Meeting Abstract

9.3  Sunday, Jan. 4  Glucocorticoid physiology during incubation fasts in Laysan Albatross SPRAGUE, R.S.**; SPRAGUE, J.C.; BREUNER, C.W.; University of Montana, Missoula; University of Montana, Missoula; University of Montana, Missoula rachel.sprague@umontana.edu

Laysan Albatross undergo repeated 2-3 week fasts throughout incubation, during which they can drop 25% of their body mass. It is known that during short, unpredictable fasts, glucocorticoid stress hormones (corticosterone in birds: CORT) rise as body mass declines. However, it is not clear whether the relationship between CORT and body mass holds during long-term, predictable fasting. Given that elevated CORT levels are associated with nest abandonment, species with repeated, long fasts during incubation may delay or depress the secretion of CORT to preserve their reproductive effort. We monitored body mass, CORT, and, for the first time, corticosteroid binding globulin (CBG), during incubation fasts over the entire incubation period in Laysan Albatross (Phoebastria immutabilis). As expected, body mass declined both within fasts and over the season. At the same time, total CORT increased both within individual incubation shifts and over the season. As supported by many other studies, baseline CORT was negatively correlated with body mass. CBG did not significantly change as the incubation season progressed, though it increased during individual incubation fasts and was positively correlated with total CORT: as mass declined during fasts, total CORT levels and CBG capacity both increased. This contradicts previous studies that have shown decreases in CBG capacity with falling body mass. In summary, we found that CORT secretion does increase during long, repeated fasts in this species, though CBG may also rise to protect the reproductive attempt from the inhibitory effects of CORT on parental behavior.