ONCE AGAIN a set of young peregrine falcons can be seen driving through Washington's summer skies. At least there is one creature alive in this town that can still move fast in this heat. But these six fledgling falcons -- three females and three males -- are not alone. They, alone with 200 other captive-bred falcons, are part of a group that has been released by Cornell University's Falcon Fund in the East over the past six years.

The Falcon Fund, a group that breeds peregrines in its lab in Ithaca, N.Y., and places the young birds in man-made nests throughout the East, hopes to save the peregrine from extinction. Endangered by the use of the chemical pesticide DDT over past decades, native peregrines vanished from east of the Mississippi River by the mid-1960s.

Since then, the Falcon Fund has been largely responsible for the return of peregrine falcons. The fund had usually freed these birds in rural or isolated areas. But a bird named Scarlet changed that, when she set up house in downtown Baltimore last summer. The Cornell scientists decided to expand their recovery effort to nearby Washington. Brought to the Smithsonian from Ithaca at the end of June, these peregrines became the second set to settle in the capital. Last summer, with the help of Interior Secretary Cecil Andrus, four young falcons nested on the roof of the Interior Department building, raising anxieties among some Washington downtown lunch time picnickers-in-the-parks that their tuna sandwiches would be torn from their lips and lofted to the skies by screeching fowl before the experiment was done. Happily, this fearsome prospect has not been realized. Today six peregrines live in the Smithsonian castle's south tower.

The urban setting, according to ornithologists, is more attractive to their clients than you might at first think. Apparently, buildings in downtown Washington are the next best thing to cliffs, and pigeons are plentiful prey. But as they mature, these birds, like people, stray farther from their nests. In the event these peregrines return to Washington in two years to breed -- as planned -- they will be provided large gravel nesting boxes to complete the cycle they began here. They will have about the same chance of survival as do falcons born in the wild.

Unfortunately, two of the four peregrines released last summer are now dead. One bird according to the Fish and Wildlife Service, was found shot in northern New Jersey and another in Baltimore, both identified by their numbered leg bands. But captive-bred peregrines have successfully bred in the wild this year for the first time, which is encouraging. The recovery program being pursued by the Falcon Fund is starting to show success.