10 USGS/BRD/ITR-2000-0012 



Hatching Success 



1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 



1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 



Breeding Success 



1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 



Figure 1.5. Reproductive success for first eggs 

 of the common murre in the Upper Shubrick Point 

 study plot at the South Farallon Islands, California, 

 1972-1 983 (adapted from Boekelheideetal. 1990; 

 see Table 1.1). Mean ( 2 standard errors) values 

 are presented. 



6% were abandoned, 3% were broken, 2% were 

 depredated by western gulls (Larus occidentalis), 2% 

 were dislodged during fights or interference with other 

 murres or Brandt's cormorants (Phalacrocorax 

 penic Hiatus), and 1% were wedged in rocks 

 (Boekelheide et al. 1990). Losses from eggs rolling away 

 from breeding sites were rarely observed at the study 

 plot, whereas predation by western gulls was noted 

 frequently (Spear 1993). In general, 12.2% of first eggs 

 (n = 1,506 eggs from 1972 to 1983) and 30% of 

 replacement eggs (n = 54 eggs from 1 972 to 1 983) were 

 lost during incubation (Boekelheide et al. 1990). About 

 3.2% of all eggs (n - 1,560 first and replacement eggs 

 from 1972 to 1983) failed to hatch despite being fully 

 incubated. 



For 1 1 colonies in North Pacific Ocean, Byrd et al. 

 (1993) reported mean hatching success values per 

 colony. For first eggs, 1 1 colonies ranged between 34 

 and 81%. For replacement eggs, four colonies ranged 

 between 47 and 65%. For 12 colonies in the Pacific and 

 Atlantic Oceans, Murphy and Schauer (1994) also 

 reported mean hatching success values per colony. For 



first eggs, 12 colonies ranged between 60 and 85%. For 

 replacement eggs, eight colonies ranged between 43 

 and 72% (Table 1.2). Reasons for egg loss vary between 

 colonies, owing to many different natural and 

 anthropogenic factors that affect breeding and feeding 

 (e.g., Harris and Wanless 1988). 



A summary of reproductive and other 

 characteristics of the common murre is presented in 

 Table 1.3. 



Fledging Success 



Most chick deaths occur in the few days after 

 hatching when very small chicks can be dislodged or 

 roll away from breeding sites, especially if disturbed by 

 humans. After six days of age, murre chicks are better 

 able to avoid the detrimental effects of colony 

 disturbances and are increasingly more capable of 

 returning to natal sites if dislodged a short distance 

 (Tuck 1961). In Newfoundland, chicks reaching 13 days 

 of age had high survivorship until colony departure 

 (greater than 80%; Burger and Piatt 1 990). At the South 



