Snag abundance for primary cavity-nesting birds on nonfederal forest lands in Oregon and Washington

More than 100 species of vertebrates in thePacific Northwest use standing dead trees(snags) at one time or another in their lifecycle(Thomas et al. 1979a, Neitro et al. 1985). Withfew exceptions, investigators have found sig-nificant correlations between snag density andthe abundance of primary cavity-nesters inNorth American coniferous forests (Raphaeland White 1984:47-53, Madsen 1985, Zarno-witz and Manuwal 1985, McComb et al. 1986,Land et al. 1989, Carey et al. 1991, Schreiberand deCalesta 1992). Similar relationships havebeen detected for secondary cavity-nesters(Schreiber and deCalesta 1992). Thomas et al.(1979a) and Neitro et al. (1985) suggested thattimber management practices and changingland-use patterns in the Northwest are reduc-ing snag abundance and thus dependent pop-ulations of wildlife species (also see Morrisonet al. 1986 and Schreiber and deCalesta 1992).Snag abundance in unmanaged Douglas-fir(Pseudotsuga menziesii) forests >40 years oldhave been quantified by Spies et al. (1988),Carey et al. (1991), and Spies and Franklin(1991). However, patterns of snag abundanceacross a broader region, especially in youngmanaged stands, are poorly understood. Re-gional assessments can help guide planning andpolicy for managing Northwest forests for wood production and wildlife in public and privateforests. In this study we assessed patterns ofsnag abundance among plant communities andstand conditions in managed and natural for-ests on nonfederal lands in Oregon and Wash-ington. Our objectives were to: (1) quantifydensities and characteristics of snags across arange of forest conditions; (2) assess snag ori-gin, whether from death of trees in the presentstand or carried over from a previous stand;(3) use models of snag-bird relationships to pre-dict the role that nonfederal lands might playin providing habitat for primary cavity-nest-ers; and (4) discuss implications for fu:est man-agement in the Northwest.