52 USGS/BRD/ITR-2000-0012 



Table 2.4. Numbers of common murres counted at seven colonies formed in Oregon 

 between 1989 and 1995. 



"Birds present in small numbers. 



averaging fewer than 100 birds per count; (3) 7 

 recently-formed (since 1988) and regularly-attended 

 colonies (Table 2.4), including 6 that are still active 

 and one colony abandoned in 1991 (Colony number 

 219-057); (4) 2 colonies abandoned after 1979 (Colony 

 numbers 219-007 and 219-029); and (5) two rocks 

 attended by small numbers (fewer than 1 birds) without 

 confirmed breeding. Breeding has been confirmed with 

 observations of eggs or chicks at all regularly-attended 

 colonies in 1988-95. The most complete and accurate 

 survey was conducted in 1 988 (R. W. Lowe, unpublished 

 data). Sixty-six attended locations were identified with 

 59 surveyed using aerial photography and 7 surveyed 

 visually by boat. The largest colony (more than 1 32,000 

 breeding birds) was located at Shag Rock within Three 

 Arch Rocks (Colony number 219-056). The Oregon 

 breeding population was estimated at 71 1 ,900 breeding 

 birds. Although colonies exist within several colony 

 complexes in Oregon (Figure 2.7), count data were not 

 available for all colonies within complexes. 

 Consequently, murre numbers and trends at the colony 

 complex level in Oregon were not described or assessed. 



Population Trends in Oregon, 1988-1995 



To measure population trends in Oregon from 1988 

 to 1995, we analyzed data for 15 sample colonies 

 surveyed and counted annually during this period 

 (Table 2.5; Appendix E). This sample of colonies is 

 spread along the entire Oregon coast. The largest 

 colonies are not included because of extensive counting 

 time required. Most colonies (80% of 75 attended 

 locations in 1988) and most of the Oregon population 

 (87.5% of 426,278 birds counted in 1988) were not 

 counted, except in 1988 when all colonies were counted. 

 In addition, two of the 15 sample locations were not 

 attended until after 1988 (see below). Analyses of 

 population trends were hampered by initiation of 

 standardized aerial photographic surveys of Oregon 

 murre colonies after major declines in central California 

 and Washington in 1979-86. Also, trends from 1988 to 

 1995 for 15 sample colonies might not be representative 

 of all colonies although obvious differences were not 

 noted (R. W. Lowe, unpublished data). 



In addition to USFWS surveys, murre colony counts 

 in Oregon were conducted by a private consulting firm 



Table 2.5. Average and maximum sizes for 1 5 selected breeding colonies of common murres in Oregon, 1 988-1 995 (see Appendix E). 

 Symbols and format as in Table 2.1 . 



