You have full access to this open access article. The measurement of faecal glucocorticoid metabolites is used as a non-invasive technique to study stress in animal populations. They have been used most widely in mammals, and mammalian studies have also treated issues such as sample stability and storage methods. In birds, faecal corticosterone metabolite CM assays have been validated for a small number of species, and adequate storage under field conditions has not been addressed explicitly in previous studies.
Furthermore, while it is well-established that baseline plasma corticosterone levels in birds rise with declining body condition, no study so far investigated if this relationship is also reflected in faecal samples. We here present data of a field study in wild Upland geese Chloephaga picta leucoptera on the Falkland Islands, testing different storage methods and investigating the relationship of faecal CM concentrations to body condition and reproductive parameters. We found that faecal CM measures are significantly repeatable within individuals, higher in individuals with lower body condition in both male and female wild Upland geese and higher in later breeding females with smaller broods.
These results suggest that measuring faecal CM values may be a valuable non-invasive tool to monitor the relative condition or health of individuals and populations, especially in areas where there still is intense hunting practice.
The measurement of faecal glucocorticoid metabolites GCM in faeces has become a valuable tool in conservation biology and ecology to study stress load, enabling researchers to monitor the physiological state of wild animals both non-invasively and repeatedly. Faecal GCM have been used most widely in mammals, and mammalian studies have also treated issues such as sample stability and storage methods. One important question arising especially in studies in remote areas is the appropriate storage of faecal samples from the time of collection until later laboratory analysis.
Studies with captive mammals showed that faecal samples are most stable when stored at sub-zero temperatures, followed by cool storage, drying and preservation in ethanol reviewed in Wasser et al. However, as glucocorticoids are metabolised in a species-specific manner before excretion and assays need to be validated for each species, we wanted to test whether these findings from studies in primates may be transferred to an avian system.
