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POPULATION-LEVEL RESPONSE OF CAROLINA CHICKADEES TO THE EXPANSION OF HOUSE WRENS IN APPALACHIAN GEORGIA**

Abstract

Predators and competitors are important components of the environment, affecting the growth and evolution of populations with whom they interact. House wrens (Troglodytes aedon) occupy both of these roles because they cause direct mortality of eggs and nestlings as they usurp nest cavities from other bird species with whom they compete for this limited resource. Although native to North America, house wrens have expanded their breeding range to proliferate into the south eastern United States, where they now predate on and compete with other species, such as Carolina chickadees (Poecile carolinensis). Prior to the house wren expansion, parts of the breeding range of Carolina chickadees had not overlapped with that of house wrens, including in Appalachian Georgia where house wrens were historically absent. As part of a larger study on the evolution of adaptive behavior by Carolina chickadees to this novel competitor and predator, I am conducting a study on the population-level effect of this new interspecific interaction. The goals of this project are (1) to determine the approximate date for the expansion of house wrens into Appalachian Georgia, and (2) to quantify the change in house wren and Carolina chickadee populations over time in this area. Furthermore, I will test my hypothesis that the Carolina chickadee population has decreased as the house wren population has increased in Appalachian Georgia since the 1970s. To test my hypothesis, I am utilizing checklists submitted to eBird, a citizen science database that collects and archives bird sightings from around the world. I will analyze how the frequency of house wren and Carolina chickadee sightings (a proxy for population size) during the breeding season has changed over time in Appalachian Georgia, and test for a correlation between the sightings of the two species.

Acknowledgements

This research could not have been possible without the thousands of bird watchers who have voluntarily contributed their observations to eBird. We also thank the faculty, students and staff at Young Harris College for their continued support.

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