Investigating Life History Tradeoffs in an Opportunisitc Bredding Songbird, the Red Crossbill (Loxia Curvirostra) in Grand Teton National Park

Abstract

Because available energy is finite, organisms must be selective with how and when energetic resources are allocated to demanding physiological processes such as reproduction or self-maintenance like immune function. Historically, research to understand how organisms orchestrate their annual cycles with respect to these costly and conflicting processes has focused narrowly on seasonal breeders that constrain reproduction to times of year when thermoregulatory demand is low (i.e., summer), which provide limited opportunities to reveal how physiological costs of different processes may interact with environmental conditions to influence the evolution of investment strategies. In this study, we are examining seasonal and interannual variation in environmental conditions (temperature, precipitation, food supply) and investment patterns in survival and reproduction in a reproductively flexible songbird, the red crossbill (Loxia curvirostra), which can reproduce opportunistically in both summer and winter in Grand Teton National Park. In addition, crossbills provide a perfect model to investigate these environmental and physiological interactions. Preliminary results from this study have indicated that food availability may play an important role in determining how much crossbills will invest in survival (specifically immune function) and reproduction; e.g., crossbills will invest more in innate immunity and reproduction when food availability is high. Overall, results from this study will provide information on how species in general and crossbills specifically respond to rapidly changing environments, which has become increasingly important in light of the effects of anthropogenic change.