Varoujean and Williams 



ChapterSl 



Abundance and Distribution in Oregon and Washington 



Table 2 Marbled Murrelet population estimate based on an aerial survey conducted on the Washington outer coast on 4- 

 5 September 1993. The study area extended from TWamook Head, Oregon north to Cape Flattery, Washington. The projected 

 population estimate for each latitudinal block is the density estimate (derived from the number of observed murrelets divided 

 by the actual area surveyed) times the total study area in each block, assuming a study area width of 4,000 m 



'Location is represented as the extent of coastline between latitudinal listings 



* AD = Adults in alternate plumage; B W = Black/White plumage, which includes adults in bask plumage and hatch-year birds. 



to shore, with approximately 75 percent of the sightings 

 occurring on the onshore survey line. 



By early September, which is late in the nesting season 

 (Hamer and Nelson, this volume a), Marbled Murrelets 

 were found to be most abundant off the rocky shores in the 

 north part of the Washington outer coast from Destruction 

 Island to Cape Flattery (table 2). In contrast, murrelets 

 were present in densities of <1.0 bird/km 2 south of 

 Destruction Island. Distribution maps presented in Varoujean 

 and Williams ( 1994b) indicate that murrelets are not present 

 in abundance off the entrances to the Columbia River, 

 Willapa Bay and Grays Harbor. These areas, however, 

 may play a role as murrelet habitat. Even though fewer 

 than ten Marbled Murrelets were seen inside these 

 embayments, a more thorough temporal coverage of these 

 tidally dominated waters may find them to be important 

 foraging areas in the summer months. 



Overall only 10 percent of the murrelet sightings occurred 

 beyond 2,000 m from shore (table 8). The continental shelf 



in southern Washington, relative to the northern one-third, is 

 broad and exhibits a gradual bathymetric gradient from shore 

 out to sea. Marbled Murrelets along the southern two-thirds 

 of the state appear to be distributed evenly out to 4,000 m 

 from shore. In this region waters are typically <10 m deep 

 within 2,000 m of shore, and 10-20 m deep in the area 

 between 2,000-4,000 m. From Cape Elizabeth north, the 

 offshore bathymetric gradient is steeper, so that within 2,000 

 m from shore the water is up to 20 m deep. The depth ranges 

 between 20 and 30 m from 2,000-4,000 m offshore. Murrelet 

 abundance in this part of the study area is not evenly 

 distributed, with an estimated density of 0.9 birds/km 2 in the 

 outer half. This is approximately one-eighth of the density 

 reported for waters <20 m deep in the inner half. Such low 

 density, however, does correspond to the low densities of 

 murrelets reported in the southern two-thirds of the state. 



Based on distribution maps presented in Varoujean 

 and Williams (1994a, b), the distribution of single birds, 

 pairs of birds and larger groups, whether adults in alternate 



USDA Forest Service Gen. Tech. Rep. PS W- 152. 1995. 



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