Varoujean and Williams 



Chapter 31 



Abundance and Distribution in Oregon and Washington 



and others (1992) took place later than August, whereas our 

 survey was carried out in early September. It is possible 

 that by early September, murrelets from British Columbia 

 and Puget Sound have dispersed to the northern Washington 

 outer coast. But the overall patterns of population shifts are 

 unknown for this region (Rodway and others 1992), so 

 there is no direct evidence indicating that the September 

 1993 estimates include birds from outside the study area. 

 Therefore, at present we must conclude that the higher 

 population estimate of the 1993 aerial survey does not 

 represent a real increase in murrelet numbers due to either 

 intrinsic population growth or the immigration of birds 

 from outside the study area. If this is so, then there has been 

 no marked change in the population size of Marbled 

 Murrelets inhabiting the outer coast and western Strait of 

 Washington in the last 10 years. 



Distribution 



Marbled Murrelet abundances as documented by the 

 1993 aerial surveys and the 1992-1993 boat surveys (Strong 

 and others 1993; Strong, pers. comm.) were highest in the 

 central portion of the state and lowest at the south and north 

 ends of the study area. Additionally, this distribution 

 corresponds to that described by Nelson and others (1992), 

 and to the distribution of the remaining older-aged forest 

 stands in Oregon, with the exception of the area between the 

 Umpqua River and Coos Bay. This area exhibits high murrelet 

 abundance even though there are only small, scattered stands 

 of older-aged conifers located within 30-70 km inland of 

 this section of Oregon's coast. 



Ralph and Miller (pers. comm.) recorded a density estimate 

 of 4.0 birds/km 2 based on a boat survey of an onshore and 

 offshore line out to 1,400 m from shore conducted on 28 

 September 1992. This survey extended from Cape Sebastian 

 south to the Smith River in California. But from the border 

 south 6 km to the mouth of the Smith River, they documented 

 a density of 37.2 birds/km 2 . Potentially then, the numbers of 

 murrelets frequenting waters near the border may be variable, 

 and most likely at times represent birds from the northern 

 California breeding population, which may account for our 

 relatively high density estimate of 12. 1 birds/km 2 for the area 

 between Pt. Saint George and the border (table 1). 



There is an indication from the aerial survey data that 

 murrelets were present in greater numbers off the mouths of 

 rivers and entrances to embayments in Oregon, as shown in 

 Figures 1 and 2 of the report by Varoujean and Williams 

 (1994a), and that murrelet numbers were variable off sandy 

 shores. As regards Marbled Murrelet distribution and shore 

 type in Oregon, Strong and others (1993) reported that bird 

 densities were highest off sandy beach and mixed (sandy/ 

 rock) shores. In contrast, Varoujean and Williams (1987) 

 noted that murrelet densities were significantly higher off 

 (and within 3 km) of the mouths of major rivers and 

 embayments as compared to either sandy beaches or rocky 

 shores. Part of this disparity, however, may be attributed to 



the different areas surveyed and differences in survey effort. 

 The survey by Strong and others (1993) occurred over the 

 entire length of coast between Yaquina Bay and Coos Bay, 

 whereas Varoujean and Williams (1987), in general, surveyed 

 up to only 10 km north and south of the entrances to Yaquina 

 and Coos Bay, and the mouths of the Siuslaw and Umpqua 

 River. Strong and others (1993), Varoujean and Williams 

 (1987) and Varoujean and others (1989) each documented 

 that murrelet abundance is most variable off sandy shores. 



Speich and others (1992) suggested that the Marbled 

 Murrelet population on the Pacific Ocean coast of 

 Washington was largely found north of Pt. Grenville with 

 an uncertain number found in the waters off the southern 

 coast, although the numbers there were thought to be low. 

 This pattern was confirmed by the September 1993 aerial 

 survey of the coast. 



The southern portion of the state does not seem to be as 

 important to murrelets during the breeding season as does 

 the northern part of the Washington outer coast. It may 

 however play an important role as a wintering area, based on 

 22 years of records collected off Grays Harbor (Speich and 

 Wahl, this volume). Seabird surveys out of Grays Harbor 

 were conducted on charter boats, and occurred during various 

 seasons from 1971 to 1991. Although not specifically designed 

 to do so, these surveys do provide information pertaining to 

 the distribution and abundance of Marbled Murrelets. The 

 general pattern of murrelet occurrence was one of high 

 average abundances during the spring, fall and winter months, 

 and higher abundances in habitats closer to shore (numbers 

 encountered ranged from 0.4-2.8 birds/km travelled). Overall, 

 the highest abundances occurred in Grays Harbor channel 

 out to the 50 m depth contour; only rarely were Marbled 

 Murrelets recorded in deeper habitat areas. Furthermore, 

 murrelets were rarely seen during August and September 

 surveys, a pattern that corresponds to the low abundance 

 figures obtained during the September 1993 aerial surveys 

 for this section of the Washington coast. 



Production 



Based on analyses conducted by Beissinger (this volume), 

 the hatch-year proportion estimates of 4.9 percent in Oregon 

 and 5.4 percent in Washington are too low for population 

 maintenance, if these figures are used as measures of 

 productivity in a population growth model. However, to 

 conclude that the murrelet populations in Oregon and 

 Washington are in general decline may be premature. There 

 is an indication that other seabird species nesting in the area 

 experienced low production rates during the 1993 nesting 

 season (Varoujean and Williams 1994a, b). Western Gulls 

 (Larus occidentalis), Glaucous-winged Gulls (L. glaucescens) 

 and their intergrades, and California Gulls (L. californicus) 

 had hatch-year proportions that ranged from 5-7 percent of 

 the total population, and the proportion of Common Murre 

 (Uria aalge) hatch-years was 1.6 percent. Preliminarily, 

 these low measures of production are most likely attributable 



336 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



