[Residual chlorinated pesticides and polychlorinated biphenyls in the eggs and adipose tissue of wild birds].

In 1983 and 1984, in the State Veterinary Institute at Jihlava, 129 samples of eggs of wild birds of 14 species were analyzed coming from different regions of the Czech Socialist Republic for the presence of residues of chlorinated pesticides and polychlorinated biphenyls (PCB). Apart from this, nine samples of hawk fat and 27 samples of buzzard fat were examined. The method of gas chromatography with a detector of electron capture was used for the analysis. The analyzed samples were found to contain residues of PCB, DDT (and mainly its metabolite DDE), HCB, alpha-HCH, gamma-HCH. No residues of other chlorinated carbohydrates were detected. The residue levels of these substances in the eggs and fatty tissues of different species of wild birds vary within a very wide range. A significant influence is exerted on these levels by the differences in food spectrum, the age of the birds, lack of food causing mobilization of food reserves, and mainly the environment where the birds live. The highest levels of residues were found in the eggs and fatty tissues of predatory birds with a narrow spectrum of food, i.e. those feeding on other birds (sparrow-hawk 33.00 mg.kg-1 in the dry matter of eggs, hawk 239.98 mg.kg-1 in fat) or those associated with water (great crested grebe 11.97 mg.kg-1, sea-gull 11.24 mg.kg-1 in the dry matter of eggs). Much lower levels of the residues of the chemicals were recorded in the species feeding mainly on small rodents (kestrel 0.681 mg.kg-1, buzzard 2.456 mg.kg-1 in the dry matter of eggs and 11.398 mg.kg-1 in fat). Some of the samples under study contained dead embryos. These embryos had particularly high residue levels, often higher than the levels regarded in literature as toxic.