4 USGS/BRD/ITR-2000-0012 



where the Point Reyes Bird Observatory and U.S. Fish 

 and Wildlife Service (USFWS) have operated a long- 

 term seabird research and monitoring program since 

 1972 (e.g., Ainley and Boekelheide 1990; Boekelheide 

 et al. 1990; Sydeman 1993). Studies of breeding 

 colonies of murres also have been conducted at Tatoosh 

 Island, Washington, by the University of Washington 

 during the 1990s (e.g., Parrish 1995; Parrish and Paine 

 1996); and Triangle Island, British Columbia, by the 

 Canadian Wildlife Service and Simon Fraser University 

 during some years since the 1970s (e.g., Rodway 1990). 

 In addition, the USFWS, Humboldt State University, 

 and National Audubon Society initiated studies in 1996 

 in central California at three colony complexes Point 

 Reyes, Devil's Slide, and Castle-Hurricane (Parker et 

 al. 1997, 1998, 1999). Many important studies of the 

 breeding biology of the common murre have been 

 conducted in northern Europe, eastern Canada, and 

 Alaska (see summaries in Nettleship and Birkhead 1 985; 

 Murphy and Schauer 1994; Gaston and Jones 1998; 

 Ainley et al., in preparation). Where necessary, we rely 

 on studies from other parts of the range of the common 

 murre to describe known breeding biology and 

 demography. 



During the 1970s and 1980s, several Federal 

 agencies (especially Minerals Management Service, 

 National Oceanic and Atmospheric Administration, and 

 the Environmental Protection Agency) sponsored major 

 at-sea survey programs conducted by the University of 

 California, University of Washington, and Ecological 

 Consulting Incorporated to describe the overall 

 abundance and distribution of seabirds in California, 

 Oregon, and Washington in marine habitats (e.g., Wahl 

 et al. 1981; Briggs et al. 1987, 1992). In British 

 Columbia, at-sea surveys have been conducted in many 

 parts of the province in the 1970s and 1980s, mainly by 

 the Canadian Wildlife Service (e.g., Vermeeret al. 1983; 

 Morgan et al. 1991). We have relied extensively on 

 these major sources to describe at-sea distribution and 

 movements. To describe foraging ecology, diet, and other 

 aspects of the at-sea biology of the common murre, we 

 collated information from available studies in this 

 geographic area and elsewhere in the world. 



Overview of the Biology of the 

 Common Murre 



Alcids exhibit a suite of morphological, behavioral, 

 and life-history traits characterized by wing-propelled 

 diving, high adult survivorship, delayed maturity, and 

 a low clutch size of one egg (except for two eggs in the 

 genera Cepphus and Synthliboramphus). 

 Wing-propelled diving likely evolved in alcids for 

 efficient exploitation of subsurface marine fish and 



invertebrates, which are often abundant during the 

 breeding season, may be sparse during other times of 

 the year, and can show a high degree of annual variation. 

 Alcids probably originated in the North Pacific Ocean 

 (Udvardy 1963; Bedard 1969, 1985) and radiated 

 extensively, although there are only 23 extant species 

 within 5 tribes (after Strauch 1985): (1) Alcini (genera 

 Uria, Alca, and Alle), (2) Cepphini (genera Cepphus 

 and Synthliboramphus), (3) Brachyramphini (genus 

 Brachyramphus), (4) Aethiini (genera Aethia and 

 Ptychoramphus), and (5) Fraterulini (genera Fratercula 

 and Cerorhinca). Alcids have been ecologically 

 successful and form a dominant component of breeding 

 seabird communities in subarctic and arctic waters in 

 the North Pacific and North Atlantic Oceans. The 

 common murre and the thick-billed murre (Uria lomvia) 

 are among the most abundant alcids that breed and 

 winter throughout most of these northern waters. 



Alcids have strong bills for capturing, carrying, and 

 holding prey, small wings as a compromise adaptation 

 for diving and flying, and specialized breeding plumage 

 (exhibited in most species). Similar to most alcids, murres 

 exhibit a common "black above and white below" body 

 plumage of pursuit-diving seabirds with a striking 

 blackish-brown head plumage during the breeding 

 season (Figure 1.1). This body plumage type may have 

 evolved to reduce conspicuousness to potential prey 

 when feeding in midwater, although the dark back also 

 may assist thermal regulation along with large body 

 size for surface breeding or retard feather wear from solar 

 radiation (Ashmole 1971; Birkhead and Harris 1985; 

 Cairns 1986). Unlike most alcids but like other species 

 in the genera Uria, Cepphus, and Brachyramphus, 

 common murres carry single prey items to their chicks 

 and have a long bill with large palatal denticles for 

 capturing, holding, and carrying fish (Bedard 1969). 

 Although common murres share many similarities with 

 other alcids, they also have evolved several different 

 adaptations, largely related to feeding, which have 

 produced a unique life history pattern. Three main 

 adaptations are large body size, intermediate pattern of 

 post-hatching development, and surface breeding in 

 dense colonies. Common murres are the largest (800- 

 1300 g) of the extant alcids (Nettleship 1996). The 

 extinct Great Auk (Pinguinus impennis) and other 

 extinct alcids were larger but flightless. Large body size 

 allows murres to exploit deeper water (for fish and 

 invertebrate prey) than most other alcids. They have 

 been recorded to dive as deep as 180 m (Piatt and 

 Nettleship 1985). Chicks are raised partly at the colony 

 and partly at sea, a pattern intermediate between most 

 other alcids (Sealy 1973; Gaston 1985; Nettleship 1996; 

 Gaston and Jones 1998). In contrast, "precocial" alcids 



