Meeting Abstract
One of the fundamental goals in an organism’s life is to reproduce. Raising young is an energy intensive enterprise. The older the young are, the more energy the parents have invested in them. Thus, older offspring could be considered more valuable and this increased value may make parents more likely to increase offspring defense. In this study, we looked for correlations between parental nest defense behaviors, nest stage, time of year, and environmental features at the nest boxes of eastern bluebirds (Sialia sialis) and tree swallows (Tachycineta bicolor), two species of cavity nesting birds common in southwest Virginia. This study followed populations breeding at two sites for three years. We monitored nest stage and observed the parental defense behaviors, such as dives and beak clicks, associated with each nesting stage. Analysis of previous seasons’ behavioral data suggests that parents of both species increase nest defense behaviors as their nests advance from the incubation to nestling stage. Analysis of environmental factors and how they correlate with nest defense behaviors is on-going, but we expect heightened nest defense behavior at late-season nests, especially when temperatures are moderate and boxes have nearby perches, both environmental features that may reduce the energetic costs and risk of nest defense. Understanding how offspring age and local environment impact parental investment may illuminate previously overlooked trade-offs of reproduction in cavity-nesting songbirds.
