Crater Lake National Park Biological Sound Station Research: 2015 Annual Report

Whyte, Katherine; Ross, Corinne; Mohren, Sean

Beginning in 1992 the wildlife team at Crater Lake National Park began implementing the USFWS northern spotted owl (NSO) monitoring protocol to determine distribution, abundance, and reproductive success of NSOs in Crater Lake National Park. As the years progressed, reductions in budgets 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 USFWS 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 NSO and barred owl, an owl that directly competes with NSOs 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 the 2012-2013 pilot study, we believe using acoustic stations to supplement traditional NSO monitoring methods provides us with a cost effective way to improve our ability to document the presence of NSOs and barred owls. Beginning in the summer of 2014 we began full implementation of an acoustic survey protocol to document NSO and barred owls in the park. The 2015 survey effort represents our second year of full implementation and the details of this effort are described in this report. The primary goal for 2015 was to document NSOs and barred owls at 1) known NSO activity centers and 2) areas of the Park that has high quality NSO nesting. In the summer of 2015, 32 sound stations were deployed at 7 known NSO activity centers and 9 locations that were determined to have suitable NSO nesting habitat. The known NSO activity sites included: Bear Bluff, Bybee Creek, Crater Peak, Grayback Ridge, Little Copeland Creek, Thousand Springs and Sun Creek. The areas of NSO nesting habitat encompassed: Cascade Springs, Cavern Creek, Kerr Valley, North Maklaks Crater, Mazama Rock, Oasis Butte, Timber Crater, Trapper Creek, and Union Creek Springs. We deployed 2 sound stations at each site for an average of 14.5 days. A NSO was recorded at three known owl activity centers including; Bear Bluff, Grayback Ridge, and Thousand Springs. Field crews implementing USFWS NSO monitoring protocols also documented NSOs at these sites. Barred owls were documented at 8 sites using acoustic stations. Of those 8 sites, 4 overlapped with NSO surveys. Acoustic stations picked up a barred at 3 overlapping sites while field crews documented barred owls at one. From the data gathered using the acoustic stations in 2015, as well as in 2014, it is clear that their implementation is a beneficial asset in monitoring for NSOs and barred owls. Not only have they helped compliment the USFWS standard surveys, they have also allowed us to survey for NSOs and barred owls in a myriad of new locations. With proof of the acoustic stations value being demonstrated over the last two year, we plan to continue to use them in 2016 to increase our understanding of NSOs and barred owls distribution within the park.

Crater Lake National Park Biological Sound Station Research: 2015 Annual Report

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