Meeting Abstract
Many physiological traits are plastic: to maintain allostasis, an organism alters its central nervous, immune, and endocrine systems to respond to changing environments and energetic demands. However, organisms can also exhibit consistent individual differences relative to other individuals. This contrast between individual plasticity and consistency raises the question: to what extent does a single measurement of these labile traits represent individual differences? To address this question, we measured three physiological traits in 56 free-ranging black-capped chickadees (Poecile atricapillus) at two time points during the non-breeding season. Specifically, we measured the stress hormone corticosterone, which is important in regulating behavioral and physiological responses to challenges; total antioxidant capacity and reactive oxygen metabolites, which provide a measure of oxidative stress; and the hemolytic activity of plasma, which provides an index of immune function. We present the repeatability of these three metrics and their interrelationships. Many field biologists seek to characterize study subjects in terms of parameters of condition, fitness, or quality using a single measurement of a physiological trait. Our findings will help inform interpretations of such point measures of physiological traits.
