The bald eagle was one of the first species placed on the Endangered Species List. It was endangered primarily because the pesticide DDT caused the shells of its eggs to be too thin to support the weight of the brooding adult. Since DDT was banned the population has recovered.
Bald eagles often mate for life and return to the same nest each year adding more material to it. Nests may grow to 5 feet across and weigh several thousand pounds.