MISAWA AIR BASE, Japan — The screeching distress call and puff of smoke are meant to scare not joggers but birds.

Eleven propane cannons with a tape player set up along the airfield perimeter — some near the walking path — are just one measure this northern Japan base uses to control birds that pose a potential threat to moving aircraft.

But the noisy devices can’t solve one bird conundrum that spans an invisible political boundary: A flock of gray heron — similar to North America’s great blue heron — is roosting south of the airfield — off base. They routinely fly across the runway to ponds on the east and west sides, where they retrieve nesting materials.

The flight path of the long-necked fowl puts them on a direct collision course with aircraft operating on Misawa’s runway.

A bird sucked into a plane engine can cause catastrophic damage. For example, in 2003, a U.S. F-16 at Osan Air Base, South Korea, crashed just after takeoff when its engine ingested a spot-billed duck, said Master Sgt. David Hollister, noting the pilot ejected safely.

Hollister manages Misawa’s Bird/Wildlife Aircraft Strike Hazard (BASH), an Air Force program designed to reduce aircraft collisions with fowl and mammals. BASH has been around for years but became more proactive after the 1995 crash of an Airborne Warning and Control System (AWACS) plane that flew into a flock of Canadian geese after takeoff from Elmendorf Air Force Base, Alaska, killing all 24 people aboard, Hollister said.

Misawa BASH members use a combination of nonlethal methods — propane cannons, pyrotechnics, habitat management — and lethal ones — shotguns — to control bird populations on and near the airfield. Strikes occur — about 12 year — but none have downed an aircraft.

The herons are of particular concern due to their size and direct flight path across the runway, officials said. But since they nest outside the base perimeter, the birds are protected by Japanese wildlife laws: The Air Force can’t destroy or harass them off base.

So the BASH team called in the experts to help it outsmart the flock. Daniel Vice and Jason Gibbons from the U.S. Department of Agriculture Animal and Plant Health Inspection Service/Wildlife Services recently visited Misawa to assess the problem, consult with researchers and biologists and recommend action.

“We were looking for techniques to manage” the herons, Hollister said.

Wildlife Services works in places where birds and mammals create problems for people, including airfields; Vice and Gibbons are based on Guam, where the invasive brown tree snake has wiped out many native bird species.

Earlier this month they spent several days on base surveying bird populations that use Misawa’s airfield, conducting surveys at sunrise, midday and sunset.

Given Misawa’s habitat and bird varieties, issues between the U.S. and Japanese governments, nearness to the ocean and seasonal changes, Vice said, “we’ve discovered there’s a fairly complex problem here.”

“Just in a very brief look, we probably identified 30 different bird species on the airfield,” from tiny Asian tree sparrows to large raptors, he said.

In fact, Vice and Gibbons identified three other types of birds, besides the gray heron, that pose the greatest risk to aircraft: The black-crowned night heron, which maintains a large nesting colony just outside the base perimeter; raptors, including hawks, falcons, kites and other birds of prey; crows, both jungle and carrion; and water fowl, primarily the spot-billed duck.

“Given the habitat around here during the fall and spring migration, there’s probably a much larger problem presented by ducks and geese,” Vice noted.

Vice and Gibbons will write up a management plan, they said, using an integrated approach based on scientifically sound and humane methods.

“We look for nonlethal control tools first — propane cannons, hand-launched pyrotechnics; they scream, they whistle, they explode — you can harass birds on foot, with vehicles, with sirens,” Vice said. “The idea is to try to keep the birds off-balance.”

Most important is commitment and resources, he said. “Whether harassing birds, scaring birds, managing their habitat or catching and relocating birds, you need to have the people and equipment in place to make it happen.”

Vice, Gibbons and Hollister believe the gray herons have been nesting at Misawa for years; thus far, they’ve eluded aircraft but still present a very real risk, they said.

“It’s a very instantaneous thing, where they fly across the airfield and they’re gone,” Vice said. “The risk or the probability of a single bird flying across the airfield and getting ingested by an aircraft is relatively slight. However, when you add up 50 birds making daily passages back and forth, combined with hundreds of aircraft movement a day, that risk starts to grow over time.”