IT'S BEEN a quiet week at Avenel, home of the Kemper Open. The winners and losers have departed. The tents have been struck, the courtesy Cadillacs have vanished like Cinderella's coach, and the electronic leader boards are dark.

Just beyond the main scoreboard a female bluebird sits serenely on four blue eggs, just as she sat throughout the tournament, unnoticed by passersby with eyes only for the main event. On a low branch nearby her faithful mate keeps an eye on the house and on the younger generation flitting through the trees that edge the putting green.

With a superb sense of timing, the bluebirds launched their first brood the week before the tournament, and promptly settled down to start their second family of the season. By the time Larry Mize teed off on opening day, the fledglings were expert fliers, sailing confidently above the golfers and spectators. This is their turf. It was bluebird turf long before Avenel became the newest stop on the Tournament Players Tour, even before Avenel was a hundred-acre Montgomery County horse farm.

It was on the old farm that my husband and I discovered the bluebirds while surveying Maryland breeding birds. We recorded several pairs at Avenel, nesting in tree cavities and feeding happily on grasshoppers in the green fields among the grazing horses. On our visits to the farm we became accustomed to their quiet presence and gentle music.

Eastern Bluebirds are softspoken and modest in demeanor, but their color! Blue jays are positively dull compared to the bluebirds, with their vivid royal-blue backs and light underparts, brightened by a flush of russet-orange across the breast. A male bluebird in a shaft of sunlight is an electric shock. The female's a subdued shadow of her mate.

They are a handsome and devoted couple, fighting for survival against great odds: the scourge of house sparrows and starlings that preempt their nesting sites, destroy their eggs, and even kill their young; the disappearance of old orchards and hospitable farmlands in the inexorable advance of bulldozers and cement mixers.

We watched development come to Avenel Farm. Bulldozers scalped the hills where bobwhite and killdeer had nested, preparing the ground, we were told, for a splendid new golf course. Chain saws roared through the woods where wild turkeys had lurked. Pavement criss-crossed the old farm, and houses sprang up in fields that had long been way-stations for hundreds of bobolinks in spring migration.

But the bluebirds were still there, struggling to maintain their turf.

"Bluebirds are very tolerant," observes Ed McKnight of Bethesda, who for 20 years has provided housing for these endangered birds on his West Virginia retreat.

Tolerance is a key to their survival. But it takes more than tolerance for bluebirds to survive in a changing environment. They need a little help from their friends.

The bluebirds found friends at Avenel.

In a race against time to get the new course ready for the Kemper in June, manager Jim Seeley was not too busy to listen to the story of the bluebirds. On a snowy day in January, we had counted 20 wintering birds in a sheltered grove of trees, many of which were already marked for cutting. With proper housing to replace natural nesting cavities, we thought the bluebirds could be induced to stay. Their numbers might well be augmented in the spring by others arriving from points south.

Seeley was enthusiastic about helping the bluebirds, as was grounds superintendent Dave Anderson. The Audubon Naturalist Society was enlisted to establish a "bluebird trail" of starling-proof boxes, following the specifications of Larry Zeleny, founder of the North American Bluebird Society and widely acclaimed for his crusade to save the endangered birds.

On a brisk day in March we walked the course with Mark Swick and Darryl Speicher of the Audubon Society, selecting nestbox sites. Bob Lavell, former president of the Society, advised on placement. The boxes should face east to catch the warmth of the morning sun, and, for safety, away from fairways and golf-cart trails. They should be near open grassy areas where the birds could browse for insects, but not where crowds of spectators could be expected to gather.

Bluebirds, eager to build, looked over our shoulders as Mark and Darryl anchored a numbered box to a beech tree. Twelve boxes were distributed at hundred-yard intervals.

With Lavell, we checked the boxes at least once a week to guard against predators and insects, to discourage sparrows, and to clean out old nests to make way for new ones.

Three pairs of bluebirds promptly began nesting in the manmade homes; others chose sites in the woods. When we made our rounds of the boxes, the trusting females vacated their nests and waited patiently while we peeked inside at the blue eggs and, later, the young hatchlings. The brilliant males were never far off.

Like anxious parents the week before graduation, we watched the youngsters change from naked to downy to feathered, hoping their wings would grow fast enough to get them airborne before the hordes descended on Avenel for the big tournament. If Kemper was a test for Avenel, it was a test, too, for the bluebirds.

The bluebirds passed. In the cool of a May morning, before the golfers had displaced the deer from the fairways, they launched their new families, a total of 10, and led them into the seclusion of the adjacent woods for flight training. In another week they were on their own, ready for their first tournament and paying no more heed to the crowds than the crowds paid them.

Avenel is not the only golf course in the area to extend its hospitality to bluebirds. Just across Persimmon Tree Road, Congressional Country Club has a bluebird trail, which was established several years ago by grounds superintendent Bill Black and is monitored now by Audubon volunteer Sally Revoile. In his enthusiasm, Black overbuilt; with 75 boxes, the supply exceeded the demand, but the rate of occupancy is quite satisfying nevertheless.

In a more modest project at Columbia Country Club, the Audubons maintain a dozen boxes, defying the popular conviction that bluebirds don't nest inside the Beltway. They have nested successfully at Columbia, says a triumphant Mark Swick, who keeps tabs on the project. The first five were fledged in May.

Swick hopes to encourage other clubs to follow suit. Golf courses, as Zeleny pointed out years ago, offer ideal conditions for nesting bluebirds, who prefer expanses of close-cut grass where they can easily capture insects spotted from overhead perches.

It isn't hard to convince anyone that bluebirds are an asset to a golf course, lending a touch of color and beauty to the total scene. Their soft music and gentle ways have a soothing effect on those who take time to watch and listen.

Regular players and grounds crews at Avenel have learned to watch for the bright blue flashes along the fairways. They ask about the bluebirds' private lives and prospects.

A grim-lipped golfer, unhappy with his game, pauses beside his cart and watches as the Audubon volunteer peers into a nesting box at the edge of the woods. What's she doing, and why, he wants to know. She explains, and his features relax as he becomes absorbed in the life struggle of the bluebirds.

"Are you a famous golfer?" she asks.

He laughs. "No, I'm not in that class, and never will be. I think I might do better watching bluebirds."

Lola Oberman, a reformed Washington speechwriter, is a columnist and free-lance writer and author of The Pleasures of Watching Birds (Prentice Hall Press).