Efforts mitigate danger of aircraft bird strikes

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Carla Dove of the Smithsonian Institution Feather Identification Lab examines feathers after aviation bird strikes. Source: Arrow Media

During a typical day on the job, Carla Dove heads to the mail room of the Smithsonian Institution Feather Identification Lab in the National Museum of Natural History to examine the latest dead birds she's received. 

Sometimes Dove, the program manager for the lab, is fortunate to receive whole birds or partial carcasses. That's when her job identifying the bird type is easiest. Other times, she receives nothing more than a bloody fragment of a single feather, pulled off an engine blade of a jet aircraft. 

In those cases, the 620,000 feathers housed at the Feather Identification Lab might come in handy. So might DNA analysis or a technique developed by the Smithsonian more than 50 years ago whereby scientists scrutinize microscopic features of the feather's downy base.

"It's really like a puzzle," Dove said. "Every case is different."

Dove and her team at the Smithsonian are one piece of a little-known but well-organized effort also involving the federal government and airports across the U.S. to reduce the risk to aviation of bird strikes. 

It's an effort that was well underway before U.S. Airways Flight 1549 flew into a flock of Canada geese just moments after takeoff 10 years ago, on Jan. 15, 2009, causing both of the Airbus A320's engines to fail. But it's also an effort that has benefitted from what came to be known as the Miracle on the Hudson, when Capt. Chesley "Sully" Sullenberger chose to land Flight 1549 on the Hudson River where it flows past Manhattan's Upper West Side, saving the lives of all 155 passengers and crew.

Between 2008, the year before the Miracle on the Hudson, and 2017, the number of reported bird strikes by commercial and private U.S. aircraft jumped from approximately 7,000 to just shy of 14,000. The lion's share of those reports are for commercial flights. The leap, officials have said, is due to increased reporting rather than a surge in actual bird strikes.

"The Miracle on the Hudson brought forward that this could happen, that birds could go into engines on the plane and cause a serious problem," said Mike Begier, national coordinator of the U.S. Department of Agriculture's (USDA) Airport Wildlife Hazards Program.

Though the number of strikes sounds exceptionally high, most don't damage aircraft. Richard Dolbeer, an FAA science adviser who oversees the agency's wildlife strike database, said that only about 5% of bird strikes make enough impact on planes to cause a significant problem, such as damage or an aborted takeoff. 

Crashes are exceptionally rare, he added. The most recent fatal bird strike over U.S. skies occurred in November 2017 when a medical transport helicopter crashed after flying through a flock of snow geese over Southern Arkansas. Three people died. 

Bird strikes cost upwards of $500 million per year in the U.S., Dolbeer said, with the majority of that cost being shouldered by airlines. 

The strike database dates to 1990 and now contains almost 210,000 records of bird and other wildlife strikes, Dolbeer said, though bird strikes account for 97% of them. 

When possible, the database includes a great deal of detailed information about each strike, including the phase of the flight at which it occurred, the altitude at which it occurred, the bird species involved and much more. 

For example, the data shows that in a typical year, somewhere around 75% of strikes occur below 1,500 feet, in what would be the early ascent or late landing phase of a commercial flight. (The Miracle on the Hudson strike occurred at 2,818 feet.) The data also shows analysts what species most frequently cause damaging strikes at specific airports. 

Airport wildlife biologists then use that information to develop location-specific plans to reduce bird populations on and around airfields. 

"The idea," Begier said, "is, how do we tweak that system so that airports don't provide food, water and cover" for birds. 

At Denver Airport, where more than 300 bird strikes were reported in 2017, the five-person wildlife team uses a variety of techniques to control bird populations, said USDA biologist Levi Hodson, who is based at the airport. The largest number of strikes involve small birds, notably horned larks, which don't tend to cause major damage to aircraft. So the Denver wildlife team expends more of its effort to control populations of larger birds, such as hawks, eagles and owls. 

Within the 53-square-mile airport property, the team cuts grasses, making the habitat less hospitable to bird prey, such as mice, rabbits and prairie dogs. They affix bird spikes to airfield navigational aids so that raptors can't perch on them. And to chase birds away they employ harassment techniques, using small firecrackers, lights and sirens. 

The airport also relocates approximately 200 raptors per year, Hodson said.

Denver Airport's wildlife team also liaisons with nearby property owners and towns, offering suggestions on how to reduce or manage bird populations. 

That's not always an easy proposition, Hodson conceded, because their risk to aviation notwithstanding, birds provide ecological benefits and are often desired by landowners and other government agencies. For example, the 16,000-acre Rocky Mountain Arsenal National Wildlife Refuge sits approximately a mile west of airport property. 

"Birds are aesthetically pleasing," Hodson said. "A lot of people do manage their property specifically to attract birds." 

Still, he said, his team strives to create awareness about the airport's concerns relating to birds, and they also offer advice on how to attract bird species that aren't a major concern to aviation. 

Nationwide in 2017, Dolbeer said, mourning doves were the species most frequently involved in aircraft bird strikes, followed by barn swallows. Canada geese, the cause of the Miracle on the Hudson crash a decade ago, were 20th on the list. Still, Canada geese are a species that are commonly controlled around airports through the most controversial technique in wildlife managers' toolbox: culling. Biologists usually round up the geese during the June molting season, when they are temporarily flightless, and euthanize them with carbon dioxide. 

"One of the things about Canada geese is that they have adapted to these urban environments," Dolbeer said. "They have virtually no predators, so the populations have to be managed in some way, and this is how."

The USDA rounds up approximately 20,000 Canada geese per year, he said. 

Dolbeer acknowledged that culling is controversial, though he asserted it is done carefully and with permits. 

"It's a very complex and emotional issue in many cases," he said.

In a recent report, Dolbeer and Begier concluded that the various bird-strike mitigation efforts employed by airports are working. Between 2000 and 2017, the number of reported civil aviation-related bird strikes in the U.S. increased 144%, but the number of damaging strikes declined 16%, they wrote. 

Notably, the decline has occurred at commercial airports, where wildlife teams are more common and larger, but not in the general aviation sector. Further, the declines have occurred at altitudes of 1,500 feet and below, where birds are more directly impacted by the airport environment, but not at higher altitudes. 

"These data demonstrate progress in wildlife hazard management programs at airports certified for passenger traffic," Dolbeer and Begier wrote. 

The Smithsonian Channel will debut a special on bird strikes and aviation, "Bird v. Plane: Miracle on the Hudson," on Tuesday, Jan. 15.

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