78 



D. A. MANUWAL AND R. W. CAMPBELL 



Table 4. Breeding seabird population estimates for British Columbia*-* 3 



a Estimates only for colonies of 100 or more birds. 

 b Estimates are in number of pairs. 



short, grassy, shrubby vegetation. In general, 

 these islands are not suitable for burrowing 

 species. 



In the Strait of Juan de Fuca, the two most 

 important sites are Smith and Protection is- 

 lands. Both are composed of glacial deposits 

 and heavy sod that has developed under dense 

 grassy vegetation (Fig. 7). Consequently, 

 these two islands support most of the burrow- 

 ing seabirds in the region. Unfortunately, 

 both islands have historically been subjected 

 to much human disturbance (Richardson 

 1961; Manuwal 1974). 



The existing information on seabird colo- 

 nies in both the coastal and San Juan Island 

 areas has been largely derived from aerial sur- 

 veys by the U. S. Fish and Wildlife Service. 

 These surveys are inherently biased toward 

 surface-nesting species such as gulls and cor- 

 morants. Population estimates for guillemots, 

 auklets, storm-petrels, and puffins are less 

 accurate. Some additional information ob- 

 tained by direct island visitation has been pro- 

 vided by Kenyon and Scheffer (1961), 

 Richardson (1961), Thoresen and Galusha 

 (1971), G. Eddy (unpublished data), and D. A. 

 Manuwal (unpublished data). Although other 

 accounts of Washington seabirds are avail- 

 able, the references listed above are specifi- 

 cally oriented toward population assessment. 



Olympic Peninsula 



Despite the large number of offshore rocks, 

 islets, and islands along the Pacific coast of 

 Washington, significant seabird colonies are 

 present only on about 30 islands. Since 

 Table 5 summarizes the population estimates 



JUAN DE FUCA 



PACIFIC 

 OCEAN 



Fig. 4. Map of the Olympic Peninsula of 

 Washington State showing sites of major seabird 

 breeding colonies: 1 Protection Island; 2 

 Carroll Island; 3 Destruction Island. 



for 12 species of seabirds breeding on 24 

 major sites, it represents only the majority 

 and not the total number of breeding seabirds 

 on the Pacific coast of Washington. About 

 74% of the entire Washington seabird popula- 

 tion resides on the coastal rocks and islands. 



Major colony sites with more than 2,500 

 breeding pairs are Grenville Arch, 



