84 



D. A. MANUWAL AND R. W. CAMPBELL 



Table 8. Proportional nest-site preferences of Pacific coast seabirds.* 



Estimated number of pairs 



Percent of population 



British Columbia 



British Columbia 



"Data for southeastern Alaska were inadequate to enable estimates of breeding pairs. 



seabirds still underestimate the more secre- 

 tive, nocturnal, burrow-nesting species. 



Population Changes 



The available data are inadequate to detect 

 changes in population distribution and den- 

 sity for most species (Table 9). In Washing- 

 ton, for instance, limited unsubstantiated in- 

 formation suggests an overall decline of the 

 double-crested cormorant and tufted puffin in 

 the San Juan Island area. Likewise, there 

 seems to be an increase in glaucous-winged 

 gulls there. In British Columbia, Drent and 

 Guiguet (1961) were able to detect changes in 

 some species. For example, they noted in- 

 creases in the double-crested cormorant, pela- 

 gic cormorant, and glaucous-winged gull. No 

 change was observed in the tufted puffin. 

 Since then, the Brandt's cormorant has estab- 

 lished a colony in Barkley Sound (Guiguet 

 1971). The data in southeastern Alaska are in- 

 adequate for all species except, perhaps, the 

 Cassin's auklet which Gabrielson and Lincoln 

 (1959) reported to be declining throughout 

 Alaska. In short, no definitive statements can 

 now be made concerning changes in seabird 

 population numbers. 



Species Accounts 



Fork-tailed Storm-petrel 

 (Oceanodroma furcata) 



Storm-petrels are especially difficult to cen- 

 sus because they are nocturnal, and the bur- 

 rows and rock crevices where they breed are 

 often difficult to locate, especially in mixed- 

 species colonies. The census data are inade- 

 quate to determine whether there have been 

 changes in population density and distribu- 



tion. Indeed, the biology of this species is per- 

 haps the least known of the North Pacific 

 colonial seabirds. In southeastern Alaska, 

 this species is outnumbered by at least 5 to 1 

 by the Leach's storm-petrel (Oceanodroma 

 leucorhoa). The reasons for this are poorly 

 understood. There is some evidence that the 

 numbers of breeding fork-tailed storm-petrels 

 on Forrester Island may fluctuate drastically 

 from one year to the next (Gabrielson and 

 Lincoln 1959). 



Leach's Storm-petrel (Oceanodroma 

 leucorhoa) 



Of the two subspecies of this petrel (O. I. leu- 

 corhoa and O. I. beali), only O. I. beali is found 

 in southeastern Alaska. The leucorhoa sub- 

 species is more northerly in distribution. 

 Where both fork-tailed and Leach's storm- 

 petrels are sympatric, Leach's predominates; 

 however, this relationship becomes more un- 

 predictable in British Columbia and Washing- 

 ton. This species is undoubtedly widespread 

 in the forested islands of the Alexander 

 Archipelago. 



Double-crested Cormorant 

 (Phalacrocorax auritus) 



The double-crested cormorant apparently 

 does not breed in southeastern Alaska since 

 Willett (1912), Gabrielson and Lincoln (1959), 

 and S. Patten (personal communication) do 

 not report breeding colonies for the area. The 

 largest populations occur in southern British 

 Columbia principally in the Gulf Islands, 

 where 71% of all breeding double-crested cor- 

 morants are found (Table 10). According to 

 Jewett et al. (1953), this species was less com- 

 mon in Puget Sound than was Brandt's cor- 

 morant, but is certainly not the case today 

 (D. A. Manuwal, unpublished data). The only 



