Lead exposure and poisoning in bald eagles and golden eagles in the Canadian prairie provinces

Abstract

The prevalence of high lead exposure and lead poisoning was examined in dead bald eagles and golden eagles from the Canadian prairie provinces from 1990–96. Of 127 eagles, 12% were lead-poisoned based on lead concentrations >20 ppm dry weight in kidney or 30 ppm in liver. A further 5% exhibited elevated lead concentrations based on kidney lead concentrations >8 ppm or liver lead concentrations >6 ppm. The prevalence of elevated lead concentrations did not differ ( p=0.23) between the two species although statistical power was low (0.4). When both species were combined, a higher proportion of adult and subadult birds had elevated tissue lead concentrations than immature birds ( p<0.05). Golden eagles that exhibited high lead exposure were found closer to the hunting season than those that exhibited low lead exposure ( p=0.07) Such was not the case in bald eagles ( p=0.89). There was a greater prevalence of high lead exposure in bald eagles found in areas of high waterfowl hunting intensity than in their counterparts found in areas of low waterfowl hunting intensity ( p=0.07). In contrast, golden eagles with high lead exposure were associated with areas of lower waterfowl hunting activity than those with low lead exposure ( p=0.04). In our study area, prevalences of lead poisoning in bald eagles and golden eagles were approximately equal. For bald eagles, lead shot associated with waterfowl hunting was probably the main source of lead. Other sources of lead, including lead ammunition in upland game birds and mammals were more likely sources for golden eagles. ©