Four baby peregrine falcons will be released in Washington this summer under a Cornell University program to return to the eastern United States what once was the world's most widespread, and fastest, bird of prey.

In June, the peregrine chicks will be placed in a special cage on top of the eight-story Department of Interior building at 18th and C streets NW and released, probably within two weeks, when they're old enough to fly and recognize the nation's capital as their new home territory.

The spectacular falcons, which have been extinct east of the Rocky Mountains for almost two decades because of widespread use of pesticides such as DDT, are being bred in captivity under an unusual wild bird program at Cornel. Already more than 150 falcons have been released around the country, according to Dr. Thomas Cade, the research scientist who heads the peregrine project. The falcons are among the 67 U.S. birds on the nation's endangered species list, and among 211 bird species considered endangered worldwide.

At least 100 fledgling falcons, now just eggs in Cornell's large hawk barn, are expected to be released this summer, in the eastern and western parts of the country.The birds to be released in the west are part of a second Cornell project at Fort Collins, Colo., being conducted with the state division of wildlife.

While many of the birds that have been released are surviving well in the wild, and are sighted frequently, said Cade, so far none is known to be nesting and reproducing. Peregrines are hard to keep track of, however, except for those that make tall city buildings their cliffs. In any case the falcons do not usually mate until they are at least 3 years old.

A 35-story Baltimore insurance company building two years ago became home to one of the falcons released at the Army's Aberdeen Proving Ground on Chesapeake Bay. Other released falcons are now reported soaring and roosting around skyscrapers in Norfolk, Boston and Montreal, says Cade.

In addition to the four birds to be released in the District, falcons will be set free in the east this summer on a barrier island near Norfolk, at Aberdeen, in the Connecticut River Valley between Vermont and New Hampshire, and possibly in another city, said Cade. "We're considering Harrisburg, but they've had owl problems there." Owls are AMONG THE FLEDGLING FALCONS' major enemies and are especially dangerous to Cade's birds because the peregrines have no parent birds to protect them.

The Baltimore bird, a female called Fancy by hundreds of U.S. Fidelity and Guaranty (USF&G) employes who watch it through the tinted glass windows of the building, first appeared at the Baltimore zoo, where it feasted on pigeons and starlings, staples in an urban falcon's diet.

The flight of Fancy, and her 100-to-150 mile-an-hour dives on pigeons below, has fascinated humans but so far has not attracted any male falcons to downtown Baltimore. This week, however, a male was flown in from Texas to see if he might tickle Fancy's fancy.

The male, an 11-year-old bird trained in falconry and named Blue Meanie, is "extremely fit, in fine shape, but has never mated before," said Dr. Scott Ward, chief of ecology at the Army's Edgewood Arsenal at Aberdeen.

Ward, an expert on falcons who has been working with Cade, said Fancy, or Scarlett as she was named by the Cornell group, apparently is now ready to mate.

"She has been flying around conspicuously, then returning to the nest and scraping around in the sand," he said. To encourage her, Ward has placed a sand-filled granite box eyrie on top of the USF&G building.

Because female falcons are larger than males and can be extremely aggressive, Blue Meanie will be kept caged for about two weeks on top of a nearby 10-story telephone company building while enticing, tape-recorded falcon siren songs are emitted from a roof-top speaker system, Ward said.

If Fancy-Scarlett appears friendly and interested, "and we don't know if it's going to work because this has never been tried before, we'll release Blue Meanie and hope for the best," says Ward. However, "a back-up male at Cornell," one of the 70 resident falcons used for breeding, might be brought down to Baltimore if the Blue Meanie is spurned.

The four young falcons Washington will get in June will be the first to be "hacked" or released, from a central city site. The month-old, downy chicks brought here will have partially developed tail and wing feathers and within a few days "will be given freedom to run all over the Interior Department roof, try out their wings and shed their down... which comes off like snow," said Ward, who will assist Cornell scientists in the Washington falcon experiment.

This period is crucial in the life of the falcons, said Ward, because "they imprint on the area, it becomes their home, the place they return to." The birds will be fed by unseen human hands and will have food regularly available at the roof-top cage for some time after they are out flying and catching their own food. The birds also will have minute radio transmitters and bands attached to their legs so scientists can keep track of the falcons' peregrinations.

The Interior building was chosen as a safe roof, after Cade visited the Smithsonian Institution towers here this winter and found them too small, both in height and in area. They also have been home to owls for many years. Cade was forced to abandon the old Post Office's 350-foot grantie tower, which he thought ideal, because it is undergoing restoration. The Interior building is appropriate, Cade said, because the department's endangered species funds are helping support the Cornell program.

Once free, the falcons may perch or even nest on these buildings of their own accord, said Cade. Or they may possibly choose a 234-foot Washington Cathedral spire, as church steeples and castles are frequent roosts for falcons in Europe. The 80 known subspecies of peregrine falcons - the differences are so minor only experts can spot them - once were seen in many U.S. cities, in cluding Washington and Manhattan, and so widespread they were common everywhere in the world except Iceland and Antarctica, said Ward.

Efforts to bring back the falcons in this country have been made possible by the Cornell program and the government ban on DDT, which accumulates in birds of prey and weakens their eggs' shells, according to Ward. The program is similar to two other wild bird breeding programs, he added.

Eggs from the near-extinct whooping crane are taken from th esole remaining wild flock of whoopers in Canada and a captive flock at Patuxent Wildlife Research Center in Laurel and flown to Idaho, where they are placed in nests of the plentiful sand crane. The sand cranes have been rearing the large ugly-duckling whoopers as their own, but so far, out of the 61 eggs delivered since 1975, only seven whoopers remain and they have yet to mate.

Cade said the population of the nearly extinct masked bob white is beginning to grow under a similar program in Arizona and New Mexico.

But nothing like the peregrine falcon breeding program has been tried before. One advantage with the falcons, says Cade, is that there are many trained falconers in the world familiar with handling the bird.

"After all, we've had some experience.Man has been working with falcons for more than 3,000 years," he said.