Tom J. Cade, an ornithologist who was a leader of a remarkable effort that re-established the majestic peregrine falcon on the East Coast after the pesticide DDT had wiped it out there, died on Feb. 6 in Boise, Idaho. He was 91.

The Peregrine Fund, a conservation organization he helped found, announced his death.

Dr. Cade was director of the ornithology laboratory at Cornell University in the late 1960s when he and others began contemplating how to help the endangered peregrine falcon. The bird had disappeared from the East Coast and was struggling elsewhere in the United States because use of DDT had had the unintended effect of weakening the shells of its eggs.

Dr. Cade rallied falconers, conservationists, universities, businesses and more to join in trying to reintroduce the bird in areas where it had once thrived. But that required overcoming all sorts of obstacles, including how to breed birds in captivity and how to acclimate them to life in the wild.

By the early 1970s Dr. Cade and associates had successfully bred peregrine falcons in captivity, and by 1980 falcons released in the East had reproduced in the wild.