After the war, Puleston was appointed Director of Technical Information at
Brookhaven National Laboratory on
Long Island. A keen ornithologist since childhood, Puleston was happy to watch the ospreys that came to the island every year. On his arrival at Long Island in 1948 he wrote "they were everywhere, repairing their huge stick nests on dead trees, utility poles and platforms erected especially for them. They even nested in the middle of towns and raised chicks right along the highways, oblivious to traffic." They bred so successfully that on a 1948 visit to the nearby
Gardiners Island wildlife reserve he counted some 300 nests, with an average of more than two chicks fledging from each active nest. Puleston began keeping records of the nests on Gardiners Island and their reproductive history, and over several years a dramatic fall in the number of active nests and chicks became apparent. Investigating further, he found that the eggs in the nests had been dented and crushed by the weight of the parent birds as they incubated the eggs. In 1962 the landmark book
Silent Spring by
Rachel Carson had been published. The book discussed the detrimental effects of pesticides on the environment, particularly on birds. Carson said that DDT had been found to cause thinner egg shells, reproductive problems and ultimately the death of birds. Puleston tested eggs that had failed to hatch at Brookhaven National Laboratory, where he worked. High concentrations of DDT residues were found in the eggs, with scientists concluding that the pesticide must interfere with the female osprey's ability to produce normal eggshells. "Using DDT to control mosquitos was like torpedoing the
QEII to get rid of the rats on board", Puleston wrote. The Suffolk County Mosquito Control Commission regularly sprayed the Long Island countryside with DDT, and refused to accept evidence that this was having any deleterious effect on ospreys and other wildlife. By 1966, there were fewer than 50 active nests on Gardiners Island, with only four chicks in total. It became clear that unless urgent action was taken, the osprey would no longer breed in the Long Island area. That same year, Puleston and a group of others filed a
class action in the
New York State Supreme Court to force the Commission to stop using DDT. Puleston presented the court with seven watercolours that he had painted to illustrate how DDT was destroying the food chain of the local wildlife. One showed how the
blue-claw crab ingested DDT from the
mussels it ate. The judge remarked "So that's why there are no more crabs in
Great South Bay." The case convinced the Suffolk County Legislature to ban DDT. The following year, 1967, Puleston and his colleagues founded the
Environmental Defense Fund (EDF) and Puleston became its first chairman, a position he held for five years. The EDF went on to win further bans in other states and finally, its goal of a nationwide ban in 1972. It subsequently became one of the largest environmental organisations in America. As Puleston and his colleagues had hoped, as the amount of DDT residues in the environment dropped, osprey numbers on Long Island began to recover. By 1992, there were 226 nests on the island and more than 60 on Gardiners Island with 260 fledged chicks. Other species including
bald eagles,
peregrine falcons and dozens of fish species have also seen a substantial recovery since the DDT ban was imposed. Puleston retired from Brookhaven National Laboratory in 1970. He subsequently made more than 200 trips around the world as a lecturer, and acted as senior naturalist on two scientific expeditions to the Siberian
Arctic. In his later years, Puleston concentrated on painting and writing about Long Island wildlife. In 1993 he published a month by month guide called
A Nature Journal, which became a best seller. The "Dennis Puleston Osprey Fund" was set up in his memory by his family and friends. ==Personal life==