Meeting Abstract

30.2  Sunday, Jan. 5 08:30  The migration-breeding transition: integrating behavior, stress physiology and experience from a long term data set BREUNER, C.W.*; HAHN, T.P.; The University of Montana; Univ. Of California, Davis creagh.breuner@umontana.edu

The transition from migration to breeding requires major changes in morphology, physiology and behavior. Many long-distance migrants need to be highly flexible during this transition, given the disconnect between conditions on the wintering grounds and at the breeding site. Arrival at the breeding site may be followed by immediate initiation of nesting (in mild years), or an extended wait for nest sites to become available (in more extreme years). The mountain white-crowned sparrow is such a species. Nest initiation date can vary interannually by as much as 6 weeks depending on local snow pack and weather. We have studied the arrival biology of the mountain white-crowned sparrow for 15 years, evaluating the role of stress physiology in behavioral transitions from migration into nesting. In this presentation I will discuss data demonstrating that glucocorticoids extend flexibility during this migration/breeding transition: as winter-like conditions persist on the breeding site, glucocorticoids temper the increasing focus on the nesting site; higher glucocorticoids are associated with earlier territorial abandonment during spring storms; and, exogenous glucocorticoids induce movement away from the breeding site down to lower elevation staging areas. Taken together, this glucocorticoid-induced increase in flexibility may enhance survival in years with more inclement weather.