NESTS OF NORTHERN-SPOTTED OWLS ON THE OLYMPIC PENINSULA, WASHINGTON

We located 155 nests in 82 territories occupied by Northern Spotted Ow ls (Strix occidentalis caurina) on the Olympic Peninsula, Washington. All nests were in trees. Of 116 nests that were measured, 105 were in cavities and 11 were in external platforms on tree limbs. Cavity nests were typically in large holes in the side of the trunk or in the brok en top of the trunk. Aspect of cavity entrances was non-random, with t he majority of cavities facing east-north-east. Location of nest trees did not differ from expected values for slope aspect or position on s lope. Proportions of nest sites in different percent slope categories differed from availability, with more nests than expected in the highe r percent slope categories. Nests usually were in stands with high ove rall canopy closure (greater than or equal to 70%), but canopy closure in the immediate vicinity of the nest varied from 35-90%. Most nests (87%) were in multilayered stands dominated by large trees. Nests in y ounger stands were typically in stands where remnant old trees were pr esent. Owls changed nests between successive nesting events in 80% of all cases. Changes in pair members on a territory did not influence th e frequency with which pairs switched to a new nest tree in the next n esting year. Based on observed rates of attrition, the expected life s pan of nests was 120 years.