Stand structures used by Northern Spotted Owls in managed forests

We compared vegetative structures in 4-16-ha patches in forest stands used by 12 pairs of Northern Spotted Owls (Strix occidentalis caurina) for nesti ng (N = 44) and foraging (N = 38) with habitat structures in 50 stands loca ted randomly throughout annual home ranges in a young and mid-successional forest landscape (25-79 yr-old stands) in the foothills of the western Casc ades in Oregon. Forest stand structures influenced selection for stands use d for foraging and nesting by Spotted Owls, and abundance of these structur es varied with successional development as represented by five age classes. Conifer saplings (10-19 cm in diameter at breast height [dbh]) and trees 5 0-79 cm dbh were more abundant in foraging areas than nest sites or random sites. Large snags (>40 cm dbh) tended to be more abundant, down woody debr is was more abundant, and cover of herbs and low-growing shrubs (<0.5 m) wa s lower in stands in which owls hunted frequently than in randomly located stands of the same age classes. Owls nested in trees as young as 41 yr old, although 65% of nest trees were older than 120 yr of age. We found 22 (50% ) nests in forest stands 46-79 yr of age, whereas owls repeatedly foraged i n stands as young as 27 yr of age. Silviculturists should be able to create foraging habitat for Northern Spotted Owls in managed forests by emphasizi ng control of tree densities and form, woody debris, and understory vegetat ion. Suitable nesting habitat might best be facilitated via retaining legac y trees. Future research should determine the relative contribution of mana ged forests to owl conservation.