RESEARCH ARTICLE Drawing the baseline of trace element levels in the vulnerable Mediterranean osprey Pandion haliaetus: variations by breeding location, habitats, and egg components Flavio Monti 1 & Nicola Bianchi 1 & Andrea Sforzi 2 & Claudio Leonzio 1 & Stefania Ancora 1 Received: 4 October 2019 /Accepted: 29 December 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract 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. Keywords Eggs . Trace elements . Raptor . Bioindicators . Contamination . Mediterranean Sea . Pandion haliaetus Introduction Wildlife species have been historically used for ascertaining and monitoring the presence of persistent contaminants in natural ecosystems (Dmowski 1999 ; Burger 2006 ). Ecotoxicological analyses, conducted on such species with the role of ecological sentinels, have been used to detect the presence of specific contaminant levels and to identify polluted areas (Burger 2006; Jackson et al. 2016). Among birds, raptors have been largely used in this effort (e.g., Garcıa-Fernandez et al. 2008; Espín et al. 2016). As top pred- ators, these birds are useful bioindicators for monitoring how certain substances move up in food web in progressively higher concentrations as they are incorporated into the diet of prey organisms (e.g., biomagnification process; Des Granges et al. 1998). Overall, there is an extensive set of studies examining the effects of contaminants on population parameters of different raptor species (Gómez-Ramírez et al. 2014). This is the case for the peregrine falcon Falco peregrinus (e.g., Garcıa-Fernandez et al. 2008; Fernie and Letcher 2010), the bald eagle Haliaeetus leucocephalus (e.g., Bechard et al. 2009), the white-tailed eagle Haliaeetus albicilla (e.g., Kitowski et al. 2017a), the common buzzard Buteo buteo (Kitowski et al. 2017b), and the osprey Pandion haliaetus (e.g., Grove et al. 2009). The osprey is a long-lived fish-eating raptor at the top of the aquatic food web, which can adapt to anthropized envi- ronments (Poole 1989). Life history traits and other peculiar ecological characteristics make this species particularly Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-019-07591-9) contains supplementary material, which is available to authorized users. * Flavio Monti flaviomonti00@gmail.com 1 Department of Physical Sciences, Earth and Environment, University of Siena, Via Mattioli, 4, 53100 Siena, Italy 2 Maremma Natural History Museum, Strada Corsini 5, 58100 Grosseto, Italy Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-07591-9