Wildlife Research and Management - Wildlife Research
Date Published: August 2009
Number of Pages: 19
Author(s): Gary Falxa, Deanna Lynch, and the Marbled Murrelet Monitoring Team members
This report summarizes activities of the Marbled Murrelet (Brachyramphus marmoratus) Effectiveness Monitoring Program in the area of the Northwest Forest Plan (NWFP), from the start of monitoring in 2000 through 2008. The purpose of the effectiveness monitoring is to assess status and trends of murrelet populations and nesting habitat. This report includes results of the annual at-sea population surveys including an initial trend analysis, and an update on modeling of nesting habitat.
The objectives of the murrelet population monitoring are to estimate (1) population trends and (2) population size during the breeding season within and across five murrelet conservation zones in coastal waters adjacent to the NWFP area. The 2008 estimated population of murrelets in the NWFP target (sampling) area is 17,800 (95 percent confidence interval = 14,600 to 21,000), with the largest Zone population estimate (about 6,200) occurring in Conservation Zone 3 (Columbia River to North Bend, Oregon). At the conservation zone scale, murrelet at-sea density estimates in 2008 ranged from 0.14/km2 in Zone 5 (California coast, just south of Shelter Cove to San Francisco Bay) to 4.14 birds/km2 in Zone 4 (North Bend, Oregon to just south of Shelter Cove, California).
For the 5-zone area combined, the population declined over the years 2000 to 2008. The estimated rate of annual decline for that period was 2.4 percent, which is equivalent to an average decline of about 488 (standard error = 241) birds per year. The estimated rate of decline from year 2001 to 2008 was greater, averaging 4.3 percent or 867 (standard error = 129) birds per year. Additional at-sea monitoring will be needed to test for population declines at the scale of individual conservation zones, and to evaluate whether the declines observed to date continue into the future, and if so, at what rate.
Under the habitat monitoring component of the Effectiveness Monitoring Program, the habitat team continued to develop modifications to the existing habitat models, and to evaluate model performance using the GNN-IMAP vegetation maps that are under development. The team decided to pursue resource selection function models as the preferred approach for modeling the amount and distribution of murrelet nest habitat, for Northwest Forest Plan’s 15-year report cycle.
Falxa, G.A., J. Baldwin, D. Lynch, S.K. Nelson, S.L. Miller, S.F. Pearson, M.G. Raphael, C. Strong, T. Bloxton, B. Galleher, B. Hogoboom, M. Lance, and R. Young. 2009. Marbled murrelet effectiveness monitoring, Northwest Forest Plan: 2008 summary report. 19 p.