Bald Eagle Lead Exposure in the Upper Midwest

In 2012, we examined lead exposure in 58 bald eagles Haliaeetus leucocephalus found dead in Iowa, Minnesota, and Wisconsin. We determined lead concentrations in livers, examined differences in exposure among ages and between sexes, and recorded clinical signs consistent with lead poisoning. Most (60%) of the bald eagles had detectable lead concentrations, and 38% of the 58 had concentrations within the lethal range for lead poisoning. We found no differences in exposure based on sex or age, but we did find an inverse relationship between body and liver mass and liver lead concentration. The high percentage of lead-exposed bald eagles encouraged us to further examine potential sources of lead in our local environment. We initiated a study on the Fish and Wildlife Service's Upper Mississippi River National Wildlife and Fish Refuge to investigate if discarded offal piles from hunter-killed deer were a potential source of lead exposure to scavenging wildlife such as the bald eagle. Radiographs showed that 36% of offal piles in our sample area contained lead fragments ranging from 1 to 107 particles per pile. Our study indicated that 1) lead exposure rates for bald eagles found dead in our Upper Midwest study area were high, 2) more than one-third of the bald eagles found dead in Iowa, Minnesota, and Wisconsin had liver lead concentrations consistent with lead poisoning, and 3) discarded offal piles from deer shot with lead ammunition can be a potential source of lead exposure for bald eagles.

Pathomorphologc Findings of Lead Poisoning in White-fronted Geese (Anser albifrons)

Nineteen lead-poisoned white-fronted geese ( Anser albifrons), including nine immature birds, were examined pathologically. Subacute lead poisoning due to ingestion of spent lead shots was diagnosed pathologically and confirmed by demonstrating high lead concentration in the liver. The liver lead concentration ranged from 6.9 to 67.7 mg/kg wet weight. The most suggestive gross lesions were mottled bile-stained liver in eight geese and proventricular impaction and/or the presence of lead pellets in the gizzard. Histologic lesions of the liver consisted of Kupffer cell hemosiderosis, large bile plugs in dilated canaliculi, bile pigmentation in hepatocytes, and bile extravasation and associated hepatic necrosis. Seven geese of the remaining 11 birds also had hepatic necrosis in the liver, the greenish discoloration of which was obscure macroscopically. The liver discoloration was considered a jaundice due to both rapid overproduction of bile from increased breakdown of erythrocytes and intrahepatic impaired excretion of bile. The severity of lesions was not correlated to the liver lead concentrations. All examined geese had hemosiderosis of mononuclear phagocytic system cells in the spleen and hypoplasia or edema of the bone marrow with increased numbers of polychromatic erythroblasts. These prominent changes probably resulted from excess breakdown of erythrocytes, hypercholia followed by intrahepatic cholestasis, and disrupted crythropoiesis in bone marrow caused by lead.