THEY sprint through the woods, tank up on peanut butter and Dr Pepper, and get by on three hours of sleep. They have a team manager, a corporate sponsor and a winning record they aim to keep. And they're all under 25.

This is bird watching?

It is for the Swift Wildbirders, who will defend their title in a marathon of bird pursuit next week at the Great Texas Birding Classic in Beaumont.

An outsider stuck on the stereotype of the tweedy, fuss-and-feathers bird lover, draped in binoculars and toting a thermos of tea, might be startled by the concept of birding as an extreme wilderness sport. Some sophisticated devotees question it, too. Upstarts not long out of Boy Scout camp are pushing into grueling territory where not everyone is ready to follow.

''It is disappointing to me that birding, when performed as a competitive sport, by individuals or teams, has increasingly replaced more protracted bird-watching studies that are most often performed by dedicated individuals over periods of many years,'' said Paul Johnsgard, 72, an ornithologist at the University of Nebraska who has written 45 books, mostly about birds. ''These well-publicized big-day events by star birders do nothing to advance the regional studies of birds or document their often declining population trends, which are serious conservation issues these days.''

They do, however, attract the young to an activity often dismissed as stodgy. And that is meaningful not only to bird lovers worried about the long-term survival of their kind, but to birding-dependent businesses like Wildbird magazine and the binoculars maker Swift Instruments, the sponsors that pick up airline, hotel and Whataburgers bills for the Wildbirders. Amy Hooper, the team manager and editor of Wildbird, said backing this young team is a conscious effort to provide role models for teenage birders and to give birding a cool image.

In preparation for the Great Texas, the country's most prestigious intensive birding contest, contestants send advance scouting teams, burn through bird-sound CD's and memorize bird books.

There is a one-day competition for the less adventurous, but the signature contest requires competitors to spend five rigorous days chasing through marshes, coastal prairies, dunes, oyster reefs, oak savanna, scrub shrub, bottomland hardwood forests and inland lakes in a Virginia-size area of Texas, all in pursuit of sightings -- seeing and identifying as many bird species as possible.

(Texas in April, a migratory hot spot long on every birder's Audubon calendar, also lures the compulsive birders whose battle to sight the most birds in North America in a single year is described in the current book ''The Big Year,'' by Mark Obmascik.)

The Great Texas is a magnet for young bird bums who aren't content to spend years compiling a life list of birds spotted and admired. Michael Retter, 23, captain of the Wildbirders, plans to spend the week crisscrossing Texas, putting in 20-hour days driving on country roads, munching on junk food and racing around on foot toting spotting scopes and tripods.

It's a far cry from an event like the recent Salton Sea International Bird Festival in California, which had guided tours and exhibits by optics companies and outfitters drumming up business for birding lodges.

One morning at that event, a group of mostly older birders, with $1,000 binoculars, uniform tan crumpled hats and special vests for holding bird books, and led by a professional guide named Mike Overton, gasped in admiration as thousands of snow geese, long-billed curlews and other birds whooshed through an orange sky at dawn. They were electrified by the sight of a rarely observed yellow-footed gull. But after seven hours they climbed back on the bus that had brought them and headed back to a warm hotel room for an afternoon nap before going out to watch owls.

''Younger birders don't go to birding festivals or wear birding clothes,'' Mr. Retter said. ''And we don't have any money.''

They are especially unnerved by the age-old obsession with listing, or ticking, in which the overriding concern is the record compiled of all the birds you have ever seen. Leading a group of older birders recently, Mr. Retter said, he saw a hybrid of an oriole, a rare find. ''It was in the sun singing away, a very interesting bird, but it was a subspecies and they couldn't check it off their life list, so they ignored it,'' he said.

The young crowd respects expert birders young and old alike, he insisted, but have found that establishment bird-watchers can be elitist and discriminatory -- even, on occasion, treacherous. When a friend identified a rare bird and told an older birder, Mr. Retter said, citing an example, the veteran first dismissed the find and later took credit for it himself.

Birders have always been passionate -- how many other people habitually tramp out into mosquito-ridden swamps with binoculars at 5 a.m.? But some in the new wave threaten to out-obsess their elders.

Michael Andersen, 21, a Cornell University student who is on the Wildbirders, plans to spend the next two years -- maybe longer -- as a bird bum, working odd jobs and free to pursue his passion. ''A bird bum learns to appreciate the subtle beauties of a car or a tent as a five-star hotel when cash is tight,'' he said. ''Some of us are interested in being professors, some want to be bird guides. But right now we can eat mac 'n' cheese, hang out with friends and talk birds.''