There is increasing evidence that lead from ammunition has entered the food chain of many ecosystems, largely through the activities of scavengers, including the otherwise iconic American bald eagle. Understanding the effects of this chronic toxic load is challenging, however, especially in cases where data collection is not designed for this purpose. Hanley et al. examined count and necropsy data over 30 years from bald eagles in the northeastern United States to determine if and how lead has affected the population. Although the eagle population size has increased as the species recovers from the influence of DDT, differences were discerned in population structure between lead-exposed and lead-free bird populations. In lead-exposed groups, breeding individuals and hatchlings showed decreased survival, and population reorganization resulted in more nonbreeding females. Although these changes in population structure often go unnoticed, they can affect eagle resilience over time, and stricter control on the use of lead in ammunition is required to resolve this.
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