According to New York State Department of Environmental Conservation, a century ago more than 70 pairs of bald eagles nested in the state; by 1960, that number was reduced to a single known active nest in New York State. Hundreds of eagles had wintered along the Upper Delaware; by the 1960s, a sighting was rare.
- Human competition for and loss of habitat.
- Heavy use of pesticides, especially DDT, which inhibited successful reproduction.
- Large numbers of eagles killed indiscriminately prior to federal protection under the Bald Eagle Act of 1940.
The outlook for the bald eagle is increasingly promising.
The banning of DDT in 1972 was among recent inroads made toward a cleaner environment, which also benefitted eagle populations.
While still protected by the Bald Eagle Act, eagles in most states have been upgraded from "endangered species" to "threatened," largely due to intensive protection and restoration efforts.
Regionally, the Upper Delaware River has played an important role in this population growth.
Both New York State Department of Environmental Conservation and Pennsylvania Game Commission have had bald eagle restoration or "hacking" programs.
Biologists from both states continue to monitor and track the progress of their bald eagle populations.