BIOLOGY AND CONSERVATION OF THE COMMON MURRE 41 

 Table 2.1. Average and maximum sizes for nine breeding colonies of common murres in central California, 1 979-1 995 (see Appendixes C and D). 



a Ranked in order of mean colony size. 



b Only sites with at least five years of data considered suitable for trend analysis were included. Lower quality data for certain 



years and colonies were not included. 



c Number of breeding adults was obtained by multiplying mean or maximum count by a A: correction factor of 1 .67, and 



rounding to the nearest hundred. 



d No breeding occurred from 1986 to 1995 (see text). 



A new colony, "Bench Mark-227x," was 

 temporarily established within the Castle-Hurricane 

 complex in 1996-98 but subsequent breeding did not 

 occur in 1999-2001 (Parker et al. 1998, 1999; 

 McChesney et al. 1999; M. W. Parker, unpublished 

 data). In March-June 1999, 3-9 murres attended but 

 did not breed at Prince Island, in association with 

 nesting Brandt's cormorants (Phalacrocorax 

 penicillatus; H. R. Carter, unpublished data). Use of the 

 Bench Mark-227x colony area had not been noted 

 previously, but murres had been recorded in the vicinity 

 of Prince Island since 1991 (Carter et al. 1992; 

 McChesney et al. 1995). 



In northern California, colonies are most often on 

 offshore rocks within 1 km of the mainland, except for 

 the small isolated colony at Redding Rock --7 km 

 offshore. The largest colony complex in northern 

 California (and the state) in recent decades was at Castle 

 Rock, where 142,400 breeding birds were estimated in 

 1982 (Briggs et al. 1983; Appendix C). However, 1979- 

 82 counts may have overestimated the size of this dense 

 colony, which was estimated to be about 100,000 and 



107,700 breeding birds in 1986 and 1989, respectively 

 (Takekawa et al. 1990; Carter et al. 1992). Four other 

 large colony complexes are found at False Klamath, 

 Trinidad (including colonies at White Rock, Green 

 Rock, Flatiron Rock, Blank Rock, and Pilot Rock), Cape 

 Mendocino (including False Cape Rocks and Steamboat 

 Rock colonies), and Vizcaino (including Cape Vizcaino 

 and Rockport Rocks colonies; Table 2.2). Mainland 

 breeding occurs only at one subcolony on an 

 inaccessible point at Rockport Rocks. Smaller colonies 

 are present at Sister Rocks (within the False Klamath 

 complex) and Redding Rock. By 1995, the 

 southernmost colony (where breeding was certain) in 

 northern California was Cape Vizcaino. However, in 

 1997, breeding was confirmed at three small colonies 

 (Newport Rocks, Kibesillah Rock, and Goat Island Area) 

 south of Cape Vizcaino in northern Mendocino County 

 where attendance had been noted in recent years (Carter 

 et al. 1992, 1996; see below). 



Between 1979 and 1995, murres attended several 

 rocks in California where breeding was not confirmed 

 (Sowlsetal. 1980, unpublished data; Briggs etal. 1983; 



Table 22. Average and maximum sizes for eight breeding colonies of common murres in northern California. 1 979-1 995 (see Appendixes C and 

 D)'. 



"The largest colony at Castle Rock was excluded (see text). Symbols and format as in Table 2. 1 . 



