The best about hunting ducks on Virginia's upland rivers is that it is essentially impossible. Close shots are rare and the birds often flush while the gunner is running a rapid in a tippy canoe or jon boat, making the odds about even whether the duck or the hunter will splash.

To have any chance at all to bag a duck the hunter must go slowly and inconspicuously, studying the landcape. He still probably won't get any duck, but he will see hawks and sometimes an osprey or bald eagle: he will surprise muskrats and beaver; kingfishers will scold him and swallows swoop over him; and now and then one of the cows along the banks will at second glance be a deer. Whether he shoots any ducks will seem almost beside the point.

Traditional hunters of the Eastern Shore call the 3 1/2-day October season the silly season, but the upper reaches of the Chesapeake Bay's tributaries there are a few wet, tired and happy duck hunters who know better. The early season embraces all unprotected ducks and is statewise, but basically it is designed to give Virginians a chance at th e wily wood duck. By the opening of the regular season in November the abundant local woodies are long gone to the sunnier South.

Upriver ducking is hunting . It is not a matter of sitting in a blind calling birds in over decoys for sucker shots, but requires first-class boat-handling and patient stalking along the banks. One careless thump of paddle against gunwale is likely to spook wood ducks at 300 yards, and trying to creep up on a flock of them through tangled underbush is an exercise in discipline and frustration.

Along the Shenandoah this season, one hunter stalked a flock for several hundred yards, taking baby steps and moving so stealthily that at one point he got within 10 feet of a pileated woodpecker before it saw him. At last the crept within a dozen yards of eight wood ducks. They splashed and gabbled unaware until he tried to slip past so that they would flush back toward his companions, who had grounded their canoes upriver to wait.

But the bank was step and muddy and he slipped. The ducks winged safely away downriver as the gunner landed up to his knees in ooze. Later he undertook a mile-long the vertical face of a ridge and got within 35 yards of 23 woodies sunning themselves on the rocks jutting out of a rapid. When he stood up to flush them he found he was blocked by a bush. (Shooting sitting ducks is legal. but. . .)

"They're so beautiful it's a pleasure to watch them get away," said Joe Sottosanti of Shenandoah River Outfitters in Luray, who had furnished the canoes and his intimate knowledge of the river. Total bag for six gunners on the second day: three wood ducks, a coot, a squirrel and a dove.

And in most hunting, opening day was the most productiv*e. The woodies had seen thousands of canoeists on the river through the summer, and would sometimes let the boats approach within reasonable shotgun range before abandoning the eddies where they were slurping up duck grass. That why the game commission doesn't permit hunting until noon on opening day. .

After the sound of the first flew flurries of shots had gone rolling down the river the birds grew more wary, and Don Liscomb, Scottosanti's partner, switched to the stalking tactic. When a flock was spotted he would go ashore and work his way inland to a spot the birds, which when flushed would sometimes fly within range of the waiting boats. The method is effective, but most of the land most of Virginia's river is posted; extensive advance scouting and permission-seeking is advisable,

The opening-day bag for four gunners was 15 woodies, a green-wingled teal and a coot. During the early season, wood ducks count 25 points each; later, when the sparser northern woodies have moved in, they are 70-point duck, making the limit two per day. (Under the point system the bag limit is reached when the last bird taken puts the total at over 100 points.)

By the third day the wood ducks had learned more about hunters than the hunters had learned about them. They flocked in midriver rather than under the banks, often in the center of a rapid where they could see hundreds of yards in every direction. Each flock posted at least one sentinel, usually a gaudy-plumaged drake, which typically would slow only its head above, the level of the drop-off of the rapid. He would flush, dfollowed by his fellow, the moment the bow of a canoe showed around a bend. The bag, for three rain-shocked hunters: two coots. "That's about the way it goes," Scottosanti said. "A duck that is smart enough to nest in a hollow tree and eat acorns doesn't take long to learn how to deal with clowns like us."

The fourth and final day of the season brought winds that would have made canoeing foolish, followed by frost and a freak snowstorm that sent tbirds off to mock the gunners of the southern swamps.