Can excrement and feathers of nestling songbirds be used as biomonitors for heavy metal pollution?

Although birds have been frequently used as indicators of heavy metal pollu tion, few studies have examined pollutant levels in nestling passerines. In this paper we determined the levels of two essential (zinc and copper) and three nonessential heavy metals (lead, cadmium, and arsenic) in the excrem ent and feathers of great (Parus major) and blue tit (Parus caeruleus) nest lings at a polluted site (near a metallurgic factory) and a reference site (4 km farther east). The excrement of both great and blue tit nestlings con tained significantly higher concentrations of arsenic, cadmium, copper, and lead at the polluted site. Zinc concentrations did not differ significantl y between sites for both species. The feathers of great and blue tit nestli ngs accumulated significantly higher concentrations of lead at the polluted site than at the reference site. Zinc levels in the feathers of great tit nestlings were significantly higher at the reference site than at the pollu ted site. For all other elements considered, concentrations did not differ significantly between the two sites. There were no interspecific difference s in metal levels between great and blue tits in both excrement and feather s. There was a significant positive correlation between the lead concentrat ion in the excrement and feathers for both great and blue tits. We therefor e conclude that excrement of great and blue tit nestlings can be used as a biomonitor for heavy metals (lead, cadmium, arsenic, and copper), whereas f eathers appear only to be suitable as a biomonitor for lead pollution.