Effects of forest management on breeding bird populations of mixed deciduous forests of southern Indiana
Declining population trends of breeding birds associated with mature forests of the eastern and central United States have been a major concern for conservationists and land managers. As a landscape-scale, long-term, manipulative experiment, the Hardwood Ecosystem Experiment (HEE) may provide important insights into factors associated with these declines. By employing various timber harvest practices, this project enabled me to compare the effects of uneven-aged management and even-aged management with unharvested control sites. I also quantified the characteristics of the breeding bird community at the HEE sites during the pre-treatment period alone. The harvests took place in winter 2008, allowing collection of 3 years of pre-treatment data and 2 years of post-treatment data. From 2006-2010, I observed 85 species of birds across 240 survey points, and a total of 32,270 detections. Based on general habitat requirements, I chose 5 species to represent the early successional guild and 7 species for the mature forest guild. After making adjustments for differences in detectability, I used analysis of variance to compare the means of each species' population in the management types. Within the pre-treatment data, there were no significant effects among the treatment types when the mean of the 3 years was used for the analysis. The bird communities were also similar to the nearby Hoosier National Forest, which provides further evidence that the pre-treatment data will be useful in detecting changes associated with the HEE treatments. With the exception of Brown-headed Cowbird (Molothrus ater, which had no significant effects) the other early successional species responded positively to the treatments. Indigo Bunting (Passerina cyanea) and Eastern Towhee (Pipilo erythrophthalmus) populations significantly increased in uneven- and even-aged management units, while Carolina Wren (Thryothorus ludovicianus) populations significantly increased in all 3 management types. Mature forest species had a much more varied response to treatments. Red-eyed Vireo (Vireo olivaceus ), Scarlet Tanager (Piranga olivacea), Worm-eating Warbler (Helmitheros vermivorum), and Wood Thrush ( Hylocichla mustelina) did not respond significantly to treatments. Acadian Flycatcher (Empidonax virescens) abundance increased pre- to post-treatment in control units and uneven-aged units, while Cerulean Warbler (Setophaga cerulea) abundance increased in even-aged and uneven-aged units. Ovenbird (Seiurus aurocapilla) populations significantly declined in uneven-aged units, but remained stable in even-aged management units and control units. My results suggest that not all members of a species guild are likely to respond similarly to forest harvesting, and that management practices must be tailored to the species of concern.
Dunning, Purdue University.
Wildlife Management|Forestry|Natural Resource Management
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