Corticosterone levels correlate in wild-grown and lab-grown feathers in greenfinches (Carduelis chloris) and predict behaviour and survival in captivity.

Level of corticosterone (CORT), which is a predominant glucocorticoid in birds, has become the main indicator for assessing the stress level of birds in ecological studies. Feather corticosterone (CORT_f) provides information about corticosterone levels during feather growth, however, the underlying causes of individual variation of CORT_f between individuals and individual persistency of CORT_f are not yet fully understood. Therefore, this study addresses individual consistency in CORT_f and the association of variation in CORT_f with behaviour that results in damage to tail feathers. We studied relations between CORT_f, plasma CORT, and behaviour in wild-caught male greenfinches in captivity. CORT_f in wild-grown feathers correlated positively with CORT_f in lab-grown feathers. CORT_f levels were about 20% lower in lab-grown feathers than in those grown in the wild. Four birds that died in captivity had significantly higher average CORT_f levels in wild-grown feathers than the survivors. Plasma CORT levels of two measurements taken in the lab seven days apart correlated positively, however, no correlations between plasma CORT and CORT_f were found. In order to study the link between CORT_f and behaviour, the extent of tail damage from flapping against cage bar was assessed. Contrary to our prediction, birds with higher CORT_f had less tail damage. This study adds to the evidence that CORT_f levels can be considered as informative markers of some persistent component of individual phenotypic quality that can predict survival under standardized laboratory conditions.