Drawing the baseline of trace element levels in the vulnerable Mediterranean osprey Pandion haliaetus: variations by breeding location, habitats, and egg components

Due to its peculiarity to accumulate environmental contaminants, the osprey Pandion haliaetus is a sentinel species for the biomonitoring of contaminants in aquatic ecosystems. Despite this, no information on trace element concentration exists for the Mediterranean area, where relict and vulnerable osprey populations exist. We evaluated the geographical patterns of heavy metals and selenium in osprey eggs from three different populations of the Mediterranean basin (Balearic Islands, Corsica, and Tuscany), to identify any possible contaminant sources. Pattern of metal concentration followed the order: Fe > Zn > Cu > Se > Hg > Pb > Cd. Differences in contaminant concentrations between habitats and among egg components were found. Egg content and inner membrane showed higher mercury levels (1.06 ± 0.89 and 0.67 ± 0.62 mg/kg dw, respectively) than those recorded in the eggshell. Mercury concentration was ca. two times higher in marine than in wetland samples, and even higher (3.6 times) when referred to the eggshell. Cu, Fe, Zn, and Se had higher concentration in the inner membrane. We stress how the choice of the biological material can have significant implications for the correct evaluation of contamination. Our study represents a first regional scale survey for the vulnerable Mediterranean osprey populations and provides baseline data for their long-term biomonitoring.