A research paper submitted in partial fulfillment of the requirements for the degree of Master of Arts for Teachers in the Field of Biological Sciences. University of Washington

Abstract

Arctic breeding birds face two major environmental constraints:a shortened breeding season and unpredictable, severe weather conditions. This study examined the behavioral effects of a simulated stressor in an arctic breeding population of Savannah sparrows, Passerculus sandwichensis. Ten territorial male Savannah sparrows were given subcutaneous implants of corticosterone (cort) in silastic tubing. A second group of ten territorial males were given empty implants and served as the control for hormone administration. A third unimplanted group was observed to determine the anticipated response with free-living unmanipulated birds. Aggressive behaviors of the implanted groups of birds were measured 1 - 3 days after the implant, using a simulated territorial intrusion (STI). There were no significant differences in aggressive behaviors between cort implanted and control birds. However, aggressive behavior between implanted birds that responded to the STI and unimplanted birds subjected to STI differed significantly. This suggests the capture and handling process of implanting may have some impact on territorial behavior. This decreased sensitivity to cort, a hormone associated with stress, demonstrates a possible adaptive strategy for arctic breeding birds to maximize their fitness.