Spotted Owl Monitoring in Olympic National Park: 2012 Annual Report

Gremel, Scott

This report summarizes progress on the northern spotted owl (Strix occidentalis caurina) monitoring program in Olympic National Park (ONP) in 2012. Monitored spotted owl territories in the national park, together with those visited by U.S. Forest Service Pacific Northwest Research Station in the surrounding Olympic National Forest, make up the Olympic Peninsula Demographic Study Area. This is one of eight study areas called for in the Northwest Forest Plan to estimate spotted owl population trends from demographic data and monitor the effectiveness of the plan. The spotted owl territories in the NPS portion of the study have now been monitored for an average of 20.4 years. In 2012, National Park Service personnel monitored and managed data on a sample of 52 spotted owl territories (hereafter "sites") to determine their occupancy and reproductive status. Cresw made 239 monitoring visits to spotted owl sites and 95% of visits were daytime surveys. This year 10 sites were occupied by spotted owl pairs and 13 by single spotted owls. This was the highest overall rate of site occupancy since 2006, but was made up of an unusually high number of single owls, many of which we could not relocate on subsequent visits. Seven pairs attempted to nest, fledging a total of ten young, and the average fecundity was 0.56 female offspirng per adult female. We banded five new adult spotted owls and one juvenile. At sites where any spotted owls responded, they were found on an average of 49% of monitoring visits. Data collected 1990-2008 were analyzed at a workshop in Corvallis, OR in January of 2009. This analysis estimated a range-wide rate of population decline of 2.9% a year, and a 4.3% annual decline for the Olympic Peninsula. Female fecundity appeared stable in the Olympics, but the more important estimate of adult survival was declining here and on nine of 10 other areas studied. The next meta-analysis of spotted owl demography data is scheduled for the end of the 2013 field season. Barred owls (Strix varia) were first documented on the Olympic Peninsula in 1985, and competition with this species is now the primary threat to the conservation of spotted owls in protected areas. Occupancy rates of spotted owls in ONP have declined significantly following the first detection of barred owls at a site. Spotted owls which have remained on territories following detections of barred owls have both moved farther and increased in elevation relative to sites where barred owls are absent. Barred owls have not been detected within 800 meters of 88% of monitored spotted owl sites in ONP. This year we confirmed barred owl presence at 81% of monitored spotted owl sites. Although barred owls now occupy portions of most spotted owl territories here, the majority of spotted owl sightings occur greater than 800 meters from any recorded barred owl detection. Models suggest that barred owls are less likely to occupy spotted owl sites on the steepest, driest slopes, and the movement of the remaining spotted owls to steeper slopes and higher elevations is making access and complete survey more difficult at many sites.

Spotted Owl Monitoring in Olympic National Park: 2012 Annual Report

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