Fecal glucocorticoid metabolites as stress biomarkers in common buzzards (Buteo buteo) across rehabilitation phases: implications for raptor welfare

Taking wildlife into human care is a balancing act between benefits and harms, as handling and captivity can cause chronic stress that can lead to permanent physiological changes. Therefore, it is necessary to investigate stress levels during the rehabilitation of wild animals such as raptors. Fecal samples from 15 Common Buzzards ( Buteo buteo ) were taken to determine fecal glucocorticoid metabolite concentrations as a biomarker for stress across the rehabilitation phases. Significantly higher concentrations of fecal glucocorticoid metabolites were found during housing phase 1, when the birds were housed in small cages and handled at least once a day for medical treatment, compared to housing phase 2, when they were housed in larger and more undisturbed aviaries. The day of rehabilitation had no significant impact on fecal glucocorticoid metabolite concentrations alone or in interaction with the housing phases. The cause of admission (acute or chronic) and the eventual outcome for the birds (release or euthanasia) also had no statistically significant effect. The results suggest that handling and restraint could be main stressors during rehabilitation and should be critically evaluated throughout the rehabilitation process. Recommendations were derived from our findings to improve the welfare of birds of prey in wildlife rehabilitation.