Bird communities in managed conifer stands in the Oregon Cascades: habitat associations and nest predation

Green-tree retention is being implemented on state andfederal lands in Oregon. Silvicultural prescriptions withtree and snag retention are thought to mimic naturaldisturbance patterns in the Pacific Northwest more closelythan traditional silvicultural practices, which reducestructural complexity. The effects of green-tree retentionon native bird species in the Pacific Northwest are largelyunknown. Consequently, this study examined aviancommunities, indtvidual species abundances, habitatassociations, and artificial nest predation in the West-central Oregon Cascade Range. Between May and August 1992,4 clearcut, 4 green-tree retention, and 4 mature coniferstands were studied. Species diversity was greater inmature stands than in clearcuts. Total bird abundance and species richness did not differ among stand types, butcommunity composition did. Differences in communitycomposition were related to differences in vegetationstructure and composition. Species showed individualisticresponses to stand types, and individual species abundanceswere correlated with conifer and snag densities more thanwith other variables. Green-tree retention stands providedhabitat for some birds that are associated with early- andlate-seral habitats. Predation on ground nests was greaterin clearcuts than retention stands. Shrub nest predationwas greater in retention stands than in clearcuts or maturestands. These results support the hypothesis that treesand snags which are retained in harvest units serve asperches which facilitate the location of shrub nests bypredators. Retention stands may be sink habitats forspecies which nest in them unsuccessfully. Open canopyspecies which are negatively associated with green-treeretention may show further declines in population if green-tree retention stands replace clearcuts on state andfederal lands in Oregon. In order to provide habitat fornative species, a variety of stand conditions should bemaintained across the landscape and management objectivesshould be tailored to individual species or communities.