Contaminant residues, especially from DDT, were found in adult birds, eggs and nestlings as well as in the eagles' food sources. Contaminants in adult bald eagles result in abnormal breeding behavior, thin eggshells and dead embryos within the eggs. Other pesticides, such as Dieldrin and Endrin, were implicated most often in acute poisonings, those resulting in immediate death of individual birds. Lead poisoning from the ingestion of spent lead shot has been identified as a serious mortality factor in waterfowl. Eagles have died from lead poisoning after feeding on dead or crippled waterfowl and ingesting lead pellets imbedded in the waterfowl's flesh or gizzard.
Eagles also accumulate toxic levels of lead directly from contaminated flesh.
Habitat destruction and human related disturbance of wintering and nesting eagles is continuing. Intensive grazing of roosting and nesting tree areas can prohibit the natural regeneration of tree groves that would ensure future use of these sites. Bank stabilization activities along Nebraska rivers often require tree removal, which may eliminate valuable feeding and loafing perches. Reduced or altered river flows as a result of diversions and dams can severely affect the ability of the aquatic system to attract wintering waterfowl or to support an adequate fishery for nesting or wintering eagles. Although it has been illegal to shoot bald eagles since 1953, shooting remains a major cause of death.