Biomonitoring with the BuzzardButeo buteo in the Netherlands: Heavy metals and sources of variation

The feasibility of using Buzzards found dead as indicators of environmental contamination was tested. Liver, kidney, and tibia specimens were examined for the presence of Cd, Cu, Pb, Mn, and Fe, which were used as markers. All buzzards submitted to the Veterinary Institute in 1992 were examined for cause of death and condition. Results showed that more than half had been poisoned or shot. As the condition of the birds worsened, fat reserves were depleted before protein reserves. Concentrations of the heavy metals rose in liver and kidney as nutrient reserves fell. Since the content of heavy metal per organ was not related to body condition, content was considered a better measure for biomonitoring. The concentrations of Cd, Cu, Pb, Mn, or Fe measured in buzzards were not toxic. In several places buzzards had recently ingested relatively large amounts Cd and/or Pb. Buzzards with high contents of Cd, Cu, Pb, and Mn were found in areas having more than average contamination. The North-South gradient in aerosol deposition and soil content of heavy metals (especially Cd & Pb) was reflected in the Buzzard. We concluded that the Buzzard is a suitable and cost-effective biomonitor, to investigate the bioavailability of ecocontaminants in large areas, to signal gross changes in food webs, and to monitor raptor persecution.