Regulation of the hypothalamic-pituitary-adrenal axis in free-living pigeons

We studied feral free-living pigeons (Columba livia) to determine whether e ither unstressed or stress-induced corticosterone release was altered durin g a prebasic molt. The pigeons were at various stages of molt throughout th e study, but corticosterone responses in molting and nonmolting birds did n ot differ. This was further reflected in equivalent adrenal responses to ex ogenous adrenocorticotropic hormone (ACTH), suggesting equivalent steroidog enic capacity of adrenal tissues during both physiological states. There wa s a slight change, however, in pituitary regulation during molt. Whereas ex ogenous arginine vasotocin (AVT) elevated corticosterone levels in nonmolti ng birds, during molt an equivalent dose of AVT was ineffective, suggesting that the pituitary is less sensitive to an AVT signal during molt. AVT als o appears to be more effective than corticotropin-releasing factor at elici ting ACTH release in pigeons. Overall, these data indicate that pigeons reg ulate their corticosterone release differently during molt than other avian species studied to date.