Temporal trends of inorganic elements in a common kestrel (Falco tinnunculus) population from south west Spain

Highlights: • Little information exists on inorganic elements exposure of raptors in SW Spain. • Most of the inorganic elements analyzed showed significant increasing trends overtime. • δ¹⁵N signatures suggest trophic changes and possible biomagnification processes. • The high levels found for some toxic metals are worrying for this kestrel population. Historical variations (1966–2016) in the exposure to inorganic elements in raptors of South West Spain have been little studied. Therefore, uncertainty exists concerning whether environmental or anthropogenic inputs, as well as dietary strategy shift, may cause changes in exposure patterns. To address this gap, essential and non-essential inorganic elements were measured in Common kestrel (Falco tinnunculus) feathers from museum specimens and free-living individuals spanning a 50-year period. Moreover, stable isotopes of δ¹³C and δ¹⁵N were also measured as proxies of Common kestrel feeding ecology over time. In general, all elements showed significant increasing trends overtime, suggesting changes of inputs from local sources. Moreover, δ¹⁵N signatures were correlated to the variations in Al, Cr, Cu, Fe, K, Li, Mg, Mn, Ni, P, Pb, Rb, Sr, Ti, V and Zn concentrations, suggesting trophic changes in this kestrel population as well as possible biomagnification processes. Finally, some values of Cr, Mn and Pb were above the threshold concentrations of potential toxicity.