The peregrine falcon, once almost wiped out by DDT, is thriving in the Yellowstone ecosystem, an official of the Peregrine Fund says.

Peregrine Fund members this year counted 27 pairs in the Yellowstone ecosystem, up from 19 pairs in 1989 and 11 in 1988, said operating manager Bill Heinrich of Boise, Idaho. Five of the six Montana nest sites are in the Centennial Valley, west of West Yellowstone.Biologists have said the entire peregrine falcon population appeared to be gone from the Greater Yellowstone area before the Peregrine Fund began releasing the birds there in 1980.

In a effort to ensure the survival of one of the fastest-flying birds in the world, helicopters deposit boxes that serve as bird nests on high cliffs. The Peregrine Fund hires attendants to carry the young peregrines to their new nest sites and the attendants feed the birds for about eight weeks.

The peregrine falcons are doing so well in the Greater Yellowstone area that the birds are being released in other locations. Ten were released in the Gates of the Mountains area near Helena this summer, and nine survived, Heinrich said.

The Peregrine Fund has released about 500 falcons in the Greater Yellowstone ecosystem since 1980. The ecosystem includes Yellowstone and Grand Teton national parks, and surrounding national forests in Montana, Wyoming and Idaho.