16 



PCB's, to such mortality remains to be 

 determined. 



A glaucous gull (Larus hyperboreus) found 

 in convulsions on Bear Island in the Arctic 

 contained 311 ppm of PCB's and 67 ppm 

 DDE in the liver (Bogan and Bourne 1972); its 

 weakened condition and abnormal coordina- 

 tion were attributed to these high levels. The 

 glaucous gulls in this colony were feeding on 

 the eggs of other seabirds. 



Necropsy findings and the high level of 

 DDD (200 ppm) in the brain of a common loon 

 (Gavia immer) found in a soybean field in 

 Madison County, Mississippi, indicate that 

 the bird died of DDD poisoning (Prouty et al. 

 1975). 



Experiments have been conducted with cap- 

 tive birds to determine which tissue might 

 contain chemical residues that are diagnostic 

 of organochlorine poisoning (L. F. Stickel et 

 al. 1966; W. H. Stickel et al. 1969, 1970, 1973; 

 Stickel and Stickel 1970). There is little doubt 

 that many closely related compounds have a 

 lethal additive effect in the nervous system 

 (Ludke 1976; J. L. Ludke and W. H. Stickel, 

 personal communication). Chemical residues 

 in the brain, in association with pathological 

 conditions of the body, may reveal that the 

 compounds caused death. Lethal ranges have 

 been established for DDT, DDD, DDE, diel- 

 drin, and mirex. Suggestions also have been 

 made for weighing and summing brain resi- 

 dues of DDT, DDD, and DDE for interpreta- 

 tion of field specimens. 



Recent studies of the induction of hepatic 

 enzymes by PCB's have been reviewed 

 (Peakall 1975). Levels of PCB in many sea- 

 birds may be assumed to be sufficient to in- 

 crease the activity of various mixed function 

 oxidase enzymes. Elevated activity levels of 

 these enzymes also enhance steroid metab- 

 olism and degrade nonpolar compounds of 

 foreign origin. The biological consequences of 

 increased steroid metabolism are unknown 

 but birds may compensate for the higher level 

 of steroid metabolism by increasing levels of 

 synthesis. 



Teratogenic effects observed in experi,- 

 mental feeding studies with PCB's have in- 

 cluded malformations of the eye, legs, and 

 beaks (Carlson and Duby 1973; Tumasonis et 

 al. 1973; Cecil et al. 1974). Such abnormalities 

 may have been caused by contaminant di- 

 benzofurans in the PCB mixtures (Vos et al. 



1970; Bowes et al. 1975). Similar abnormali- 

 ties have been found in common terns breed- 

 ing in Long Island Sound (Hays and Rise- 

 brough 1972) but the cause remains unknown; 

 a link with PCB or chlorinated dibenzofurans 

 has not yet been proven. 



Diets containing 10 and 30 ppm (dry 

 weight) DDE were fed to black ducks (Anas 

 rubripes), and diets containing 1, 5, and 

 10 ppm (dry weight) DDE were fed to mal- 

 lards (Longcore et al. 1971a). Among the 

 results were the following changes in black 

 duck eggshell composition: (1) significant in- 

 crease in the percentage of magnesium, (2) sig- 

 nificant decreases in barium and strontium, 

 (3) increases (which approached significance) 

 in average percentage of eggshell sodium and 

 copper, (4) a decrease in shell calcium that ap- 

 proached significance, (5) patterns of mineral 

 correlations that in some instances were dis- 

 tinct to dosage groups, and (6) inverse correla- 

 tions in the control group between eggshell 

 thickness, magnesium, and sodium. 



Changes in mallard eggshells were: (1) signi- 

 ficant increase in percentage of magnesium at 

 5 and 10 ppm DDE, (2) significant decrease in 

 aluminum at 5 and 10 ppm DDE, (3) a signifi- 

 cant decrease of calcium in the 10 ppm DDE 

 group, and (4) an increase in average per- 

 centage of sodium in eggshells from DDE- 

 dosed ducks that approached significance. 



Blood samples were taken for 2 successive 

 years from canvasback ducks (Ay thy a valis- 

 ineria) trapped in the Chesapeake Bay (Dieter 

 et al. 1976). The first winter (1972-73), five 

 plasma enzymes known to respond to organo- 

 chlorine poisoning were examined. Altera- 

 tions in enzyme activity indicated tissue dam- 

 age (specifically in membrane permeability) at 

 the cellular level. Abnormal enzyme eleva- 

 tions suggested that 20% of the population 

 sampled (23 of 115 ducks) might contain ele- 

 vated levels of organochlorine contaminants, 

 but no residue analyses were performed. The 

 second winter (1973-74), two of the same en- 

 zymes, aspartate aminotransferase and lac- 

 tate dehydrogenase, were assayed in 95 blood 

 samples. The PCB concentrations in represen- 

 tative blood samples were significantly 

 (P < 0.05) correlated with plasma aspartate 

 aminotransferase activity. 



Male coturnix quail (Coturnix coturnix) 

 were fed diets containing graded levels of 

 DDE, PCB (Aroclor 1254), malathion, and 



