Assessment of the exposure to heavy metals and arsenic in captive and free-living black kites ( Milvus migrans ) nesting in Portugal

Abstract Due to their high trophic level, raptor species may serve as important indicators of environmental contamination by heavy metals. This study was conducted to determine if the habitat of the black kite ( Milvus migrans ) is contaminated by heavy metals and arsenic and to assess the degree and type of exposure that may be present. For this purpose, this study was conducted on a group of captive birds (n = 12) and on a group of free-living birds admitted to two wildlife rehabilitation centers (n = 31). Blood samples were taken for analysis of arsenic (As), mercury (Hg) and lead (Pb) concentrations by inductively coupled plasma mass spectrometry (ICP-MS). Captive birds had the lowest blood concentrations for all toxic elements examined, but significant differences from the concentrations found in free-living birds were only observed for Hg and Pb (p