For 30 years the man has been living a lie, and he is proud of it. He has gone skulking through marshes slaughtering protected waterfowl, he has gunned down endangered species with professional poachers, he has bought bald eagle claws and feathers by the bushel on the black market. His countless game law violations would be worth several long lifetimes in federal prison because there is virtually no outlaw hunter's dirty trick he hasn't pulled.

And in fact his companions on these illegal hunts usually have wound up henind bars or paying stiff fines, because this mild-mannered, innocent-seeming man of middle years is the top undercover agent for the U.S. Fish & Wildlife Service.

Agent Holstead, as we shall call him - because that is his real name, and he hardly ever uses it - has engineered rude surprises for thousands of scofflaws from Chesapeake Bay to Hawaii, form Alaska to Key West and from Maine to the Rio Grande.

On a given Sunday morning he may be crouched on a California ridge with guides who have promised to produce an illegal Rocky Mountain goat; the following Friday he may be buying a smuggled Bengal tiger skin at a fancy Les Champs shop in the Watergate complex.

"The only place I can be pretty sure I won't be iat home," Holstead said during an interview in his Washington office. "A Fish & Wildlife agent can only be as effective as his wife will let him be, because you can't enforce game laws on a 9 to 5 schedule, and you can't ever promise to be home on a given day. That just isn't fair, and if she can't accept it, you'd better take up another line of work. It is an unthankful and impossible job, and nobody can stick it without cheerful support from home.

"These investigations take an enormous amount of time. There are only 180 federal game agents to cover the entire country," Holstead said, spreading his palms over the stacks of paper before him, "and a lot of those are desk jobs.

"You have to do a lot traveling, you have spend long afternoons around potebellied stoves in crossroads stores gaining the local people's confidence, you have to spend long days and nights out in the fields with binoculars, you have to spend day after day in court. If your wife isn't willing to put up with that, you can't do the job. I an blessed with the finest wife any man could ask for, and kids who understood why Daddy was never home."

The children are grown and gone now, but Mrs. Holstead had to do without her husband for much of the past three winters while he led an undercover investigation on Virginia's Tangier Island that led to the largest and most successful raid in the 92-year history of the service. Island guides were offering unlimited shooting, in and out of season, at anything that flew, to hundreds of hunters from all over the country.

Tangier has been a trial to state and federal game agents since market hunting was outlawed in the late 19th Century. Some of the islanders never have been reconciled to limits and seasons set by mainland bureaucrats, and since nearly everybody there is related to nearly all his neighbors, those who do obey the laws protect those who don't.

"It's even tougher now that all the watermen have CB radios," Holstead said "Tangier is way out there in the Bay, surrounded by open water and flat marsh, and they can see a stranger coming for miles. Everything is thrown overboard or buried long before you even get close. You can catch one or two at a time by coming in fast and low with a seaplane, but to get solid evidence on something as large-scale as they had going on there is no substitute for agents in place."

Holstead visited the island time after time and winter after winter until he was familiar as an old shoe, never once making any of the tiny slips that would have given him away to the islanders, who for generations have handed down the fine art of sniffing out federales. Other agents, including women, came and went, but Holstead abided.

"I love those people," he said. "They are splendid. They nursed me once when I was sick, they took me into their homes, they are some of the finest people in the world. I didn't enjoy having to turn them around like that, but this thing had been going on for eight or 10 years, getting more flagrant all the time. I don't get too excited about a man shooting a few illegal ducks for his dinner, but this kind of commercial slaughter is disgusting.

"Just in the three winters I was there I estimate they killed off at least a third of the canvasback and redhead ducks (both protected species) that overwinter in the lower Bay. I sat in a blind and watched two hunters kill 70 redheads on one day. Lots of hunters were shooting birds they had no idea of eating: they'd just gun them and let them drift away."

To play his part Holstead had to join in killing protected birds. "I popped a lot of caps, but my wing shooting falls off something terrible in a situation like that," he said. "Anyway, everybody was firing at the same time, so the fact I was shooting to miss wasn't too obvious."

The raiders, 28 agents in small boats and light planes, swarmed onto Tangier before dawn in a January icestorm, collecting thousands of illegal birds and issuing hundreds of citations, including one to Holstead, who make his way back to the dock at Crisfield, Md.

With him he took film of dozens of hunters who had posed proudly with their illegal bags, along with memorized observations of the details of scores of violations about which he could not safely take notes. Later he exchanged letters and pictures with doctors and lawyers and other pillars of various communities whom he had met on the island.

"When I was learning my way into undercover work I used to worry a lot about how to sneak along a camera, because there is nothing that will convice a jury like a picture," Holstead said."Finally I learned that the thing to do is hang the camera aroung your neck; everybody assumes you're a tourist, and sometimes a poacher will beg you to take his picture.

"They really felt betrayed when our agents showed up to serve summonses on them," he said. "Somehow I don't feel too bad about it. I'm used to being despised by poachers who thought I was their friend. My daddy was the game agent in charge of the Eastern Shore of Virginia, and I used to take beatings at school all the time because of it, from boys whose fathers he had arrested.

"To do this sort of work you have to measure yourself from inside, and the thing that counts with me is that I have never led anybody into doing something illegal, I have just taken what was offered.

"Our game laws are damn near impossible to enforce anyway, and you're lucky when you can nail somebody tight enough for it to stand up before a local jury. It's getting better, but a lot of people still have the attitude that the game will always be there and it's their right to take whatever they want.

"For some of them the game laws are just that, games that they play with the law; they care more about beating the law than the hunting."

For all that he has to spent most of his professional life among slob hunters and traffickers in illegal pelts, Holstead's view of the average hunter is far from jaded.

"I think most hunters obey the laws," he said. "I also think about 70 to 90 percent of them would violate the law from time to time if they were really sure they could get away with it. Hell, a man saves his money and his vacation time to go hunting and maybe he gets blanked for three days; then on the last day he limits out, he's packing up and then comes another flock . . . Our job is to keep that doubt in his mind.

"Perhaps the most serious problem is ignorance. Ignorance of the law in some cases but mostly ignorance about the species they're hunting. I don't think one hunter in 10 can distinguish legal from illegal birds on the wing. A man will come into the dock holding up a couple of brant and ask you if you're ever seen a finer pair of black ducks.

"What bohers me the most is that the outlaw hunters play into the hands of the anti-hunting groups, and the situation is getting worse all the time. People hear about hunters shooting polar bears from airplanes and Congressmen hunting over baited fields and they join up with the anti-hunters. Seasons and bag limits already are unreasonably low for many species in some areas, and the animals are in serious trouble as their habitats shrink. It isn't hunting but highways and sub-divisions and pollution that threaten most of the endangered species.

"If it goes on like this, the time may come when all hunting will be outlawed, and then only starvation and disease will keep wild populations in check. That would be a cruel and a criminal waste.

"But the hunters don't police each other. In all those years that the Tangier operation was going on we got two complains from hunters who were disgusted by what they had seen on the island. Two complaints, out of God knows how many hundreds of hunters who knew about it."

Holstead will be retiring at the end of the year, and he's looking forward to it. "The service is changing," he said. "A lot of our agents now are not hunters, and they don't understand people like the watermen. An effective law enforcement officer has to know how and why lawbreakers do what they do, and the only way to learn it is to live it.

"One of the toughest cases I ever made was a duck trapper out on Assawoman Bay. I worked on that old devil for weeks before I caught him cold with a couple of mallards, one of them a banded pen-raised bird released in Pennsylvania. He defended himself in court, with a local jury, and he did a beautiful job of it, but I convicted him.

"Afterwards, I was sorry. He wasn't a commercial trapper, he wasn't hurting the duck population, and he had as much respect and affection for wildlife as any man I've ever met. He was a good man, a better man than I am, and he became my good friend. He taught me a lot. He made me a better hunter and a better game agent, and I still go hunting with his grandson."

"I've tried telling that story to young agents, but they don't get the point, and beside, the way the game laws are written an agent doesn't have much latitude for exercising his own judgement anyway, even if he has any."

Holstead leaned back in his swivel chair and smiled. "I guess it's time for this old boy to get out of here and let somebody else worry about it."

His retirement plans?

"Oh, I'm going to do me some hunting, just me and a good friend or two, out there with the wing and the water."