Environmental contaminants in tissues of bald eagles sampled in southwestern Montana, 2006-2008

Abstract

Blood and feathers of Bald Eagles (Haliaeetus leucocephalus) banded as nestlings (n = 17), captured as free-flying (n = 91), or submitted for rehabilitation (n = 29) in southwestern Montana between December 2005 and April 2008 were sampled for mercury (Hg), selenium (Se), lead (Pb), seven other trace elements, and organochlorines. Hg concentrations in blood (hereafter “HgB”) did not differ between captured eagles and those submitted for rehabilitation, and HgB in both were higher than concentrations in nestlings (P < 0.01). Se concentrations in blood (“SeB”) were similar among groups. Pb concentrations in blood (“PbB”) were higher in captured eagles than in those submitted for rehabilitation (P = 0.05). No bird submitted for rehabilitation exhibited toxic levels of PbB, but 9% of captured eagles did. HgB and PbB in captured eagles declined as date of capture advanced from autumn to spring. Hg and Se concentrations in feathers (“HgF”; “SeF”) tended to increase with age-class. HgB and SeB, and HgB and HgF were correlated in nestlings and captured eagles (P < 0.05) but not in birds submitted for rehabilitation. Birds captured in autumn during this study had higher HgB (P < 0.05) than birds captured in autumn in the early 1990s, but SeB did not differ. HgB and SeB in birds captured in spring during this study were similar to those of birds captured in spring in the early 1990s, but PbB was lower. Five eagles were recaptured and resampled for contaminants up to 18 yr after initial banding and sampling but no time-trends were detected in contaminant concentrations due to small sample size. Other trace elements and organochlorines if detected in blood were at very low concentrations.