BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 1 



Farallon Islands, high "fledging success" (i.e., percent of 

 hatched chicks that depart from the colony) occurred for 

 chicks hatched from first eggs between 1972 and 1982 

 (mean = 95%; 1972-82 range, 85-100%; Table 1.1; 

 Figure 1.5; Boekelheide et al. 1990). Chicks from 

 replacement eggs had lower fledging success 

 (mean = 68%; 1972-82 range, 0-100%). Very low 

 success in 1983 (15% for first eggs with no replacement 

 eggs laid) coincided with severe El Nino conditions and 

 high gull predation (Boekelheide et al. 1990; Spear 

 1993). 



For 1 1 colonies in the North Pacific Ocean. Byrd et 

 al. (1993) reported mean fledging success values per 

 colony. For chicks hatched from first eggs, 1 1 colonies 

 ranged between 67 and 91%. For chicks hatched from 

 replacement eggs, four colonies ranged between 1 7 and 

 83%. For 1 2 colonies in the Pacific and Atlantic Oceans. 

 Murphy and Schauer ( 1 994) also reported mean fledging 

 success values per colony (Table 1 .2). For chicks hatched 

 from first eggs, 1 2 colonies ranged between 60 and 85%. 

 For chicks hatched from replacement eggs, eight colonies 

 ranged between 43 and 72%. 



Little quantification of chicks lost during colony 

 departure has been attempted in available studies. Most 



chick losses are from predation by gulls or other avian 

 species or injury from hitting rocks or ledges as the 

 chicks jump off cliffs or steep slopes when leaving the 

 colony (Tuck 1 96 1 ). Most murre fledging occurs during 

 evening twilight, which reduces predation during 

 colony departure and the first few hours at sea. 



When breeding on cliffs or steep slopes, fledging 

 chicks flutter down from a cliff to the water at a steep 

 angle. From low-lying or flat breeding habitats, chicks 

 walk to the water, at times accompanied for all or a 

 portion of the journey by an adult. At the water, they 

 are met by an adult, usually the male parent (Scott 

 1990). At Three Arch Rocks, Oregon, chicks are often 

 accompanied by an adult during their descent from 

 the rock and immediately dive on reaching the water 

 (R. W. Lowe, personal observation). Parent-chick 

 recognition occurs through intense vocalizing at this 

 time by parents and chicks. Failure to link up with the 

 male also may contribute to chick losses at this time. 

 Occasionally, chicks face aggression from nonparental 

 adults on the water (Fisher and Lockley 1954; Kenyon 

 1959; R. W. Lowe, personal observation). At the South 

 Farallon Islands, California sea lions (Zalophus 

 californianus) also may harass and prey on fledging 



Table 1.2. Reproductive success of the common murre in the Pacific and Atlantic Oceans (from Murphy and Schauer 1 994). a 



'Values reflect means and standard deviations. Codes: HS, hatching success (i.e.. percent of eggs laid that hatch): FS. fledging 

 success (i.e.. percent of chicks hatched that depart from the colony): breeding success (i.e.. percent of chicks that depart from the 

 colony from sites where eggs were laid): nd. no data. 



"Sources: 1 (Birkhead 1976b);2(Birkhead 1980):3(Hatchwell 1988);4(HatchwellandBirkhead 1991): 5 (Harris and Wanless 

 1988): 6 (Hedgren 1980): 7 (Birkhead and Nettleship 1987b): 8 (Boekelheide et al. 1990): 9 (Hatch and Hatch 1990); 10 (Byrd 

 et al. 1993); 1 1 (Dragoo and Sundseth 1993); 12 (Climo 1993): 13 (Haggblom and Mendenhall 1991); 14 (Haggblom and 

 Mendenhall 1993): 15(Piattetal. 1988); 16 (Murphy and Schauer 1994). 



'At Stora Karlso, data were pooled between years. 



"Values for the S. Farallon Islands included all 12 years of data from 1972 to 1983 (Boekelheide etal. 1 990: see Table 1.1). 



c At St. George Island, St. Paul Island, and Cape Pierce, success was reported per site and thus included first and replacement eggs. 



