100% 



California Colonies 



Catalog Total 



310 birds; 

 = colony sites 

 o = former sites 



Percent of California 

 Breeding Population. 



Breeding Chronology 



North.ro C.lifornu 



lncub.tionPor.od- 37-68dayi 

 Nettling Period - 66 d.yi 



Cntr.l CIHofn 





la 



references 



Not BrMding 



parentheses 

 r"ron which ve 





(14,17,24,10) 



correspond 



to the 

 btained the data'. 



Jan. | Feb. ] Mar. | Apf. | My [ June | July I Au. | Sp. | Oct. | Nov. | Oc. 



population shows that extremely unfavorable 

 weather conditions or insufficient food supplies 

 will cause parents to temporarily abandon eggs 

 and chicks (Boersma et al. 1980). Such temporary 

 abandonment of nests reduces viability of eggs, 

 causes death among chicks, and lengthens the 

 breeding season (Boersma and Wheelwright 1979, 

 Boersma et al. 1980). 



Fork-tailed Storm-Petrels are most vulner- 

 able to oil pollution during the summer months 

 when their movements are restricted to nearshore 

 areas by breeding activities (Lensink et al. 1978, 

 Wiens et al. 1978.) While these petrels generally 

 feed in waters over the continental shelf (Lensink 

 et al. 1978), they are usually uncommon in the 

 coastal zone of California and become more 

 abundant only during years of unreasonably cold 

 water (Ainley 1976). Considering this species' 

 small population size, restricted number of 

 breeding sites, and low reproductive potential, 

 any major disturbances to their breeding colonies 

 could be disastrous to the California populations. 



Fork-tailed Storm-Petrels, like all procellari iformes, 

 have a tube-nose. 



Our count for photograph, page 19 : Common Murre = 4,000; Brandt's Cormorant = 1 



21 



