Meeting Abstract

52.1  Saturday, Jan. 5  Corticosterone response to nest-directed disturbances in two migratory songbirds BUTLER, Luke K*; BISSON, Isabelle; HAYDEN, Timothy J; WIKELSKI, Martin; ROMERO, L. Michael; Tufts University; Princeton University; Army Endangered Species Research Program; Princeton University; Tufts University luke.butler@tufts.edu

In an attempt to measure the susceptibility of an endangered songbird to chronic stress, we exposed adult black-capped vireos to several days of nest-directed activities, noises, and objects, each of which we assumed would cause an increase in corticosterone (CORT), and, after several days, would result in the suppressed CORT typical of chronically-stressed animals. Surprisingly, our disturbances failed to cause suppressed CORT in black-caps or in the related but common white-eyed vireo. Therefore we followed that experiment by testing the alternative hypotheses that 1) nest-directed disturbances cause no acute increase in CORT and therefore are not chronically stressful over the long term, and 2) nest-directed disturbances cause an increase in CORT initially, but adults habituate rapidly and thus avoid suppressed CORT. We measured CORT levels in free-living adults after 10-60 minutes of a human standing near (< 1 m), or a crow (predator) decoy peering into, their active nests. We compared the CORT response after the initial disturbance to the CORT response after five or six days of rotating stressors. Our results illustrate the CORT response to potentially stressful conditions that migratory songbirds probably encounter often: one-time and repeated nest-directed disturbances by people and predators. Further, we explain why an endangered and a common songbird avoid suppressed CORT after repeated nest-directed disturbance.