Diet of the golden eagle Aquila chrysaetos during the breeding season in Sweden

During a five-year period, 1975–1979, a total of 2881 prey individuals of 65 prey species were collected at 162 golden eagle nests from northern Sweden and from the island of Gotland. In northern Sweden birds are taken in higher numbers than mammals but calculated as weight the two categories are of equal importance, The main prey during the breeding season are capercaillie, black grouse, willow grouse, ptarmigan, mountain hare and reindeer fawns which together form 91% of the total food biomass. The capercaillie and the black grouse are taken more in the southern part of the coniferous region than in the northern. In contrast, in northern areas, reindeer fawns are more preyed upon than in the South, Ptarmigan and willow grouse are the most commonly captured prey species in mountain areas. The total number of reindeer fawns taken (dead and/or alive) by the Swedish golden eagle population during one summer is estimated at 600 individuals. On Gotland the golden eagles take mammals more often than in its northern distribution area. Rabbit and hedgehog arc the most important species.     

Prey abundance and reproductive success of the golden eagle Aquila chrysaetos in Sweden

Reproductive output of the golden eagle Aquila chrysaetos (L.), was studied in two areas within the species distribution in northern Sweden during 1975–1980. Reproductive success was compared with the abundance (based on hunting bag statistics) of small game prey species and with the microtine cycles. The proportion of golden eagle pairs with successful breeding and the number of young produced per occupied territory varied greatly between years (21–85% and 0.27–1.24, respectively). In the northern study area I found a significant correlation between the proportion of pairs with successful breeding versus total hunting bag of small game species. There were also significant correlations between vole density and breeding success one year later. This was not the case in the southern study area, mainly due to a good reproductive year for golden eagles in 1977 when small game species were scarce. The good reproductive output in 1977 may be explained by favourable weather conditions that spring. Whether breeding occurs or not is probably determined by prey abundance early in spring just before the golden eagle female lays her eggs.     

Short-term oscillations in avian molt intensity: evidence from the golden eagle Aquila chrysaetos

From a year-long study of molt in the golden eagle Aquila chrysaetos , we recorded 2069 contour feathers replaced in 137 d (6 May-19 September). Very few contour feathers were lost outside this period. From precise daily counts of feathers lost, and using time series analysis, we identified short-term fluctuations (i.e., 19-d subcycles) around a midsummer peak (i.e., a left-skewed normal distribution). Because these subcycles have never before been reported and because the physiological basis for many aspects of avian molt is poorly known, we offer only hypothetical explanations for the controls responsible for the subcycles.     

Fifteen microsatellite loci characterized in the golden eagle Aquila chrysaetos (Accipitridae,Aves)

Polymorphic microsatellite loci were identified in order to study golden eagle (Aquila chrysaetos) population fragmentation. Twenty‐six published Aquila and eight published Haliaeetus microsatellite loci were tested for polymorphism in A. chrysaetos. Fifteen loci were polymorphic with between two and six alleles detected per locus. Observed heterozygosity ranged from 0.15 to 0.77 among 177 unrelated individuals from Scotland. There was no evidence for null alleles. Two pairs of loci (Hal‐10 & Aa15 and Hal‐10 & Aa26) displayed linkage disequilibrium.     

Taphonomic signature of golden eagles (Aquila chrysaetos) on bone prey remains

Abstract

The golden eagle (Aquila chrysaetos) is one of the most important birds of prey in the Northern Hemisphere. This raptor is used to building large nests in high cliffs to which they return for several breeding years accumulating important amounts of their prey skeletal remains. This makes the golden eagle one of the major predators able to accumulate faunal remains in archaeological sites. Despite this fact, the taphonomic signature of golden eagles has not been properly characterized. Here we present the analysis of ingested and non-ingested faunal remains predated and accumulated by this raptor in two different nesting areas from the Iberian Peninsula. Results show how the faunal taxonomic record may vary depending on the ecological zone. Leporids and terrestrial carnivores are the best represented. The observed anatomical representation, breakage and bone surface modification patterns are discussed for different taxa. The taphonomic pattern varies depending on the type of prey and the origin of skeletal materials (non-ingested vs. pellets). Finally, after comparing our results with marks left by other predators, several characteristic features are noted to recognise golden eagles as agents of animal bones accumulations in the fossil record.     

Nonmotorized recreation and motorized recreation in shrub‐steppe habitats affects behavior and reproduction of golden eagles (Aquila chrysaetos)

Different forms of outdoor recreation have different spatiotemporal activity patterns that may have interactive or cumulative effects on wildlife through human disturbance, physical habitat change, or both. In western North America, shrub‐steppe habitats near urban areas are popular sites for motorized recreation and nonmotorized recreation and can provide important habitat for protected species, including golden eagles. Our objective was to determine whether recreation use (i.e., number of recreationists) or recreation features (e.g., trails or campsites) predicted golden eagle territory occupancy, egg‐laying, or the probability a breeding attempt resulted in ≥1 offspring (nest survival). We monitored egg‐laying, hatching and fledging success, eagle behavior, and recreation activity within 23 eagle territories near Boise, Idaho, USA. Territories with more off‐road vehicle (ORV) use were less likely to be occupied than territories with less ORV use (β = ?1.6, 85% CI: ?2.8 to ?0.8). At occupied territories, early season pedestrian use (β = ?1.6, 85% CI: ?3.8 to ?0.2) and other nonmotorized use (β = ?3.6, 85% CI: ?10.7 to ?0.3) reduced the probability of egg‐laying. At territories where eagles laid eggs, short, interval‐specific peaks in ORV use were associated with decreased nest survival (β = ?0.5, 85% CI: ?0.8 to ?0.2). Pedestrians, who often arrived near eagle nests via motorized vehicles, were associated with reduced nest attendance (β = ?11.9, 85% CI: ?19.2 to ?4.5), an important predictor of nest survival. Multiple forms of recreation may have cumulative effects on local populations by reducing occupancy at otherwise suitable territories, decreasing breeding attempts, and causing nesting failure. Seasonal no‐stopping zones for motorized vehicles may be an alternative to trail closures for managing disturbance. This study demonstrates the importance of considering human disturbance across different parts of the annual cycle, particularly where multiple forms of recreation have varying spatiotemporal use patterns that create human–wildlife interactions.     

Factors constraining the distribution of Golden Eagles Aquila chrysaetos in Scotland

Capsule Between 1992 and 2003 persecution appeared to be the main influential factor.

Aims To utilize temporal changes in the distribution and occupation of Golden Eagle territories in Scotland between the 1992 and 2003 national censuses to assess potential causes of regional and national population trends, by examining spatial associations with a number of potential constraints on the population.

Methods The distribution of occupied and vacant territories in the 1992 and 2003 censuses were entered as layers in a Geographical Information System (GIS), along with boundaries of biogeographical regions (Natural Heritage Zones) for regional analyses. Additional GIS layers were created for potential factors that may constrain the eagle population: the distribution and abundance of persecution incidents, new commercial conifer forests, popular mountains for hillwalkers (as surrogates for recreational activity), and the density of sheep and Red Deer (as surrogates for carrion abundance), drawn from comparable time periods to the national eagle censuses. Analyses then looked for spatial associations between eagle territory status and those constraint factors that may have influenced change in territory status.

Results We found little evidence to suggest that recreational disturbance was influential on the occupation of Golden Eagle territories, although some local effects may have occurred and further analyses are warranted. We could find evidence of only a limited number of territories having being abandoned recently due to the planting of commercial conifer forests. We also rejected the hypothesis that changes in territory occupation between national Golden Eagle censuses were influenced by change in carrion abundance. By contrast, results were consistent with the hypothesis that persecution was influential in the observed change in territory occupation between censuses, so that occupied eagle territories tended to decline where persecution was probably still influential and tended to increase where persecution had probably declined.

Conclusion In accordance with earlier predictions based on models of the demographic influence of persecution, in the central and eastern Highlands where grouse moor management predominates, the eagle population continued to decline to levels where increasingly large areas of suitable habitat are unoccupied by breeding pairs.     

Using probability of occurrence to assess potential interaction between wind farms and a residual population of golden eagle Aquila chrysaetos in NW Spain

We evaluate the areas with potential negative impacts in a golden eagle population derived of the development of wind farms. At present, the entire golden eagle Galician population (5–6 pairs) is located within an area of about 2,000 km². Grid squares of 10 × 10 km UTM in the province were scored for current and future wind turbine density and probability of occurrence of golden eagle. This probability was obtained using cartographic models of habitat selection for two different historic periods. Potential risk index (PRI) was calculated for each grid square by multiplying the wind turbine density score by the probability of occurrence score. With the PRIs obtained a cartographic model of potential impact of wind farms on the golden eagle population was constructed. No significant correlation was observed between current wind turbine density and the probability of occurrence of golden eagle. A significant positive correlation was observed between current and future wind turbine density and the probability of occurrence of golden eagle. The areas with highest potential risk are eastern and the central mountains of Ourense where the species breeds. The risk model presented could be applied to future wind farm proposals and monitor potential interactions of golden eagles with wind farms in the Province of Ourense.     

Hemoglobin of the golden eagle (Aquila chrysaetos, Accipitriformes): amino acid sequence of the alpha A- and beta chains of the principal component

The primary structures of the alpha A- and beta-chains from the major hemoglobin component of Golden Eagle (Aquila chrysaetos) are given. By homologous comparison, Greylag Goose (Anser anser) hemoglobin and Golden Eagle alpha A-chains differ by 17 amino acids or 19 nucleotides (2 two-point mutations), beta-chains by 9 exchanges. Five substitutions have modified alpha 1 beta 1-contacts, one substitution, one alpha 1 beta 2-contact and one alpha 1 alpha 1-contact. Differences by homologous comparison to other hemoglobins of birds are discussed.     

Mitochondrial DNA analysis reveals Holarctic homogeneity and a distinct Mediterranean lineage in the Golden eagle (Aquila chrysaetos)

The Golden eagle (Aquila chrysaetos) is among the most widespread of the birds of prey, covering basically the whole Palaearctic from Europe and North Africa through Asia and Japan, to the North American continent. Only few studies have addressed the species’ genetic structure and the consequences of its demographic history so far, and none of them has covered larger areas of the distribution range. Our present study aims at closing this gap. Based on 283 samples (mostly feathers collected in the field or from museum collections) across the species’ distribution, but with a focus on Europe, we uncover the phylogeography of the Golden eagle. Results imply a phylogeographic split between mainly Northern Europe, Continental Asia, Japan and North America on the one hand and Central–Southern Europe on the other. The observed pattern is likely to be caused by the Last Ice Age, when the population survived in two reproductively isolated glacial refugia. Repopulation of Northern Europe occurred from a presumed Asian refugium, whereas the Alpine range was probably repopulated from a refugium in the Mediterranean region. In Eastern Europe, the Mediterranean and Alpine region we find a co‐occurrence of both lineages that heavily influences the local genetic diversity. This pattern is unlike that in most other large raptors in which usually a western and an eastern Eurasian lineage have been recovered.     

Regional and temporal variations in prey selected by Golden Eagles Aquila chrysaetos during the nestling period in Japan

We examined regional and temporal variations in prey selection by Golden Eagles Aquila chrysaetos during the nestling period in Japan. We made direct video recordings of a pair of Golden Eagles in Akita prefecture as they delivered prey to the nest for two consecutive nestling periods. We also assembled data from previous studies in Japan, eventually obtaining 14 data sets with which we compared prey composition during nestling periods. Among them, four sets of data were recorded daily by video and used to investigate the temporal change in prey selection and the amount delivered to the nest. The prey item composition varied considerably among the data sets. Japanese Hares Lepus brachyurus were predominantly selected in three data sets, reflecting the lowest dietary breadths that were determined by prey composition. Data sets with higher dietary breadths consisted mainly of Japanese Hares, snakes and Copper Pheasants Syrmaticus soemmerringii . Temporal change in prey selection during nestling periods showed marked variation, but similarities were found in later deliveries of snakes and in total prey weights (83.7–89.9 kg) delivered to successfully fledged broods. Taken together, our results suggest that during nestling periods Golden Eagles in Japan specialized on Japanese Hare. Diet breadth increased through feeding predominantly on snakes, a temporarily available prey, to satisfy the breeding dietary requirement. Regionally varied temporal prey selection may be a key factor for sustaining Eagle populations in the forested mountain habitats of Japan, where prey and habitat conditions change dramatically during the breeding season.     

Long‐term breeding demography and density dependence in an increasing population of Golden Eagles Aquila chrysaetos

Few studies have quantified the dynamics of recovering populations of large raptors using long‐term, spatially explicit studies. Using data collected over 37 years in the western Italian Alps, we assessed the trends in distribution, abundance, fecundity and breeding population structure of Golden Eagles Aquila chrysaetos. Using the spatial distribution of territory centroids in 2007, we found that the spatial distribution of eagle territories was over‐dispersed up to 3 km. Although population size and total productivity increased from 1972 to 2008, the proportion of pairs that laid eggs showed a strong decline, falling to no more than 50% after 2003. On average, 15% of successful nests produced two fledglings, and productivity also declined over time. No significant relationship between population growth rate and total population size was detected, but the percentage of pairs that bred and breeding success showed evidence of density dependence, as they declined significantly with increasing density. Our results suggest that density dependence, operating across heterogeneous habitats, is currently regulating this population, while the carrying capacity may still be increasing. This may explain the apparent paradox of reduced breeding effort despite increasing total productivity.     

金雕肾脏的组织学观察

利用生物显微技术观察了金雕Aquila chrysaetos肾脏的组织结构.结果表明,金雕肾实质由许多肾小叶构成,每个肾小叶可分为皮质和髓质两部分.肾单位由一个肾小体和一条与其相连的肾小管构成.肾小体由肾小囊和肾小球组成.肾小管分为近曲小管、髓袢、远曲小管和连接小管.集合管分为小叶周集合小管和髓质集合管两部分.具有发达的极周细胞.     

Spatial distribution of undulating flight displays of territorial Golden Eagles Aquila chrysaetos in Lewis,Scotland

ABSTRACT

Capsule: The undulating display flight of Golden Eagles Aquila chrysaetos has a territorial function on current consensus: we found that displays could occur at any location within a home range of territorial birds and were not more frequent at the territorial limits (as documented by a previous study) or around the nest site.

Aims: To test the null hypothesis that display activity does not spatially differ within the home range of territorial Golden Eagles.

Methods: We used 1488?h of observations of Golden Eagles between April 2003 and October 2004 (excluding November through January inclusive) on the Isle of Lewis, northwest Scotland involving primarily four territories. Territorial boundaries and nest sites were determined by the behaviour of the focal territorial birds. All flight activity was cast into three spatial categories (near-boundary, near-nest and elsewhere) and the relative occurrence of displays was referenced by overall flight activity recorded in these spatial categories.

Results: We failed to reject the null hypothesis. Prior findings of greater display rate at territory limits were not confirmed. Territorial Golden Eagles apparently displayed wherever they happened to be in their home range. There was no difference in display frequency between successful and failed breeding pairs and, within pairs, between successful and failed breeding seasons. Monthly changes in display activity did not differ from monthly changes in the presence of ‘intruding’ sub-adults. A peak in non-territorial bird activity in August and September was not reflected by a peak in display, however, we could not distinguish recently fledged ‘non-threatening’ birds in this period.

Conclusions: Undulating flight displays of Golden Eagles focused neither on territory boundaries nor the nest. Displays may be spontaneous or occur in response to the detection of potential trespassers or neighbours, however, we could not rule out any role of pair-bonding.     

Genetic signatures of population change in the British golden eagle (<Emphasis Type="Italic">Aquila chrysaetos</Emphasis>)

The golden eagle (Aquila chrysaetos) was once widely distributed in the uplands of the British Isles, but is now extinct in Ireland, and largely confined to the highlands and islands of Scotland. As the precise extent and severity of the reduction in population size are unclear, it is important to understand how the population was affected by the decline. We therefore genotyped 13 polymorphic microsatellite loci in 172 individuals from the contemporary British population and compared their genetic diversity to 70 British and 9 Irish museum specimens. Despite the recent population decline, there is only slight evidence for a concomitant loss of genetic variation. Instead, two likelihood-based Bayesian methods provided evidence for a severe ancient genetic bottleneck, possibly caused by the fragmentation of a large mainland European population and/or the founding effects of colonising the British Isles. As the population persisted despite this ancient bottleneck, our conclusion is that there is limited need for intervention to augment the present-day genetic diversity. The main short-term objective of conservation measures should be to increase population sizes by continuous safeguarding of individuals and habitat management. Finally, we also confirmed that, for management purposes, the species should be considered a single population unit and that the extinct Irish population was not differentiated from the British one.     

Genetic structure and viability selection in the golden eagle (<Emphasis Type="Italic">Aquila chrysaetos</Emphasis>), a vagile raptor with a Holarctic distribution

Molecular markers can reveal interesting aspects of organismal ecology and evolution, especially when surveyed in rare or elusive species. Herein, we provide a preliminary assessment of golden eagle (Aquila chrysaetos) population structure in North America using novel single nucleotide polymorphisms (SNPs). These SNPs included one molecular sexing marker, two mitochondrial markers, 85 putatively neutral markers that were derived from noncoding regions within large intergenic intervals, and 74 putatively nonneutral markers found in or very near protein-coding genes. We genotyped 523 eagle samples at these 162 SNPs and quantified genotyping error rates and variability at each marker. Our samples corresponded to 344 individual golden eagles as assessed by unique multilocus genotypes. Observed heterozygosity of known adults was significantly higher than of chicks, as was the number of heterozygous loci, indicating that mean zygosity measured across all 159 autosomal markers was an indicator of fitness as it is associated with eagle survival to adulthood. Finally, we used chick samples of known provenance to test for population differentiation across portions of North America and found pronounced structure among geographic sampling sites. These data indicate that cryptic genetic population structure is likely widespread in the golden eagle gene pool, and that extensive field sampling and genotyping will be required to more clearly delineate management units within North America and elsewhere.     

Genetic characteristics of endangered Japanese golden eagles (Aquila chrysaetos japonica) based on mitochondrial DNA D-loop sequences and karyotypes

Mitochondrial DNA D-loop sequences (472 bases) for endangered Japanese golden eagles (Aquila chrysaetos japonica) were investigated to evaluate-intrapopulational genetic variations. Among 23 golden eagles, including origin-known eagles caught in the wild and origin-unknown eagles, 10 variable sites were found in the 472 base-sequences. From the nucleotide substitutions, five haplotypes of D-loop sequences were identified, indicating the occurrence of at least three maternal lineages in golden eagles around Japan. Distribution patterns of D-loop haplotypes suggested a wide genetic communication between local populations around Japan prior to a recent habitat fragmentation and a decrease in the population size. In addition, cytogenetic analysis showed that a karyotype specific to the Japanese golden eagle is consistently 2n=62 including eight microchromosomes. Based on mitochondrial DNA and karyotype data, it is likely that golden eagle populations from Japan and the Korean Peninsula together form a common conservation unit. These results provide an important framework for conservation actions for Japanese golden eagle populations in zoos, and in situ reintroduction and translocation programs. Zoo Biol 17:111–121, 1998. © 1998 Wiley-Liss, Inc.     

Organochlorines and mercury in the eggs of Golden Eagles Aquila chrysaetos from Scotland

This paper documents the organochlorine levels found in unhatched eggs from 234 clutches of Golden Eagles Aquila chrysaetos obtained in Scotland during 1963-86. Organochlorine levels were highest in eggs from western coastal districts, somewhat lower in eggs from western inland districts, and lower still in eggs from eastern districts. These regional trends were associated with corresponding dietary differences.
Levels of HEOD declined in western districts during the period 1963-86, but not in eastern districts where they were low throughout. Levels of DDE declined generally, but significantly only in the east. In contrast, levels of PCBs increased generally, but significantly only in western inland districts.
No differences in organochlorine levels were found between clutches that produced no young and those that produced one young.
Mercury residues were examined in eggs from 66 clutches obtained during 1981-86. Low levels were detected in 10 out of 29 eggs from western coastal districts, in 2 out of 27 eggs from western inland districts, and in none out of 10 eggs from eastern districts.