Title page for ETD etd-12012008-122250


Type of Document Master's Thesis
Author Lessig, Heather
URN etd-12012008-122250
Title Species Distribution and Richness Patterns of Bird Communities in the High Elevation Forests of Virginia
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Walters, Jeffrey R. Committee Chair
Belden, Lisa K. Committee Member
McShea, William J. Committee Member
Keywords
  • species richness
  • elevational gradient
  • Southern Appalachians
  • elevation sensitive
  • island biogeography
  • migrant
  • multi-scale habitat
Date of Defense 2008-11-05
Availability unrestricted
Abstract
Island biogeography theory predicts that the patterns and distributions of spatially isolated populations are governed by large scale processes. The high elevations forests in the Southern Appalachians represent a series of naturally fragmented islands that harbor many isolated populations of species at the southern limits of their range. Understanding the governing forces of population dynamics in this region will enhance the probability of species persistence in the face of threats such as global warming and human development. We surveyed bird populations across multiple elevations in Virginia and combined this with a multi-scale habitat analysis to determine influences of species presence and species richness. We detected 101 species across the elevation gradient, including 12 species with special conservation status and ten species whose presence increased with increasing elevation. These ten elevation sensitive species responded to habitat variables at both the microhabitat and landscape scale, with species-specific patterns of habitat variable correlation emerging. Habitat type was least effective in predicting species presence for any elevation sensitive species. Species richness declined over the elevation gradient until the highest elevations, where this trend reversed and richness began to increase. This pattern was driven by an increase in short-distance migrants beginning at mid-elevations, which ultimately overpowered a corresponding decrease in long-distance migrants beginning at similar elevations. Habitat analysis linked these patterns to a preference of short-distance migrants for smaller, more isolated non-forested patches, and a historical lack of persistence for long-distance migrants. Conservation and management decisions for the region should focus on a multi-scale approach that preserves all habitat types for continued species presence and high species richness, although the persistence of particular elevation sensitive species is compounded by unique species-habitat relationships and the perception of islands as species-specific. Continued monitoring of these fragmented populations in light of both short- and long-term threats which span multiple scales of influence will maintain high species richness and ensure the persistence of crucial breeding habitat.
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