus remain unprotected by existing European PAs. Policymakers should consider the conservation needs of such species when designating new PAs, especially as Spain holds the largest global wintering kite population, and the species is categorised as "In danger of extinction" in the Spanish National Catalogue of Threatened Species. Improving protection of wintering kites in Iberia remains an urgent conservation priority.

Understanding bird avoidance behaviour at wind turbines is essential for accurate collision risk assessment. We provide one of the first empirical analyses of both micro-avoidance (avoidance of rotor-swept airspace) and meso-avoidance (avoidance of the entire turbine) in Red Kites (Milvus milvus), based on high-resolution GPS telemetry integrated with turbine operational data and simulation-based error correction. Red Kites showed consistently high avoidance rates: meso-avoidance averaged ~ 90% and micro-avoidance ~ 80%, resulting in an overall avoidance probability of ~ 98%. Avoidance varied with individual experience-birds with greater prior exposure to turbines showed lower meso-avoidance. Whether this reflects habituation and increased collision risk or improved spatial awareness remains to be investigated. Environmental conditions also modulated avoidance: higher wind speeds and increased cloud cover were associated with stronger avoidance responses. This suggests that under unfavourable weather, Red Kites adopt more cautious flight behaviour that may be associated with lower collision risk. In contrast, turbine-specific features (e.g. tower height or rotor diameter) had no significant effect. These findings indicate that Red Kites flexibly adjust their spatial behaviour in response to turbine exposure and environmental context. By refining species-specific avoidance estimates and identifying mechanisms influencing risk, our findings improve the empirical basis for collision risk assessment in Red Kites and highlight that avoidance behaviour may vary with environmental conditions and turbine experience.

Migration is a complex phenomenon influenced by several factors, including environmental conditions and individual preferences. We investigated the unique loop migration of Central-European Red Kites Milvus milvus to and from their wintering grounds in Italy. Utilising telemetry data from nineteen tagged birds, we analysed migration routes and route consistency in relation to wind conditions. Our results revealed distinct patterns between autumn and spring migrations. During autumn, most birds chose a shorter route over the Adriatic Sea, facilitated by the katabatic Bora wind, while in spring, the majority chose a continental route along the east coast of Italy. Despite the fact that the risky sea-crossing offered a shortcut, migration duration remained similar, as some birds waited along the Croatian coast for supportive winds. Route choice showed high consistency, suggesting a fixed strategy influenced by experience and individual preference. Wind conditions played a crucial role, with the Bora wind facilitating autumn migrations but hindering spring crossings. Nevertheless, despite adverse conditions, some birds opted for sea crossings in spring, indicating flexibility in response to atmospheric conditions. Our findings underscore the ecological importance of coastal stopovers and over-sea passages for Red Kites and, potentially, other soaring raptors. Overall, our study provides useful insights into the intricate relationship between environmental factors and migration strategies.-Skrabal, J., Raab, R. & Literak, I. (2025). Central-European Red Kites Milvus milvus perform a unique loop migration over the Adriatic Sea.

.-There are many raptor rehabilitation centers around the world that receive and care for wild raptors. Wildlife rehabilitation is a labor- and cost-intensive part of addressing animal welfare. Apart from the compassionate aspect of taking responsibility for an injured animal, there remains an open question as to whether doing so contributes to animal conservation. The fates of such animals after their rehabilitation and release have rarely been studied. Long-term post-release monitoring is needed to assess survival and reproduction. Here, we investigate the post-release fates of 22 White-tailed Eagles (Haliaeetus albicilla), including juveniles, immature birds, and adults in Austria, the Czech Republic, Germany, and Slovakia. Using GPS tracking, we monitored the eagles for 2-2639 d (median 1/4 340 d) between 2005 and 2023. The longest-surviving eagle was tracked for more than 7 yr. Release was followed by a short 6-d period of high mortality, followed in turn by a long-term annual adult survival rate of 74.6%. Anthropogenic factors contributed to 70% of the long-term mortality cases. Reason for admission, length of hospital stay, and use of flight aviaries had no statistically significant effect on long-term survival. Five eagles successfully bred and produced a total of 10 fledglings. Traveling as much as 1378 km, the released eagles dispersed throughout central, northern, and eastern Europe. Thus, it can be concluded that successful rehabilitation of White-tailed Eagles resulted in high survival rates; and in five cases, successful reproduction indicated effective reintegration into the wild population.

The pathogenicity of haemogregarines and their effects on the health status of ectothermic hosts remain largely unexplored. In this study, we examined the impact of Hemolivia mauritanica (Sergent et Sergent, 1904) infection on the differential leukocyte count (DLC) as a measurable indicator of health in tortoise hosts. A total of 206 blood smears were analysed, including 181 from spur-thighed tortoises (Testudo graeca Linnaeus) and 25 from marginated tortoises (Testudo marginata Schoepff). Light microscopy was used to identify infected individuals, determine DLC, and quantify parasitaemia levels. Overall, H. mauritanica was detected in 125 of 181 (69%) T. graeca samples and 21 of 25 (84%) T. marginata samples. To assess whether infection influenced DLC, we statistically compared leukocyte profiles between infected and uninfected individuals. Additionally, we evaluated the effects of other factors, including host species, parasitaemia intensity, sex, age, and the month and year of blood collection. Wilcoxon rank-sum tests revealed that parasitaemia and age had a statistically significant effect on DLC in T. graeca. Further analysis using linear models showed a significant association between parasitaemia and DLC, specifically affecting azurophils in T. graeca and basophils in T. marginata. Nine T. graeca tortoises positive for H. mauritanica were co-infected with haemosporidian parasites of the genus Haemocystidium Castellani et Willey, 1904, specifically three with Haemocystidium anatolicum (Orkun et Güven, 2013) and six with Haemocystidium caucasicum (Krasilnikov, 1965). Although co-infection itself was not statistically significant, a separate analysis of Haemocystidium parasitaemia revealed a significant effect on lymphocyte DLC. Furthermore, the frequent presence of mitotic and polychromatophilous erythrocytes in H. mauritanica-infected tortoises suggests a potential increase in erythrocyte regeneration.

Most species of migrating birds use a combination of innate vector-based orientation programs and social information to facilitate accurate navigation during their life. A number of various interspecies hybridisations have been reported in birds. The traits of parents are expressed in hybrids in typical ways which are either intermediate, combined or heterotic. Here, we analyse the different migration behaviours of medium-sized raptors, i.e., Red Kites Milvus milvus, Black Kites Milvus migrans, and their hybrids. We chose six well-established parameters to compare the behaviour of Kite hybrids with those of both parental species. When comparing 16 quantified behavioural characteristics between Red Kites and F1 hybrids and between Black Kites and F1 hybrids, significant differences were found in 10 characteristics between Red Kites and F1 hybrids but only one of the 16 characteristics between Black Kites and F1 hybrids. Hence, F1 hybrid individuals showed behaviour much more similar to Black Kites than Red Kites. It implies that the basis of the migratory behaviour of Kites is an innate program with the dominance of genetic determinants supplemented by the use of social learning from individuals of the parent species.

Wind turbines are important for achieving renewable energy goals, but present a considerable threat to wildlife, especially birds and bats. This study reports 41 confirmed collisions of GPS-tracked Red Kites (Milvus milvus) with wind turbines across Europe (2017-2024). We compared environmental and turbine-specific factors during collisions and non-collision movements within 500 m of turbines. Collisions occurred year-round, with the highest mean number of collisions per day during spring and autumn migration. Rotor clearance and diameter were significant predictors of collision risk: turbines with greater clearance exhibited lower probabilities of collision, likely due to reduced overlap with typical Red Kite flight altitudes. Based on our model, a 25.5 m increase in rotor diameter was associated with a fivefold increase in collision probability; mitigating this risk would require increasing rotor clearance by approximately 19.3 m. Variation in collision probability was greater between wind parks than between individual birds. No significant effects were found for cloud cover, precipitation, wind speed, or turbine density within 500 m. Our findings suggest that turbines with rotor diameters <= 90 m and clearances >= 60 m may pose a lower relative threat to Red Kites. Increasing rotor diameters without adjusting height restrictions reduces clearance and increases the risk of collisions. These results highlight the need for turbine designs minimizing overlap with bird flight heights and underscore the importance of legislative adjustments to height restrictions.

ABSTRACT Anthropogenic activities threaten many wildlife populations by increasing mortality rates, making it crucial to identify the locations and causes of mortality to inform conservation actions. Technological advancements, such as GPS satellite tracking, enable precise recording of wildlife movements. High‐resolution data from such devices can facilitate rapid carcass recovery and provide insights into the mortality causes of tagged individuals. Obtaining required information to determine these causes is complex, and standardized approaches can overcome these limitations. In this study, we introduce the LIFE EUROKITE Assessment Protocol (LEAP), a framework for determining the timing, locations, and causes of mortality in GPS‐tagged birds. LEAP is a multifaceted approach that integrates: (1) GPS tracking data, (2) evidence from the mortality location (site investigation), and (3) necropsy results to derive the mortality cause and a corresponding certainty score. We supplement the detailed description of LEAP with case studies assessing its effectiveness. Using 329 deceased GPS‐tagged red kites (Milvus milvus) we compared conditions of the carcasses processed using LEAP with 145 opportunistically collected raptor carcasses. We also show that LEAP improves carcass condition and therefore allows for higher quality necropsy results. Additionally, we assessed how availability among sources of information (tracking, site investigation and necropsy) influences the quality of mortality assessments. Applying LEAP with all data sources provided the highest quality assessments in 64% of cases. Some 35% of cases were of high quality without necropsy, instead drawing evidence only from tracking data and site investigations. Predation related mortality was less prevalent (11%) when relying on necropsy compared to cases without necropsy (36%), while poisoning showed the opposite trend. Furthermore, we provide guidelines and empirical examples of mortality assessments. Our standardized LEAP approach ensures the best use of all available information regarding mortality events in GPS‐tagged birds and advances wildlife mortality research as a valuable tool for conservationists and wildlife managers.

The breeding behaviour of raptors is determined by many characteristics, such as courtship and mating patterns, nest building, foraging, territorial defence activities, clutch incubation, and caring for the young. Here, we study the breeding behaviour of the Red Kite (Milvus milvus), a European native bird of prey. From a period between 2018 and 2022, we analysed data for 33 adult Red Kites (14 males and 19 females) during 70 successful breeding episodes in Austria, the Czech Republic, and Slovakia. Using satellite telemetry and in situ observations, we found differences between males and females in the size of the home range, number of nights on the nest, and maximum distances from the nest. We analysed the influence of different factors on movement activity, breeding productivity, and home range size. Females spent significantly more nights on the nest than did males, flew shorter distances from the eyrie, and occupied smaller areas. Red Kites with two or more breeding experiences arrived significantly earlier than did unexperienced Kites in their first breeding attempts. Juveniles departed from the nest sooner than did their parents. Birds with more fledged juveniles occupied smaller home ranges. Our study reveals new knowledge of substantially different breeding behaviours in male and female Central European Red Kites.

The main reasons for the global biodiversity decline are the destruction and degradation of natural habitats caused by human activity by transforming them into agricultural lands. Although this transformation has been linked with decreased biodiversity, some bird species might have learned how to benefit from newly created habitats. We studied home ranges and habitat preferences for daytime activity and roosting of two sedentary Marsh Harriers (Circus aeruginosus) from the Evros Delta and the Mediterranean coast of the Iberian Peninsula using the results of satellite telemetry tracking. The size of the home range for the bird tagged in the Evros Delta was 158 km2 (dynamic Brownian Bridge Movement Model, 95 %), while for the Iberian bird, this was more than nine times greater (1488 km2). Monthly home ranges noticeably increased during winter in Evros Delta in both years.. The birds chose habitats such as non-irrigated arable land, watercourses, inland marshes, and dump sites for daytime activity. In contrast, they avoided habitats like rice fields and complex cultivation patterns. Water-related natural habitats like inland and salt marshes were intensively used as nocturnal roosts. Despite the general negative effect of human pressure, our results showed that the species seemed to tolerate and benefit from some types of humanized environments of estuarine landscapes.

Migration and over-wintering strategy of raptors can be influenced by many factors such as sex, age and experience of birds, habitat variability and food availability. Based on the telemetry data of nine Red Kites (Milvus milvus), we observed in situ their wintering grounds in southern Italy during winter 2019/2020. Red Kites originated from Austria and the Czech Republic arrived to their wintering grounds from 10th September to 5th December 2019 and departed between 9th February and 7th May 2020. Tagged Kites stayed in their wintering grounds from 73 to 207 days (mean 135±46 SD). These birds occupied home range and the core area from 39 to 9,351 km2 (KDE 95%; mean 3,591±3,460 SD) and 6 to 1,998 km2 (KDE 50%; mean 566±483 SD), respectively. We observed a total of 242 Red Kites at nine communal roost sites (min. = 14, max. = 45 individuals) used by tagged Red Kites. Roosts were situated at an average altitude of 630 m above sea level. Agricultural countryside with small or large fields, small or large forest patches, meadows, pastures, sheep or cattle farms surrounded areas around communal roosts of Red Kites.

In a study of the extent and timing of Red Kite Milvus milvus dispersal movements from Central Europe (Austria, the Czech Republic and Slovakia) using GPS telemetry, we found support for the hypothesis that Red Kite dispersal, including migration behaviour, is dependent on both age and sex. Examination of the tendency to stay in, or return to, a particular area in Red Kites indicated that, while part of the population remained in the natal area, most migrated to overwintering sites across a broad belt of southern European sites stretching from the Iberian Peninsula to the Balkans. Red Kites first bred at 2 years old, i.e. in their 3rd calendar year. Migration routes were significantly longer in females than males, while natal philopatry was significantly higher in males than females. The lengths of single-year migration routes decreased significantly over consecutive years, and breeding philopatry increased significantly in cases where previous breeding was successful.

The Black Kite (Milvus migrans) is one of the most widespread raptors in the world. The Palaearctic is populated by two migrating subspecies, Milvus migrans migrans and Milvus migrans lineatus, in the western and eastern part of this realm, respectively. There is a large intergradation zone of M. m. migrans/M. m. lineatus in-between. Although the migration routes of M. m. migrans from Europe to Sub-Saharan Africa and the Middle East are well known, detailed information about migration routes of Black Kites from intergradation zone are missing. Using satellite telemetry we are able to fill this gap in our knowledge of these birds. We tagged with GPS/SMS/GPRS telemetry loggers 13 and 6 Black Kite pulli in lowland around Biysk (Altai Krai, Russia) and in mountains around Kosh-Agach (Altai Republic, Russia), respectively. After fledging, Black Kites from both subpopulations stayed in a small, non-overlapping areas and then migrated to southern Asia through narrow corridors. Black Kites originating from Biysk migrated through the Western Circum-Himalayan Corridor. Black Kites originating from Kosh-Agach used the Trans-Himalayan Corridor crossing the Himalayas in altitudes of up to 6256 m asl. The average total distance travelled of Black Kites from both subpopulations was 9166 km without any significant differences between these subpopulations. Timing of both spring and autumn migration did not vary along different age groups. Black Kites from both subpopulations wintered in low elevations of Pakistan and India. Birds wintered on average for 190 days, and the mean area of individual home ranges in winter was 4704 km(2). During the breeding period, birds dwelled in south-western Siberia, where they spent on average 125 days with an average home range size 3537 km(2). We found that ontogenetic shifts in migratory behaviour of Black Kites from Eastern Russia differ from those in population/subspecies in Europe. Black Kites crossing the Himalayas fly and, moreover, stay for hours resting at night in the environment of mountains at altitudes over 5000 m.

The Red Kite Milvus milvus is endemic to the western Palearctic. While the largest breeding population is in Germany, the population density decreases substantially from central to eastern Europe. In 2015, we tagged two young Red Kite females with telemetry loggers in an area with very low kite density in the northeastern part of Slovakia. One of these females failed to breed over her seven-year lifespan. After leaving her post-fledging area she never returned. During her first two years, she undertook two exploratory flights to Croatia and Romania, but remained exclusively in southwestern Slovakia and northeastern Hungary over the rest of her life. Throughout this period, she always wintered alone and no other Red Kites were ever observed in her wintering grounds. During the pre-breeding period (March–April), she remained outside the area that held breeding kite pairs, and there were no signs of breeding based on her positions during the breeding season. This seven-year-old is the oldest Red Kite floater recorded to date. Owing to the low density of Red Kite breeding pairs in Slovakia and Hungary, it is likely that she was unable to find a suitable mate prior to the beginning of the breeding season. In such areas, the role of floaters may prove critical for the persistence of low-density Red Kite populations.

Abstract. Understanding the year-round movement behaviour is fundamental for the effective conservation management of an ecologically important species. In the heavily human-modified landscape of Central Europe, Saker Falcons Falco cherrug have adapted to intensively managed agricultural habitats, often nesting and roosting on electrical pylons. We studied the ranging behaviour and habitat selection of one juvenile and three adult Saker Falcons equipped with GPS/GSM loggers in the Czech Republic and Austria between 2015–2017. Upon release from a rescue centre, the juvenile Saker Falcon used temporary settlement areas (TSAs) with a median size of 231 km2 (minimum convex polygons, MCP 95%). Median of breeding season home ranges for the three adults was 15 km2 over six breeding events. After breeding period, the adults remained close to the nest site, occupying an area with median of 10 km2 until they departed for their autumn migration. Departure dates ranged from 21 September to 9 November. Winter TSA sizes had median of 99 km2. Adults returned to the breeding area between 12 February and 4 March. Annual breeding home ranges overlapped by approximately 84–99% indicating high site fidelity. The most utilised land cover types within winter TSAs included arable land and heterogeneous agricultural areas. Analysis of night-time roosting sites showed a substantial preference for high voltage pylons compared to trees. Our results could benefit conservation planning and species management practices, focusing on both improving the safety of anthropogenic elements and increasing habitat diversity.

In the 19th century, Red kite (Milvus milvus) was very common and widespread in Sardinia, but in the mid-900 an important decline occurred. Since the 1970s the species has been studied more continuously, but in recent years the published data seem contradictory. In 2018-2020, authors carried out specific research to collect data on the population of the Red kite in Sardinia exploring both the historical range of the species and areas where the species was reported in the past. In 2018-2020, we estimated 10-13 breeding pairs in an area of about 3,440 km2 located in the north west of Sardinia. As regard wintering, we estimated 30-40 birds in winters 2018-2019 and 2019-2020, whereas 90-110 birds were counted in winter 2020-2021.

Capsule: Some birds of the central European population of Red Kite Milvus milvus are non-migratory and winter within their natal area, whereas others migrate to southern Europe or even to northern Africa. Aims: To determine what factors affect the area use and communal roost use by Red Kites wintering in their natal area. Methods: We studied spatiotemporal activity and factors affecting area use by Red Kites wintering in their natal area in the tripoint border area of Austria, the Czech Republic, and Slovakia, using GPS/GSM telemetry devices. Results: We characterized home ranges used by wintering Red Kites in natal areas. Birds wintered for an average of 146 days and spent 88% of the time within temporary settlement areas (TSAs). The number of TSAs used by one Red Kite during the winter varied from 1-4 (mean +/- sd = 2 +/- 1); the mean (+/- sd) size of the home range of TSAs was 190 +/- 144 km(2) as a 95% minimum convex polygon, 136 +/- 82 km(2) as a 95% kernel density estimate, and 41 +/- 34 km(2) as a 50% kernel density estimate (core activity area). Age, breeding status, and percentage of forest habitat were the main factors negatively related to home range size. Winter duration and the number of TSAs were positively related to the size of the home range. Young birds (before first breeding) and males explored larger areas and used more TSAs during winter. Conclusion: Wintering of Red Kites in their natal area may relate to the social refuge-territory prospecting hypothesis, breeding site fidelity, wintering site fidelity, and/or mate loyalty, and this understanding could lead to better conservation of Red Kites in central Europe.

From 2014 to 2020, 32 black kites from various European countries were tagged with telemetry devices and tracked to study their spatiotemporal behaviour. Eleven birds which crossed the Mediterranean Sea and the Black Sea directly over large water bodies out of traditional migration routes over the Strait of Gibraltar, the Dardanelles/the Bosporus area and the east coast of the Black Sea were selected for this study. Ten birds attempted to cross the Mediterranean Sea and one attempted to cross the Black Sea. All black kites crossed the sea successfully but in one case the bird failed. The maximum water crossing length was recorded at 542 km. The average speed of the birds crossing the sea included a broad range from 27.7 to 97 kph. There was a correlation between average speed and tail-wind speed during the crossing. We conclude that the most favourable conditions for black kites when crossing large water bodies such as the Mediterranean and Black seas were sunny to partly cloudy weather with temperatures over 20 °C, the speed of the tailwind of 1.1–10.8 m/s and the air pressure over the standard value of 1013 hPa.

Europe is commonly occupied by Black Kites of the nominal subspecies Milvus migrans migrans. In recent years, there has been an increase in the number of sightings of Black Kites with morphological features of Milvus migrans lineatus suggesting the spreading of M. m. lineatus and a subsequent hybridization zone between M. m. migrans and M. m. lineatus in a westerly direction from Siberia across continental Europe. Furthermore, it appears that the emergence of Black Kites with lineatus features in Europe coincides with new observations of wintering Black Kites in some areas of southern Europe.