Term of Award

Fall 2018

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Biology

Committee Chair

C. Ray Chandler

Committee Member 1

Michelle Cawthorn

Committee Member 2

John Schenk

Abstract

Classical views on community structure emphasized deterministic processes and the importance of competition in shaping communities. However, the processes responsible for shaping avian communities remain controversial. Attempts to understand distributions and abundances of species are complicated by the fact that birds are highly mobile. Many species migrate biannually between summer breeding grounds and wintering grounds. The goal of this study was to test four hypotheses that attempt to explain how migratory species integrate into resident assemblages of birds (Empty-Niche Hypothesis, Competitive-Exclusion Hypothesis, Niche-Partitioning Hypothesis, and Generalist-Migrant Hypothesis). I collected data on birds foraging during the winter of 2017-2018 in Magnolia Springs State Park, Jenkins County, Georgia, U.S.A. Foraging behavior, substrate, perch height, horizontal location, plant used, and habitat type were recorded for each observation. Three focal species, Tufted Titmouse (resident), Ruby-crowned Kinglet (migratory), and Yellow-rumped Warbler (migratory), were chosen to test the above hypotheses by comparing their niche location, breadth, and overlap.

Tufted Titmice changed their niche location after migrant arrival, but neither of the focal migrant species moved into the exact niche space vacated by residents. This satisfies most of the predictions for the Competitive-Exclusion Hypothesis, but not the prediction that migrants would move into habitat vacated by residents. Because Tufted Titmice did not change their niche breadth after migrant arrival and did not decrease their niche overlap with migrants significantly after migrant arrival, I reject the Niche-Partitioning Hypothesis. I also reject the Generalist-Migrant Hypothesis because resident focal species did not differ significantly in their niche breadth from migratory species. While several predictions were met for the Empty-Niche Hypothesis, resident species did change their niche location, in contradiction of one prediction for Empty-Niche Hypothesis. To determine if competition or other seasonal factors are responsible for this change in niche location for resident birds, future studies should account for all members of the bird community and quantify resource availability.

Research Data and Supplementary Material

No

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