Main mortality factors for the Eastern Imperial Eagle (Aquila heliaca Savigny, 1809) in Bulgaria

The Eastern Imperial Eagle is a globally threatened species, represented with not more than 35–40 pairs in Bulgaria. As a facultative scavenger feeding on carcasses and parts of dead domestic and wild animals, this species is extremely vulnerable to poisonous baits and toxic agents, intentionally or accidentally set up in its food. The present study identified electrocution and poisoning as the main mortality factors for the eagles in Bulgaria. We analysed a total of 56 cases among which 44 cases were related to the mortality of non-territorial eagles in different age classes, and we found 12 dead or distressed territorial birds recorded between 1992–2019. The main mortality factor was electrocution, accounted for 30.4% of fatalities. The poisoning was the cause of mortality in 12.5% of the non-territorial and 10.7% of the breeding birds. Some of the cases were laboratory confirmed as intoxication, while the others, based on the history, clinical symptoms and field evidence, indicated poisoning. The most commonly used toxic agents were anticholinesterase’s inhibitors. As a result of a timely therapy applied to the live birds found in distress with symptoms of poisoning, six eagles were successfully treated and released back in the wild. We found that mortality of eagles depended on the age of birds, breeding or dispersal grounds, while season had no significant effect

Genetic structure of a patchily distributed philopatric migrant: implications for management and conservation

Significant demographic fluctuations can have major genetic consequences in wild populations. The lesser kestrel (Falco naumanni) has suffered both population declines and range fragmentation during the second half of the 20 century. In this study we analysed multilocus microsatellite data to assess the genetic structure of the species. Our analysis revealed significant genetic structuring of lesser kestrel populations, not only at the cross-continental scale, but also regionally within the Central and Eastern (CE) Mediterranean region. We detected signs of genetic bottlenecks in some of the peripheral populations coupled with small effective population sizes. Values of genetic differentiation among the largest populations were low, albeit significant, whereas the small peripheral CE Mediterranean populations showed higher levels of differentiation from all other populations. Gene flow levels were relatively low among the discontinuously distributed populations of the CE Mediterranean region. We argue that the observed spatial genetic structure can be attributed at some level to the past demographic decline experienced by the species. Finally, we identify management units in the region, and inform the design of conservation actions aimed at the increase of population sizes and dispersal rates among peripheral populations. t

Genetic structure of a patchily distributed philopatric migrant: Implications for management and conservation

Significant demographic fluctuations can have major genetic consequences in wild populations. The lesser kestrel (Falco naumanni) has suffered both population declines and range fragmentation during the second half of the 20th century. In this study we analysed multilocus microsatellite data to assess the genetic structure of the species. Our analysis revealed significant genetic structuring of lesser kestrel populations, not only at the cross-continental scale, but also regionally within the Central and Eastern (CE) Mediterranean region. We detected signs of genetic bottlenecks in some of the peripheral populations coupled with small effective population sizes. Values of genetic differentiation among the largest populations were low, albeit significant, whereas the small peripheral CE Mediterranean populations showed higher levels of differentiation from all other populations. Gene flow levels were relatively low among the discontinuously distributed populations of the CE Mediterranean region. We argue that the observed spatial genetic structure can be attributed at some level to the past demographic decline experienced by the species. Finally, we identify management units in the region, and inform the design of conservation actions aimed at the increase of population sizes and dispersal rates among peripheral populations.We are grateful to Action for Wildlife and ANIMA rehabilitation centres, the Lesser Kestrel Recovery project team (LIFE11 NAT/BG/360), J. Hernandez-Pliego and G. Giglio for helping with sample collection. D. Vavylis, G. Vakis and E. Toli assisted with fieldwork. LIFE for the Lesser Kestrel project team (LIFE+ 11 NAT/GR/1011), and namely K. Vlachopoulos, S. Polymeros and A. This study was financially supported by a scholarship awarded to A.B. by the A.G. Leventis Foundation

Broad‐front migration leads to strong migratory connectivity in the lesser kestrel (Falco naumanni)

Aim: Migratory animals regularly move between often distant breeding and non‐breeding ranges. Knowledge about how these ranges are linked by movements of individuals from different populations is crucial for unravelling temporal variability in population spatial structuring and for identifying environmental drivers of population dynamics acting at different spatio‐temporal scales. We performed a large‐scale individual‐based migration tracking study of an Afro‐Palaearctic migratory raptor, to determine the patterns of migratory connectivity of European breeding populations. Location: Europe, Africa. Methods: Migration data were recorded using different devices (geolocators, satellite transmitters, Global Positioning System dataloggers) from 87 individuals breeding in the three core European populations, located in the Iberian, Italian and Balkan peninsulas. We estimated connectivity by the Mantel correlation coefficient (rM), and computed both the degree of separation between the non‐breeding areas of individuals from the same population (i.e. the population spread) and the relative size of the non‐breeding range (i.e. the non‐breeding range spread). Results: European lesser kestrels migrated on a broad front across the Mediterranean Sea and Sahara Desert, with different populations using different routes. Iberian birds migrated to western Sahel (Senegal, Mauritania, western Mali), Balkan birds migrated chiefly to central‐eastern Sahel (Niger, Nigeria, Chad), whereas Italian ones spread from eastern Mali to Nigeria. Spatial differentiation of non‐breeding areas led to a strong migratory connectivity (rM = .58), associated with a relatively high population (637 km) and non‐breeding range (1,149 km) spread. Main conclusions: Our comprehensive analysis of the non‐breeding distribution of European lesser kestrel populations revealed a strong migratory connectivity, a rare occurrence in long‐distance avian migrants. The geographical conformation of the species’ breeding and non‐breeding ranges, together with broad‐front migration across ecological barriers, promoted the differentiation of migratory routes and non‐breeding areas. Strong connectivity could then arise because of both high population spread and broad non‐breeding range.CLH; FCC Energía/Enerstar Villena S.A.; Alcalá de Henares Municipality; EDF Énergies Nouvelles S.A.; EuroNatur; Fundación Iberdrola España, Grant/Award Number: Project Migra; MAVA Foundation; French Ministry of Ecology, Grant/Award Number: Lesser Kestrel National Action Plan; Greek Green Fund; European Commission, Grant/Award Number: LIFE11 NAT/IT/000068, LIFE11 NAT/BG/000360 and NAT/GR/001011; Córdoba Zoo; Seiit‐R‐4; Consejería de Agricultura, Medio Ambiente y Desarrollo Rural de Castilla‐La Mancha; MIUR, Grant/Award Number: PRIN 2010‐2011/20180‐TZKHC

Tracking data highlight the importance of human-induced mortality for large migratory birds at a flyway scale

Human-induced direct mortality affects huge numbers of birds each year, threatening hundreds of species worldwide. Tracking technologies can be an important tool to investigate temporal and spatial patterns of bird mortality as well as their drivers. We compiled 1704 mortality records from tracking studies across the African-Eurasian flyway for 45 species, including raptors, storks, and cranes, covering the period from 2003 to 2021. Our results show a higher frequency of human-induced causes of mortality than natural causes across taxonomic groups, geographical areas, and age classes. Moreover, we found that the frequency of human-induced mortality remained stable over the study period. From the human-induced mortality events with a known cause (n = 637), three main causes were identified: electrocution (40.5 %), illegal killing (21.7 %), and poisoning (16.3 %). Additionally, combined energy infrastructure-related mortality (i.e., electrocution, power line collision, and wind-farm collision) represented 49 % of all human-induced mortality events. Using a random forest model, the main predictors of human-induced mortality were found to be taxonomic group, geographic location (latitude and longitude), and human footprint index value at the location of mortality. Despite conservation efforts, human drivers of bird mortality in the African-Eurasian flyway do not appear to have declined over the last 15 years for the studied group of species. Results suggest that stronger conservation actions to address these threats across the flyway can reduce their impacts on species. In particular, projected future development of energy infrastructure is a representative example where application of planning, operation, and mitigation measures can enhance bird conservation.publishedVersio