Table 2. Percent frequency of occurrence of organochlorine residues in eggs of Alaskan seabirds (all species combined), 
by region and collection site, 1973-76.* 




Residues 
No, of Heptachlor Frequency 
Region and collection site samples DDD DDT Dieldrin epoxide Mirex_Oxychlordane Cis-chlordane> Cis-nonachlor HCB  Toxaphene _ index¢ 
Gulf of Alaska 
Copper River Delta 3630.6 2.8 59.6 33.3 11.1 47.2 22.2 13.9 97.2 0.0 0.385 
Hinchinbrook Island 30 70.0 36.7 76.7 83.3 46.7 100.0 70.0 36.7 93.3 20.0 0.641 
Middleton Island 4] 48.8 46.3 65.9 63.4 0.0 95.1 68.3 34.1 2.4 46.3 0.518 
Barren Islands 16 «681.38 «656.3 —-100.0 68.5 56,3 100.0 93.7 68.7 93.8 0.0 0.707 
Amalik Bay 5 0.0 20.0 100.0 60.0 0.0 80.0 20.0 20.0 80.0 0.0 0.446 
Kodiak Island 47 46.8 36.2 76.6 10,2 8.5 95.7 61.7 27.7 68.1 53.2 0.573 
Ugaiushak Island 59 45.8 15.3 52.5 55.9 17.0 78.0 59.3 49.1 94.9 40.7 0.545 
Semidi Islands 330—CtC778.8 075.8 51.5 45.5 54.6 93.9 39.4 18.2 84.9 3.0 0.573 
Shumagin Islands 16 56.3 313 62.3 68.8 37.5 81.3 62.5 12.5 93.8 18.8 0,558 
Total 283 52.6 34.3 65.4 59.7 23.0 85.2 56.9 32.5 75.6 27.6 0.547 
Aleutian Islands 
Bogoslof Island 10 10.0 20.0 90.0 40.0 30.0 90.0 10.0 40.0 90.0 0.0 0.477 
Buldir Island 45 48.9 42.2 26.7 37.8 31.1 57.8 60.0 46.7 91.1 62.2 0.542 
Attu Island 6 66.7 0.0 100.0 66.7 0.0 100.0 50.0 0.0 100.0 83.3 0.590 
Total 61 44.3 34.4 44.3 41.0 27.9 67.2 50.8 41.0 91.8 54.1 0.536 
Bristol Bay 
Round Island 10 0.0 0.0 100.0 40.0 20.0 80.0 0.0 60.0 90.0 0.0 0.454 
Shaiak Island 20 = 25.0 15.0 90.0 60.0 40.0 79.0 35.0 75.0 95.0 0.0 0.546 
Total 30 16.7 = 10.0 93.3 53.3 33.3 76.7 23.3 70.0 93.3 0.0 0.515 
Pribilof Islands 
St. George Island 17 «88.2 94.1 70.6 82.3 11.8 100.0 11.8 11.8 100.0 88.2 0.601 
St. Paul Island 20 5.0 0.0 35.0 70.0 0.0 100.0 5.0 10.0 100.0 90.0 0.473 
Total 37 43,2 43,2 51.3 75.7 7.5 100.0 8.1 10.8 100.0 89.2 0.559 
Seward Peninsula 
Bluff Seabird Cliffs 19 «57.9 0.0 15.8 42.1 10.5 100.0 42.1 26.3 100.0 0.0 0.457 
King Island 10. = 70.0 0.0 40.0 70.0 10.0 100.0 40.0 20.0 100.0 20.0 0.515 
Total 99 =««62..1 0.0 24.1 51.7 10.3 100.0 41.4 24.1 100.0 6.9 0.477 
Grand Total 440 48.9 31.1 60.5 of.o 22.0 84.3 48.4 33.9 82.7 33.2 0.540 

aln addition to compounds listed here, DDE was found in all samples and PCB's were detected in all eggs except five from the Copper River Delta (i-e., they 
were present in 86.1% of the samples from that site). Endrin occurred in one sample from Middleton Island. 
bOr trans-nonachlor, or both (see Methods). 
eComputed as total occurrences/ possible occurrences. Total occurrences = number of times any of the 13 organochlorines were detected in eggs from that 
region or site; possible occurrences = number of clutches from that region or site x 13 chemicals. 
mean concentrations of these chemicals in eggs of the same 
species from the different sites (or from different regions) 
and among different species from the same site (or region). 
Organochlorine Residues 
Nineteen species were represented by a total of 440 
clutches of eggs (Table 1; this table also shows common 
and scientific names of birds mentioned in the text). Most 
eggs were collected in 1976 (250 clutches), but some were 
collected in each of the preceding 3 years (45 in 1973; 54 in 
1974; 91 in 1975). 
The most commonly detected pollutant in all species 
combined was DDE; PCB’s were second, and oxychlor- 
dane and HCB were about equal in prevalence and the 
third and fourth most common (Table 2). Endrin was 
found in only one egg (that of a black-legged kittiwake), 
but all of the 12 other chemicals occurred in at least 22 % 
of the total samples. Both frequency of occurrence and 
concentration of residues in the eggs differed geographi- 
cally and by species. 
In Table 2, as well as in certain other tables referred to 
later, data for different sites or species have been com- 
bined to reflect regional patterns in residue frequency and 
concentration. Other tables and Appendix III present data 
in greater detail (including 95% confidence intervals) to 
enable comparisons among collection sites within species 
and among species within individual sites for each chemi- 
cal. These comparisons by individual site and species are 
the more valid biologically and statistically, but they be- 
come more meaningful when compared with the overall 
regional patterns that are described. 
Mean concentrations of eight of the organochlorines 
were highest in eggs of glaucous-winged gulls from three 
sites (Appendix II): DDE (5.16 ppm), dieldrin (0.214 ppm), 
oxychlordane (0.251 ppm), and PCB’s (3.55 ppm) in eggs 
from Bogoslof Island; heptachlor epoxide (0.037 ppm), 
cis-chlordane (0.075 ppm), and HCB (0.188 ppm) in eggs 
from Buldir Island; and cis-nonachlor (0.026 ppm) in eggs 
from the Semidi Islands. (Cis-nonachlor was nearly as 
high —0.023 ppm —in eggs of ancient murrelets from Bul- 
dir Island.) 

