We have found that the breeding success of two insectivorous forest passerines, the great tit Parus major and the pied flycatcher Ficedula hypoleuca, has markedly improved in the vicinity of a copper-smelting plant during the seven years since it reduced its emissions of heavy metals. Our results demonstrate that reduced pollution loads can positively affect breeding performance of wild bird populations over a relatively short period, even in an area that has suffered decades of heavy-metal pollution.