BIOLOGY AND CONSERVATION OF THE COMMON MURRE 59 



35- 



30H 



RgureZIZ Trends in whole-colony counts ~ 

 for common murres in southern * 

 Washington. 1 979-1 995 (see Appendix H). 



s 



5 



I 



25- 



20- 



15- 



10 



5- 



Southern Washington 



period r-square p-value 



1979-1995 0.710 <0.001 



1979-1986 0.743 0.006 



1984-1995 0.371 0.035 



1984 



1994 19% 



Population Trends in Southern Washington, 

 1979-1995 



Overall numbers of breeding murres in Washington 

 declined 32.9% per annum between 1979 and 1986 

 (P= 0.006; Figure 2.10). Most decline between 1979 

 and 1986 occurred in southern Washington where steep 

 downward trends occurred at colony complexes (Figure 

 2.11), as well as for southern Washington overall (43.7% 

 per annum, P - 0.006; Figure 2.12). During the period 

 1979-82, the southern Washington population was 

 much higher than between 1983 and 1995. when 

 numbers varied extensively at colonies and colony 

 complexes (Figure 2.11: Appendix F). Murre attendance 

 at the Point Grenville complex decreased greatly from 

 1979 to 1981 before rebounding in 1982. At the 

 Willoughby-Split complex, both colonies decreased 

 greatly in 1980 between similar peak numbers in 1979 

 and 1982. Large differences in the numbers of murres 

 attending colonies in southern Washington between 

 1979 and 1982 apparently were related to natural and 

 anthropogenic factors. In 1981, reduced colony 

 attendance probably reflected a response to unusually 

 warm surface waters (similar to moderate El Ninos) off 

 the Washington coast between January and April 1 98 1 

 (Wilson 1991). Numbers of murres attending colonies 

 increased in 1982. apparently reflecting the return of 

 birds that did not breed, remained at sea, or moved 

 temporarily to other colonies in 1980-81. In addition 

 to the warm water episode, various human disturbances 

 such as overflights and military activity occurred along 

 the Washington coast on a regular basis in the late 1 970s 

 and early 1980s (Speich and Thompson 1987). These 



disturbances may have contributed to oscillating 

 colony attendance. Death of common murres from 

 entanglement in Washington gill-net fisheries (i.e., 

 Willapa Bay, Grays Harbor, Puget Sound) in the 1970s 

 and early 1980s probably occurred but was poorly 

 documented. 



In 1983, widespread colony abandonment 

 occurred in association with severe El Nino conditions 

 (Wilson 1 99 1 ). Almost complete abandonment occurred 

 at the Willoughby-Split complex by 1984-86. Impacts 

 from chronic colony disturbances and the 1981 warm 

 water event also may have contributed to this steep 

 decline. The negative effects of private aircraft 

 overflights and military practice bombing of Sea Lion 

 Rock on murre attendance at southern Washington 

 colonies in 1984-85 was documented by Speich et al. 

 (1987). Colony attendance was significantly reduced 

 because of lingering effects of the 1982-83 El Nino 

 during this study, therefore, the full effect of these 

 military disturbances on breeding colonies was unclear. 

 However, such disturbances undoubtedly affected many 

 murre colonies until military bombing and aircraft 

 overflights were greatly reduced in 1992. In 198485, 

 disturbance by commercial ground-fishing boats was 

 noted at Point Grenville and Willoughby Rock (S. M. 

 Speich. personal communication). Limited increase 

 between 1984 and 1988 may have reflected the return 

 of some birds and the recruitment of subadults from 

 higher populations in 1981-82. 



In 1988, numbers of murres attending colonies 

 again began to dwindle to very low levels during the 



