Summary

Description

Fiftyone livers were extracted from bald eagle carcasses recovered in Maine between 2001 and 2007. Approximately 50 of the birds were collected during the spring months March May with the remaining carcasses being recovered equally among the other three seasons. Causes of death included electrocution, collisions, gunshot, lightning, and starvation; but the majority died of undetermined causes. Qualitative estimates of body condition based on muscle mass and subcutaneous and intraabdominal fat content suggested that 69 of the birds were in poor physical condition. Total PCB Arithmetic mean 27.32 90.40 gg wet weight, max. 570 gg ww and DDE 3.46 9.66 gg ww, max. 64.2 gg ww were detected in all samples. Average concentrations by month of collection appeared similar for both compounds with the highest levels recorded in May and September. Three eagles had PCB liver levels indicative of acute toxicity 100 gg ww. DDE liver levels did not approach acute toxicity thresholds. Mercury Arithmetic mean Hg, 23.04 30.45 gg dry weight and lead Pb, 13.21 32.96 gg dw were also detected in all samples. Thirtythree livers had low Hg levels 20 gg dw, 16 had moderately elevated Hg levels 20 80 gg dw and two had toxic Hg levels 80 gg dw including one with 191 g Hgg dw. Liver Hg varied by month with no apparent pattern among season of collection. Fortythree liver samples exhibited low Pb levels 6 gg dw, but eight had concentrations indicative of Pb poisoning 30 gg dw. Two livers had Pb levels in excess of 130 gg dw. The highest Pb concentrations were detected in birds recovered during the winter and spring months. Although the bald eagle has been removed from the U.S. and some state endangered species lists, environmental contaminants may still be pose a threat and accumulate to toxic levels in some birds. The USFWS postdelisting monitoring strategy encourages periodic evaluations of trends in bald eagle abundance and contaminants exposure in vulnerable regions.