The sky-filling flights of ducks winging across Idaho's fall sunset have been thinning out in recent years, and state experts are moving beyond the borders to reverse the decline.

Migrating ducks on the Pacific Flyway through Idaho are suffering from an environmental Murphy's Law, where everything that can go wrong for them has gone wrong.Ponds in the Canadian prairie provinces that serve as summer ground for millions of ducks and geese are bone-dry from a long drought. Habitat at the southern end of the migration route in California's Central Valley is falling victim to the bulldozer or plow.

"We're really losing habitat at both ends," said Gary Will, state game bird manager for the Idaho Department of Fish and Game.

But Fish and Game's interest in Alberta, Canada, real estate eventually may add thousands of acres of marshland to serve as "duck factories" for the coming years.

For the first time, the Idaho Fish and Game Commission has approved allocation of $146,000 this fiscal year to go to a cooperative agreement between Ducks Unlimited-Canada and private landowners in Alberta.

"We feel, even if we're developing wetland in Idaho, we can't make up the shortfall in Canada," Will said.

At the other end of the flyway, the Central Valley Joint Venture in California is working to regain bird habitat lost through cultivation or construction. And the historic North American Waterfowl Management Plan between the United States and Canada holds great promise, setting a strong framework for waterfowl management into the next century.

Idaho officials have the authority to transfer 20 percent of the money gained from waterfowl artwork to reclamation projects in Alberta or British Columbia, Will said. The art prints depict the new Idaho Migratory Waterfowl Stamp approved by the state Legislature two years ago.

About $74,200 in state money will help build dikes and dams on ponds in the Kanegawa project, covering nearly 130 acres of open water, Will said.

The balance is targeted for the larger 341-acre Keho Lake project to trap water from an existing irrigation reservoir for use by waterfowl during the summer, he said. The Keho project costs $340,700. More Idaho money will be set aside in subsequent years. No outright purchase of land by Idaho is involved.

"The ducks, the landowners and the irrigators win through this," Will said. "It improves the movement of water through the structures, improves the vegetation and reduces erosion.'

Waterfowl need three basics: food, water and groundcover. But the drought and encroachment of man are eliminating them at an accelerating rate.

As the shallow marshlands in Canada dry up, species of plants the ducks feed on are lost and farmers are free to construct ditches and bring the former swamp land under the plow.

Then, even if normal precipitation returns to the prairies, the historic marsh is gone for good, said Chuck Peck, project leader of the U.S. Fish and Wildlife Service's Southeastern Idaho Refuge Complex.

The nationwide population of duck breeding pairs declined 16 percent in 1988 from the average over the previous 30 years, Peck said. The familiar mallard, or "green head," is down 20 percent. Canvasback numbers have dropped 22 percent, and blue wing teal populations have dropped 25 percent.

Perhaps the most severe loss is in pintail ranks - down 54 percent, Peck said.

Surprisingly, Canada geese populations in Idaho have mushroomed at the same time. Peck said geese are distributed more widely in their northern grounds and seem to nest on rivers or lakes where water can be found more readily during a dry spell.

Only recently has Ducks Unlimited-Canada started gathering money for marshland. Ducks Unlimited in the United States contributes about $35 million a year to Canada from duck hunter banquets featuring auctions for shotguns and artwork.

Four million acres already have been set aside through the efforts of American Ducks Unlimited, said Idaho chairman Tom Arvin.

"We were losing 1,000 acres of marshland a day for a long period," he said.

Money from the state "duck stamp" goes to procure marsh land below the Canadian border. Fish and Game has purchased 1,800 acres near Hill City north of Mountain Home through its Habitat Improvement Program, Will said. The department has bought or developed land in 230 spots throughout the state under the program.

Idaho's efforts in Canada are assured at least until 1995 when the current authority for the waterfowl stamp, and artwork, lapses, Will said. State lawmakers would then decide whether to renew the stamp.

But for now, there seems to be reason for optimism about Idaho's ducks.

"I hope what we're seeing is a bottoming out," Peck said. "I hope the recovery of waterfowl starts this year, although I wouldn't expect to see a complete recovery in one year."

"It's going to be a long, hard struggle, but we'll get them back," Arvin agreed.