Ecological Relationships of Bird Communities in Forest Islands of East-Central Illinois
Blake, John Gilman
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https://hdl.handle.net/2142/77618
Description
Title
Ecological Relationships of Bird Communities in Forest Islands of East-Central Illinois
Author(s)
Blake, John Gilman
Issue Date
1983
Department of Study
Ecology, Evolution, and Conservation Biology
Discipline
Ecology, Evolution, and Conservation Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Language
eng
Abstract
East-central Illinois is devoted primarily to agriculture and remaining tracts of forest serve as valuable habitat islands for a variety of species. Preservation of many species is dependent on large blocks of forest. Bird communities in forest tracts (15 total, 1.8 to 600 ha) were studied during 1979, 1980, and 1981 to investigate ecological relationships of these communities.
During summer, total species richness of a forest and species richness at a given point within a forest were strongly correlated with forest area. Total species richness increased with area at a more rapid rate, indicating the importance of spatial segregation of species in larger forests. Much of the segregation was related to variation in habitat structure within a forest. However, habitat exerted a much weaker influence on community structure that did area. The relationship between area and species richness varied with migratory strategy and preferred breeding habitat. Neotropical migrants and species dependent on forest interior habitat were poorly represented in small forests. Many are dependent on extensive blocks of forest and continued reduction and fragmentation of forests may adversely affect such species.
Small forests were dominated by omnivores; larger forests had greater numbers of foliage and bark insectivores. Species richness in major trophic groups was correlated with area. Bird communities of small forests also supported a morphologically diverse set of species. Analyses based on euclidean distances indicated that species packing increased from small to larger forests (few to many species). Results differed significantly from random, indicating that species interactions likely influence community structure.
Analyses of winter communities indicated a strong correlation between species richness and area. Trophic structure varied with area although granivores were most abundant over all areas. Large forests provide food and protection from adverse weather and may be critical to overwinter survival of many species.
Results from this study indicate that large forests are neceassary for many species. Small forests of equal total size will not support the same species complement as a single large forest. Strategies for species preservation must be based on analysis of species composition, not simply on total species richness.
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