On the taxonomic status of the Indian Spotted Eagle Aquila hastata

We review the status of the two currently recognized subspecies of Lesser Spotted Eagle Aquila p. pomarina (western Eurasia) and A. p. hastata (Indian subcontinent) on the basis of museum diagnosis and field observations. We present differences between these two allopatric taxa which demonstrate that they should be treated as distinct species. Specifically, we present evidence of differences in plumage (both for adults and juveniles), external morphology, osteology, clutch size and behaviour. Particular emphasis is placed on differences in gape size and general cranial structure.     

Apparent survival rates of adult Lesser Spotted Eagle Clanga pomarina estimated by GPS-tracking,colour rings and wing-tags

Capsule: In the migratory Lesser Spotted Eagle Clanga pomarina, colour rings and Global Positioning System transmitters indicated annual survival rates similar to other large raptors, but the rate suggested by wing-tags was significantly lower due to the higher rate of tag loss.     

Sex? and species?biased gene flow in a spotted eagle hybrid zone

Background  

Recent theoretical and empirical work points toward a significant role for sex-chromosome linked genes in the evolution of traits that induce reproductive isolation and for traits that evolve under influence of sexual selection. Empirical studies including recently diverged (Pleistocene), short-lived avian species pairs with short generation times have found that introgression occurs on the autosomes but not on the Z-chromosome. Here we study genetic differentiation and gene flow in the long-lived greater spotted eagle (Aquila clanga) and lesser spotted eagle (A. pomarina), two species with comparatively long generation times.     

Coexistence of protected avian predators: does a recovering population of White-tailed Eagle threaten to exclude other avian predators?

The processes of competition and predation determine the degree to which species can coexist; the importance of competition in particular has been emphasized at high trophic levels. Competition exclusion will occur when habitat overlap between sympatric species is high. In this study, we investigated nesting habitat overlap between internationally protected diurnal tree-nesting avian predators of central Europe, namely, White-tailed Eagle (Haliaeetus albicilla), Lesser Spotted Eagle (Aquila pomarina), Black Stork (Ciconia nigra), and Osprey (Pandion haliaetus). We found significantly different nesting habitats among the study species and suggest that this could be a consequence of the resource-based segregation, but not a consequence of asymmetrical interspecific competition. The results also show that habitat of the recovering populations of White-tailed Eagle overlapped with the habitat used by the Lesser Spotted Eagle, Black Stork, and Osprey to varying extents with a niche overlap values being below the competition exclusion threshold. Nevertheless, we suggest that competition by White-tailed Eagle at a population level may limit Osprey, though not Lesser Spotted Eagle or Black Stork.     

Nesting habitat overlap between the Common Buzzard Buteo buteo and the Lesser Spotted Eagle Clanga pomarina for conservation planning in Natura 2000 sites

Capsule: The nesting habitat of the Common Buzzard Buteo buteo and Lesser Spotted Eagle Clanga pomarina extensively overlap, indicating that they exploit similar resources.

Aim: We aimed to determine the overlap in the nest platforms, nest trees and nest stands used by these raptors, find any evidence for the avoidance of the larger Lesser Spotted Eagle by the smaller Common Buzzard, and provide conservation implications for habitat protection of the former species in habitats that overlap extensively.

Methods: Nest sites were mapped during 2012–2014 in the Bir?ai Forest Spatial Protection Area, northern Lithuania. Fifty-three nest sites occupied by Common Buzzards and 26 by Lesser Spotted Eagles were compared.

Results: The nest platforms of both raptors were similarly placed in the tree canopies. Most Lesser Spotted Eagle nests were built in spruce, while the Common Buzzard usually nested in birch. The nest stands of the eagles were on wetter soil and located closer to the forest edge than those of the buzzards, otherwise, the nest stands did not differ significantly. There was no evidence for spatial avoidance of the larger raptor by the Common Buzzard.

Conclusions: The different components of the nesting habitats extensively overlapped, and the distribution of the interspecific pairs lacked spatial avoidance. We suggest that the nest sites of both raptors were a largely shared resource, especially if located close to the forest edges. We propose, as a rule of thumb, applying protection by way of buffer zones around buzzard nest sites if they are located close to eagle nest sites and the forest edge.     

Parental care,nestling growth and diet in a Spotted Eagle Aquila clanga nest

Capsule The breeding biology of the Spotted Eagle was studied and we analysed results from direct observations at a nest in Estonia.     

Geographical variation in macrohabitat use and preferences of the Lesser Spotted Eagle Aquila pomarina

Geographical variation in wildlife–habitat relationships has seldom been studied. We explored macrohabitat use and geographically distinct responses to habitat availability in the Lesser Spotted Eagle Aquila pomarina near the centre (Lithuania) and on the edge (Estonia) of its European distribution range, and in different zones within Estonia. Land cover types and distances to landscape elements, as well as landscape diversity, were measured around 198 Eagle nests and random forest points. Out of six macrohabitat characteristics, two (landscape diversity, area of optimal foraging habitat) showed no geographical variation in use, or preferences by the Eagle. Whereas variation in the use of suboptimal foraging habitats and forests could be attributed to regional differences in their availability, there were geographically distinct preferences for distances between nests and landscape elements. The species avoided anthropogenic edges in Lithuania but tended even to prefer their proximity in Estonia; Eagles selected nest-sites near remote waterbodies throughout Estonia but there was no such preference in Lithuania. The results did not support the hypothesis that latitudinal or range centre-to-periphery gradients existed in habitat relationships of the species; the main factor behind the geographical variation was probably land-use history. In general, the diversity of geographical effects indicated that extrapolating local habitat relationships to other areas may give erroneous results, and large-scale conservation planning regarding species' habitat may be ineffective.     

Genetic differentiation and hybridization between greater and lesser spotted eagles (Accipitriformes:Aquila clanga, A. pomarina)

Greater and lesser spotted eagles (Aquila clanga, A. pomarina) are two closely related forest eagles overlapping in breeding range in east-central Europe. In recent years a number of mixed pairs have been observed, some of which fledged hybrid young. Here we use mitochondrial (control region) DNA sequences and AFLP markers to estimate genetic differentiation and possible gene flow between these species. In a sample of 83 individuals (61 pomarina, 20 clanga, 2 F1-hybrids) we found 30 mitochondrial haplotypes which, in a phylogenetic network, formed two distinct clusters differing on average by 3.0% sequence divergence. The two species were significantly differentiated both at the mitochondrial and nuclear (AFLP) genetic level. However, five individuals with pomarina phenotype possessed clanga-type mtDNA, suggesting occasional gene flow. Surprisingly, AFLP markers indicated that these mismatched birds (originating from Germany, E Poland and Latvia) were genetically intermediate between the samples of individuals in which mtDNA haplotype and phenotype agreed. This indicates that mismatched birds were either F1 or recent back-cross hybrids. Mitochondrial introgression was asymmetrical (no pomarina haplotype found in clanga so far), which may be due to assortative mating by size. Gene flow of nuclear markers was estimated to be about ten times stronger than for mtDNA, indicating a sex-bias in hybrid fertility in accordance with Haldanes rule. Hybridization between the two species may be more frequent and may occur much further west than hitherto assumed. This is supported by the recent discovery of a mixed pair producing at least one fledgling in NE Germany.     

Nestling characteristics and identification of the lesser spotted eagle Aquila pomarina, greater spotted eagle A. clanga, and their hybrids

The lesser spotted eagle Aquila pomarina and the greater spotted eagle A. clanga are closely related endangered raptors whose taxonomic status, field identification, and ultimately conservation, have been complicated due to morphological similarity. However, the partial overlap in morphological features may also involve hybrids, which are known to exist, but which have so far been poorly described. This study investigated spotted eagle nestlings in Estonia, pre-identifying them according to mitochondrial DNA, nape patch and the appearance of their parents. Relative size of bill and toes (corrected for nestling growth) enabled us to separate the smaller A. pomarina, but hybrids were as large as A. clanga. All three groups had distinct plumages with hybrids being intermediate; the separation was clearest using both size and plumage indices. In all, 164 of 168 birds were correctly identified using a three-step procedure, separating: (1) A. clanga, having no nape patch; (2) 9 of 13 hybrids according to plumage index; and (3) the remaining hybrids by their large size (at least two features over the mean+2 SD values of A. pomarina). Knowing the sex helped to interpret size, but not plumage, characteristics, and its overall value for assisting identification was not high. The results support the view that spotted eagles with intermediate characters are usually hybrids which can be recognised by their appearance.Communicated by F. Bairlein     

Flight strategies of migrating raptors; a comparative study of interspecific variation in flight characteristics

The comparison of flight styles and flight parameters of migrating raptors in Israel revealed the following. (1) Climbing rate in thermal circling did not differ between species, indicating that chiefly the strength of thermal updrafts determined the climbing rate and that morphological features were less relevant. (2) In interthermal gliding, air speed was positively and gliding angle negatively related to the species' average body mass. Heavier species glided faster and had smaller gliding angles. (3) In soaring and gliding flight, cross-country speed relative to the air was positively related to the species' body mass; it was obviously the result of the gliding ability increasing with body mass. (4) Eagles and buzzards used soaring and gliding flight for more than 95% of the observation time. Additional soaring in a straight line whilst gliding was extensively used by the Steppe Eagle Aquila nipalensis, Lesser Spotted Eagle Aquila pomarina and Booted Eagle Hieraætus pennatus and even more frequently by the resident species, the Griffon Vulture Gyps fulvus and Shorttoed Eagle Circaetus gallicus. Smaller species, such as the Levant Sparrowhawk Accipiter brevipes, harriers (Circus sp.) and small falcons (Falco sp.). showed the highest proportion of flapping and gliding flight (9–33%). (5) In a comparison of the flight parameters and proportions of flight styles, a cluster analysis distinguished two main groups: The first consisted of Montagu's Harrier Circus pygargus, Pallid Harrier Circus macrourus, Levant Sparrowhawk and small falcons; their flight behaviour was characterized by both the high proportion of flapping and the low gliding performance. The second group comprised the typical soaring migrants: Steppe Eagle, Lesser Spotted Eagle, Booted Eagle, Steppe Buzzard Buteo buteo vulpinus, Honey Buzzard Pernis apivorus and Egyptian Vulture Neophron percnopterus, and they had very similar flight behaviour and were closely clustered. The Black Kite Milvus migrans and Marsh Harrier Circus aeruginosus were intermediate between typical soarers and flappers. The two resident species, Griffon Vulture and Short-toed Eagle, were grouped separately from the soaring migrants.     

Origin and formation of the Spanish Imperial Eagle ( Aquila adalberti )

A review of the paleontological records of the Eastern Imperial Eagle (Aquila heliaca) and the Spanish Imperial Eagle (Aquila adalberti) in the context of the paleoecological environment in Eurasia during the Pleistocene and Holocene epochs is presented. The Eastern Imperial Eagle expanded its range in Eurasia during the last Pleistocenic glaciation favoured by the expansion of the steppes. The first records of Spanish Imperial Eagles are from the Late Pleistocene and Early Holocene in the eastern Iberian Peninsula, and their distribution seems to have been limited to the distribution areas of Mediterranean vegetation and the European rabbit. Individuals of migrant A. heliaca could have reached the Iberian Peninsula at the end of the Pleistocene–beginning of the Holocene. These individuals could have adapted to the Mediterranean ecosystem, subsequently specializing in a diet of rabbit, a prey which is in abundance all year round. Due to the availability of such prey, A. heliaca would become more sedentary. These individuals may have overcome their breeding phenology and paired up assortatively, becoming genetically separate from the migrant populations and initiating the speciation mechanisms for sympatry or parapatry that resulted in A. adalberti. This is one possible mechanism. These findings reported here support the recent age of divergence between both taxons, and the incipient speciation supports its taxonomical considerations as a semi-species. The study reported here complies with the current laws of Spain.     

Winter diet and lead poisoning risk of Greater Spotted Eagles Clanga clanga in southeast Spain

ABSTRACT

Capsule: Diet analysis revealed high lead exposure for Greater Spotted Eagles Clanga clanga wintering in southeast Spain.

Aims: To describe the diet composition of the endangered Greater Spotted Eagle in a wintering area located in southeast Spain, and determine lead ammunition exposure through analysis of regurgitated pellets and prey remains.

Methods: Between 2008 and 2018, a total of 26 pellets, 29 prey remains and 10 direct predation observations were collected in El Hondo Natural Park, Spain. All the pellets and 10 prey remains were analysed with X-ray in order to detect metal from ammunition.

Results: Greater Spotted Eagles fed mainly on birds, with 18 different species accounting for 73.1% of prey items and 66.1% of biomass consumed. The most frequent species identified were Common Moorhen Gallinula chloropus (23.1%), rats Rattus spp. (15.4%) and Common Teal Anas crecca (8.9%). Ammunition was detected in 42.3% of regurgitated pellets and in 40.0% of prey remains analysed. Of those containing ammunition, lead shot was found in 63.9% of pellets and 25.0% of prey remains.

Conclusion: High lead shot presence in pellets and prey remains of wintering Greater Spotted Eagles in southeast Spain warns of a high risk of lead poisoning. Factors such as feeding behaviour, the large space–time overlap between the raptor presence and the waterbird hunting season and non-compliance with the ban on the use of lead ammunition are likely contributing to high lead exposure.     

Identifying key habitats for the conservation of Bonelli's Eagle Aquila fasciata using radiotracking

Identifying the priority habitats of endangered species is crucial to implementing effective conservation actions. We characterize the key habitats used by Bonelli's Eagle Aquila fasciata, an umbrella and flagship species that is endangered in Mediterranean countries. We radiotracked 17 breeding individuals (10 males and seven females) in Catalonia (NE Iberian Peninsula) and used compositional analysis to determine the key habitats in home‐ranges of both sexes. The main habitats identified within the home‐range area were scrubland, coniferous forests, cropland, sclerophyllous forests, rock outcrops and urban areas, with little difference in habitat use between the sexes. Bonelli's Eagles preferred rocky habitats as breeding areas and scrubland as foraging areas, as these hold the highest abundance of their main prey, Rabbits Oryctolagus cuniculus and Red‐legged Partridges Alectoris rufa. Habitat selection varied seasonally in foraging areas: scrubland was the most preferred habitat type during the breeding season, whereas rocky areas were preferred during the non‐breeding season (although scrubland was also highly selected). Urban areas were avoided both as breeding and as foraging areas. Home‐range size was inversely correlated with the proportion of scrubland, suggesting that this is a key habitat for Bonelli's Eagle. To conserve this species effectively, policies that ensure the preservation of the cliffs used as breeding sites, as well as suitable management of the scrubland used for foraging, should be implemented in the areas inhabited by this species. The promotion of traditional land uses and management techniques that will enhance open areas in Mediterranean landscapes should in the future play an essential role in the conservation of Bonelli's Eagle in Mediterranean habitats.     

Lack of allozyme variation in the Spanish Imperial Eagle Aquila adalberti

The breeding population of the Spanish Imperial Eagle Aquila adalberti is reduced to 126 pairs located in the southwestern quadrant of the Iberian Peninsula. Protein electrophoresis was used to determine levels of genetic variation in the seven extant subpopulations of the species. Seventeen proteins encoded by 22 putative loci showed no variation among all the individuals which were analysed. The population crashed at the beginning of this century, but the long generation time of the species makes it improbable that a population bottleneck was the only cause of the lack of genetic variation. As an alternative explanation, a natural background of low variation cannot be discounted.     

Genetic differentiation and inferred dynamics of a hybrid zone between Northern Spotted Owls (Strix occidentalis caurina) and California Spotted Owls (S. o. occidentalis) in northern California

Genetic differentiation among Spotted Owl (Strix occidentalis) subspecies has been established in prior studies. These investigations also provided evidence for introgression and hybridization among taxa but were limited by a lack of samples from geographic regions where subspecies came into close contact. We analyzed new sets of samples from Northern Spotted Owls (NSO: S. o. caurina) and California Spotted Owls (CSO: S. o. occidentalis) in northern California using mitochondrial DNA sequences (mtDNA) and 10 nuclear microsatellite loci to obtain a clearer depiction of genetic differentiation and hybridization in the region. Our analyses revealed that a NSO population close to the northern edge of the CSO range in northern California (the NSO Contact Zone population) is highly differentiated relative to other NSO populations throughout the remainder of their range. Phylogenetic analyses identified a unique lineage of mtDNA in the NSO Contact Zone, and Bayesian clustering analyses of the microsatellite data identified the Contact Zone as a third distinct population that is differentiated from CSO and NSO found in the remainder of the subspecies' range. Hybridization between NSO and CSO was readily detected in the NSO Contact Zone, with over 50% of individuals showing evidence of hybrid ancestry. Hybridization was also identified among 14% of CSO samples, which were dispersed across the subspecies' range in the Sierra Nevada Mountains. The asymmetry of hybridization suggested that the hybrid zone may be dynamic and moving. Although evidence of hybridization existed, we identified no F1 generation hybrid individuals. We instead found evidence for F2 or backcrossed individuals among our samples. The absence of F1 hybrids may indicate that (1) our 10 microsatellites were unable to distinguish hybrid types, (2) primary interactions between subspecies are occurring elsewhere on the landscape, or (3) dispersal between the subspecies' ranges is reduced relative to historical levels, potentially as a consequence of recent regional fires.     

Strong territoriality and weak density‐dependent reproduction in Lesser Spotted Eagles Clanga pomarina

We assessed whether populations of the migratory, philopatric, territorial Lesser Spotted Eagle Clanga pomarina are regulated through territoriality and density‐dependent reproduction rates. In the north‐western part of the distribution to the east of the Baltic Sea, territories were spaced regularly and consistently between years. We did not find strong support for an improvement of reproductive output with an increase in distance to the nearest neighbour or with a decrease of the number of conspecifics within a 2‐km radius around nest‐sites. Eagles differed greatly in territory spacing across three studied geographical areas, but breeding performance did not follow the same pattern. Performance of birds at the northern limit of their distribution did not differ from that in an adjacent southern area. Moreover, breeding performance fluctuated synchronously across different geographical areas, perhaps indicating climatic spatial autocorrelation or trophic interactions with synchronous vole population fluctuations over large areas. Our data suggest population regulation through territoriality but do not identify density‐dependent breeding performance in this internationally protected raptor. Population density may be a good criterion for the selection of priority sites for conservation, but synchronous fluctuations in reproductive success over large geographical areas suggest that habitat conservation should similarly be focused at large scales.     

Status of Golden Eagle Aquila chrysaetos in Britain in 2015

Capsule: A complete survey of Golden Eagles Aquila chrysaetos in Britain in 2015 found that the population had increased by 15% since 2003 to 508 territorial pairs.

Aims: The survey aimed to investigate the population size, distribution and breeding success of Golden Eagles in Britain, and to compare results with similar surveys since the early 1980s.

Methods: Every home range was visited on a minimum of three occasions between January and August 2015. First, to look for eagles or signs of their presence (January–March), then to look for evidence of breeding or further checks for occupation (April–June) and finally to record productivity of nesting pairs (July–August).

Results: The figure of 508 territorial pairs represents a 15% increase in the population from 442 pairs in 2003. The proportion of home ranges occupied was 70%. The largest increases in the proportion of occupied home ranges were in south-central Highlands (71%), northern moors and flows (38%) and northwest Highlands (29%), with modest increases of up to 10% in the other regions. Productivity was lower in 2015 than in 2003, and there was significant variation in breeding success between regions.

Conclusion: The British Golden Eagle population has increased since 2003, although the species is absent from England and Wales. The population now meets the abundance target identified to define favourable conservation status in Scotland, and while home range occupancy has increased there is regional variation, with some regions falling below the target levels. A combination of increased annual monitoring and tagging of eagles, as well as the introduction of new legislation, may serve as effective deterrents against persecution of eagles thus facilitating this population increase. However, concerns remain over low levels of home range occupancy particularly in the east Highlands, but also the proportion of sub-adult pairs holding territory in that region and in the south-central Highlands. Persecution associated with grouse moor management has been highlighted as a particular population constraint in both of these areas.     

Spatial distribution and breeding territories of Bonelli’s Eagle Aquila fasciata in the western Anti-Atlas Mountains,Morocco

The North African population of Bonelli’s Eagle Aquila fasciata (Vieillot, 1822) is limited to the south by the northern fringe of the Sahara Desert. This study provides the first data on the spatial distribution and density of breeding Bonelli’s Eagles in south-west Morocco, at the southern limit of their breeding distribution in the Western Palearctic. We used broad-scale sampling to investigate spatial patterns in occupancy of territorial pairs of Bonelli’s Eagles in an area of ～29 715 km2 in the western Anti-Atlas Mountains, southern Morocco, during 2016–2018. We found 28 nesting territories containing 40 used nests, heterogeneously distributed in areas of high topographic variation, from 60 to 1 890 m asl. The average nearest-neighbour nest distance was 14.12 ± 9.90 km and varied from 2.65 km in the north-west to 37.80 km in the pre-Saharan lands in the south-west portion of the study area. This work shows the importance of the western Anti-Atlas Mountains as one of the most significant strongholds of the species in Morocco. However, there is a need for systematic analyses of the different factors affecting the distribution of the species to implement conservation actions of this peripheral population.     

The magnitude and timing of migration by soaring raptors, pelicans and storks over Israel

The magnitude and timing of the autumn and spring migrations of 35 species of medium-and large-sized raptors, White Pelicans Pelicanus onocrotalus and White Storks Ciconia ciconia were studied in Israel. Observations were carried out from the ground by a line of observers covering most of the width of Israel across the line of migration and by radar. There was a high correlation between the counts obtained by ground observers and by radar. On average, about half a million raptors (mainly Lesser Spotted Eagles Aquila po-marina, Honey Buzzards Pernis apivorus and Levant Sparrowhawks Accipiter brevipes), 250,000 White Storks and 70,000 White Pelicans passed during autumn, and about a million raptors (mainly Honey Buzzards, Steppe Buzzards Buteo vulpinus, Steppe Eagles Aquila nipalensis and Black Kites Milvus migrans) and 450,000 White Storks passed during spring. Peak numbers were higher–over a million raptors and half a million White Storks. There was high interyear variation in the number of migrants recorded during the study, probably caused by weather and counting efforts. For some species, the whole world (Lesser Spotted Eagle and Levant Sparrowhawk) or Palaearctic (White Pelican) population passes over Israel during migration, allowing an estimate of the world populations of these species. Mean dates of arrival of most raptors are highly predictable, with confidence limits ranging between 1.5 and 5.5 days. The migration periods of White Storks and White Pelicans are longer and their mean day of appearance is less predictable (confidence limits range from 4.2 to 13.8 days). During autumn, 90% of the migrating populations of nocking species, such as Levant Sparrowhawk, Lesser Spotted Eagle, Honey Buzzard and Red-footed Falcon Falco vespertinus, pass within 13, 15, 16 and 18 days, respectively, while nonflocking species, such as Egyptian Vulture Neophron percnopterus, Marsh Harrier Circus aeruginosus and Short-toed Eagle Circaetus gallicus, generally take twice as long to pass. Similar passage periods were recorded in spring. For most species, the autumn migration period was longer than the spring migration period, probably because in autumn adults move before the young birds. Three factors affected the timing and spread of the migration wave: age at first breeding, diet and size of the breeding area.     

The use of thermals by soaring migrants

The use of thermals during the spring and autumn migration across Israel by four species of soaring birds (White Pelican Pelecanus onocrotalus, White Stork Ciconia ciconia, Lesser Spotted Eagle Aquila pomarina and Honey Buzzard Pernis apivorus) was studied by monitoring them with a motorized glider, light aircraft and radar. This is the first study in which soaring migrants have been followed in flight for any length of time and their flight performance has been recorded directly. The birds flew in an average height band between 344 and 1123 m above ground level. Altitude increased from the morning towards noon and decreased again in the afternoon. Average velocities were 29.2 km/h, 38.7 km/h, 50.9 km/h and 45.2 km/h for White Pelicans, White Storks, Lesser Spotted Eagles and Honey Buzzards, respectively. Atmospheric conditions had a major effect on flight velocity. White Storks showed a positive correlation between the flight velocity and the height between the base and top of the thermals. In White Pelicans, there was a correlation between velocity and mean height. Wing load (body mass/wing area) was positively related to the climbing time in thermals and negatively related to the mean height used by a species. There was also a positive, but not significant, relationship between wing load and velocity. Soaring birds appreciably extend the distance covered in migration in relation to the straight line from their breeding to wintering grounds (by 48–91%). The increased distance, caused through circumventing sea areas, ranged between 22–34%, while the increase resulting from soaring accounted for an additional 22–57% of the route.