Corticosterone Metabolites can be Measured Noninvasively in Excreta of European Stonechats (Saxicola torquata rubicola)

Abstract

Measurements of corticosterone levels from blood samples of birds provide accurate snapshots of systemic hormone concentrations. However, those birds must be caught and handled, which may be unfeasible especially when multiple sampling is required. Furthermore, handling causes stress and may therefore interfere with hormone measurements. Therefore a non-invasive technique was developed to measure metabolites of corticosterone in excreta of European Stonechats (Saxicola torquata rubicola) using a corticosterone enzyme-immunoassay. High-performance liquid chromatography of excreta of a female and a male stonechat injected with tritiated corticosterone showed that corticosterone is excreted in the form of numerous metabolites and that the corticosterone enzyme-immunoassay cross-reacted with most of those metabolites. Injection of adrenocorticotrophic hormone in one female and seven male stonechats led to a significant increase in the levels of excreted corticosteroid metabolites within 1 h 20 min after administration of adrenocorticotrophic hormone. These results suggest that the corticosterone enzyme-immunoassay used in this study provides a quantitative measure of excreted corticosteroid metabolite levels in European Stonechats and has the potential to replace plasma measurements of these hormones.