PORTLAND — The Cooper’s hawk was not happy. The hapless juvenile had made the mistake of hunting for a meal near a general aviation runway at the Portland International Jetport. Now it was caged and flapping around in a trap, waiting for a federal wildlife biologist to set it free.

“This past year has been the year of the hawk,” said Arthur Sewall, deputy airport director of operations. “I’ve been here 27 years, and I’ve never seen so many, mostly Cooper’s and red-tailed.”

Hawks and their feathered kin are unwelcome competition to the aircraft that fly in and out of the jetport every day. On Nov. 1, a United Continental Airlines regional jet that took off from Portland struck a flock of birds later identified as snow bunting. The plane was forced to return for an inspection — which revealed no damage — before it could continue on its flight.

Bird strikes rarely cause serious damage to commercial airline flights, but they are capable of bringing down an aircraft. That makes their elimination serious business at the nation’s airports.

In 2009, a collision between a US Airways jet taking off from LaGuardia Airport and a flock of geese knocked out both engines. The pilot was able to land safely on the Hudson River, averting disaster.

“The New York incident brought bird strikes to the forefront worldwide,” Sewall said.

Sewall and his staff try to keep birds and other wildlife away from the jetport. They do it by making the 636-acre airfield as unattractive and inaccessible to wildlife as possible, and by scaring away or trapping birds that insist on visiting. The most persistent critters, as a last resort, can be shot and killed.

Passengers rarely see this work or even know it’s happening, but their safety could depend on it.

Since 1988, more than 219 people have been killed worldwide when birds struck aircraft. Domestic civilian flights reported more than 9,600 collisions with birds and other wildlife last year alone, causing millions of dollars in damage.

Bird strikes are as old as powered flight. The first incident was reported in 1905, by Orville Wright, after he flew over a cornfield near Dayton, Ohio, according to the Federal Aviation Administration.

Portland has recorded roughly 200 bird strikes since 1990. Nine have occurred so far this year, according to an FAA database. They included passenger, freight and business flights. Four involved gulls. No damage was reported.

The only recent bird strike in Portland to cause substantial damage occurred in 1995, when a US Airways 737 cracked its nose cone after hitting an eider duck. Two other flights, in 2002 and 2006, sustained unspecified moderate damage.

Commercial pilots say bird strikes can happen at nearly any altitude, but collisions are more common at lower altitudes, during takeoff and landing.

Rex Hopkins, a furloughed American Airlines pilot and former Bangor-based US Airways Express pilot, said instances of birds hitting commercial planes are relatively uncommon. He said modern airliners climb quickly to high altitudes, where birds are scarce, and most commercial airports have effective wildlife-control measures.

However, Hopkins, who now flies low-level mosquito-control flights in the Florida Keys and has hit several birds in recent years, said strikes can cause serious damage. A bird sucked into an engine intake can break hot, brittle metal components and cause engine failure. Hopkins has heard of birds crashing through aircraft windshields and landing in pilot’s laps.

Dean Street, chief pilot at aviation service company Maine Aviation Corp. at the Portland jetport, said damage depends on the type the bird and the size and speed of the plane.

Though birds can knock out engines, he said, pilots are trained in single-engine flying.

Street, who has hit two birds during his 4,500 flight hours, said the US Airways ditching made many pilots more aware of dangers posed by wildlife.

Even so, he said, birds often cause little or no damage.

“I know guys who have thumped them and never even known,” said Street. “Then they land and find blood on the plane.”

Larger airports have developed federally approved management plans meant to reduce wildlife encounters. Portland’s plan is being updated next year. In the interim, the airport staff has used formal training and in-the-field observations to refine methods for discouraging wildlife. A tour earlier this month highlighted some of their techniques.

The Cooper’s hawk was one of two dozen raptors caught over the past two years, snared by a Swedish goshawk trap. A second trap was set out recently between a crosswind runway and adjacent woodland.

“This location has been particularly lucrative,” Sewall said.

The trap features a mesh enclosure that holds two pigeons. The pigeons look like an easy meal until the hawk touches a hinged stick that triggers spring-loaded doors that slam shut.

A hawk can do a lot of damage to an airplane, but so can other large birds, such as gulls. There’s no way to trap a flock of gulls, but they can be frightened away.

A favored tool is a propane-powered noise cannon, which emits a blast that sounds like a loud rifle shot. As a US Airways jet landed overhead, Keith Lynds, a maintenance worker, demonstrated the cannon’s operation. It can be set on a random timer, too, to startle birds that like to bask on the sun-warmed tarmac.

Flocks that are hard to reach with the propane cannon can sometimes be persuaded to move along with pistol-fired shells called “screamers” and “bangers.” Lynds also shouldered a 12-gauge shotgun and squeezed off a “shell cracker.” It exploded some 300 feet away.

“You’ve got to mix it up,” Sewall said. “If you do the same thing all the time, wildlife gets used to it. They acclimate.”

When possible, workers try to make the jetport inhospitable to birds. They mow grass long, to make foraging difficult. Last year, contractors completed a $2.6 million project to extend the main runway’s safety zone and fill a marshy area that was a bird magnet.

“In migration season, the starlings here were like an Alfred Hitchcock movie,” Sewall said.

Workers now are extending another safety zone on the crosswind runway. A water retention pond at the end can’t be filled, however, so workers will install a stainless-steel mesh covering to deter waterfowl from landing.

The jetport is completely surrounded by a chain-link fence. That keeps deer off the runway. New spans are buried underground, as well, to discourage digging. The jetport had a problem a couple of years ago with coyotes digging under the fence. They were trapped, and in some instances, shot.

The Portland jetport and Bangor International Airport get high marks for their efforts, according to Adam Vashon, a biologist with the U.S. Department of Agriculture who helps train airport staffs. Workers at Maine’s largest airports receive annual training and are getting better at controlling wildlife and documenting bird strikes, he said.

“Being aware of the problem is half the battle,” Vashon said.

Data from the FAA show that Maine had 482 reported wildlife strikes since 1990. Bangor’s recent incidents include planes hitting skunks and a saw-whet owl. In the past, moose have gotten through the fence at Bangor, Vashon said, although they weren’t hit by planes. Bald eagles haven’t been as lucky – eagle strikes have been reported.

While the number of wildlife strikes are up in Maine, that can be attributed to more flights and better reporting, Vashon said.

“And we know we’re still only getting a small portion of the strikes,” he said.

At the jetport, the young Cooper’s hawk finally was removed from the trap by a USDA wildlife biologist. The agency typically likes to relocate unwelcome visitors at least 50 miles away. This raptor was released in Auburn, at a location where it’s likely to find habitat for the winter.

The hope, anyway, is that this flier that won’t be landing in Portland anytime soon.

To search the FAA wildlife strike database:

http://wildlife-mitigation.tc.faa.gov/wildlife/default.aspx

To learn more about bird strikes:

http://www.birdstrike.org/