Public perceptions of a white‐tailed sea eagle (Haliaeetus albicilla L.) restoration program

The historic persecution and decline of European raptor populations precipitated the use of reintroduction as a species restoration tool in the late twentieth century. One of the key requirements of the World Conservation Union reintroduction guidelines concerns the need for social feasibility studies to explore the attitudes of local human populations toward restoration and reintroduction proposals. Ahead of any formal proposals to reintroduce white‐tailed sea eagles to Cumbria, United Kingdom, we conducted a baseline public attitudinal survey (n = 300). We identified broad public support for this reintroduction, which transcended differences in the demographic, geographic, and employment profiles of the study cohort. There was public recognition that white‐tailed sea eagles could deliver a broad range of socioeconomic and environmental benefits with few detrimental impacts. Although the value of attitudinal surveys of this nature has been questioned, we would argue that they provide a useful baseline “snapshot” ahead of a more structured and focused reintroduction consultation. These results reinforce the emergence of public interest in the restoration of European raptors in the late twentieth and early twenty‐first century.     

Reproduction of the white-tailed sea eagle Haliaeetus albicilla in Sweden

Sixty-eight white-tailed sea eagle territories were studied on the Swedish Baltic coast in 1964–1982 and 22 territories in Swedish Lapland in 1976–1982. Older data were assembled for comparison. The breeding frequency of adult pairs was high in both study areas (ca. 90%). Median egg-laying dates were 17 March (Baltic) and 7 April (Lapland). Average clutch size and egg volume did not differ between samples from the Baltic taken between 1856 and 1982. Average clutch size was significantly smaller in Lapland (1.6 eggs) than on the Baltic coast (2.1 eggs). Clutch size in Lapland was positively related to carrion availability during March. Nestling survival was significantly lower in Lapland, due to starvation in broods of more than one young. Brood loss was significantly more frequent in Lapland. At the Baltic, nest success decreased from 75 to 22%, and brood size from 1.8 to 1.2, from the early 1950's to the mid 1960's. Nest success in 1976-1982 was significantly lower at the Baltic (26%) than in Lapland (45%), with a much larger proportion of consistently failing pairs. The proportion of eggs laid that resulted in fledged young was estimated at 16% at the Baltic and 39% in Lapland. It is concluded that egg production and nestling survival were suppressed by limited food supply and nest success by human interference in Lapland, and that the reproductive impairment of the Baltic population was due primarily to contamination with toxic substances, mainly DDE.     

Food of the white-tailed eagle Haliaeetus albicilla in Greenland

Six nests of white-tailed eagles in the southernmost Greenland were watched during the nestling period and food items recorded photographically by remote controlled cameras. The species composition of the food was representative even for the adult eagles' diet. Fish made up a major part of 90%, various bird species and arctic fox pups the remaining 10%. The total intake of an eaglet amounted lo 50 kg from hatching to fledging. The daily requirements of fledglings, some 800 g fish food, are equal to previously reported values for older birds. The rate of food consumption of eaglets is constant through most of the nestling period.     

Growth and demography of a re‐introduced population of White‐tailed Eagles Haliaeetus albicilla

White‐tailed Eagles Haliaeetus albicilla became extinct in Britain in 1918 following prolonged persecution. Intensive conservation efforts since the 1970s have included the re‐introduction of the species to Britain through two phases of release of Norwegian fledglings in western Scotland in 1975–85 and 1993–98. Population growth and breeding success have been monitored closely to the present day, aided by the use of patagial tags to individually mark most released birds as well as a high proportion of wild‐bred nestlings. This study reviews the growth and demography of this re‐introduced population, and makes comparisons with other European populations. For the first time, we compare the demographic rates of released and wild‐bred birds in the Scottish population. Breeding success in the Scottish population has increased over time as the average age and experience of individuals in the population have increased, and success tends to be higher where one or both adults are wild‐bred. Current levels of breeding success remain low compared with some other populations in Europe, but similar to those in Norway where weather conditions and food availability are likely to be most similar. Survival rates in Scotland are similar to those recorded elsewhere, but survival rates of released birds are lower than those of wild‐bred birds, especially during the first 3 years of life. Despite the effect of lower survival rates of released birds in limiting overall population growth rate, the recent rate of growth of the Scottish population remains high relative to other recovering populations across Europe. Differences in demographic rates of wild‐bred and released birds suggest that in future re‐introduction programmes, steps to maximize the success and output of the earliest breeding attempts would help ensure the most rapid shift to a population composed largely of wild‐bred birds, which should then have a higher rate of increase.     

Density‐dependent effects on reproductive performance in a recovering population of White‐tailed Eagles Haliaeetus albicilla

Understanding the mechanisms that shape density‐dependent processes and population dynamics is often essential for species conservation. Two key mechanisms of density‐dependent reductions in reproductive performance are a limited access to foraging habitats (the habitat heterogeneity hypothesis) and territorial aggression towards conspecifics (the interference competition hypothesis) at high population densities. Disentangling the relative importance of these mechanisms within populations below their carrying capacity is important for the evaluation of the success of conservation measures. However, relatively few studies have attempted to quantify the relative importance of both mechanisms for the reproductive performance of a population. Many raptor populations are ideal model systems to investigate density‐dependent effects because they are currently recovering from human‐induced reductions during the last decades. Using a 14‐year dataset, we combined analyses of individual reproductive performance with a mechanistic population model to investigate early signs of density‐dependent regulation in a population of White‐tailed Eagles Haliaeetus albicilla in north‐east Germany. We found a negative effect of the number of neighbouring breeding pairs and a positive effect of water surface area (as a proxy for the availability of favourable foraging habitat) on breeding success and on the average number of nestlings. The mean nearest neighbour distance between breeding pairs has decreased, and the mean distance of nests to the nearest water body has increased over the last 14 years. Moreover, the population model indicates that even though the population is still growing, carrying capacity could be reached at about 500–950 territorial pairs. These results suggest that the selection of nesting sites is determined by a trade‐off between the distance to favourable foraging habitat and the distance to neighbouring breeding pairs. To avoid increasing competition with conspecifics, due to continued population growth, breeding pairs seem to select increasingly suboptimal habitats. Therefore, our results suggest that the habitat heterogeneity and interference competition hypotheses are not necessarily mutually exclusive as mechanisms of density‐dependent population regulation, but can determine the reproductive performance of a raptor population simultaneously. Thus, a future decline in breeding success does not necessarily reflect a decrease in habitat quality but may rather be a consequence of density‐dependent mechanisms. This information may be useful for the interpretation of population trends and for the development of appropriate management strategies for recovering raptor populations.     

Mitochondrial DNA and nuclear microsatellites reveal high diversity and genetic structure in an avian top predator,the white‐tailed sea eagle,in central Europe

We analysed 123 white‐tailed sea eagles (Haliaeetus albicilla) from (primarily central) Europe with respect to variability and differentiation based on 499 bp of the mitochondrial control region and genotypes at seven unlinked nuclear microsatellites. Variability was high (overall expected heterozygosity, haplotype and nucleotide diversity being 0.70, 0.764 and 0.00698, respectively) and both marker systems showed a subdivision into two main genetic clusters (microsatellites) or haplogroups (mtDNA). In line with earlier analyses focusing on populations from northern and eastern Europe, as well as from Asia, we found a high level of admixture in Europe and no signs of a bottleneck – despite a severe decline of white‐tailed sea eagle populations during the 20^th century. Europe is thus a global stronghold for this species not only with respect to the number of breeding pairs but also regarding the proportion of species‐wide genetic diversity. Our dense sampling revealed a possibly clinal variation within central Europe from north‐west to south‐east that was reflected by the distribution of mtDNA haplotypes as well as the two microsatellite‐based clusters. This population differentiation in central Europe probably originated from a geographically structured postglacial colonization and was later enhanced by recent demographic fluctuations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 727–737.     

Isolation of 22 new Haliaeetus microsatellite loci and their characterization in the critically endangered Madagascar fish‐eagle (Haliaeetus vociferoides) and three other Haliaeetus eagle species

We isolated a total of 22 microsatellite loci from two Haliaeetus species: the Madagascar fish‐eagle (Haliaeetus vociferoides) and the bald eagle (Haliaeetus leucocephalus). Five loci were monomorphic in both the Madagascar fish‐eagle (n = 24–43) and the bald eagle (n = 2–8) but were found to be polymorphic in other Haliaeetus species. Haliaeetus loci have proved useful for investigating gene flow in Haliaeetus and Aquila eagles. Ten loci were polymorphic in the critically endangered Madagascar fish‐eagle and will be used to investigate the genetic population structure and mating system in this species.     

Spatial,seasonal and individual variation in the diet of White‐tailed Eagles Haliaeetus albicilla assessed using stable isotope ratios

Many raptor species are considered to be generalists, taking a range of prey species. However, longitudinal dietary records are often scarce, although necessary for characterizing niche width of species at population and individual levels. Quantifying raptor diets at large spatio‐temporal scales is often necessary for refining conservation efforts, although it can be particularly difficult and may involve a great effort by conventional means. Therefore, we adopted the analysis of stable isotopes in tissues of predators and their potential food sources as a complementary methodology for assessing animals' diet. We examined the isotopic composition (δ¹³C and δ¹⁵N) of White‐tailed Eagles Haliaeetus albicilla from Germany, Finland and Greenland to detect patterns of dietary variation and quantify diet composition. The isotopic analysis included liver and muscle samples from Eagles of the three populations together with 16 potential food sources in the German population. Our results suggested dietary differences between German and Greenlandic Eagles, in accordance with the availability of freshwater and marine habitats in each population. Within the German population, we found seasonal shifts in isotopic ratios, suggesting the birds responded to temporal changes in food availabilities, and age‐related isotopic differences, indicating different diets in adults and juveniles. Isotopic values of liver and muscle tissues collected from the same animal showed intra‐individual short‐term changes in the German and Finnish but not Greenlandic population. This suggests that local feeding niches of this generalist predator may vary with local food supplies, which determines the niche width (from generalist to specialist) at the individual level. Our results also revealed that game mammal carcasses constitute an important food source (29.5% of diet) for the German Eagle population during the winter half‐year corresponding to the hunting season. This result is of relevance to management and conservation because the White‐tailed Eagle and other raptor species are affected by the ingestion of lead ammunition from shot mammalian carcasses.     

Development and multiplex PCR amplification of novel microsatellite markers in the White‐tailed Sea Eagle,Haliaeetus albicilla (Aves: Falconiformes,Accipitridae)

We report the development of 14 novel polymorphic microsatellite markers cloned from the White‐tailed Sea Eagle, Haliaeetus albicilla, a formerly threatened raptor that has received much conservation attention throughout Eurasia. We also present a protocol for multiplex polymerase chain reaction (PCR) amplification of the loci. Among 40 unrelated H. albicilla individuals from southern Sweden, the markers produced two to eight alleles per locus, and average observed and expected heterozygosities were 0.463 and 0.468, respectively. We further present five microsatellite markers that appeared monomorphic in H. albicilla, but which may be of interest for use in other raptor species.     

Intrinsic factors drive spatial genetic variation in a highly vagile species,the wedge‐tailed eagle Aquila audax,in Tasmania

Knowledge of dispersal in a species, both its quantity and the factors influencing it, are crucial for our understanding of ecology and evolution, and for species conservation. Here we quantified and formally assessed the potential contribution of extrinsic factors on individual dispersal in the threatened Tasmanian population of wedge‐tailed eagle Aquila audax. As successful breeding by these individuals appears strongly related to habitat, we tested the effect of landscape around sampling sites on genetic diversity and spatial genetic variation, as these are influenced by patterns of dispersal. Similarly, we also tested whether habitat intervening sampling sites could explain spatial genetic variation. Twenty microsatellites were scored, but only a small proportion of spatial genetic variation (4.6%) could be explained by extrinsic factors, namely habitat suitability and elevation between sites. However, significant clinal genetic variation was evident across Tasmania, which we explain by intrinsic factors, likely high natal philopatry and occasional long‐distance dispersal. This study demonstrates that spatial genetic variation can be detected in highly vagile species at spatial scales that are small relative to putative dispersal ability, although here there was no substantial relationship with landscape factors tested.     

Impact of white‐tailed deer on the spread of Borrelia burgdorferi

There is a public perception that the white‐tailed deer Odocoileus virginianus (Artiodactyla: Cervidae) is the main reservoir supporting the maintenance and spread of the causative agent of Lyme disease, Borrelia burgdorferi. This study examines the pathogen prevalence rate of Borrelia in adult Ixodes scapularis (Ixodida: Ixodidae), the black‐legged tick, collected from white‐tailed deer and compares it with pathogen prevalence rates in adult ticks gathered by dragging vegetation in two contiguous counties west of the Hudson Valley in upstate New York. In both Broome and Chenango Counties, attached and unattached ticks harvested from white‐tailed deer had significantly lower prevalences of B. burgdorferi than those collected from vegetation. No attached ticks on deer (n = 148) in either county, and only 2.4 and 7.3% of unattached ticks (n = 389) in Broome and Chenango Counties, respectively, were harbouring the pathogen. This contrasts with the finding that 40.8% of ticks in Broome County and 46.8% of ticks in Chenango County collected from vegetation harboured the pathogen. These data suggest that a mechanism in white‐tailed deer may aid in clearing the pathogen from attached deer ticks, although white‐tailed deer do contribute to the spatial distribution of deer tick populations and also serve as deadend host breeding sites for ticks.     

Behavioral plasticity mitigates the effect of warming on white‐tailed deer

Climate change is expected to create novel environments in which extant species cannot persist, therefore leading to the loss of them and their associated ecological functions within the ecosystem. However, animals may employ behavioral mechanisms in response to warming that could allow them to maintain their functional roles in an ecosystem despite changed temperatures. Specifically, animals may shift their activity in space or time to make use of thermal heterogeneity on the landscape. However, few studies consider the role of behavioral plasticity and spatial or temporal heterogeneity in mitigating the effects of climate change. We conducted experiments to evaluate the potential importance of behavior in mediating the net effects of warming on white‐tailed deer (Odocoileus virginianus). We used shade structures to manipulate the thermal environment around feeding stations to monitor deer feeding activity and measure total consumption. In individual experiments where deer only had access to unshaded feeders, deer fed less during the day but compensated by increasing feeding during times when temperature was lower. In group experiments where deer had access to both shaded and unshaded feeders, deer often fed during the day but disproportionally preferred the cooler, shaded feeders. Our results suggest that deer can capitalize on temporal and spatial heterogeneity in the thermal environment to meet nutritional and thermal requirements, demonstrating the importance of behavioral plasticity when predicting the net effects of climate change.     

Natural and anthropogenic influences on the population structure of white‐tailed eagles in the Carpathian Basin and central Europe

European populations of the white‐tailed eagle Haliaeetus albicilla suffered a drastic decline during the 20th century. In many countries, only a few dozen breeding pairs survived or the species disappeared completely. By today, the populations have recovered, naturally or through restocking (e.g. in Scotland or the Czech Republic). In the Carpathian Basin, which is now a stronghold in southern Europe for the species in the southern part of the distribution range with more than 500 breeding pairs, only about 50 pairs survived the bottleneck. This region provides important wintering places for individuals arriving from different regions of Eurasia. In the present study, we investigated 249 DNA samples from several European countries, using 11 microsatellites and mitochondrial control region sequences (499 bp), to answer two main questions: 1) did the Carpathian Basin population recover through local population expansion or is there a significant gene flow from more distant populations as well? 2) Does the Czech population show signs in its genetic structure of the restocking with birds of unknown origin? Our microsatellite data yielded three genetically separate lineages within Europe: northern, central and southern, the latter being present exclusively in the Carpathian Basin. Sequencing of mitochondrial DNA revealed that there is one haplotype (B12) which is not only exclusive to the Carpathian Basin but it is frequent in this population. Our results suggest that in accordance with the presumably philopatric behaviour of the species, recovery of the Carpathian Basin population was mainly local, but some of the wintering birds coming from the northern and central populations contributed to its genetic composition as well. We detected considerably higher proportions of northern birds within the Czech Republic compared to the neighbouring areas, making it likely that parents of the reintroduced birds came from northern populations.     

Genetic structuring and secondary contact in the white‐chested Amazilia hummingbird species complex

Pleistocene climate cycles have been recognized to be a major driver of postglacial northward range expansion of North American bird populations. During glacial maxima, allopatric lineages that were reproductively isolated might have come into secondary contact with one another during expansion periods and the genetic signatures of past hybridization as a result of secondary contact events should produce detectable hybrid zones. The white‐chested hummingbirds Amazilia violiceps and A. viridifrons, constitute a species complex showing phenotypic similarity across its range. One exception is the subspecies found in the Central Depression of Chiapas (A. viridifrons villadai), which shares some plumage traits with the endemic but allopatric green‐fronted populations in Oaxaca. Phylogenetic relationships, taxonomy and species limits among violiceps, viridifrons and villadai have been controversial for decades. We assessed genetic structure of populations and introgression in this species complex by analysing 95 individuals at ten nuclear microsatellites and morphology. Bayesian analysis yielded four clusters. However, only two clusters generally match previously described mtDNA haplogroups, one parental taxon in the south (villadai) and a cluster with two admixed taxa (viridifrons and violiceps) that cannot be attributed to any pure parental population. High genetic admixture was recorded in the violiceps/viridifrons range, probably as a consequence of a postglacial northern expansion of violiceps. Signs of admixture and gene flow between violiceps/viridifrons and villadai were low. Historical and contemporary migration rates and Approximate Bayesian computations support a scenario of divergence with gene flow: a Pleistocene basal split separating A. violiceps and the other two clades are derived from a second split (villadai and viridifrons) or from a merger of violiceps and villadai into viridifrons due to gene flow.     

Genetic structure among greater white‐fronted goose populations of the Pacific Flyway

An understanding of the genetic structure of populations in the wild is essential for long‐term conservation and stewardship in the face of environmental change. Knowledge of the present‐day distribution of genetic lineages (phylogeography) of a species is especially important for organisms that are exploited or utilize habitats that may be jeopardized by human intervention, including climate change. Here, we describe mitochondrial (mtDNA) and nuclear genetic (microsatellite) diversity among three populations of a migratory bird, the greater white‐fronted goose (Anser albifrons), which breeds discontinuously in western and southwestern Alaska and winters in the Pacific Flyway of North America. Significant genetic structure was evident at both marker types. All three populations were differentiated for mtDNA, whereas microsatellite analysis only differentiated geese from the Cook Inlet Basin. In sexual reproducing species, nonrandom mate selection, when occurring in concert with fine‐scale resource partitioning, can lead to phenotypic and genetic divergence as we observed in our study. If mate selection does not occur at the time of reproduction, which is not uncommon in long‐lived organisms, then mechanisms influencing the true availability of potential mates may be obscured, and the degree of genetic and phenotypic diversity may appear incongruous with presumed patterns of gene flow. Previous investigations revealed population‐specific behavioral, temporal, and spatial mechanisms that likely influence the amount of gene flow measured among greater white‐fronted goose populations. The degree of observed genetic structuring aligns well with our current understanding of population differences pertaining to seasonal movements, social structure, pairing behavior, and resource partitioning.     

Molecular phylogeography of white‐lipped tree viper (Trimeresurus; Viperidae)

The white‐lipped tree viper (Trimeresurus albolabris) is one of the most common venomous snakes with medicine importance in South East Asia. To explore the genetic diversity, population structure and evolutionary history of Trimeresurus albolabris, we collected 98 samples from 27 localities covering its entire distribution. Two mitochondrial gene fragments (cyt‐b and ND‐4) and two nuclear genes (RAG‐1 and NT‐3) were sequenced and analysed. Bayesian inference and maximum‐likelihood methods were employed to reconstruct the phylogenetic relationships among populations based on the two mitochondrial fragments, and the median‐joining networks were depicted using nuclear genes. Divergence date and ancestral area were estimated, and the population demographic history was inferred. Both phylogenetic analyses consistently uncovered that Trimeresurus albolabris was monophyletics, with five geographically structured lineages. Divergence date and ancestral area estimation indicated that T. albolabris originated in northern Thailand and eastern Myanmar at c. 7.15 Ma. Population dynamics analyses showed the southern China lineage has experienced population expansion and contraction, but the others have not. Both the interglacial expansion and the highly heterogeneous habitats resulting from the uplift of the Plateau played a joint role in shaping the present distribution and population structure. The evolutionary history of T. albolabris can be explained by a pattern of two direction dispersal: first from North to South, and then from West to East.     

Genetic structure and phylogeography of European catfish (Silurus glanis) populations

The genetic structure of Silurus glanis (Europe's largest freshwater fish species) across most of its natural distribution was investigated using 10 microsatellite loci. The revealed levels of genetic diversity were much higher than previous allozyme and restriction fragment length polymorphism mitochondrial DNA analyses had shown; relative levels of variability among populations were however, in good agreement with the previous studies. Populations from large basins (Volga and Danube rivers) were the most polymorphic, while samples from the smaller Greek rivers, which are more prone to genetic bottleneck, exhibited the lowest levels of genetic diversity. Microsatellite multilocus genotyping permitted the assignment of individual fish to their population of origin with a score as high as 98.3%. Despite the great genetic differentiation of S. glanis populations, no consistent pattern of geographical structuring was revealed, in contrast to previous studies of European freshwater fish species. A model of isolation by distance seems more probable and a hypothesis of recent dispersion from only one glacial refugium is proposed. The discovery of the highest levels of microsatellite and mitochondrial diversity in the Volga sample and the presence of river connections, during the Pleistocene, between this area and all major areas of the present catfish distribution, place this refugium around the Ponto-Caspian region. Combining these data with those from previous studies, a number of markers are now available to monitor wild and hatchery populations even at the individual level.     

Non-invasive sex identification of the white-bellied sea eagle (Haliaeetus leucogaster) through genetic analysis of feathers

The white-bellied sea eagle, Haliaeetus leucogaster, displays reversed sexual size dimorphism and is monomorphic for adult plumage coloration. Early attempts to identify sex in sexually monomorphic birds were based on morphological or chromosomal characters, but since avian W-specific DNA sequences were identified, PCR amplification has become commonly used for molecular sexing. We used a PCR test employing primers that amplify two homologous fragments of both the CHD-W gene, unique to females, and the CHD-Z gene, occurring in both sexes. This test was applied to five individuals of H. leucogaster from the Malacca Zoo and to male and female domestic chickens, Gallus domesticus, for comparison. All individuals were sexed successfully with high reproducibility. We conclude that this PCR-based test with feathers as the DNA source is a reliable sexing method for H. leucogaster. This sexing technique is objective and non-invasive and could be used to test sex ratio theories, as well as to help improve conservation and management actions for captive breeding program of this species in Malaysia.     

Beyond the browse line: complex cascade effects mediated by white‐tailed deer

In many ecosystems, browsing of large mammals can affect plant species compositions. However, much less is known about potential above‐ and below‐ground trophic interactions of large browsing mammals. This study focused on the direct and indirect effects of browsing on trophic and abiotic interactions within forest ecosystems. To quantify above‐ and below‐ground cascade effects, white‐tailed deer have been excluded for over 18 years from three 4‐ha plots, which were paired with same sized deer access plots. Our results demonstrate complex direct and indirect cascade effects on forest food webs. Deer exclusion directly altered woody species composition and significantly increased shrub and sapling density. Above‐ground cascade effects include greater leaf litter accumulation and higher arthropod density and biomass within the exclosures. Below‐ground indirect effects include significant decrease in soil nutrients, and higher arbuscular mycorrhizal fungal inoculum potential in the exclosures. Because ecosystems have finite resource availability, high deer density may imbalance the system by redirecting resources toward maintaining deer biomass at the expense of multiple trophic levels throughout the forest community. Both complex bottom up and top down trophic cascade effects demonstrated largely unidirectional negative responses suggesting that high deer density has reduced the biodiversity of the forest community.