The peregrine falcon (Falco peregrinus) as a sentinel species for environmental contamination at the human–animal–environment interface

Introduction
Within the One Health framework, sensitive non-invasive indicators are needed for surveillance at the human–animal–environment interface. This study evaluates the peregrine falcon (Falco peregrinus) as a sentinel species for trace element exposure across an environmental gradient in Italy, using feathers (long-term accumulation) and faeces (recent dietary intake).

Methods
We compared individuals from high (HEI) and low (LEI) environmental impact areas. Trace elements including mercury (Hg) and lead (Pb) were quantified in both matrices. Feathers provided integrated bioaccumulation data, while faeces reflected short-term exposure patterns. Crucially, this multi-matrix approach is rapid and painless for the raptors, involving only non-invasive collection of naturally moulted feathers and fresh faeces, with no impact on animal welfare or health. Sampling requires minimal handling and can be repeated over time without disturbing the birds or their breeding activity.

Results
Feathers from HEI falcons showed significantly higher concentrations of most trace elements, particularly Hg (p < 0.01) and Pb (p < 0.05), indicating enhanced trophic transfer in impacted environments. Faecal analyses complemented these findings, revealing elevated levels of several elements in HEI individuals, though some elements showed no differences due to rapid excretion. The combined matrix approach captured both persistent bioaccumulation and recent dietary fluctuations, offering a more complete exposure profile. Notably, faecal variability also reflected short-term changes in prey contamination, providing real-time dietary snapshots.

Conclusions
These findings support the peregrine falcon as a sensitive, non-invasive bioindicator for surveillance at the human–animal–environment interface. The feather–faecal matrix model provides a standardized, rapid, and animal-friendly framework for long-term monitoring of terrestrial ecosystem contamination, with direct applications in exposure modelling and early warning systems for emerging environmental risks to wildlife, domestic animals, and human health. This approach enables ethically sound biomonitoring programs aligned with animal welfare principles and One Health surveillance strategies.