Pacific Northwest Research Station - Ecological Process & Function - Wildlife Ecology Team

Habitat relationships of the marbled murrelet

The marbled murrelet is federally listed as Threatened throughout its range in Washington, Oregon, and California. Like the spotted owl, the marbled murrelet was another of the major drivers behind creation of the Northwest Forest Plan. Research on the marbled murrelet, and the management implications of this research, have direct affects on the people and economy of the Pacific Northwest. The team conducts research in three topics: use of radar as a monitoring tool, inland habitat relationships, and relationships of forest structure to rates of nest predation. The team is the lead investigator in portions of a broader evaluation of radar as a monitoring tool. In collaboration with another scientist (a senior associate with a private firm), studies are underway to investigate how numbers of murrelet targets vary in relation to time of day, month, and location. Results of this work will be used to conduct power analyses with the ultimate goal to determine how radar counts might be used to derive an annual estimate of murrelet population size or population trend based on subsets of the population. Results of this work will be used to determine how radar counts could provide an independent assessment of population trend complimentary to population monitoring from at-sea surveys. In conjunction with this work, the team has lead responsibility for a comparison of radar-based counts with simultaneous at-sea population estimates in waters adjacent to the radar stations. Similar work has never been done and a large number of technical hurdles must be overcome to achieve success. For example, we do not know how large an area along the coast must be sampled to reflect the source population of murrelets flying inland through a particular drainage, nor do we know if this area changes over time as the nesting season progresses. Results of this work, if successful, will lead to improved techniques for effectiveness monitoring of murrelet population trend.

The objective of the inland habitat research is to understand how the amount and distribution of nesting habitat influences nesting behavior and population size of murrelets. For this landscape-level study, the team compares rates of detection and occupancy by murrelets in three large drainages varying from slightly fragmented to highly fragmented. Habitat attributes are measured at occupied and unoccupied sites and Geographic Information System analyses are used to assess large-scale patterns of habitat around each site. At a smaller scale, we are compiling existing ground-based vegetation data and measuring additional vegetation features within stands that have been surveyed for murrelet activity. With collaborators throughout the listed range of the murrelet, we are designing predictive models to identify habitat characteristics measured at the stand scale Wildlife Ecology Team Problem Analysis October 10, 2002 Page 23 of 33 that are associated with sites occupied by murrelets compared with sites where no murrelet activity was detected. Subsequently, we will test how closely independent models developed from known nest sites match those for occupied sites, to assess if the assumption that occupied sites represent nest sites is valid. These models are a precursor to, and form the basis of, murrelet habitat maps (see below under Survey and Monitoring Protocols). Results of this work, which will be published in peer-reviewed literature, will lead to better metrics for classifying nesting habitat of the murrelet.

The team is a member of a larger group of cooperators investigating rates of predation on simulated murrelet nests in relation to stand structure, proximity to human activity, and forest fragmentation. Members of the team include a faculty member at the University of Washington, 2 senior scientists affiliated with private firms, and a senior scientist with the Washington Department of Natural Resources. Nest predation is thought to be a limiting factor on productivity of the marbled murrelet. Previous research with forest birds in the eastern U.S. suggests that forest fragmentation leads to higher rates of predation. The current research, the first of its kind on the murrelet, was initiated to test that hypothesis. The team participates in study design, analysis of results, and interpretation of results. We have lead responsibility for mapping and analyzing patterns of habitat surrounding each of the 354 artificial nests. Results of this work have been presented in meetings of scientific societies and will be published in journals. The primary utility of the work will be a better understanding of relationships between pattern of habitat (size of patches and amount and type of edge), habitat structure (old forest, younger multi-stories forest, young forest with simple structure), and human activity (areas of concentrated activity such as campgrounds) and fitness of the murrelet as estimated by risk of predation. This will lead to better formulations of habitat capability models that might predict numbers and productivity of murrelets in relation to habitat pattern and human activity.

Team lead: Martin G. Raphael and Thomas Bloxton

Cooperators: Brian A. Cooper, ABR, Inc.; John M. Marzluff, University of Washington; Daniel E. Varland, Rayonier Timberlands; Leonard S. Young and Scott P. Horton, Washington DNR; Steven P. Courtney, National Council for Air and Stream Improvement; Sherri Miller and Jim Baldwin, Pacific Southwest Research Station; Tim Max, Pacific Northwest Research Station; Patrick Jodice and Ken Ostrom, USFWS; S. Kim Nelson, Oregon State University.

USDA Forest Service - Pacific Northwest Research Station - Olympia Forestry Sciences Laboratory
Last Modified: Monday, 31 January 2011 at 16:52:51 EST