36 USGS/BRD/ITR-2000-0012 



Wildlife Service (USFWS) manages and surveys most 

 murre colonies in Washington and Oregon, and 

 important colonies in California, within the National 

 Wildlife Refuge System. In California, however, most 

 colonies are managed by the California Department of 

 Fish and Game and the National Park Service, and surveys 

 have been conducted by a combination of personnel 

 from the USFWS, Humboldt State University, U.S. 

 Geological Survey and University of California. Aerial 

 photographic surveys can be conducted by refuge staff 

 or other researchers at a reasonable cost in a short period 

 of time during the breeding season, although the 

 subsequent counting of photographs requires 

 substantial effort. In certain other parts of the breeding 

 range of the common murre, sample plots have been 

 established as the primary method for monitoring where 

 deriving accurate whole-colony counts from aerial 

 photographs of entire colonies is either too difficult, 

 too costly, or impossible. Overall, researchers have used 

 a combination of survey and census techniques to 

 monitor murre populations around the world, with 

 techniques varying between colonies and geographic 

 areas (Birkhead and Nettleship 1980; Gaston and 

 Nettleship 1981). However, standardized or 

 nonstandardized whole-colony counts at one or more 

 colonies over several years have been used by many 

 researchers to describe common murre population trends 

 in various parts of the Atlantic and Pacific Oceans 

 (Hudson 1985; Nettleship and Evans 1985; Vader et al. 

 1990; Byrd et al. 1993). Aerial photographic surveys of 

 murre colonies at Funk Island, Newfoundland, and 

 several colonies in eastern Canada have been employed 

 since 1972 (D. N. Nettleship, personal communication). 



Whole-colony counts of murres provide the best 

 available baseline information for analysis of trends in 

 the number of murres attending colonies in California, 

 Oregon, and Washington. Available data sets are 

 hampered, however, by four main factors: ( 1 ) incomplete 

 or irregular survey coverage (i.e., surveys not conducted 

 in some years, certain colonies omitted in certain years), 

 (2) incomplete colony coverage (i.e., poor quality or 

 incomplete sets of photographs at certain colonies in 

 certain years), (3) incomplete counting of available aerial 

 photographs in northern California and Oregon, and 

 (4) single counts in most years (i.e., variation in 

 whole-colony counts has not been fully assessed). For 

 central California, Oregon, and Washington, such 

 problems were limited, have been reduced over the past 

 decade, and did not greatly affect the use of 

 whole-colony counts for assessing murre population 

 trends. However, we have identified and accounted for 

 serious problems in certain cases. In northern California 

 and British Columbia, available information was much 



more limited for assessing recent trends than in other 

 areas. Under unusual circumstances, whole-colony 

 counts may not accurately reflect the actual colony size; 

 for instance, during severe El Nino-induced weather 

 conditions, large numbers of murres may not attend 

 colonies during annual surveys. Such circumstances 

 must be identified and accounted for in assessments of 

 population trends, using whole-colony count data. 



In Alaska, common murres often breed sympatrically 

 with thick-billed murres (U. lomvia) and it is often 

 difficult to determine the proportions of each species 

 (Sowls et al. 1978). This problem does not exist 

 throughout most of the geographic area of western North 

 America covered in this chapter. The current southern 

 limit of breeding thick-billed murres is at Triangle Island, 

 British Columbia, where up to 70 thick-billed murres 

 have been recorded attending the colony (Vallee and 

 Cannings 1983; Rodway 1991). 



In this chapter, we have examined population trends 

 of common murres using available information from 

 whole-colony counts, primarily from aerial photographs, 

 in California, Oregon, Washington, and British 

 Columbia through 1995. In addition, we have reported 

 estimates of the size of breeding populations of U. a. 

 califomica in different geographic areas. We have not 

 attempted to collate information on at-sea densities or 

 total-population estimates, but aspects of at-sea 

 distribution, abundance, and movements are 

 summarized in Manuwal and Carter (2001). 



Methods 



We used a broad framework for assessing murre 

 population trends within six geographic areas along 

 the west coast of North America: central California, 

 northern California, Oregon, southern Washington, 

 northern Washington, and British Columbia. 

 Information provided for each area includes summaries 

 of (1) qualitative and nonstandardized quantitative 

 historical data from 1800 to 1978 of numbers of murres 

 attending colonies and known or suspected human 

 activities at colonies, (2) current breeding population 

 size and distribution of colonies, and (3) major 

 population changes identified between 1979 and 1995 

 (using standardized whole-colony count methods) and 

 factors known or suspected to be associated with 

 changes observed. Significant events documented after 

 1995 were noted where appropriate but data used for 

 population trend analysis were restricted to the 1979- 

 95 period. 



Historical information on murres at colonies helped 

 to derive a general concept of long-term colony and 



