38 USGS/BRD/ITR-2000-0012 



1990; Carter et al. 1992; Sydeman et al. 1997). We 

 applied a k correction factor to estimate the number of 

 breeding individuals. Sydeman et al. (1997) calculated 

 k from data collected between 1985 and 1995 at the 

 South Farallon Islands in central California. An average 

 k of 1.671 (SE = 0.026: n = 1 1) was obtained with 

 relatively little variation among years (see Appendix 

 A). A k was not determined for any colony in northern 

 California, Oregon, or Washington. A very different it 

 was found for Triangle Island in British Columbia (see 

 Appendix A). For all estimates of the number of breeding 

 murres in California, Oregon, and Washington, we used 

 a constant k correction factor of 1.67. This approach 

 allowed rough estimation of population sizes for general 

 comparisons. However, given concerns about potential 

 variation in k correction factors between different parts 

 of the breeding range, season, times of day. and years, 

 we did not apply a it correction factor to whole-colony 

 count data before examining population trends. 



Summary of Population Data 



California 



Historical Background on Breeding Colonies 

 in California, 1800-1978 



The history of the common murre on the west coast 

 of North America before 1 900 is best documented in 

 California. Settlement of southern and central California 

 by the Spanish began in the eighteenth century, much 

 earlier than European colonization farther north along 

 the west coast of North America south of Alaska. 

 Frequent activity by early settlers probably occurred at 

 many colonies, mainly from the mid-nineteenth thanigh 

 the early twentieth centuries when rapid immigration 

 occurred after California was ceded to the United States 

 by Mexico in 1 848. Except at the South Farallon Islands, 

 little documentation is available. In northern California, 

 native people may have occasionally visited certain 

 murre colonies by canoe to obtain eggs or birds until 

 the late nineteenth century when populations of native 

 people were reduced to very low levels. Whereas diets 

 of native people in northern California did not focus on 

 seabirds, they did feed extensively on marine foods, 

 which probably included seabirds on occasion (Heizer 

 and Elsasser 1980). Such food gathering and hunting 

 activities were limited to accessible offshore rocky stacks 

 and islets. In central California, visitation of murre 

 colonies by native people probably was infrequent 

 because they did not use large ocean-going canoes in 

 this coastal area. Native people were not known to visit 

 the South Farallon Islands, which are located far from 

 shore. Below, we present a brief synopsis of the known 

 history of murre colonies in California, and we refer the 



reader to Appendix B for a detailed account with citation 

 to historical literature. Given extensive historical 

 changes in California murre populations, current 

 population status and trends of murres must be viewed 

 with these earlier events in mind. 



At the South Farallon Islands, the harvest of murres 

 and their eggs and the human occupation of the islands 

 for nearly two centuries have greatly impacted the murre 

 population. In 1818, the Russian sealing station on the 

 South Farallon Islands (operated from 1812 to 1838) 

 reported killing birds (paibably murres) for meat and 

 feathers. Egging was first reported in 1827. Commercial 

 egging began in 1849, was made illegal in 1881, but 

 continued until at least 1904. From 1850 to 1892, 

 between 180,000 and 600,000 eggs were harvested 

 annually, before falling to about 90,000 in 1 89(i Amle\ 

 and Lewis (1974) estimated that 400,000 birds may 

 have bred at the South Farallon Islands, based on their 

 review of egging records. However, our reinterpretation 

 of historical records suggests numbers of murres were 

 probably much higher, possibly between 1 and 3 million 

 breeding birds (Appendix B). Hunting. t'gging. human 

 occupation, and disturbance of these small islands, as 

 well as heavy oil pollution, led to a dramatic decrease 

 in the size of the murre colony at the South Farallon 

 Islands. In 1909, the North Farallon Islands were 

 included in the Farallon Reservation for Protection of 

 Native Birds (later the Farallon National Wildlife 

 Refuge). By 1 9 1 1 . there were fewer than 20,000 murres 

 and very small numbers were reported in 1923, 1 1 MO. 

 and 1933. Several thousands of murres died in the 1937 

 Frank Buck oil spill at the Golden Gate (Aldrich 1938; 

 Moffit and Orr 1938). In the 1950s and 1960s, murre 

 numbers at the South Farallon Islands gre\\ and 6.718 

 were counted in 1959. In 1969, the South Farallon Islands 

 were added to the Farallon National Wildlife Refuge. 

 Additional protection from human disturbance was 

 provided when the California Department of Fish and 

 Game prohibited low overflights (although some still 

 occurred) over the Farallon Islands Game Refuge in 

 1971. A detailed ground survey in 1972 revealed about 

 20,000-45.000 birds and the colony continued to 

 increase to about 30.000-60,000 from 1975 to 1979. 

 Estimates of population size varied widely owing to 

 differences in census techniques, the degree of 

 completeness of surveys, and irregular use of A correction 

 factors. The increase between 1950 and l l )82 reflects 

 high levels of breeding success, reduction in human 

 disturbance at the islands (especially since the earlv 

 1970s), and low levels of anthropogenic-related deaths 

 at sea except for the 1971 San Francisco oil spill when 

 many thousands died (Smail et al. 1972; Carter 1986; 

 Boekelheide et al. 1990). 



