capable of storing high concentrations of PCBs in their fat without any 

 apparent detrimental effects, and may be useful as biological indicators for 

 lipophilic substances, including PCBs (Olafsson et al . 1983). Sea turtles 

 contain relatively lower levels of PCBs than snapping turtles (Table 2). PCB 

 concentrations were higher in saltwater loggerhead turtles ( Caretta caretta ), 

 an omnivore, than green turtles ( Chelonia mydas ), which are vegetarians, again 

 demonstrating that diet is an important route of PCB transfer (McKim and 

 Johnson 1983). 



BIRDS 



In general, most bird tissues and eggs collected had measurable 

 concentrations of PCBs, and the frequency of occurrence appears to be 

 increasing. In 1976, 21% of European starlings ( Sturnus vulgaris ) collected 

 Nationwide had detectable PCBs; in 1979 it was 83% (Cain and Bunck 1983). For 

 mallards ( Anas platyrhynchos ), PCBs were detected in 39% of wing tissues in 

 1976-1977, and 95% in 1979-1980 (Fleming et al . 1983). PCBs were detected in 

 all of the eggs of six species of South African seabirds and in the majority 

 of eggs from a seventh species in 1981-1983 (de Kock and Randall 1984); in 50 

 to 55% of eggs of the black-crowned night-heron ( Nycticorax nycticorax ) from 

 Colorado, Wyoming, Washington, and Nevada taken in 1978-1980 (McEwen et al . 

 1984; Henny et al . 1984); in all Norwegian seabird fledglings in 1976-1977 

 (Fimreite and Bjerk 1983); in 77% of eggs of the black skimmer ( Rynchops 

 nigra ) from Texas in 1981 (White et al . 1984); in 85 to 100% of all gaiiii 51^ 

 tissues examined in West Germany during 1982 (Brunn et al . 1985); and in 99% 

 of the eggs of the endangered American bald eagle ( Haliaeetus leucocephalus ), 

 including 89% occurrence in breeding areas (Wiemeyer et al . 198T)^ 



Populations of double-crested cormorants ( Phalacrocorax auritus ) from 

 Lake Huron are now recovering rapidly, presumably due to a decrease in PCB and 

 other contaminant residues in eggs (Weseloh et al . 1983). In the late 1960's 

 and early 1970's, cormorants nesting on the Great Lakes, and in particular 

 Lake Huron, had eggs that were more highly contaminated with PCBs, DOE, and 

 mercury, than did cormorant eggs from anywhere else in Canada. Concomitantly, 

 egg survival, reproductive success, and colony size were either dangerously 

 low or decreasing. In 1972, colonies were small, they showed high egg 

 breakage and egg loss (95%), and nearly total reproductive failure (less than 

 0.11 young/nest). Eggshells were about 24% thinner than normal. Levels of 

 DDE (14.5 ppm fresh weight) and PCBs (23.8) in eggs collected in 1972 were 

 higher than other Canadian cormorant populations (Weseloh et al . 1983). 



In the past, PCB residues in birds tended to be higher in areas of local 

 contamination and heavy industrial use or discharge. But with the current 

 stringent restrictions on PCB use, geographical distinctions are not as clear 

 (Custer et al. 1983a; McLane et al . 1984), although residues in birds from 

 industrialized areas still remain comparatively high (Fleming et al . 1983; 

 White et al. 1984). For example, birds collected near the Sheboygan River, 

 Wisconsin, contained PCB residues that would be considered harmful to some 



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