BAYER: SEABIRDS NEAR OREGON ESTUARINE SALMON HATCHERY 



of murres simultaneously seen at the Yaquina (Table 

 4) was greater than the number of murres at 

 colonies within 45 km of the Yaquina (Table 1). 



It was somewhat surprising that more cormorants 

 and common murres were not at the Yaquina 

 Estuary in 1983, because they then had a poor 

 nesting season, probably as a result of a food short- 

 age (Bayer fn. 2). There are several possible reasons 

 why there were not more cormorants and murres 

 counted in 1983. First, the number of salmon smolts 

 available at the Yaquina Estuary might have been 

 insufficient or the distance between the Yaquina and 

 their nesting site too great for these birds to be 

 dependent solely on salmon smolt releases. If the 

 salmon smolt releases had been oftener and nearer 

 to bird nesting colonies, the numbers of birds pres- 

 ent could have been much greater. Second, there 

 may have actually been many more birds in 1983 

 than in 1982, but a single census per day regime was 

 inadequate to measure this (Table 3). Censuses 

 throughout the day in 1983 or measurements of the 

 serial use of the Yaquina Estuary in 1982 and 1983 

 might have indicated that there were dramatically 

 more birds using the Yaquina in 1983 than in 1982. 

 Finally, the lack of there not being a greater influx 

 of birds in 1983 might be because many of the 

 murres and cormorants that normally remained 

 near the Yaquina dispersed to avoid the generally 

 poor feeding conditions between releases. Many 

 Oregon pelagic and Brandt's cormorants had aban- 

 doned nesting by mid-July 1983 (see Bayer fn. 2; 

 Hodder fn. 3), and many murres may have left the 

 Oregon coast before it became apparent at the Ya- 

 quina Estuary at the end of July. Early dispersal 

 or migration is known for southern seabirds during 

 an El Nino (Duffy 1983a; Schreiber and Schreiber 

 1984). 



ACKNOWLEDGMENTS 



I am grateful to Bill McNeil, Vern Jackson, Rob 

 Lawrence, Mike Bauman, and Andy Rivinus of 

 Oregon Aqua-Foods for facilitating the logistics and 

 funding of this project; to Dan Varoujean for advice 

 about censusing murres prior to the 1982 field 

 season; and to Jan Hodder, Dan Matthews, Daniel 

 W. Anderson, Peter Stettenheim, and two anony- 

 mous reviewers for constructive comments on an 

 earlier draft of this manuscript. 



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