While East Coast duck hunters make ready for the beginning of the 1981 season next month, waterfowlers in the West are hanging onto hope that they will get a season at all. Four laboratories across the nation are testing ducks and geese from Montana for the presence of a highly toxic pesticide, endrin, which threatens to cancel the waterfowl season in 17 western states.

"We have found in some ducks levels of endrin that exceed Environmental Protection Agency standards," said Gene Allen, administrator of the Montana Wildlife Division. "We're continuing to sample, and we'll sample as many as we can before Sept. 25," when a decision on whether to close or alter the Montana hunting season will be made.

Officials elsewhere in the central and Pacific flyways are waiting to see what Montana does and are expected to act accordingly.

Endrin is a highly toxic pesticide that was sprayed on western wheat fields to ward off Army cutworms this spring and summer. Allen said endrin has been in use for several years, but this is the first time it has posed a health hazard.

He said state officials in Montana, where 125,000 acres are believed to have been sprayed, think the problem arose because a particularly early and heavy infestation of cutworms forced frequent spraying.

He confirmed that tests of a dozen ducks in Montana turned up three with doses of endrin in excess of the federal maximum level of .3 parts per million (the highest level found was 1.2 ppm). Half a dozen geese also were tested, none showing endrin in excess of the .3 ppm figure.

Since those tests were completed, Allen said, 75 to 100 other birds have been sent off for testing, with results due this week.

Initial reports about the endrin problem indicated that levels found in some ducks tested could give a 60-pound person nausea, headaches and convulsions after a single serving. A senior official of EPA's office of pesticides said this week that the report was erroneous.

"We've found that if a person consumed all of a duck with the highest levels found so far he'd be in no imminent danger of being sick," said the official. "He'd still be 40 times below the single-dose no-effect level, and five to 10 times below the chronic-intake no-effect level."

However, the official said, "that's still not a safety factor we're comfortable with."

Both Allen and the EPA official said preliminary indications are that the poison levels in ducks and geese sent out for testing will be similar to the tests of the first dozen ducks and half-dozen geese.

Alan Levitt, a spokesman for the U.S. Fish and Wildlife Service, said the federal government will leave the decision on whether to close or alter the waterfowl seasons up to the states, and will help enforce whatever decision is made.

Allen said the endrin problem first came to the attention of officials after a fish kill in southeast Montana. Then excessive endrin levels were discovered in sharptail grouse. The season on grouse opened on schedule, with a warning to sportsmen to go easy on eating grouse and to cut away all skin and fat, where endrin accumulates, before cooking.

With waterfowl the same tactics would be less effective. "There's a basic difference," Allen said. "In grouse the fatty tissue is localized and removable. In ducks and geese it runs throughout the meat. The problem is, how well can the hazard be removed?"

The EPA official said, "We're not worrying about somebody getting sick from eating one duck. But if people were to make a practice of shooting a number of birds and eating them over a long course of time, we would not be comfortable with that. Our only concern is that people not use these birds as a daily dietary source."

And, he said, it will be up to the states to determine use patterns and decide whether an open hunting season poses a health threat.

The overriding concerns at EPA are how the endrin levels came to rise and how to make sure it doesn't happen again. "Endrin has been used in the past without problems," said the official. "Obviously, something has changed."

According to government estimates, in addition to the 125,000 acres in Montana, endrin was sprayed on about 100,000 acres in Wyoming, 30,000 in South Dakota and 12,000 in Colorado.

However, ducks and geese are migrating and affected birds could be scattered throughout the two flyways.