Chapter 31: Abundance and Distribution of Marbled Murrelets in Oregon and Washington Based on Aerial Surveys

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Title: Chapter 31: Abundance and Distribution of Marbled Murrelets in Oregon and Washington Based on Aerial Surveys

Author: Varoujean II, Daniel H.; Williams, Wendy A.

Date: 1995

Source: 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. 327-338

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Station ID: GTR-PSW-152

Description: To determine the abundance and distribution of Marbled Murrelets, aerial surveys of the Oregon coast, Washington outer coast, and shores of the western Strait of Juan de Fuca were conducted in August/September 1993. Based on these marine surveys, abundance estimates are established for Oregon (6,400-6,800 birds) and the waters surveyed in Washington (3,400-3,600 birds). A comparison of these estimates to those established by other surveys indicates that boat-based surveys may give higher estimates of murrelet abundance, and that population size has probably not decidedly changed over the last 10 years in either Oregon or Washington. On the Pacific Ocean coast of both states, murrelets were found to be unevenly distributed with birds being most abundant in central Oregon and northern Washington, and present in lower abundance in southern Oregon and from northern Oregon through southern and central Washington. This distribution appears to be related to shore type, and proximity to the entrances to major river mouths and embayments, at least in Oregon, and to available inland nesting habitat in both states. The ratio of hatch-year birds to the total number of murrelets seen during the surveys was estimated to be 5 percent. As a measure of production, this estimate is too low for population maintenance, but we conclude that murrelets in Oregon and Washington may not be in a long-term population decline.

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Citation

Varoujean II, Daniel H.; Williams, Wendy A. 1995. Chapter 31: Abundance and Distribution of Marbled Murrelets in Oregon and Washington Based on Aerial Surveys 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. 327-338.