An ecological study of the breeding birds of grassland habitats within Illinois
Herkert, James R.
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https://hdl.handle.net/2142/23188
Description
Title
An ecological study of the breeding birds of grassland habitats within Illinois
Author(s)
Herkert, James R.
Issue Date
1991
Doctoral Committee Chair(s)
Sanderson, Glen
Robinson, Scott K.
Department of Study
Biology, Ecology
Agriculture, Forestry and Wildlife
Discipline
Biology, Ecology
Agriculture, Forestry and Wildlife
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Agriculture, Forestry and Wildlife
Language
eng
Abstract
The breeding bird communities of 24 grassland fragments in Illinois were studied between 1987-1990 to examine the influence of area, vegetation structure, species interactions, and habitat management on community structure. Fragment size was found to strongly influence breeding bird species richness within grasslands. Non-prairie bird species dominated small grasslands whereas prairie bird species dominated large grasslands. The distribution of birds between fragments followed a non-random pattern with a predictable subset of birds regularly found on large fragments avoiding small grasslands. Abundances of nine of the twelve species examined were significantly correlated with area, but not all in the same direction. In general, densities of prairie species were positively correlated with area whereas non-prairie bird densities were negatively correlated with area. Habitat structure also significantly influenced bird abundances within fragments, but always accounted for less than half the variation in species abundance within fragments. Species interactions were also found to significantly affect bird distributions but influenced abundances less than area and habitat structure for most species.
The analysis of the short-term effects of habitat management showed two species, the Henslow's sparrow and sedge wren, to be influenced the most by grassland management. Both species avoided sections of grasslands that had been recently burned or mowed. An ordination of bird communities from the different management units showed that bird communities on small grasslands were, in general, more similar to one another than they were to bird communities on large grasslands regardless of their management status.
I suggest that bird distribution patterns within fragments are likely the result of interplay between area related stochastic processes and area- and disturbance-mediated habitat diversity, and that other factors in addition to area, habitat structure, species interactions, and habitat management may also significantly influence grassland bird assemblages. Furthermore I suggest that optimal management strategies for small and large grasslands need not be the same. Small grasslands can be managed as complete units whereas large grasslands should be managed so as to provide a mosaic of burned and unburned, or mowed and unmowed areas.
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