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Abstract
Relationships between landscape-level patterns of forest cover and occupancy by Marbled Murrelets in the state of Washington where state-wide forest-cover information was available were investigated. Using a geographic information system, a 203-hectare circular area surrounding each of 261 previously surveyed locations was delineated. Within each area, we calculated the amount, distribution, and pattern of various classes of late-seral forest. Proportions of old-growth forest and large sawtimber were greater at sites that were occupied by murrelets than at sites where they were not detected. Mean size of patches (contiguous cover) of old growth and large sawtimber were also greater among occupied sites than among detected and undetected sites. On average, old growth and large sawtimber combined comprised about 36 percent of occupied sites (203-ha areas) vs. 30 percent and 18 percent on detected and undetected sites, respectively. Various indices of landscape pattern were less useful in distinguishing these sites, but in general, occupied sites had more complex patterns with more edge, a greater variety of cover types, and more complex shapes (greater lengths of edge relative to area of patches). Broader patterns, evaluated within large river basins, are also described, but lack of consistent survey effort among these basins precluded analyzing rates of occupancy in relation to forest cover at that scale.
Parent Publication
Citation
Raphael, Martin G.; Young, John A.; Galleher, Beth M. 1995. Chapter 18: A Landscape-Level Analysis of Marbled Murrelet Habitat in Western Washington. In: Ralph, C. John; Hunt, George L., Jr.; Raphael, Martin G.; Piatt, John F., Technical Editors. 1995. Ecology and conservation of the Marbled Murrelet. Gen. Tech. Rep. PSW-GTR-152. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; p. 177-190
