| Summary: | Despite the current increasing population trend, white-tailed eagles are still prone to many anthropogenic stressors. Mercury (Hg) is a very persistent naturally occurring element and apex predators as well as birds feeding on aquatic ecosystems are usually exposed to higher levels of Hg. Since global Hg emissions are still increasing, Hg remains as a topical health issue. The effects of mercury on wildlife have been studied extensively. Blood clinical-chemical parameters (BCCPs) can potentially be useful as biomarker endpoints for contaminant exposure. However, the effects of Hg on blood chemistry and metabolism are still poorly described. Mercury concentrations and stable isotope composition can be measured from the feathers of nestlings and the nestlings represents well the geographical area of interest. Stable isotope analyses can be used to investigate the potential dietary sources of mercury. In the experimental part we investigated the regional differences in stable isotope values, Hg concentration and BCCPs, as well as the interactions between stable isotope values and Hg exposure. We also investigated possible effects of Hg exposure on the health of WTE nestlings in three populations in Finland perceived by BCCPs. Blood and feather samples were collected from WTE nestlings in Finland during the years 2015 and 2016 in three different locations. Blood plasma was analysed for 16 different BCCPs. Feathers were analysed for total Hg concentration as well as for stable nitrogen (δ15N) and carbon (δ13C) composition. A significant difference in δ13C and δ15N values in Varsinais-Suomi and Ostrobothnia compared to Lappi was apparent and is likely to indicate variable local dietary habits. Nonetheless, the concurrent variation in δ15N and δ13C values is indicative of changes in prey composition rather than regional changes in baseline isotope signatures. We noted significantly higher Hg concentrations in Lapland population compared to the other regions. Since there was a high correlation between Hg and stable ...
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