Meeting Abstract

P1.72  Thursday, Jan. 3  Stress reactivity, environment, and condition: initial perspectives from a long-term data set PATTERSON, S. H.**; HAHN, T.P.; BREUNER, C.W.; Univ. of Montana; Univ. of California, Davis; Univ. of Montana stephen1.patterson@umontana.edu

The glucocorticoid (CORT) stress response is highly variable across individuals, seasons, and populations. We are interested in the combined effect of physiological and environmental parameters on CORT stress reactivity (baseline and max CORT, rate of increase, and integrated CORT). Since 2001, we have collected stress series (0, 15, and 30 minute samples) from white-crowned sparrows (Zonotrichia leucophrys) breeding at Tioga Pass in the Sierra Nevada (n > 450). The majority of samples were taken prior to the onset of nesting. Additionally, we have measures of individual body condition and age, temperature, barometric pressure, snow cover, and date of the first egg laid that season. We are still working on the final database, but results from our initial regression analyses on 2001-2004 (n = 250) are promising. Overall, there is no effect of sex or temperature from the previous night on any CORT measure. Surprisingly, fat score significantly predicts several parameters of the stress response (with a shallow, negative slope), while body condition does not. The strongest predictor of our stress response measures was days before the first egg was laid. As days move closer to egg lay, baseline CORT, max CORT and integrated CORT all increase. Future work will comprise two parts: 1) refining and enhancing the current analysis by including age, testosterone levels, barometric pressure, snow cover, and further temperature analyses; and 2) investigating the combined effects of environment, body condition, and stress reactivity on individual fitness as estimated by lifetime number of nestlings fledged.