BEAUFORT SEA 

Bluff Seabird 
Cliffs 
\ 
\ 
\ 
Copper River 
BERING SEA 
ND Delta 
Cs 
~ 
St. “Paul £, ® Middleton I. 
Shaiak I ® Barren Is. 
® 
PRIBILOF @SLANDS 
GULF OF ALASKA 
St. George I. 
KodiakI. 
akI. 
ERING SEA 
5 B 
Semidi Is. S@ .. Buldir I. 
Bogoslof I. 
r Attu I. ® 

cd 
° Shumagin Is. 
oo Pad |SLANDS 
ALEUTIAN PACIFIC OCEAN 
PACIFIC OCEAN ~ 
Aix ° 
oo 
> gt, sLAN 
° seuTien 
‘A 

Fig. 1. Collection sites (indicated by closed circles) for eggs of Alaskan seabirds, 1973-76. The sites were located in five regions (all capital 
letters); Gulf of Alaska, Aleutian Islands, Bristol Bay, Pribilof Islands, and Seward Peninsula. Species and sample sizes for each site are 
listed in Table 1. 
concentrations given in this report were not adjusted on 
the basis of these recoveries. The lower limit of detection 
was 0.005 ppm for pesticides other than toxaphene, and 
0.02 ppm for toxaphene and PCB’s. 
A “frequency index” was computed by dividing “total 
occurrences” by the number of “possible occurrences” to 
reflect the frequency of organochlorine residue occur- 
rences. Total occurrences are the number of times any of 
the 13 organochlorines were detected in eggs from that re- 
gion (or site); possible occurrences are the number of 
clutches from that region (or site) x 13 chemicals. 
Mean organochlorine concentrations in the samples 
were computed from individual sample values (the residue 
concentration + 1) that had been transformed to common 
logarithms. The addition of 1 facilitated the transforma- 
tion of zero values to logs. After computing mean log 
values, we subtracted 1 from the value of their antilogs. 
This returned our measurements to the original units; 
however, means are geometric rather than arithmetic. 
At most sites, eggs were collected in only 1 year. How- 
ever, in five instances (glaucous-winged gull and tufted 
puffin at Kodiak Island in 1975 and 1976, and at Ugaiu- 
shak Island in 1974 and 1976; thick-billed murre at 
Ugaiushak Island in 1974 and 1976) we collected eggs of 
the same species in 2 years at the same sites. We compared 
means for the separate years and combined them when 
they were not significantly different. When there were sig- 
nificant differences, data are presented separately for the 
2 years. 
The data were analyzed by using packaged subroutines 
from the Statistical Analysis System (Barr et al. 1976). In 
some instances the presence of many zero values prevented 
transformation to the normal distribution, but we also cal- 
culated means of these log-transformed data (see Ohlen- 
dorf et al. 1978a for further explanation). We performed a 
one-way analysis of variance on the log-transformed data 
for each chemical and used Duncan’s multiple range test 
to detect significant differences (P < 0.05) among the 

