The bald eagle, the endangered symbol of America, is being helped by Maryland scientists to reclaim the nation's skies after years of indifference by man. The mighty birds have been hit by cars, shot by hunters, electrocuted, poisoned and driven from their homes by encroaching development.

But for the last six years in a tranquil 5,000 acre federal wildlife research preserve near Laurel, the world's largest breeding center for eagles has added to the dramatic recovery of the species.

The number of eagles commanding the airy haunts across the country has been rising steadily over the past ten years--from less than 1,000 to an estimated 4,500--as the ban on the pesticide DDT in 1972 and the Endangered Species Act of 1973 begin to take effect.

At the U.S. Fish and Wildlife Service's Patuxent Wildlife Research Center, 38 eaglets have been hatched since 1976 and six more will leave this summer. They go to states where the few eagles in residence have been unable to reproduce.

Scientists hope that once the birds from Patuxent come of age, eagles will flourish again in places where they were almost extinct.

Restoring the eagle to America is the showcase operation of the U.S. Department of Interior's Office of Endangered Species. President Ronald Reagan has proclaimed Sunday "National Bald Eagle Day," the 200th anniversary of the adoption of the eagle as the national emblem. However, budget figures from the department's Fish and Wildlife Service show that the Reagan administration cut funding for endangered species programs from $22.8 million in 1981 to $17.6 million this year, with most of the reductions affecting the study and listing of more species as endangered.

FWS officials don't expect the funding cuts to affect the $38,000 eagle-breeding project at Patuxent, where researchers are augmented by a pool of willing volunteer eagle handlers, according to Dr. James Carpenter, directer of the endangered species services at the center.

Patuxent has studied endangered species since World War II, taking in the refugees from human progress for their research. It is out of that supply that the Maryland researchers began breeding endangered birds, including eagles, whooping cranes, Mississippi sandhill cranes, Aleutian Canada geese, and Andean condors, a close relative to the "Thunderbird," or California condor, a species that has been reduced to 25 birds in that state.

Patuxent's eight pairs of eagles are housed in a wood-framed, screen-sided warehouse of a birdcage, a half-block long and 20 feet high. Each couple has its own section, not unlike a condominum for birds.

"Birds are like people," Carpenter said. "They can be very selective about their mate." So biologists at the center observe preferences, according to Carpenter, fully aware that eagles mate for life.

Once the eagles mate successfully, handlers watch for eggs, which are immediately taken through a delicate disinfectant procedure. The potato-sized eggs are then incubated at a strict 99 1/4 degree temperature.

The hatchlings remain in a protected environment and are fed a blend of fish and nutrients until they get a healthy-looking dust of feathers. Some go back to their original parents. Some--seven this year--are flown out in airplanes to foster parents.

Most of the foster parents come from states such as New York and New Jersey, where eagles still lay thin-shelled eggs as a result of DDT residues in the fish they eat. The weight of the parent eagle usually crushes the defective egg, so Patuxent researchers switch it with a plaster dummy. Later the biologists shimmy up the tree when the nesters are away and trade the fake for a fluffy young eaglet.

Carpenter said relocating the new chicks not only increases the eagle population, but instills confidence in nesting eagles.

"I'm not exactly sure how eagles feel," he said, "but if they leave an egg and come back and find this huge, three-week-old chick, they must be pretty proud."

In another method, called hacking, biologists raise eaglets for eight weeks, then release them in an area where the population is low. Four young eagles at the center now are bound for Tennessee, where the last successful nesting was 20 years ago. Two others will go to Georgia, which hasn't produced a newborn eagle for 10 years.

Next year, officials at Patuxent hope to add another pair of bald eagles to the breeding cages and a new process called "double-clutching," in which newly-laid eggs are removed to induce couples to lay more. These additions could boost the yearly eaglet production to 20 from 13.

Officials keep a close eye on the eagles they release, banding each one, observing its activities through field glasses or homing devices long after it is released. In only one case did a foster eaglet disappear from the nest, according to Carpenter. All of the hacked birds from Patuxent survived their natural challenges. One in New York, however, fell victim to gunfire.

Federal laws impose a $5,000 fine and a year in prison for anyone convicted of harming eagles. Despite that protection and the elimination of DDT from domestic use, the biggest hazard remaining for eagles is the destruction of their habitat by agriculture and highway projects that drain the wetlands, according to Daniel L. James, a wildlife biologist of the FWS' Office of Endangered Species.

"The obstacle the eagles still have to face is man," said Carpenter. "We're hoping the two can be compatible."