Levels of heavy metals in House Sparrows (Passer domesticus) from urban and rural habitats of southern Finland

Abstract

Urbanization has led to increasing amounts of pollutants which can harm organisms that share our living environment. In Finland, the House Sparrow has declined by two thirds during the last couple of decades. One hypothesis suggested to lead to this decline is heavy metal pollution.We used a museum collection from the 1980s to investigate the accumulation of eight heavy metals (Al, Cr, Mn, Fe, Cu, Zn, Cd, Pb) in the livers of House Sparrows living in either rural or urban habitat. We used principal components derived from these as dependent variables in the statistical analyses, and found significantly higher heavy metal concentrations in the livers of urban than in those of rural House Sparrows. There was a tendency for males to accumulate more heavy metals, but age dependence in this respect was not found. Heavy metal levels in urban habitat were not as high as in some other House Sparrow studies. Even though heavy metal pollution is an unlikely sole cause of House Sparrow declines, pollution is more pronounced in cities and could thus contribute to declines through indirect effects, such as insect availability.