California Colonies 



Catalog Total 

 14,724 birds 

 = colony sites 



20% 



Percent of California 

 Breeding Population. 



ciutcn-,.2 * 



Incubation Period - 30 32 d.yi 

 Nestling Period 36 - 46 days 



Breeding Chronology 



Jan. | Feb. | Mar. | Apr. | May I June | July [ Aug, Sep. Oct. 



(501 010), Fish Rocks (404 003), Castle Rock 

 (325 006), Sugarloaf Island (325 041), and Prince 

 Island (325 003). Generally, however, Pigeon 

 Guillemot colonies are small. More than half the 

 sites we investigated had fewer than 30 birds. 



HISTORICAL STATUS AND VULNERABILITY 



Few data pertaining to the historical status 

 of Pigeon Guillemots are available. On the 

 Farallon Islands, Pigeon Guillemots escaped early 

 persecution by commercial egg collectors but 

 later fell victims to oil pollution (Ainley and 

 Lewis 1974). The guillemot population of the 

 Farallon Islands reached an all-time low of 200 in 

 1911. Since then it has recovered steadily, to 

 1,000 birds in 1959, 2,000 in 1972, and 3,000 at 

 present (Ainley pers. comm.). 



Elsewhere along the California coast it may 

 appear from the data that Pigeon Guillemot 

 numbers have increased dramatically. However, 

 we do not feel there is sufficient information to 

 make this judgement. Previous investigators 

 largely overlooked Pigeon Guillemots since they 

 often nest in low densities and usually do not 

 form distinct colonies. Censusing Pigeon Guille- 

 mots requires much time and manpower and 

 access to many nesting sites is poor. Time of day 

 and of year can greatly influence survey results 

 and some previous surveys were conducted after 

 Pigeon Guillemots had finished nesting. 



Compared to other seabirds such as Common 

 Murres and Brandt's Cormorants, Pigeon Guille- 

 mots are not highly prone to disturbance, primarily 



because of their comparatively tow nesting 

 densities and inaccessible nest sites. Pigeon 

 Guillemots will, however, readily desert their 

 nests if disturbed during incubation or brooding. 

 Like murres, Pigeon Guillemots are very 

 vulnerable to oil pollution. Guillemots spend 

 large amounts of time on the water, usually 

 close to land where oil exploration and develop- 

 ment are concentrated. Fortunately, the 

 population of Pigeon Guillemots in California is 

 widely distributed along the coast and any oil 

 spill would most likely affect only local buds. 



Pigeon Guillemots occasionally nest in man-made 

 structures like this tire on a Crescent City dock. 

 Photo by Anthony R. DeGange 



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