Graduate Thesis Or Dissertation
 

Bird communities in commercially thinned and unthinned Douglas-fir stands in western Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/47429d10k

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  • I studied species' abundances and habitat relationships of breeding and winter birds in commercially thinned and unthinned Douglas-fir (Pseudotsuga menziesii) stands from May 1989 to June 1991. The study was conducted in 40- to 55-year old stands in the Central Oregon Coast Ranges and the Tillamook State Forest. Total abundance and species diversity of breeding birds was greater in thinned stands. During the breeding season, Hammond's flycatchers (Empidonax hammondii), hairy woodpeckers (Picoides villosus), red-breasted nuthatches (Sitta canadensis), and dark-eyed juncos (Junco hyemalis) were more abundant in thinned than unthinned stands. Golden-crowned kinglets (Regulus satrapa), black-throated gray warblers (Dendroica nigrescens), and Pacific-slope flycatchers (Empidonax difficilis) were more abundant in unthinned stands. During the winter, red-breasted nuthatches and winter wrens (Troglodytes troglodytes) were more abundant in thinned stands. Differences in abundances of bird species between thinned and unthinned stands seemed to be related to differences in stand structure caused by thinning and to differences in hardwood densities that were probably unrelated to thinning. Differences in abundances of bird species between the Central Coast Ranges and the Tillamook State Forest were related to differences in shrub cover, and densities of hardwoods, snags, and conifers (>56 cm dbh) between the 2 regions. I recommended a thinning regime that would encourage understory and hardwood development in combination with unthinned leave areas to provide snag recruitment and habitat for species associated with dense stands. This regime is intended to maximize bird diversity and abundance in 40- to 55- year-old Douglas-fir stands in western Oregon.
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