A COMPARISON OF BLOOD LEAD LEVELS IN BALD EAGLES FROM 2 REGIONS ON THE GREAT-PLAINS OF NORTH-AMERICA

The connection between bald eagles (Haliaeetus leucocephalus) and the consumption of waterfowl, lead shotshell pellet ingestion, and subsequ ent lead exposure is well documented in the United States and is presu med also to be widespread in Canada. We compared blood lead concentrat ions in samples from bald eagles ranging in age from 0.5- to 1.5-yr-ol d at Galloway Bay, Saskatchewan, Canada (n = 97) during October-Novemb er. 1992-95 and Hauser Lake, Montana, USA (n = 81) during October-Dece mber, 1990-94, within the Great Plains region of North America. Abunda nt prey are available in the form of hunter-injured waterfowl in Saska tchewan and spawning salmon in Montana; both areas attract large numbe rs of mid-continent bald eagles during fall migration. Blood lead conc entrations suggestive of recent lead exposure (>0.201 mu g/ml) were fo und in 32% and 8% of eagles at Hauser Lake and Galloway Bay, respectiv ely, when samples from each study area were analyzed independently at two laboratories. To determine if this difference was an artifact of i nterlaboratory variation, we determined a correction factor by reanaly zing 14 Saskatchewan blood samples at each laboratory and predicted bl ood lead concentrations from Hauser Lake had the samples been analyzed at the Canadian laboratory. Adjusted blood lead concentrations of sam ples from Hauser Lake indicated that 21% of eagles were recently expos ed to lead, a proportion not significantly different from the proporti on of the same exposure category at Galloway Bay. Our data do not supp ort the supposition that a large proportion of bald eagles feeding on waterfowl in areas of high hunting pressure will be exposed to lead vi a consumption of lead shotshell pellets in waterfowl.