Exposure to chemical poisons like DDT, dieldrin, PCBs and lead has killed eagles, damaged their reproductive systems and threatened the ability of their young to survive. Bald eagles are at the top of the food web, feeding on both land and aquatic creatures depending on the season. Their diet of fish, mammals, and other birds means they are exposed to the toxics their prey have eaten before them. Given a lifespan of up to 25 years, persistent toxic chemicals can easily reach high concentrations in bald eagles' bodies. Because they do not reach maturity and reproduce until they are four or five years old, there is great opportunity for chemical impact before the next generation is born.
Lead poisoning is one acute threat to bald eagles.
Hundreds of thousands of ducks consume lead shot which has fallen into marshlands after missing its target. Ducks that are hit but not killed are also easy, but lethal, food for birds of prey. Lead poisoning is debilitating, slow and painful. DDT, while no longer used in Canada or the U.S., is used extensively in southern countries and continues to affect the Great Lakes eagle population. DDT's derivatives upset calcium levels in the female, resulting in thinner shelled eggs which tend to break before the chicks are ready to hatch.