Wildlife Research and Management - Wildlife Research
Date Published: September 2008
Number of Pages: 25
Author(s): Gary Falxa and Mark Huff
This report summarizes activities of the Marbled Murrelet (Brachyramphus marmoratus) Effectiveness Monitoring Program in the area of the Northwest Forest Plan (NWFP) during fiscal years 2004 - 2007. The purpose of the effectiveness monitoring is to assess status and trends of murrelet populations and nesting habitat. Findings for the first 10 years of the NWFP (1994-2003), including detailed analyses of the status and trends of murrelet populations and nesting habitat, are presented in the 10-year NWFP effectiveness monitoring report (Huff et al. 2006). Whereas the 10-year report did not cover the 2004-2007 period of this report, the preparation of the 10-year report by Huff and his collaborators was a primary focus during 2004- 2005, and its completion a major accomplishment. Another accomplishment was a publication describing the methods of the murrelet population monitoring program (Raphael et al. 2007).
This report includes results of the annual at-sea population surveys including an initial trend analysis, and a brief update on modeling of nesting habitat. Nesting habitat analysis was not a focus of work following publication of the 10-year report, but will be for 2008-2009, for an upcoming 15-year NWFP monitoring report.
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. Conservation Zones 1 through 4 were surveyed for murrelets in all years between 2004 and 2007. Conservation Zone 5 was not surveyed in 2006. The highest total population estimate for this area (20,500 ± 4,600 birds at the 95 percent confidence interval) was in 2004. The lowest total population estimate for this area (17,400 ± 4,600 birds at the 95 percent confidence interval) was in 2007. At these confidence levels, the 2004 through 2007 population estimates broadly overlap, as well as overlapping with estimates from 2000 through 2003. During these 4 years, murrelet density (birds per km2) was highest in Conservation Zones 3 and 4 (entire coast of Oregon to just south of Cape Mendocino, California) and lowest in Conservation Zone 5 (California coast, just south of Cape Mendocino to just north of San Francisco Bay).
For the 5 zones combined, a preliminary trend analysis indicates that a 6-to-7 percent annual decline between 2000 and 2007 is unlikely. Additional at-sea monitoring will be needed to detect population declines in the range of 2 to 5 percent with a high level of statistical power.
For the habitat monitoring component of the Effectiveness Monitoring Program, non-map and map predictive models were developed to estimate murrelet nesting habitat. Field data for the non-map model was collected from occupied and unoccupied sites across the species’ range within the NWFP area. The map-models of murrelet nesting habitat were developed from spatial attributes of occupied sites based on variables that best distinguished attributes of occupied sites compared to attributes of available habitat within the range. Results from the map and non-map models were published in the 10-year interpretive report of the effectiveness monitoring program (Huff et al. 2006). In 2007, the program began to explore modifications to the existing habitat models, to evaluate model performance using the new IMAP vegetation map that is under development, and to examine the utility of resource selection function models as an alternative to Ecological Niche Factor Analysis.
Falxa, G., J. Baldwin, D. Lynch, S.K. Nelson, S.L. Miller, S.F. Pearson, C.J. Ralph, M.G. Raphael, C. Strong, T. Bloxton, B. Galleher, B. Hogoboom, M. Lance, R. Young, and M.H. Huff. 2008. Marbled murrelet effectiveness monitoring, Northwest Forest Plan: 2004-2007 summary report. 25 pp.