Abstract
This study focused on the exposure of a terrestrial raptor, the peregrine falcon (Falco peregrinus), in the United Kingdom. In contrast to inland areas, peregrine falcons in coastal areas of North Cornwall, South-west England, have recently declined despite a decreasing trend in environmental legacy organic contaminants. Exposure to per- and polyfluoroalkyl substances (PFAS) is suspected to contribute to one of the causes of this decline. However, unlike studies on aquatic birds, research on PFAS exposure of terrestrial predatory birds remains limited, particularly in British wild birds. To fill this knowledge gap, we have measured PFAS burdens in peregrine eggs from different English areas and compared them with stable isotope and eggshell index values. Our results showed that long-chain perfluoroalkyl acids were predominantly detected in peregrine eggs. Perfluorooctane sulfonyl acid (PFOS), perfluorohexanesulfonic acid (PFHxS), and perfluorooctanoic acid (PFOA) residues significantly differed among counties: PFOS and PFHxS residues were significantly higher in eggs from Devon, the study area around urban settlements, than in Cornwall. PFOA residues were significantly higher in Lancashire, an inland study area, than in Devon. Several perfluoroalkyl carboxylic acid residues showed significant and negative correlations with δ(13)C in eggs, suggesting that the sources of these PFAS might come from terrestrial habitats. No significant relationship was observed between eggshell index and PFAS residues. Given the variation in PFAS exposure among areas, it remains challenging to determine the impact of PFAS on the Cornwall peregrine population. Further studies are needed to fill these knowledge gaps. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10646-026-03076-x.