2 USGS/BRD/ITR-2000-0012 



before breeding for the first time at about 49 years of age. Annual survival rates range from 87 to 94% for 

 adults and from 17 to 41% for juveniles. 



Mean hatching and fledging success of first clutches at the South Farallon Islands are about 85 and 95%, 

 respectively. Overall breeding success at this colony averages about 0.8 chicks fledged per pair (i.e., chicks 

 that depart from the colony per breeding site). Additional chick mortality (not well quantified) occurs after 

 colony departure and before chicks are independent of parental care and can fly. Harassment and predation by 

 bald eagles (Haliaeetus leucocephalus) and peregrine falcons (Falco peregrinus) and human disturbance 

 have reduced breeding success at some colonies. 



Murres are abundant at sea near major breeding colonies along the coast of central and northern California 

 and Oregon during the breeding season, with smaller numbers (but still common) off the coast of Washington 

 and the western and northern coasts of Vancouver Island, British Columbia. In winter, murres are most 

 abundant in northern Washington and southern British Columbia, as well as off the coasts of central and 

 northern California. Murres are uncommon in southern California and northern British Columbia during the 

 breeding season, but are more common during winter. After departing the colony, large numbers of murres 

 (including parent-chick pairs, females, and subadults) move northward from Oregon and Washington colonies 

 to complete at-sea chick rearing and prebasic molt, and winter in Juan de Fuca Strait, Strait of Georgia, Puget 

 Sound, and along the west coast of Vancouver Island. Murres from British Columbia colonies also may 

 winter in these areas. Murres return to breeding colonies in Oregon, Washington, and British Columbia in late 

 winter and early spring. In California, murres are largely resident year-round near breeding colonies, but some 

 birds disperse to southern California in winter. Insufficient evidence is available to determine whether murres 

 from Alaskan colonies winter in the area from southern British Columbia to California, although some 

 Alaskan murres (especially from the Forrester Island colony) are present in northern British Columbia in 

 summer and winter. 



Murres feed in various marine habitats on the continental shelf, from estuarine areas near shore to 

 offshore areas. Prey varies with season and location, with fish predominating during breeding, and more 

 euphausiids and squid during winter and prebreeding periods. Common prey species include northern 

 anchovy (Engraulis mordax), rockfish (Sebastes spp.), Pacific sand lance (Ammodvtes hexapterus), Pacific 

 herring (Clupea harengus), Pacific whiting (Merluccius productus), market squid (Loligo opalescens), and 

 euphausiids (e.g., Euphausia pacifica, Thysanoessa spinifera). 



Key words: Alcidae, at-sea chick rearing, at-sea distribution, breeding, British Columbia, California, colony 

 formation, common murre, demography, diet, Farallon Islands, foraging, movements, natural history, 

 nonbreeding, Oregon, predators, seabird, Uria aalge, Washington 



The common murre (Uria aalge) is a large, diving 1993). In the nineteenth and early twentieth centuries, 



seabird of the family Alcidae that breeds and feeds the southern subspecies was often referred to as the 



widely along the coasts of the northern Pacific and "California murre," either because it was then considered 



northern Atlantic Oceans (Figure 1 . 1 ). On the Pacific to be a separate species (U. californica) or the subspecies 



coast of North America, two subspecies currently are U. a. californica was thought to be restricted to the type 



recognized that breed widely from northwestern Alaska locality at the Farallon Islands, California (Sharpe 1 897; 



to central California (American Ornithologists' Union Coues 1903; Salomonsen 1944). Bent (1919) lumped 



1 983). Some morphological differences have been noted both Pacific subspecies under Uria troille californica 



between the two Pacific and five Atlantic subspecies, and referred to them as "California Murres". 

 but much overlap in measurements occurs, museum Storer ( , 952) assigned al , bree ding murres in 



specimens examined may be biased, and most Califomiaj Oregon and Washington to U. a. californica 



subspecies primarily represent major world populations and remarked further tnat the Ceding birds of Oregon 



of murres in different geographic areas (Salomonsen and Britjsh Columbia are both intermediate between U. 



1944; Storer 1952; Bedard 1985; Gaston and Jones a ca iif ornica an d U. a. inornata, and the amount of 



1 998). In the Pacific Ocean, population sizes of the overlap in size ^^ p Opulations is too g rea t to permit 



northern subspecies (U. a. inornata) in Alaska and subspeci fi c identification of birds of the mixed 



northeastern Asia are much larger than those of the w j nte ring population. Consequently, all wintering birds 



southern subspecies (U. a. californica) that ranges from taken in British Columbia have been arbitrarily listed 



British Columbia to California (Figure 1.2; Byrd et al. under rj_ a _ inornata ." Several other sources have 



