The clues are everywhere but they are subtle: a farmer or two fewer at the morning coffee and bull session in the Wimbledon Cafe, a row of empty food lockers in the freezer behind the Red Owl Market, and the neat brown squares of cardboard that postmaster Robert G. Brown uses to seal up his unused postal boxes.

"Every year," says Brown with a sigh as he looks over the lines of cardboard squares, "the farms get bigger and a few more families pick up and leave."

Somewhere else rural America may be under-going what some experts like to call a "renaissance," but out here on the Great Plains, that broad swath of wide open farm and ranch land stretching from the Dakota to West Texas, the country towns are dying.

It is a complicated and slow process. Not like the roaring dustbowls of the '30s that once emptied the lanscape of the southern plains in just few years. Land here in the rich North Dakota wheat country sells for $500 to $700 an acre and the farmers usually leave with money in their pockets.

Wimbledon's mayor, Howard C. Olson, has been here about a dozen years and has seen the change take place. "Maybe," he said a little wistfully, "if the big farmers go broke we'll see it go back to the way it used to be. I'd like to see it boom here again." But meanwhile, Wimbledon withers.

One way to tell is from the heat tabulations that Stanley V. Voelker keeps in the U.S. Agriculture Department's Economic Research Service office at North Dakota State University in Fargo, 90 miles southeast of here.

Voelker's figures show that at its high point in 1950 Wimbledon had 449 residents. The total dropped at 10-year intervals to 402 and then 337. There are 314 people officially listed as living here now.

Wimbledon, Voelker said, is a typical Great Plains town. The figures the Agriculture Department has compiled for rural American communities are somewhat deceiving. Between 1960 and 1970 only 184 rural communities disincorporated - traditionally a final act of dying towns - while about 500 new ones incorporated.

The federal figures show that North Dakota is now losing about 500 farms per year while the average size of a North Dakota farm has climbed from 752 acres in 1960 to 1.015 acres in 1975.

The new towns, howere, sprang up in suburbs, or the Southwest's Sun Belt, or booming vacation and retirement centers like northern Michigan, or in the Ozarks where decentralizing business firms are moving. None of these phenomena is taking place on the Great Plains, Voelker said.

The map on Voelker's wall shows where rural growth is occuring. The map breaks the United States down into 3,200 counties, with growth counties listed in blue and declining counties in red. A long band of red stretches from North Dakota to Texas. The only other concentrations of red are through the South's rural Black Belt and those places that are dependent on military installations.

The military, said Voelker, was once a rural growth industry. But since the end of the Vietnam war, military bases in rural areas have been steadily cut back or closed, bringing hard times for many of those areas.

In small towns like Wimbledon it sometimes doesn't take a major event like a military base closing to cause problems. The ecology of rural populations is a delicate one that can be radically altered by lesser crises. One such crisis, for example, took place here when the school buses were purchased.

"A couple of years ago," said Michael Schlecht, manager of the Red Owl, "the farm parents would drive their kids into town to school in the morning. They'd stop off at the cafe for a cup of coffee and some talk and then run over and buy something at one of the stores before they left."

Then, said Schlecht, the Wimbledon public school brought five large yellow buses. The buses rumble over the snow swept farm roads here each morning picking up children. Now the farmers and their wives drink their coffee at home and many do their shopping at the regional shopping center in Jamestown, 30 miles from here.

Schlecht, 30, is a civic booster of sorts and one of the few non-farmers here who can trace his roots in the community back several generations.

"Our business is holding on but we're working harder to draw customers from a larger and larger area." Schlecht said. "We have to in order to survive because the farm people just aren't there anymore in the numbers they once were."

Despite his ethusiasm for the town. Schlecht said he, too, has seen the small signs of decline. A few years ago, he said, he ran a survey to find out what the people of Wimbledon wanted most in the way of public services.

The vote went overwhelmingly for a new television repairman, and Wencil Samke was enticed to move here and set up a TV repair business. The business closed after it became clear there just aren't enough TV sets left in Wimbledon to repair. Samke now works part-time at the John Deere farm implements store to make ends meet.

The bees in Ernie's Hotel are another clue. The small hotel here closed after business dropped off and the owner died a few years ago. It was purchased by a honey processing company. The old hotel is now filled with bees hibernating from the below-zero winds that often rake Wimbledon streets.

"Sometimes." said Voelker, the federal agriculture economist, "these places can be deceiving. In small declining towns business people often hang on long after they should. A lot of then take terrific property losses because they can't bring themselves to shut down and leave."

Voelker recently surveyed more than a hundred rural North Dakota communities with populations of less than 1,500 to determine what kinds of businesses they have left in them. What he found was a sort of small-town process of economic natural selection.

Most towns with more than 300 people, for example, still had a post office, cafe, grocery store and insurance agent. At populations of 600, most had a bank, motel, weekly or semi-weekly newspaper and an appliance sales-room. At 1,000 most towns added a steak house, attorney, department store, laundromat and funeral home.

"It's hard to find a rural community here anymore of under 1,000 that's not on the decline," said Voelker. Most, he said, are being propped up by some form of federal subsidy such as an unneeded post office, federal housing projects, or federal water project.

"A lot of these places never were needed and probably would die out if you took the federal help away," Voelker said. "But Congress will never do it. They're on the same plane as apple pie and motherhood and things that tug at your heart."