Residue of organochlorine compounds and mercury in birds' eggs from the Niagara Peninsula, Ontario

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Abstract
Eggs (307) were collected in 1971 from twenty species of birds with a variety of feeding habits from the Niagara Peninsula. This area of Ontario is intensively developed for agriculture and heavy industry and has a large urban population. Representative species were obtained from both the terrestrial and aquatic food chains. Eggs were analyzed for organochlorine insecticides, polychlorinated biphenyls, and total mercury. Eggs from carnivorous species at the top of the aquatic food chain had the highest mean residues of ΣDDT (7.6 to 22.4 ppm), PCB (3.5 to 74.0 ppm) and total mercury (0.64 to 0.83 ppm). Eggs from some terrestrial carnivores (red-tailed hawk and great horned owl) also had relatively high residues (2.5 to 3.9 ppm of ΣDDT, 0.2 to 1.0 ppm of PCB, 0.06 to 0.09 ppm of mercury), however levels were much lower than those found in eggs from aquatic-feeding carnivores. Eggs from one red-shouldered hawk had residues comparable to the aquatic feeding carnivores. Eggs from herbivorous and insectivorous birds of both aquatic and terrestrial environments contained much lower residues. PCB residues were slightly lower in eggs among the terrestrial feeding species (0.05 to 2.0 ppm) than among the aquatic feeders (0.14 to 4.0 ppm) and tended to be lower in eggs from terrestrial species collected in rural than in city environs. Levels of ΣDDT were similar in both groups with eggs from terrestrial feeders containing mean residues between 0.15 and 2.64 ppm and those from aquatic feeders between 0.33 and 2.79 ppm.