Firmly planted in this corner, wearing the blue T-shirt and the brown running shoes, we have Kathy Klimkiewicz, master bird-bander, friend to the feathered, and one tough cookie to her friends.

Up there, swooping across the great vault of the sky, circling, hovering, filing on the empty bleachers, on the overhead wires, the fences, zooming in toward the orchard are 100,000 purple martins, give or take a few. It is not every day that 100,000 birds choose to roost in one spot. So far as anyone can remember, there's never been a purple martin roost this large on the Eastern Shore. But today is not like every other day, either for Kathy, who has been waiting for this moment for years, or for the purple martins, who might be willing to wait a little longer.

Hushed, awed, if not entirely cowed, her respectful troops surround her, a band of 25 or so assembled beneath the darkening sky on a dirt road between the playing fields of Salisbury State College and an old and overgrown peach orchard. There is no one, they say, who knows the purple martins like Kathy.

She -- and they -- are about to become more intimately acquainted.

On Saturday evening Kathy is prepared to band 30,000 birds, catching them in nets that have been raised in a 600-foot lane cleared through the orchard.

"They're coming in now! They're coming in low!"

"Let's get some ground rules here," shouts Kathy. "No pictures of birds hanging in nets. It offends people's sensibilities." Scenes of carnage flash before the mind's eye. The word is out that members of the Society for the Rights of Birds can be quite vehement in their opposition to this sort of thing.

"You didn't bring a hat, did you, Dad?" a junior birdman asks. It is a reasonable question, what with the hazards natural to so large a flight of birds, but the reply is drowned out in the squawking, feathered rush.

"If we get deluged with several thousand birds, we'll need all the help we can get," says Kathy, who has never seen a roost this large or this low. The trees are only 15 to 20 feet high, and no one knows quite what to expect. Klimkiewicz, a wildlife biologist in the Office of Migratory Bird Management at the Patuxent Wildlife Research Center, has been studying their breeding and migration patterns since 1972, and the purpose of this operation is to further that study.

The purple martin is the largest North American swallow, weighing in at 47 grams. It summers in the milder regions of Canada and the northern United States, nesting in colonies that may run to 200 pairs in what appear to be apartment houses on poles or, though they find these less desirable, in trees that have been drilled by woodpeckers. The birds feed on mosquitoes and other insects, and are prized for that reason.

The purple martins in Salisbury left their nests sometime in July for their roost in the peach orchard, a staging area for their migration to the Amazon basin where they spend the winter. Considering their numbers, one would not expect to find a mosquito within 30 miles or so of Salisbury, that being their feeding range. It can be scientifically reported, however, that this is not the case, perhaps because the purple martins have been eating too many dragonflies, which, in turn, eat mosquito larvae.

Within two minutes, from a signal known only to the birds but thought to be related to the intensity of the light, the birds disappear into the bush, except for those now snared in the nets. There are not 30,000 of them -- mercifully for the banders, who might have been laboring on through the night and the day, and for the birds, who could have raised quite a squawk.

The martins themselves are docile creatures and Kathy can free a martin from the net every 40 seconds. "A moment's roughness is better than having a bird struggling for half an hour in the net," she says, though her own touch is remarkably gentle, gentler with the birds than with her minions.

By 8:15 those birds that weren't settling down in the orchard were flapping in the nets. By 10:50 they had all been extricated and by 12:30 they had been banded and freed, except for those unfortunate few who gave their all for science and were placed in the cooler. "Hawk food. Or skins." Skins, it was explained, are what birders look at for markings and identification.

The final count was: 200 purple martins, 161 brown-headed cowbirds, 3 common grackles, 3 barn swallows, 2 starlings, 1 song sparrow, 1 red-winged blackbird and 1 gray catbird. Those in the cooler weren't counted, or, if they were, the results were classified. People's sensibilities have to be considered.

The campus cop, who showed up late in the proceedings in a squad car, shook his head: "The last time I came over here and saw this many people there was a big, wild party. Oh boy, was it a good party! Kegs of beer! Lots of kegs of beer." It can be reported that there were no kegs of beer Saturday night, despite the balmy temperatures and the full moon.