Genomic diversity and differentiation between island and mainland populations of white-tailed eagles (Haliaeetus albicilla)

Divergence in the face of high dispersal capabilities is a documented but poorly understood phenomenon. The white-tailed eagle (Haliaeetus albicilla) has a large geographic dispersal capability and should theoretically be able to maintain genetic homogeneity across its dispersal range. However, following analysis of the genomic variation of white-tailed eagles, from both historical and contemporary samples, clear signatures of ancient biogeographic substructure across Europe and the North-East Atlantic is observed. The greatest genomic differentiation was observed between island (Greenland and Iceland) and mainland (Denmark, Norway and Estonia) populations. The two island populations share a common ancestry from a single mainland population, distinct from the other sampled mainland populations, and despite the potential for high connectivity between Iceland and Greenland they are well separated from each other and are characterized by inbreeding and little variation. Temporal differences also highlight a pattern of regional populations persisting despite the potential for admixture. All sampled populations generally showed a decline in effective population size over time, which may have been shaped by four historical events: (1) Isolation of refugia during the last glacial period 110-115,000 years ago, (2) population divergence following the colonization of the deglaciated areas ~10,000 years ago, (3) human population expansion, which led to the settlement in Iceland ~1100 years ago, and (4) human persecution and exposure to toxic pollutants during the last two centuries.

A review of constraints and solutions for collecting raptor samples and contextual data for a European Raptor Biomonitoring Facility

The COST Action 'European Raptor Biomonitoring Facility' (ERBFacility) aims to develop pan-European raptor biomonitoring in support of better chemicals management in Europe, using raptors as sentinel species. This presents a significant challenge involving a range of constraints that must be identified and addressed. The aims of this study were to: (1) carry out a comprehensive review of the constraints that may limit the gathering in the field of raptor samples and contextual data, and assess their relative importance across Europe; and (2) identify and discuss possible solutions to the key constraints that were identified. We applied a participatory approach to identify constraints and to discuss feasible solutions. Thirty-one constraints were identified, which were divided into four categories: legal, methodological, spatial coverage, and skills constraints. To assess the importance of the constraints and their possible solutions, we collected information through scientific workshops and by distributing a questionnaire to stakeholders in all the countries involved in ERBFacility. We obtained 74 answers to the questionnaire, from 24 of the 39 COST participating countries. The most important constraints identified were related to the collection of complex contextual data about sources of contamination, and the low number of existing raptor population national/regional monitoring schemes and ecological studies that could provide raptor samples. Legal constraints, such as permits to allow the collection of invasive samples, and skills constraints, such as the lack of expertise to practice necropsies, were also highlighted. Here, we present solutions for all the constraints identified, thus suggesting the feasibility of establishing a long-term European Raptor Sampling Programme as a key element of the planned European Raptor Biomonitoring Facility.

Towards harmonisation of chemical monitoring using avian apex predators: Identification of key species for pan-European biomonitoring

Biomonitoring in raptors can be used to study long-term and large-scale changes in environmental pollution. In Europe, such monitoring is needed to assess environmental risks and outcomes of chemicals regulation, which is harmonised across the European Union. To be effective, the most appropriate sentinels need to be monitored. Our aim was to identify which European raptor species are the likely most appropriate biomonitors when pollutant quantification is based on analysing tissues. Our current study was restricted to terrestrial exposure pathways and considered four priority pollutant groups: toxic metals (lead and mercury), anticoagulant rodenticides, pesticides and medicinal products. We evaluated information on the distribution and key ecological traits (food web, foraging trait, diet, preferred habitat, and migratory behaviour) of European raptors to identify the most appropriate sentinel species. Common buzzard (Buteo buteo) and/or tawny owl (Strix aluco) proved the most suitable candidates for many of the pollutants considered. Moreover, they are abundant in Europe, enhancing the likelihood that samples can be collected. However, other species may be better sentinels for certain pollutants, such as the golden eagle (Aquila chrysaetos) for lead, the northern goshawk (Accipiter gentilis) for mercury across areas including Northern Europe, and vultures (where they occur in Europe) are likely best suited for monitoring non-steroidal anti-inflammatory drugs (NSAIDs). Overall, however, we argue the selection of candidate species for widescale monitoring of a range of pollutants can be reduced to very few raptor species. We recommend that the common buzzard and tawny owl should be the initial focus of any pan-European raptor monitoring. The lack of previous widespread monitoring using these species suggests that their utility as sentinels for environmnetal pollution has not been widely recognised. Finally, although the current study focussed on Europe, our trait-based approach for identifying raptor biomonitors can be applied to other continents and contaminants.