106 USGS/BRD/ITR-2000-0012 



can be calculated. Since low counts may have occurred 

 prior to egg laying, rough counting techniques were 

 used, and visual counts were made, the actual number 

 was probably between 10,000 and 15,000 pairs. 



Clay (HSU-SCL unpublished field notes) did not 

 note murres on several egg collecting trips to "Off 

 Trinidad Rock" (i.e., Flatiron Rock) on 22 May 1910, 

 1 6 July 1 9 1 1 , and 2 1 July 1912. Osborne ( 1 972) reported 

 Clay's lack of murre observations in these years and in 

 1 934. Greater accessibility of this rock by canoe (native 

 people) or boat (eggers) may have resulted in earlier 

 colony extirpation. However, on 31 May 1947, W. 

 Anderson (HSU-SCL unpublished field notes) noted that 

 murres were "apparently nesting in considerable 

 numbers on two islands in Trinidad region." On 1 3 July 

 1947, Anderson (HSU-SCL unpublished field notes) 

 further noted: "Great numbers of half-grown downy 

 young seen from skiff on the larger of the 2 Murre rocks. 

 Adults bringing single fish on each trip." Murres likely 

 expanded from Green Rock onto Flatiron Rock, which 

 has extensive breeding habitat and is located near Green 

 Rock. Osborne (1969) reported 1 ,000 breeding pairs in 

 July-August 1969. Osborne (1971, 1972) and Osborne 

 and Reynolds (1971) noted 2,500 breeding pairs in 



1970, based on the highest mainland count of 5,000 

 birds on 5 April 1 970. In fact, counts ranged from 1 , 1 00 

 to 5,000 in April-June 1970 and murres began 

 attendance of the colony in early February 1970 

 (Osborne 1971). Osborne (1971) also noted an estimate 

 of 2,000 breeding pairs that seems to be an error. Osborne 

 (1972) reported 5,200. Varoujean (1979) and Sowls et 

 al. (1980) cited this value as 5,000 breeding pairs in 

 1969-70. If a k correction factor was applied to 1970 

 counts, 2,000-8,000 breeding birds or 1,000-4,000 

 pairs can be calculated. Because low counts may have 

 occurred prior to egg laying, rough counting techniques 

 were used, and aerial photograph counts are often greater 

 than visual estimates, the upper end of this range is 

 compared to 1979 (see Chapter 2 text). On 6 February 



1971, 5,000 birds (95% in breeding plumage) were 

 reported at Flatiron Rock (DeSante and Wang 1971; R. 

 A. Rowlett and R. Le Valley, American Birds Files). 



Several observations of murres at Green and Flatiron 

 rocks were recorded by R. A. Erickson, T. S. Schulenberg, 

 and others between 1 973 and 1 976 (R. A. Erickson and 

 T. S. Schulenberg, unpublished data; American Birds 

 Files), including many hundreds on 16 April 1973; 

 6,000 on 1 7 March 1 974 (Greenburg and Stallcup 1 974); 

 5,000 on 6 April 1974; 5,500 on 19 April 1974; 4,500 

 on 4 May 1974; 4,500 on 8 June 1974; 2,000 on 4 May 

 1975; 12 on 17 August 1975; and 2,500 on 12 June 

 1976. 



Osborne (1972) reported murres at Pilot Rock in 

 1 969 although breeding was not noted there by Osborne 

 and Reynolds (1971). Murres also were noted in 1966- 

 69 by S. W. Harris (Osborne 1972). 



Murres were not reported breeding at Blank Rock 

 in 1969-70 (Osborne 1969, 1971, 1972; Osborne and 

 Reynolds 1971). However, 1 ,000 and 5,000 murres were 

 reported at Blank Rock on 13 and 21 March 1965, 

 respectively, by F. Zeillemaker (R. A. Erickson, 

 unpublished data, American Birds Files). 



Osborne (1971, 1972) and Osborne and Reynolds 

 ( 1 97 1 ) noted 600 breeding pairs at White Rock in 1 969, 

 based on mainland counts. Osborne ( 1 969) reported 250 

 breeding pairs in July-August 1969. 



Clay and Hallmark (Osborne 1972) noted that 

 murres bred on Sea Lion Rock before the 1950s when 

 the entire south half of the rock fell into the water. 

 Previously, murres had bred on the flat top of the rock. 

 Breeding has not been reported since then (Osborne 

 1972; Sowls et al. 1980; Carter et al. 1992). 



Cape Mendocino Complex 

 (False Cape Rocks and Steamboat Hock) 



Osborne ( 1 969) first reported 350 breeding pairs at 

 False Cape Rocks in July-August 1969. In 1969-70, 

 Osborne ( 1 97 1 ) and Osborne and Reynolds ( 1 97 1 ) noted 

 600 breeding pairs at False Cape Rocks (based on a 

 July 1969 aerial count). Osborne (1972) reported 800 

 breeding pairs at False Cape Rocks in 1 969, based on 

 an aerial count (reported as 1970 in Varoujean 1979 

 and Sowls et al. 1980). Clay (HSU-SCL unpublished 

 field notes) did not report any earlier visits to False 

 Cape Rocks. 



On 7 July 1917, Clay (HSU-SCL unpublished field 

 notes) did not note murres at Steamboat Rock but did 

 note that "... a great many Brandt cormorants were seen 

 and they appeared to be nesting in great numbers." It is 

 possible that no murres bred within this complex at this 

 time, given this observation and Clay's comment on 10 

 May 1941 that murres bred only at Green Rock "in 

 these parts" (see above). However, this observation was 

 made from the adjacent mainland and most of the murre 

 breeding areas on this rock are not visible from shore. 

 Osborne (1969) reported 150 breeding pairs at 

 Steamboat Rock in July-August 1969. Osborne (1972) 

 indicated that 300 birds were observed on 1 6 July 1 969. 

 In 1970, 300 pairs bred, based on ground and aerial 

 counts in 1969-70 (Osborne 1971; 1972; Osborne and 

 Reynolds 1971). 



