Bird Use of Forest Structural Classes in Grand Fir Forests of the Blue Mountains, Oregon

Abstract

Abstract We sampled breeding birds in 83 stands in the Blue Mountains, northeastern Oregon, 1994–1996, to describe bird use of forest structural classes in grand fir (Abies grandis) forests. We classified stands, based on basal area in different tree-size categories, into six forest structural classes: (1) stand initiation (SI); (2) stem exclusion, open canopy (SEOC); (3) stem exclusion, closed canopy (SECC); (4) understory reinitiation (UR); (5) young forest, multistory (YFMS); and (6) old forest, multistory (OFMS). Most species were detected in all structural classes, but slightly more than onethird of species analyzed (13 of 38) differed in abundance among structural classes (P < 0.004). Cluster analysis, based on structural attributes measured in each stand and weighted by avian abundance, grouped birds with similar habitat associations and allowed us to identify “non-SI associates,” “SI associates,” “structural class generalists,” and “mature forest associates.” We did not identify any species that could be considered strictly “OFMS associates.” With the exception of some SI associates, such as the mountain bluebird (Sialia currucoides) and house wren (Troglodytes aedon), we found little evidence of structural class specialization by birds. In grand fir forests of the Blue Mountains, ecologists and managers should focus on understanding how specific silvicultural prescriptions influence structural attributes that are correlated with avian abundance, rather than on stand age per se. FOR. SCI. 48(2):311–321.