Crater Lake National Park Biological Sound Station Research: 2017 Annual Report

Mohren, Sean; Stevens, Andrew; Perez-Jimenez, Janette

Beginning in 1992 the wildlife team at Crater Lake National Park started implementing the US Fish and Wildlife Service northern spotted owl monitoring protocol to determine distribution, abundance, and reproductive success of northern spotted owls in Crater Lake National Park. As the years progressed, reductions in budgets, shifting priorities and increased awareness of safety has reduced our ability to implement this monitoring protocol, in its entirety, at the Park. In general, the wildlife staff is presently capable of implementing 1-3 noncompliance surveys at each known owl activity center in any given year versus the 6 surveys recommended in the US Fish and Wildlife Service spotted owl monitoring protocol. In addition, there is currently no staff time available to survey areas of the park that contains high quality habitat but is not currently listed as a known owl activity center. In an effort to help improve our ability to determine the occupancy and distribution of northern spotted owl and barred owl, an owl that directly competes with northern spotted owls for habitat and resources, the wildlife team began exploring the use of acoustic stations to help supplement our survey efforts. Based on the results of our 2012-2017 sampling efforts, we believe using acoustic stations to supplement traditional northern spotted owl monitoring methods provides us with an efficient and cost effective way to improve our ability to document the presence of northern spotted owls and barred owls at Crater Lake National Park. The 2017 survey effort represents our fourth year of full implementation and the details of this effort are described below. The primary goals for 2017 were to document northern spotted owls and barred owls at 1) known northern spotted owl activity centers and 2) areas of the Park that contain high quality spotted owl habitat. In the summer of 2017, 21 sound stations were deployed at 6 known northern spotted owl activity centers and 5 locations that were determined to have suitable northern spotted owl nesting habitat. In general, we deployed 2 sound stations at each site for an average of 14.82 days. Northern spotted owls were recorded at two sites that were previously unknown to contain spotted owls. Unfortunately field crews were unable to verify these results due to the close proximity of wildfires in the Park that started shortly after we identified spotted owls using these locations. The acoustic station at the Grayback Ridge known spotted owl activity center recorded a single spotted owl and a unknown Strix species was documented at the Thousand Springs known spotted owl activity center but the individual was too far away to be confidently identified to species. Barred owls were documented at 6 of the 21 sites surveyed including 4 known spotted owl activity centers and 2 areas that were sampled because of the presence of spotted owl nesting habitat.