FISHERY BULLETIN: VOL. 84, NO. 2 



Table 5.— Comparison of bird numbers at regions A-C during 1 

 June-30 August period in 1982 with 1983. Day(s) = days post- 

 release of salmon smolts, N = number of censuses (1 census/d 

 within 2 h of low tides before 1500 PDT), and MAX = maximum 

 number of birds counted. 



1 1 d vs. 2 d vs. 3 

 Kruskal-Wallis H c = 

 0.07, df = 28, P > 



2 1 d vs. 2 d vs. 3 

 Kruskal-Wallis H c = 

 = 107,P>0.10;2d, 

 U = 14, P> 0.10. 



31 d vs. 2 d vs. 3- 

 Kruskal-Wallis H c = 

 = 142.5, P< 0.02; 2 

 U = 20, P>0.10. 



6 d: 1982, Kruskal-Wallis H c = 0.44, P > 0.10; 1983, 

 14.62, P < 0.01. 1982 vs. 1983; 1 d, student's f = 



0.10; 2 d, student's f = 0.25, df = 14, P > 0.10. 



6 d: 1982, Kruskal-Wallis H c = 2.44, P > 0.10; 1983, 

 8.71, P< 0.02. 1982 vs. 1983: 1 d, Mann-Whitney U 

 Mann-WhitneyU = 32.5, P>0.10; 3-6 d, Mann-Whitney 



6 d: 1982, Kruskal-Wallis H c = 1.84, P > 0.10; 1983, 

 6.14, P < 0.05. 1982 vs. 1983: 1 d, Mann-Whitney U 

 d, Mann-Whitney U = 49, P< 0.10; 3-6 d, Mann-Whitney 



Yearly Variation in Bird Numbers 



Cormorants were significantly more abundant for 



1 and 2 d postrelease in 1983 than in 1982 but not 

 for 3-6 d postrelease (Table 5). Brown pelicans were 

 about as numerous in 1983 as in 1982 in the 1 

 June-30 August period (Table 5). 



Gulls were not significantly more abundant in 

 1983 than in 1982 in the 1 June-30 August period 

 (Table 5), and their nesting success was also not 

 lower in 1983 than in other years (Bayer fn. 2). But 

 Caspian terns were significantly more abundant dur- 

 ing the 11 July-5 August period (when many 

 emigrated) in 1983 than in 1982 (Bayer 1984). 



There were an average of about 650 more com- 

 mon murres per census in 1983 than in 1982 dur- 

 ing the 1 June-31 July period for either 1 or 2 d post- 

 release, but the differences were only significant for 



2 d postrelease (Table 4). In contrast, there were 

 more murres in 1982 than in 1983 during this period 

 for 3-6 d postrelease, but there were only two 

 samples in 1982 (Table 4). 



In the 1-30 August period, there were significantly 

 fewer murres in 1983 than in 1982 (Table 4). The 

 low numbers in 1983 resulted from the mass exodus 

 of murres after 31 July, whereas in 1982 murre num- 

 bers did not decline as dramatically until after 12 

 August. In fact, there were still more murres pres- 

 ent within 2 h of low tides on 3 and 16 September 

 1982 (186 and 318 murres, respectively) than in 10 

 censuses on different days between 1 and 18 August 



1983 (i.e., <56 murres). The early exodus of murres 

 in 1983 probably resulted from them migrating 

 north early because they were unusually numerous 

 in inland marine waters of Washington during the 

 summer of 1983 (Mattocks et al. 1983). 



During the June through August period at regions 

 A-C, pigeon guillemot numbers were about 29% 

 greater during 1982 (x = 23.9, SD = 11.0, N = 13 

 d) than in 1983 (x = 17.1, SD = 7.8, N = 35 d), a 

 significant difference (t = 2.39, df = 46, P < 0.05). 

 This decrease could have resulted from the large 

 number of mortalities in the spring of 1983 

 (Hodder 3 ). 



Marbled murrelets were not observed in any of 

 120 censuses of regions A-D in the June through 20 

 August period of 1982. In 1983 at regions A-C, they 

 were observed in only 1 of 21 censuses in June and 

 August, but an average of 3.9 murrelets/census (SD 

 = 8.7, range 0-32, N = 17 censuses) were counted 

 in July. The difference in the number of murrelets 

 per census in July was significantly greater in 1983 

 than in 1982 (normalized Mann-Whitney z = 2.18, 

 P < 0.05). They were only observed at region A. 



CONCLUSIONS 



It is not possible to relate the number of birds 

 nesting near the Yaquina Estuary with the number 

 feeding there for several reasons. First, the num- 

 ber of nesting and nonbreeding birds is unknown, 

 so it is not possible to determine what proportion 

 of the birds censused were nonbreeders. Second, 

 censuses of feeding birds represent the number of 

 birds feeding at only one point in time, but nesting 

 birds probably fed serially at the Yaquina Estuary 

 (i.e., birds came and went as individuals or small 

 flocks not as massive synchronous flocks). With 

 serial use, the number of nesting birds using the Ya- 

 quina Estuary could be much larger than indicated 

 by censuses. Unfortunately, birds would have to be 

 individually recognizable to determine the degree 

 of serial use, and this was beyond the scope of this 

 study. 



It also was not possible to tell from how far nest- 

 ing birds came to feed at the Yaquina Estuary in 

 either year because birds were not individually 

 marked. Murres, however, may have come from 

 long distances. In both years, the average number 

 of murres one day after a salmon release (Table 4) 

 was greater than the number of murres at a colony 

 <7 km away (Table 1), and the maximum number 



3 J. Hodder, Institute of Marine Biology, Charleston, OR 97420, 

 pers. commun., 1984. 



284 



