According to a report by the U.S. Fish and Wildlife Service, New Jersey is home to 135 bald-eagle pairings. That impressive number — in 1982 the state had only one bald eagle nest, which failed to produce eaglets for six consecutive years — is due to the efforts of New Jersey’s Endangered and Nongame Species Program.
DDT contamination was the main reason for the precipitous decline in the eagle population. The toxic pesticide saturated the area around the Bear Swamp nest, and caused the eggs to develop abnormally thin shells. As a result, the ENSP had to remove them from the nest so that they could be raised in a safe environment, which was accomplished by carefully switching the eggs in the nest for fake ones, while the real items were taken to a Maryland research center.
Eventually, this program produced eagles uncontaminated by DDT who were capable of laying and hatching eggs normally. The ENSP also managed to replenish the eagle population by bringing in wild eagles from Canada and releasing them in New Jersey. The birds still face disturbances and habitat loss, but their status as a protected species and the banning of DDT have helped them recover.