BIOLOGY AND CONSERVATION OF THE COMMON MURRE 21 



are present in high numbers in southern Alaska (e.g., 

 Forsell and Gould 1981; Gould et al. 1982). 



Breeding murres in California are resident and 

 remain near colonies throughout the year as evidenced 

 by ( 1 ) high at-sea densities near colony areas throughout 

 the year (see earlier); (2) extensive winter attendance of 

 monitored plots in breeding areas at the South Farallon 

 Islands (Boekelheide et al. 1990; Sydeman et al. 1997; 

 Hastings et al. 1998); (3) winter attendance at many 

 other colonies in central and northern California (Ainley 

 1976; DeGange and Sowls 1981; Parker et al. 1997, 

 1998; Carter et al. 2001); and (4) at-sea chick rearing 

 and prebasic molt occurring near colony areas (Stenzel 

 et al. 1988; Boekelheide et al. 1990; Croll 1990; Carter 

 1 9%). Year-round residency of common murres has been 

 demonstrated with banded birds in the Baltic Sea (Olsson 

 et al. 2000). However, some northward movement of 

 murres from northern California may occur after colony 

 departure or after completion of prebasic molt. At-sea 

 densities, total population estimates, and distribution 

 of murres in California in winter are largely consistent 

 with summer numbers if adjusted for colony attendance, 

 populations of subadult murres, changes in local at-sea 

 distribution, and survey error. In fact, the overall mean 

 density for northern and central California combined in 

 July (5.14 12.52 birds per km 2 ) was higher than in 

 December (3.54 7.71 birds per km 2 ; Tyler et al. 1993). 

 Limited banding data support little or no movement of 

 murres away from central California (see above). 



Higher winter at-sea numbers in northern California 

 after December may indicate some limited movement 

 of murres from Oregon in January and February in certain 

 years, although colony attendance, populations of 

 subadult murres, changes in at-sea distribution, and 

 survey error also may be involved (Briggs et al. 1983, 

 1987; Tyler et al. 1993). Such movement may occur as 

 Oregon murres move south and return to colony areas 

 but before regular attendance at colonies. However, if 

 substantial northward movement of northern California 

 murres occurs in early fall, higher numbers in December 

 may simply reflect return of northern California murres. 

 Smail et al. ( 1 972) considered that some northern murres 

 (U. a. inornata) were killed in the 1971 San Francisco 

 oil spill; this conclusion was based on morphometric 

 comparisons using data in Storer (1952) but there is 

 now doubt over their approach (Warheit 1995). 

 Movements of large numbers of murres to central 

 California from other populations between December 

 and April are not confirmed with existing data. However, 

 small numbers of common murres from Alaska (U. a. 

 inornata) may be present from southern British 

 Columbia to California in winter. For instance, small 



numbers of thick-billed murres have been noted far south 

 of major colonies in Alaska in certain years (e.g., Scott 

 and Nehls 1974; Roberson 1985). 



In southern California, moderate numbers of murres 

 are present in fall and winter and small numbers during 

 summer (Briggs etal. 1983, 1987; Lehman 1994; Carter 

 et al. 200 1 ), presumably from central California colonies. 

 Male-chick groups have been noted in July as far south 

 as northern Santa Barbara County in some years (Lehman 

 1994). Murres are most common in Santa Barbara and 

 San Luis Obispo Counties from July to January (Briggs 

 et al. 1983, 1987). R. Rowlett (unpublished data), 

 however, recorded 2,030 murres between 5 and 1 2 May 

 1 996 off Point Piedras Blancas. Smaller numbers occur 

 south to San Diego County and northern Baja California 

 mainly in November-January, with stragglers as late as 

 June (Unitt 1984; Howell and Webb 1995). 



In late summer and early fall (August to October), 

 common murres from Triangle Island, British Columbia, 

 probably move south to the northwest or northeast 

 coasts of Vancouver Island. Small numbers of parent- 

 chick pairs observed in Kyuquot Sound and Checleset 

 Bay on northwestern Vancouver Island may originate 

 from Triangle Island or Oregon and Washington 

 colonies, depending on observation date (Guiguet 

 1972; Campbell et al. 1990). By late fall and winter, 

 these murres may stay in northern Vancouver Island 

 waters or move south and join large numbers in the 

 Straits of Juan de Fuca, Strait of Georgia, Puget Sound, 

 or southwest Vancouver Island. Higher numbers of 

 murres in Hecate Strait and Dixon Entrance in spring 

 and fall likely indicate southward movement of some 

 Alaskan birds, especially from the isolated Forrester 

 Island colony located just north of Dixon Entrance in 

 southeast Alaska (Sowls etal. 1978; Vermeer etal. 1983; 

 Campbell et al. 1990, Morgan et al. 1991; Carter et al. 

 2001). In early October 1986 and 1997, several adult- 

 chick pairs were observed in Skidegate Inlet on the east 

 coast of the Queen Charlotte Islands (S. G. Sealy, 

 personal communication). 



Other winter movements probably occur, especially 

 by some younger subadults which are known to travel 

 more widely in winter than adults in Europe (e.g., 

 Birkhead 1974; Mead 1974; Olsson et al. 2000). Two 

 murres banded at the South Farallon Islands have been 

 recovered off the Washington and Oregon coasts (U.S. 

 Geological Survey, Bird Banding Laboratory, 

 unpublished data). Three birds banded in Oregon were 

 recovered in central California (Storer 1952;Tuck 1961; 

 Bayer and Ferris 1987). 



