BOREAL OWL MATING HABITAT IN THE NORTHWESTERN UNITED-STATES

We examined boreal owl (Aegolius funereus) mating habitat in the Sierr a Madre range of the Medicine Bow National Forest in Wyoming in the no rthwestern United States during 1992-93. In nocturnal surveys, we foun d 22 boreal owl singing locations which we compared to 68 random locat ions in the study area. Owls used stands dominated by Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) more often ( 77%) than stands of lodgepole pine (Pinus contorta). Stand size ranged from 0.2-122.8 ha though adjacent stand type (forest or opening) was not investigated. All boreal owls were found in areas with old forest characteristics including high basal areas of trees, tall snags, many large down logs, and a tall overstory canopy. Some boreal owls sang fr om old forest stands adjacent to clearcuts, one as close as 15 m. Olde r forests may provide nest holes for boreal owls which are obligate ca vity nesters.