CYR, N.E.*; ROMERO, L.M.; Tufts Univ.; Tufts Univ.: Molt Alters the Avian Cardiovascular Stress Response

Basal and stress induced heart rate (HR) and Corticosterone (B) were monitored in 8 captive European starlings, Sturnus vulgaris, during and following a prebasic molt. Throughout a 24hour period basal HR was significantly higher in molting birds, potentially reflecting a cost to this energetically expensive process. Furthermore, the cardiovascular stress response during molt was different than during non-molt. Birds were subjected to 4 (30min) acute stressors: two of degrees of acute density stress (adding 1 or 5 novel birds (intruders) to a resident�s cage), restraint, and an auditory stressor (loud music). Despite a lower basal HR, maximal HR was higher in non-molting birds in response to restraint and both acute density stressors. HR increased slightly when molting resident birds were subjected to a single intruder, whereas all other stressors elicited a significant increase in HR during both physiological states. Molting birds recovered to basal HR levels faster than non-molting birds during restraint, whereas recovery time was similar between molting and non-molting birds for all other stressors. Basal B levels were similar in both physiological states. Neither acute density stressor increased B above basal levels in either molting or non-molting birds. However, restraint and the auditory stressor triggered a significant increase in B levels in both molting and non-molting birds, and in both cases B levels were highest following restraint. Moreover, molting birds had significantly lower B levels following restraint and the auditory stressor. These data mirror earlier work that B is lower during molt. HR data extend this observation and indicate that physiological consequences to molt affect the cardiovascular stress response. Our data suggest that molt dramatically impacts the overall stress response.