12 USGS/BRD/ITR-2000-0012 



Table 1.3. Summary of reproductive and other characteristics of the common murre in California, Oregon, Washington, and British Columbia. 



Attribute 



Description 



Open slopes and cliffs on islands; cliffs on mainland; occasionally small caves 



Regular attendance during breeding season; no attendance during at-sea chick rearing and 



prebasic molt; regular but punctuated winter attendance in central and California, rare or not 



known in Oregon, Washington, and British Columbia 



Depression or crack in surface of rock, guano, or soil 



1 



Single, medial 



Common 



No 



mean 32 days (range, 26-39; South Farallon Islands) 



mean 86% (range, 80-93; South Farallon Islands) 



mean 23 days (range, 17-35; South Farallon Islands) 



range 85-100% (South Farallon Islands) 



mean 0.85 chicks per pair (range, 0.78-0.91 ; South Farallon Islands) 



Chick jumps off cliff, flutters, or walks to sea, accompanied by male parent 



Probably 1-2 months; fed and accompanied by male parent; learns to dive and capture fish before 



independence 



1-2 months between July and November; overlaps breeding for males rearing chicks at sea; 



complete; remiges lost rapidly causing flightlessness 



1 month between December and March; partial; black head plumage attained; flight not affected 



Mostly fish, some invertebrates, and squid; variable by location, season, and year 



Fish or squid 4- 15 cm in length; variable species by location and year 



4-9 years; mostly 5-7 years 



94% (South Farallon Islands) 



Oregon-Washington populations winter in northern Washington and southern British Columbia; 



central and northern California populations resident year-round in California; British Columbia 



population probably winters in British Columbia, and possibly northern Washington. 



a First egg data from 1972 to 1983, excluding years of poor success in 1983 or 1978 (Table 1.1; Boekelheideet al. 1990). 

 h Data for a new subcolony (77%) were excluded. 



Breeding habitat 

 Colony attendance 



Breeding site 

 Clutch size 

 Brood patch type 

 Replacement clutch 

 Second clutch 

 Incubation period 

 Hatching success 8 

 Nestling period 

 Fledging success 3 

 Breeding success 3 

 Colony departure 

 At-sea rearing period 



Prebasic molt 



Prealternate molt 



Adult diet 



Chick diet (at colony) 



Age at first breeding 



Adult survival 11 



Movements 



murre chicks on occasion (W. J. Sydeman, personal 

 communication). Gull predation at some colonies can 

 be high during fledging. Often, however, the number of 

 deaths has been difficult to ascertain because of low 

 light levels. 



Breeding Success 



For 10 colonies in the North Pacific Ocean, Byrd et 

 al. (1993) reported mean breeding success values (i.e., 

 percent of chicks that depart from the colony from sites 

 where eggs were laid or fledglings per breeding pair or 

 site), which ranged between 27 and 77%. For 12 colonies 

 in the Pacific and Atlantic Oceans, Murphy and Schauer 

 (1994) also reported mean breeding success values per 

 colony, which ranged between 53 and 83% (Table 1.2). 

 Breeding success did not appear to vary much with 

 latitude. At the South Farallon Islands, relatively high 

 average success has been found compared to other 

 locations. Murres averaged 0.8 chicks per site (or about 

 80%) from 1972 to 1982 (range, 0.7-0.9 chicks per site), 

 but much lower site success occurred in 1 983 (0. 1 chicks 

 per site) during severe El Nino conditions (Table 1.1; 

 Figure 1.5; Boekelheide et al. 1990). 



Breeding success is affected by many natural and 

 anthropogenic factors, including prey resources within 

 foraging distances of colonies, predators, other breeding 

 seabirds at the colony, human disturbance, and 

 mortality. High breeding success of murres at the South 

 Farallon Islands in 1972-82 reflected adequate prey 

 resources and low impacts from natural predators, human 

 disturbance, and human-caused mortality at sea 

 (Boekelheide et al. 1990; Takekawa et al. 1990; Carter 

 et al. 2001 ). In contrast, heavy predation and disturbance 

 by eagles and falcons as well as other factors resulted in 

 lower breeding success at Tatoosh Island, Washington. 

 (Parrish 1995). Reduced breeding success during severe 

 El Nino events in 1982-83 and 1992-93 occurred 

 widely at murre colonies in California, Oregon, 

 Washington, and British Columbia (Boekelheide et al. 

 1990; Takekawa et al. 1990; Bayer et al. 1991; Wilson 

 1991; Carter et al. 2001). Severe El Nino events 

 apparently resulted in poor prey conditions, which 

 greatly impacted the proportion of adults that breed 

 and breeding conditions for adults that laid eggs. 

 Extensive colony disturbances by humans and 

 predators also has reduced breeding success at certain 



