In the early 1950’s and 60s there were as many as 500 nest in NJ. By 1974 due to the effects of DDT in the food chain only 50 nest remained. As a result the state of New Jersey listed the Osprey as an endangered species
DDT was banned in 1968 and biologist began to place both young nestlings and eggs from nests where DDT was not used as heavily into NJ nests that failed to produce young, year after year. They also coordinated efforts to supply man-made nest platforms for the birds. These new artificial nest platforms replaced the snags and trees that were lost to weather and as the barrier islands became more developed.
It has now been over 40 years since the osprey were first listed as an endangered species in New Jersey. Last year (2014) a total of 420 active nests were recorded with an overall population of 567 pairs. They are off the list!
Ref: The 2014 Osprey Project in New Jersey - Kathleen Clark,
Endangered and Non-game Species Program NJ Division of Fish and Wildlife and Benjamin Wurst, Conserve Wildlife Foundation of NJ
Update 2020 :Summary of results from the 2019 New Jersey Osprey Project survey where a total of 669 occupied nests were found. Of those a total of 488 active nests produced 932 young.