Validation of a non-invasive technique for quantifying a stress-associated biomarker in a southern African hornbill

Quantification of glucocorticoids and their metabolites as a central component of the physiological stress response has many potential applications in ornithological research, but require careful species-specific validations. We established a reliable non-invasive method to measure faecal glucocorticoid metabolites (fGCM) in the southern yellow-billed hornbill (Tockus leucomelas). Following an adrenocorticotropic hormone (ACTH) challenge, plasma corticosterone levels increased by 110%, with a tetrahydrocorticosterone enzyme immunoassay (EIA) revealing a ~ fourfold increase in fGCM concentrations approximately 3 h post-injection. These data reveal droppings are a suitable matrix for monitoring stress-associated biomarkers in this species and suggest the tetrahydrocorticosterone EIA may often be appropriate for wild birds.