You drive 2 1/2 hours before you even launch the boat, then go four miles through unmarked marsh channels to a cove where the ducks feed. You set out 50 decoys and fashion a makeshift blind, hide the boat, slog back on foot, conceal yourself, load the gun and wait for dawn.

You wait through bitter first light, listening to the whistle of wingbeats overhead. Twenty minutes later it's bright enough to see. A pair of drake mallards buzzes the decoys. You shoot well, and wade out in the cold water to retrieve the pair.

Quitting time.

*

In response to population declines, the U.S. Fish and Wildlife Service two years ago instituted emergency measures to reduce the annual "harvest" of black ducks.

The result, a one-black-duck-and-go-home limit, proved an inconvenience to hunters hereabouts, only a few of whom seriously pursue these wary denizens of the deepest marsh.

But now Fish and Wildlife is on the verge of major steps to protect the most popular and abundant game duck in the region and the nation -- the mallard. Already, protests are being raised.

Federal scientists in the northern prairies this month are checking the nesting success of about 10 duck species. They are most concerned with mallards and pintails, both at all-time-low breeding populations after four years of northern drought.

If nesting is as poor as USFWS anticipates, the agency will push for deep cuts nationwide in the bag limit or length of hunting season for mallards and pintails.

"And it looks even worse than we expected," Rollin Sparrowe, chief of the agency's migratory bird management office, said yesterday.

Sparrowe said Fish and Wildlife, which oversees local duck hunting regulations because the birds cross state boundaries, wants to reduce the mallard and pintail kill by 25 percent if populations are below pre-established minimums, as he expects they will be.

To cut the harvest by a quarter, he said, the bag limit or season may have to be cut in half. That likely would mean a two-mallard a day limit in Maryland and Virginia, where hunters last year could take up to four mallards a day.

(Pintails are common in the western and central flyways, but are not widely hunted in the East.)

Several hunting-oriented organizations responded negatively to the prospect of new restrictions on grounds data to support the changes isn't in hand yet.

"It's our guess that the Fish and Wildlife Service has locked itself into reductions before it gets the current data," said Jim Dudas of Ducks Unlimited.

"We feel they should wait," Dudas said, until the prairie nesting survey closes at the end of this month. Dudas said the National Rifle Association, National Wildlife Federation, Izaak Walton League and Wildlife Legislative Fund share that view.

Dudas also said a severe reduction in season or bag limit for the two popular species could have a profound effect on the number of people who bother to duck hunt.

"It's a psychological thing," said Dudas. Even though the average hunter bags less than one duck a day, he said all hunters entertain the hope they may have a banner day.

"If you say to a hunter, 'You can't shoot four, you can only shoot two,' even though four is unlikely he might say, 'Why buy a license, why buy a duck stamp, why buy all that equipment?' "

Dudas said the federal and state governments depend on taxes from hunting equipment sales and revenues from licenses and stamps to support their game management and habitat protection programs, and by making hunting less appealing they would be hurting their own programs.

Sparrowe said Fish and Wildlife recognizes those problems, "but our first priority under the law is to wisely use and protect the migratory bird resource."

He said a survey in May showed pintail and mallard populations so low that even if both species bred successfully this summer, recovery to acceptable population levels was unlikely this year. Though final decisions won't be made until Aug. 1, after nesting data is in, he said, "It's a critical situation that requires extraordinary measures, both short- and long-term."

"It's ridiculous," responded Manuel Munoz-Carrasco, a duck hunter from the District, "to go through all the hassle -- boats and trailers and decoys and tramping through the marsh, and then shoot twice and go home. Who's going to do it? You'd have to be nuts."

"It sounds to me," added Tom Hardesty, a Metropolitan Police officer and avid duck hunter, "like a guy could go to the grocery store, buy a couple of Cornish hens and come out way ahead of the game."