Meeting Abstract
Ten years ago two reviews clarified the need to tie glucocorticoid levels directly to survival and reproductive measures. Three primary hypotheses emerged from that work: The CORT-fitness hypothesis, the CORT-adaptation hypothesis, and the CORT-tradeoff hypothesis. Over the last 10 years those two articles have been cited over 800 times, but no clear consensus has emerged supporting one hypothesis over another. We propose that the discrepancy in results may be due to variation in resource availability. In free-living animals, trade-offs may be masked by high resource availability in good years, but evident in poor years. Current literature testing between these hypotheses rarely incorporates metrics of resource availability. In 1986 Van Noordwijk and de Jong proposed the acquisition/allocation model to explain positive vs. negative correlations between reproduction and survival across individuals. Their model identifies resources as critical to evaluating individual allocation strategies (favoring reproduction vs survival), and therefore provides the ideal model for testing across the three CORT hypotheses. Here we will 1) review the three hypotheses in light of the last 10 years of data, 2) review the relatively small subset of fitness/glucocorticoid papers that incorporate a resource perspective, 3) introduce the Van Noordwijk and de Jong framework as a model for fitness/glucocorticoid hypothesis testing, and 4) discuss recent results testing the effects of resource limitation on tradeoffs between feather structure and color in mountain bluebirds (Sialia currucoides).
