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VARIATION IN STRUCTURAL NEST PROPERTIES AND THEIR EFFECTS ON REPRODUCTIVE SUCCESS IN CAROLINA CHICKADEES**

Abstract

Birds' nests serve a variety of functions including the thermoregulation of eggs and young during incubation and brooding, respectively. This is particularly important for birds that nest in cold climates and have altricial young because these young are not able to thermoregulate during their first few days after hatching. Therefore, altricial young are dependent on both the structural characteristics of the nest and on the adult birds' brooding for thermoregulation. Carolina chickadees (Poecile carolinensis) are small, cavity nesting passerines which have altricial young. Carolina chickadees are found across the eastern United States, breed in early spring and nest in artificial bird boxes. Since structural characteristics of nests influence their thermal environment, we hypothesized that structural characteristics of nests also affect reproductive success of birds with altricial young. We predicted that the structural characteristics of Carolina chickadee nests will be positively correlated to the proportion of eggs laid that hatched and survived to be at least eight days old. We monitored 100 standardized nest boxes in northern Georgia for Carolina chickadee nesting, clutch size, hatching success, and brood size eight days after hatching. After the end of the breeding season, we measured the total nest height, height of the moss and fiber components of the nest, and cup depth. We collected and dried the nests and weighed their moss and fiber components. Data analysis is currently ongoing but we plan on analyzing if the structural characteristics that improve the thermoregulatory environment of the nest have a positive effect on reproductive success. Specifically, we will use an information theoretic approach by comparing multiple competing hypotheses, including a null hypothesis, to evaluate the evidence for each nest characteristic as an explanatory variable for the proportion of eggs laid that hatched and survived to be at least eight days old.

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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