BIOLOGY AND CONSERVATION OF THE COMMON MURRE 19 



(i.e., offshore or inshore) may be abandoned when 

 declines in oceanic productivity result in substantially 

 fewer prey (Ainley et al. 1990; Croll 1990). 



Oregon 



At-sea distribution of murres was studied in Oregon 

 in 1989 and 1990(Briggsetal. 1992; Tyler etal. 1993). 

 Murres frequented the shelf-edge banks for most of the 

 year and near-shore coastal waters were used in late 

 summer. Numbers of murres peaked during late summer 

 when adults and dependent chicks concentrated in 

 coastal waters as they moved north. Shallow waters with 

 murre concentrations coincided with the mid-shelf 

 thermohaline fronts associated with the southward edge 

 of the Columbia River plume (Landry et al. 1989). Murre 

 densities from boat transects in the early 1970s ranged 

 from 20 to 60 birds per knr within 25 km of shore (Wiens 

 and Scott 1975). These densities were consistent with 

 those derived by Briggs et al. ( 1 992) in southern Oregon 

 and from northern Oregon to Grays Harbor. Washington. 

 In general, few murres are present in Oregon during the 

 nonbreeding season, with small number off southern 

 Oregon and moderate numbers off northern Oregon 

 (R. G. Ford, personal communication). 



Washington 



On the outer coast, murres feed close to shore and 

 farther offshore, at times in waters as deep as 1 ,000- 

 2,500 m (Wahl 1975; Briggs et al. 1992; Wahl et al. 

 1993; Thompson 1997). In January, April, May, and 

 June, murres were found mainly in water depths of 1 25- 

 140m in 1989-90 (Briggs etal. 1992; Tyler etal. 1993). 

 During the breeding season, murres fed 1 8-27 km from 

 known colony sites. From April to May, murres were 

 found mostly along a narrow strip close to shore where 

 local densities varied from 24 to 240 birds per km 2 . In 



July, murres were well dispersed over most of the 

 continental shelf. Off Grays Harbor, murres were found 

 commonly in shallow nearshore waters (50-100 m) 

 during summer-fall 1972-88 (Wahl 1975; Wahl et al. 

 1993). Moderate numbers are found off southwest 

 Washington between November and January (R. G. Ford, 

 personal communication). 



Peak numbers of murres in the protected marine 

 waters of Washington are present in August through 

 mid-October, after adult-chick pairs from Washington 

 and Oregon colonies have departed from colonies and 

 moved north (Table 1 .4; see below). For example, more 

 than 200,000 murres were estimated in September 1978 

 (Manuwal et al. 1979; Wahl et al. 1981). In September 

 1989-90, murres were present on the outer coast in lower 

 densities (18-183 birds per km-), but distributed 

 similarly to July (Briggs et al. 1992). By November, 

 murre numbers in protected marine waters had declined 

 substantially, indicating movement northward into 

 Georgia Strait, British Columbia, or to outer coast areas 

 off the entrance to Juan de Fuca Strait (Table 1 .4). 



British Columbia 



During outer coast at-sea surveys in 1 972 and 1 973. 

 and 1981 to 1990, common murres were common in all 

 seasons off the west coast of Vancouver Island with a 

 lower number present farther north off the Queen 

 Charlotte Islands (Robertson 1974; Vermeer etal. 1983, 

 1989; Morgan et al. 1991; Vermeer and Morgan 1992). 

 In spring, murres were present in colder, less saline 

 inshore waters, but occasionally fed far offshore. Highest 

 densities occurred in summer-fall in shallow waters (less 

 than 60 m) on the broad continental shelf, as well as 

 inshore and fiord waters, off southwestern Vancouver 

 Island between Barkley and Clayoquot sounds. The 



Table 1.4. Seasonal projected total number of common murres in the protected marine waters of Washington and southern British Columbia 

 during 1978-1 979 (from Wahl etal. 1981). 



' Active Pass. Gulf Islands. Sidney approach. 



