2019 Washington At-Sea Marbled Murrelet Population Monitoring: Research Progress Report

In 1992, the marbled murrelet (Brachyramphus marmoratus) was listed as a Threatened species by U.S. Fish and Wildlife Service in California, Oregon, and Washington under the Endangered Species Act and as Threatened by Washington State. A federal recovery plan was published in 1997 that outlined recovery strategies including developing and conducting standardized at-sea surveys. In addition to meeting the requirements of the Endangered Species Act, marbled murrelet monitoring was designed to evaluate the effectiveness of the Northwest Forest Plan (Madsen et al. 1999), which is a large-scale ecosystem management plan for federal lands in the Pacific Northwest.

As part of the Effectiveness Monitoring Program of the Northwest Forest Plan, Washington Department of Fish and Wildlife, USDA Forest Service Pacific Northwest Research Station, U.S. Fish and Wildlife Service, Crescent Coastal Research, and other state, federal, and private researchers have participated in a program to estimate marbled murrelet population size and trends during the breeding season between San Francisco Bay and Washington state since 2000. The information derived from this effort is the only information available to assess population size and trends in this geographic area for this species. This monitoring program uses at-sea line transects within 8 km of the Washington, Oregon, and northern California coastline in the area covered by the Northwest Forest Plan. There are five monitoring zones or Conservation Zones throughout this range, two of which are located in Washington: (Zone 1) Strait of Juan de Fuca, Puget Sound, Hood Canal, and the San Juan Islands; and (Zone 2) the outer coast of Washington. Both zones are currently monitored by the Washington Department of Fish and Wildlife. The U.S. Forest Service monitored Zone 1 from 2000-2012.

Between 2000 and 2015 we conducted annual surveys of both of Washington’s Conservation Zones. Starting in 2016 we implemented a reduced-sampling effort design, where Conservation Zone 1 is sampled in even years and Conservation Zone 2 is sampled in odd years. In Washington, this sampling design was implemented in 2016 with surveys conducted in Conservation 1 but not in Zone 2 and we have alternated between Zones since. This report focuses on monitoring results from Conservation Zone 2 during the 2019 monitoring season (15 May - 31 July).

The population estimate for the Washington outer coast for 2019 (Zone 2) was 1,657 birds (95% confidence interval = 745 – 2,752 birds). No trend was detected for Conservation Zone 2; while the trend was negative (-2.2%), the evidence for a trend was not conclusive because the estimate’s 95% confidence interval overlapped zero (-5.8% to 1.5%).