Term of Award

Spring 1999

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)


Department of Biology

Committee Chair

C. Ray Chandler

Committee Member 1

Stephen P. Vives

Committee Member 2

Lorne M. Wolfe


A main goal of ecological research is to understand the factors influencing patterns of diversity in ecological communities. On a broad scale, climate and habitat availability are thought to be important factors in generating community patterns. However, on a local scale, where climate and habitat are relatively homogeneous, species interactions, such as competition, are thought to play an important role in regulating species abundance. In avian communities, competition results in three mechanisms permitting coexistence: 1) interspecific territoriality/aggression, 2) differential habitat selection, and 3) differences in foraging strategy. Several studies within the genus Vireo have revealed that interspecific territoriality/aggression, habitat selection, and foraging strategies may play an important role in permitting coexistence of congeners. However, the intensity of these interactions varies geographically. Red-eyed and Blue-headed Vireos are widely sympatric in eastern North America and are similar in terms of habitat use, foraging strategy, and diet. Therefore it is plausible to assume that competition may be an important factor in permitting their coexistence. Therefore, the objective of this research was to elucidate the ecological interactions of Red-eyed and Blue-headed Vireos where they are sympatric at Mountain Lake Biological Station. Song playback experiments, behavioral observations, and habitat analysis were used to assess the potential for competition between these two species.

Red-eyed and Blue-headed Vireos held overlapping territories and responded infrequently to playback of the other species' song. Red-eyed and Blue-headed Vireo habitats were structurally similar, however, there were quantitative differences in tree and shrub composition within habitats. In addition to absence of interspecific aggression and the presence of structural differences between habitats, Red-eyed and Blue-headed Vireos also employed similar foraging strategies. For example, they searched for prey at similar rates, foraged at similar heights, and used similar foraging maneuvers. However, there is an apparent segregation of habitat by tree species used as a foraging site and the substrate at which foraging maneuvers are directed.

Spatial overlap, low grade response to congeneric song, and broad habitat similarities indicate that interference competition does not occur between Red-eyed and Blue-headed Vireos at MLBS. However, differences in habitat composition and shifts in foraging behavior indicate that exploitative competition may play a role in structuring the coexistence between these two species. However, it remains unclear whether these patterns are the result of competition or individualistic responses to habitat.


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