2009 At-Sea Marbled Murrelet Population Monitoring: Research Progress Report
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2009 At-Sea Marbled Murrelet Population Monitoring: Research Progress Report

Category: Wildlife Research and Management - Wildlife Research

Date Published: March 2010

Number of Pages: 21

Author(s): Scott F. Pearson, Martin G. Raphael, Monique M. Lance and Thomas D. Bloxton, Jr.

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, long-term 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.

Washington Department of Fish and Wildlife, USDA Forest Service Pacific Northwest Research Station, and other state, federal and private researchers have participated in a program to estimate marbled murrelet population size and trends 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. 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 (Conservation Zones) throughout this range, two of which are located in Washington; Zone 1 includes the Strait of Juan de Fuca, Puget Sound, Hood Canal and the San Juan Islands and is monitored by the U.S.D.A. Forest Service Pacific Northwest Research Station; Zone 2 includes the Washington outer coast and is monitored by Washington Department of Fish and Wildlife. Within Zone 1 there are three geographic strata defined by murrelet density and ecological factors: Stratum 1: Strait of Juan de Fuca; Stratum 2: San Juan Islands, Whidbey and Camano islands, Port Townsend, Admiralty Inlet, and most of Hood Canal; and Stratum 3: south Hood Canal and central/south Puget Sound. Within Zone 2 there are two geographic strata based on marbled murrelet density: Stratum 1 (north of Pt. Grenville – high density) and Stratum 2 (south of Pt. Grenville – low density). Each stratum is divided into primary sampling units (PSUs), which are roughly rectangular areas along approximately 20 km of coastline.

This report focuses on monitoring results from Conservation Zones 1 and 2 during the 2009 monitoring season. At-sea survey effort began 15 May and ended 31 July. As designed, all PSUs in Zone 1 were visited 2 times. All PSUs in Stratum 1 of Zone 2 were sampled three times. All PSUs in Stratum 2 of Zone 2 were sampled once.

The marbled murrelet population estimate for all zones in the Northwest Forest Plan area in 2009 was 17,791 (95% confidence interval 14,631 – 20,952). The population estimate has ranged from 17,354 – 23,673 over the 9 years of monitoring. The population estimate for inland Washington waters for 2009 was 5,623 birds (95% confidence interval = 3,922 – 8,352 birds) with a 7.0% (standard error = 1.8%) annual rate of decline for the 2001-2009 period. The population estimate for the Washington coast for 2009 (Zone 2) was 1,266 birds (95% confidence interval = 751 – 1,881 birds) with no significant decline. For Washington State (Zones 1 and 2 combined), there was a significant decline in murrelet density for the 2001-2009 period (r2 Linear = 0.65, P = 0.009).

Suggested Citation:
Pearson, S.F., M.G. Raphael, M.M. Lance, and T. D. Bloxton, Jr. 2010. Washington 2009 at-sea marbled murrelet population monitoring: Research Progress Report. Washington Department of Fish and Wildlife, Wildlife Science Division and USDA Forest Service Pacific Northwest Research Station, Olympia, WA.