In addition to the adverse effects of DDT, bald eagles also died from lead poisoning as a result of feeding on hunter-killed or crippled waterfowl containing lead shot and from lead shot that was inadvertently ingested by the waterfowl. Patuxent's scientists enhanced the species' breeding potential by removing the bald eagle's first clutch of eggs and incubating them artificially. The bald eagles would usually then lay a second clutch, which the birds were allowed to incubate themselves. These captive-hatched bald eagles were an important source for restocking wild populations in certain areas of the country and helped to reestablish a broader distribution. Patuxent's program came to an end in 1988, as bald eagles began to reproduce more successfully in the wild, and the center turned its efforts toward other more critically endangered species.
Some states continue reintroduction efforts, and two methods are generally used.
Eaglets used for reintroduction may be captive-hatched or, since usually only two young per nest survive, they may be transferred from a bald eagle nest with a clutch of more than two. Another method, called hacking, is a procedure adapted from the sport of falconry. At 8 weeks of age, nestling eaglets are placed on manmade towers located in remote areas where bald eagle populations are low or non-existent. The eaglets are kept in an enclosure and fed by humans who stay out of sight. When the birds are capable of flight, at about 12 weeks old, the enclosure around the artificial nest is opened and the birds are free to leave.