Meeting Abstract
Traits that confer advantages during female choice or during male-male competition are said to be under sexual selection. While condition dependence of sexually selected traits is well supported in the literature, condition is difficult to define, leading to confusion in the field. Understanding how individual variation in response to challenge affects trait production is an important goal for the field of sexual selection. The endocrine system is an important mediator of condition dependence because hormones respond to environmental conditions to regulate internal response and resulting phenotype. The hormone corticosterone (CORT) is released by the adrenal glands in response to challenge to divert resources towards self-preservation and away from other purposes. Individuals vary in their stress responsiveness (the amount of CORT secreted in response to challenge), and the downstream response of other systems to CORT secretion. Using CORT physiology to study sexual selection allows for the exploration of dynamic changes in ornament production across environmental conditions. We studied the effects of food availability and corticosterone physiology on coloration and feather structure in the Mountain Bluebird. We brought 21 hatch year males into the lab and divided them into three treatment groups with n=7 birds each; food deprivation (80% food availability), corticosterone implant (Innovative Research of America), or CORT implant x food deprivation. Each bird grew one control set of feathers and one treatment set of feathers in a paired study design (n=7 birds). We evaluated ornamentation, feather structure, and stress physiology in response to the different treatments to determine how environmental and physiological conditions affect the various functions of feathers. We will discuss potential trade-offs between survival functions (feather structure), and internal and external conditions.
