Meeting Abstract
Environmental fluctuations trigger changes in glucocorticoids (GCs) that promote profound individual physiological and behavioral adjustments as well as shifts in life-history stages. Baseline (BLs, low levels for predictable fluctuations) and stress-induced GC levels (SLs, high levels typical for unpredictable fluctuations) mediate metabolic and behavioral changes to obtain and utilize energy depending on needs. BLs are expected to covary with seasonal energy demands while SLs are thought to mediate life history trade-offs when unpredictable disturbances occur, like promoting survival processes at the expense of reproduction. We will employ comparative methods to analyse seasonal changes in GCs within the class Aves to identify broad-scale patterns across taxa. We will extract population GC means for breeding versus non-breeding seasons from HormoneBase, and from those calculate changes (‘population scopes’) in seasonal GC changes. We assume breeding is the more energetically demanding life-history stage, and therefore predict that BLs are higher during the breeding season, and a larger seasonal scope is positively related to fecundity. Conversely, we expect SLs are lower during the breeding season to minimize reproductive disruptions, and scope is negatively associated with fecundity. Controlling for phylogeny, we will construct analyses that include sex, size, metabolic rate, environmental and life history variables to understand how seasonal changes in GCs covary with life-history traits and environmental conditions of populations.
