P2.114 Thursday, Jan. 5 Measuring Allostatic Load in Wintering Gambel's White-crowned Sparrows, Zonotrichia leucophrys gambelii WORD, K R*; WINGFIELD, J C; Univ. of California, Davis; Univ. of California, Davis email@example.com
Regulation of energetic expenditure, considered here as allostatic load, is central to organism-environment interactions, and the value of responses that modify behavior or physiology is often measured in terms of energetic benefits. In this study, I assessed the total energetic costs incurred by white-crowned sparrows, zonotrichia leucophrys gambelii, in real time through the use of heart-rate transmitters. I present data validating the use of heart rate as a proxy for metabolic rate via flow-through respirometry and doubly-labeled water. Experiments measuring heart rate in outdoor aviaries and preliminary field tests on free-ranging birds indicate that these birds depress metabolism on cold winter nights when temperature alone would be predicted to lead to increased energetic expenditure. Implications and future directions for this research will be discussed.