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EVOLUTION OF ANTI-PREDATORY BEHAVIOR AMONG CAROLINA CHICKADEES (POECILE CAROLINESIS) IN RESPONSE TO A NOVEL PREDATOR, THE HOUSE WREN (TROGLODYTES AEDEON)**

Abstract

House wrens (Troglodytes aedeon) have been expanding their breeding distribution into the southeastern United States. These passerines compete for limited nesting cavities by actively usurping other birds' nests and even killing their eggs and altricial young. Therefore, house wrens are novel predators and competitors in parts of their new range. This study focuses on their interaction with another cavity nester in Appalachian Georgia, the Carolina chickadee (Poecile carolinesis), for whom house wrens are novel predators and competitors. It is unknown whether Carolina chickadees behave adaptively to defend their nests against house wrens. Despite this being a relatively new interspecific interaction, we hypothesized that because nest usurpation and direct nestling mortality are strong selective pressures, Carolina chickadees have already evolved to recognize house wrens as predators and to respond adaptively. We tested this hypothesis by monitoring 100 nest boxes for Carolina chickadee nesting activity during spring 2017. We randomly allocated three predator treatments to nests with 8-day old nestlings, including models of a long-established predator (eastern gray squirrel, Sciurus carolinensis), the recently-established predator (house wren), and a non-predatory control (mourning dove, Zenaida macroura). We recorded one hour of feeding visits at each nest immediately before, and again immediately after, placing a predator model near each nest. Parent Carolina chickadees should reduce their feeding rate in response to visual predators so as to not expose the location of their nest. Therefore, we used the change in feeding rate as our response variable to the simulated predators. We predict that there will be no change in the feeding rate in response to the mourning dove treatment. However, for the squirrel and house wren treatments, we predict that the feeding rate will significantly decrease after the presentation of the respective models because Carolina chickadees have evolved adaptive behaviors to both predators.

Acknowledgements

Our greatest thanks goes to the various land owners who allowed us to install bird boxes on their properties, including Young Harris College, Brasstown Valley Resort & Spa, Brasstown Valley Golf Course, U.S. Forest Service and many others. We could not have accomplished this without the continued support of the faculty, students and staff at Young Harris College. We are also deeply grateful to the funding recieved from the Young Harris College Undergraduate Research Fund and the Highlands Plateau Audubon Society.

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