METAL ACCUMULATION AND METALLOTHIONEIN CONCENTRATIONS IN TREE SWALLOW NESTLINGS NEAR ACIDIFIED LAKES

We studied metal accumulation in hepatic and renal tissues of tree swallow (Tachycineta bicolor) nestlings at acidified and nonacid reference lakes in northwestern Ontario. Hepatic concentrations of metallothionein (metal-binding proteins, MT) in tree swallow nestlings were negatively correlated with pH of the nest-site take. Combined concentrations of Cu and Zn in the liver were correlated with liver MT concentrations, but Cd was not. Although no overt signs of metal toxicity were observed in nestlings near acid lakes, our results clearly provided evidence that metals are transferred from acid lakes to birds and that these metals are correlated with increases in hepatic MT production.