Mercury Exposure in Birds of Prey from Norway: Relation to Stable Carbon and Nitrogen Isotope Signatures in Body Feathers

Abstract

Mercury (Hg) and stable carbon and nitrogen isotope ratios were analysed in body feathers from nestlings of white-tailed eagles (Haliaeetus albicilla) (WTE; n=13) and Northern goshawks (Accipiter gentilis) (NG; n=8) and in red blood cells (RBC) from NG (n=11) from Norway. According to linear mixed model, species factor was signifcant in explaining the Hg concentration in feathers (LMM; p<0.001, estimate (WTE)=2.51, 95% CI=1.26, 3.76), with concentrations higher in WTE (3.01±1.34 µg g−1 dry weight) than in NG (0.51±0.34 µg g−1 dry weight). This diference and the isotopic patterns for each species, likely refect their diet, as WTE predominantly feed on a marine and higher trophic-chain diet compared to the terrestrial NG. In addition, Hg concentrations in RBCs of NG nestlings were positively correlated with feather Hg concentrations (Rho=0.77, p=0.03), supporting the potential usefulness of nestling body feathers to biomonitor and estimate Hg exposure. Hg levels in both species were generally below the commonly applied toxicity threshold of 5 µg g−1 in feathers, although exceeded in two WTE (6.08 and 5.19 µg g−1 dry weight). Biomonitoring · Feather · Erythrocytes · Red blood cells · Metals