The Bird ‘Snarge’ Menacing Air Travel

Richard Dolbeer was once the man to call if millions of blackbirds or fruit bats were ravaging your fields. When he joined the US Department of Agriculture in 1972, Dolbeer chose to specialize in handling what he and his fellow biologists term “human-wildlife conflicts”—situations in which animals wreak havoc in places that Homo sapiens have claimed as their own. Though based at a research station in northern Ohio, Dolbeer spent much of his early career on the road, teaching farmers from the Dakotas to the Maldives how to repel vertebrate pests by altering harvest schedules, erecting mesh nets, or broadcasting bursts of intolerable noise.

In the waning months of the 1980s, Dolbeer was surprised to receive a sudden influx of inquiries from American airports. None of the calls had anything to do with crops: The aviation officials were panicked about the geese, ospreys, and egrets gathering by their runways in unprecedented numbers. This avian population boom was generally good news, proof that stricter environmental laws were boosting species endangered by pesticides and pollution. The problem was that too many of these king-sized birds were ending up as snarge.

A portmanteau of “snot” with “garbage,” snarge is pilot slang for the goo left when an unfortunate bird slams into a moving plane. This residue is usually just a nuisance—a viscous smear of blood and guts that no one notices until the post-flight inspection. But on occasion, snarge can cause catastrophic damage that costs millions of dollars or dozens of lives. Aviation history is littered with fatal crashes in which birds gunked up engines or knocked ailerons askew. The airports seeking Dolbeer’s help worried that such disasters would soon become commonplace unless they thinned out their feathered ranks.

After listening to the airport executives’ bird-related angst, Dolbeer decided the time had come for him to shift professional gears: He would henceforth devote himself to preventing midair collisions between birds and planes. “I realized this was going to be a big deal,” Dolbeer says in the mellifluous western Tennessee accent he never shed from childhood. “I saw an opportunity, and I jumped on it like a flea on a hound dog.”

In 1991, he partnered with the Federal Aviation Administration to begin collecting the data necessary to understand the full dimensions of the bird-strike threat—a project that evolved into the Wildlife Strike Database, a searchable compendium that now contains accounts of more than 231,000 violent encounters between animals and aircraft. That same year, Dolbeer also cofounded Bird Strike Committee USA, an association of biologists, bureaucrats, and aviation safety experts whose shared goal is a future in which travelers needn’t worry about dying due to splattered mallards, swifts, or mourning doves.


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The 74-year-old Dolbeer is now regarded as the elder statesman of the bird-strike world, a tight-knit group of researchers and practitioners who gather regularly to discuss the best methods to minimize snarge. Their work has transformed how modern airports function, though not in ways that are readily observable to most passengers. The never-ending war on birds takes place far from the terminals, in the swaths of grass that lie beyond the zones where jets taxi to and fro. These verdant nooks are where Dolbeer’s disciples use an array of sophisticated hardware to frighten, frustrate, and sometimes slaughter their winged adversaries, all in the name of protecting millions of flyers who are oblivious to the struggle.

The bird-strike community can safely claim to have the upper hand at the moment. The number of damaging collisions per year has declined by 8 percent since 2000, and fewer than three dozen American lives have been lost in such incidents since 1990. Yet Dolbeer, who remains active in bird-strike circles despite having retired from the federal government in 2008, believes that planes are still too vulnerable once they soar beyond an airport’s boundaries.

That is because little has been done to help pilots detect avian threats that materialize at altitudes above 2,500 feet, the portion of the troposphere where roughly 10 percent of bird strikes occur. (The vast majority of strikes occur as planes are either taking off or landing: More than 70 percent of incidents take place at altitudes beneath 500 feet.)

To make his point, Dolbeer notes that a decade has passed since the “Miracle on the Hudson,” the US Airways flight that Captain Chesley “Sully” Sullenberger famously piloted to a water landing after colliding with a flock of geese at 2,800 feet, 4.5 miles from LaGuardia Airport. It was the sort of disturbing near-miss that should have convinced the aviation industry that merely shooing birds away from airports can’t prevent some of the most cataclysmic strikes. “But we’re really no further along in terms of preventing another accident like that from happening,” Dolbeer says. “I’m disappointed.”

Calbraith Perry Rodgers’ run as a celebrity aviator was both glorious and brief. In September 1911, just three months after he learned to fly at the Wright Brothers’ school in Ohio, Rodgers attempted to become the first pilot to cross the entire US; if he could complete the journey in less than 30 days, he stood to earn a $50,000 prize from newspaper tycoon William Randolph Hearst.

The task proved harder than he expected, and he crashed 16 times while heading west from Brooklyn in a biplane called the Vin Fiz. (He enlisted local mechanics to repair the flimsy aircraft along the way.) On November 5, Rodgers finally touched down in Pasadena, California; a crowd of 10,000 cheered his arrival even though he’d missed Hearst’s deadline by nearly three weeks.

But Rodgers didn’t get much of an opportunity to enjoy his newfound fame. In April 1912, while flying a Wright Model B in Long Beach, California, he smacked into a seagull that got stuck in the cables he used to control the rudder. His plane plummeted into the Pacific Ocean and Rodgers suffered a broken neck and crushed thorax on impact. His death was the first in the Aviation Era to be attributed to a bird strike.

Calbraith Perry Rodgers, an aviation pioneer, died in 1912 after a seagull collided with his aircraft.

Photograph: APIC/Getty Images

Bird collisions were otherwise rare over the next few decades, when commercial flights were still a relative luxury: They were cited in just three crashes between 1913 and 1959, only one of which involved more than a single fatality.

But then came the tragedy of Eastern Air Lines Flight 375, which departed from Boston’s Logan International Airport on October 4, 1960. Just moments after takeoff, the plane ran into a flock of starlings and three of its four turboprop engines were incapacitated to varying degrees; 62 passengers lost their lives after the Electra L-188 plummeted into Boston Harbor. Two years later, some ill-fated whistling swans destroyed the left horizontal stabilizer of United Airlines Flight 297 in the skies west of Baltimore; all 17 people aboard were killed in the resulting crash. Notably, the United Airlines disaster occurred at an altitude well above 2,500 feet.

Now acutely aware that bird strikes were bound to increase as air travel opened up to the masses, federal regulators took steps to ensure that planes became more bird-resistant. At the same New Jersey laboratory where the first air-traffic control systems were developed, government researchers assessed the robustness of aircraft engines by catapulting freeze-dried bird corpses into their propellers or turbines.

These tests led to the development of manufacturing standards that required engines be tough enough to withstand the impact of multiple 1.5-pound birds at once, or a single 4-pound goose. (Similar tests are still conducted today to verify whether engines are physically up to snuff, but they now use artificial birds made of gelatin.)

The disasters of the early 1960s also motivated airports to make themselves less hospitable to avian squatters. In addition to trying to remove tasty plants and garbage from their grounds, some airports also purchased propane-fueled sound cannons that drive off birds with deafening booms.

But airport countermeasures remained fairly low-tech until the 1980s, when the populations of North America’s largest birds began to explode after years on the skids. Between 1988 and 1993, for example, the number of non-migratory Canada geese more than doubled to over 2 million. Airports knew a crisis was at hand as their skies became noticeably clogged with birds ranging from pelicans to sandhill cranes, and as visiting pilots increasingly griped about having their cockpit windows smeared with snarge.

But as they confessed to Richard Dolbeer when they initially approached him for assistance, airport officials didn’t have any concrete statistics on how many bird strikes were occurring, what environmental conditions made those collisions more likely, or which species were the primary culprits.

At the behest of Dolbeer and several of his scientific peers, who would go on to form Bird Strike Committee USA at an Atlantic City technical conference in August 1991, the Federal Aviation Administration began to urge airlines and airports to report all bird strikes, no matter how trivial. A standard form was created so that the details of each incident could be recorded, including the type of bird involved and whether the pilot had been warned about the presence of flocks in the area.

If it wasn’t possible to identify the exact species because the snarge was pulped beyond recognition, airports were asked to ship biological samples to the Smithsonian’s Feather Identification Lab for analysis. For all of 1991, the FAA gathered specifics on more than 2,300 strikes, nearly 400 of which were judged to have caused damage to aircraft.

The number of reported strikes rose steadily from that point on, reaching nearly 6,000 by 2000. The rise can partly be attributed to airports becoming more diligent about complying with their reporting obligations: Maintenance crews were issued snarge collection kits consisting of alcohol wipes, disposable gloves, and special cards that preserve the DNA in blood samples. But bird-strike experts also theorize that collisions became more frequent due to advances in jet technology. “We were going from large passenger jets that had three or four engines to aircraft with only two engines—turbofan engines, which are much quieter than the old ones,” Dolbeer says. “So birds were less able to hear them and get out of the way in time.”

The worrying trends captured in the Federal Aviation Administration’s data led airports—which feared the prospect of being sued over snarge-related crashes—to get more serious about ejecting their feathered guests. Since the bulk of strikes happen within a few hundred feet of airport tarmacs, this was clearly the most efficient approach to the problem.

Airports were so eager to rid themselves of birds that they occasionally resorted to ghoulish methods: In 1991, for example, agents from the US Department of Agriculture used shotguns to kill 14,886 seagulls at John F. Kennedy Airport. (The tabloid New York Post featured the massacre on its front page, accompanied by one of its typically sardonic headlines: “Bye, Bye Birdie!”) But brutality is seldom effective at resolving human-wildlife conflicts over the long-term, and airports also saw fit to invest in more gentle means of persuading birds to settle elsewhere.

To lead their anti-bird campaigns, airports hired full-time biologists who understand the peculiarities of avian behavior. These scientists have often devised “habitat modification” programs that involve subtly altering landscapes to discourage birds. When Nick Atwell became the resident biologist at Oregon’s Portland International Airport in 1998, for example, he noticed that much of the facility’s green space was flat, and more significant, free of any obstacles.

So he oversaw the erection of simple barriers that caused a wave of anxiety among the airport’s most troublesome birds. “Geese like to go to large open areas where they have the ability to escape and avoid predation,” Atwell says. “When you break up their line of sight, they don’t have the confidence that there’s not a predator around the other side of that barrier. That uncertainty kind of keeps them moving.”

Aside from tweaking the topography of airports, biologists have also deployed an array of hardware designed to irritate birds. The propane cannons of yesteryear are still in use, but now they’re networked and can be fired remotely—either from a laptop or by tuning a field radio to a specific frequency. Airport biologists who are fans of sonic weapons have also invested heavily in portable speaker systems like the HyperSpike, which emits undulating wails that can exceed 150 decibels—far louder than even the loudest bands on earth.

There is current interest among bird-strike specialists for lasers—surprising, perhaps, given the many instances in which pilots have reported being temporarily blinded by scoundrels wielding laser pointers. Tools such as the handheld Aerolaser allow airport personnel to focus green beams on birds that otherwise won’t budge. Since birds have more green cones in their eyes than mammals, the tactic is particularly effective. “You illuminate that beam right by them and you slowly cross it over their mid-body, and they’re seeing it as a large threatening object—sort of like a lightsaber from Star Wars,” Atwell says. “So they think they’re going to get hit by something, and they get up and go.”

At the latest North American Bird Strike Conference, an annual event held last August in Halifax, Nova Scotia, the snazziest gadget was Robird, a drone styled to resemble a peregrine falcon. It works because most birds are hardwired to scatter when they see the feared predator approaching. The Robird, which is being tested at airports in Edmonton, Alberta, and Grand Forks, North Dakota, is meant to trick real birds into thinking they’ll become meals if they fail to scram. And because it needn’t eat or rest, the drone is advertised as being more efficient than the trained flesh-and-blood falcons that have been enlisted to patrol some airports.

Yet despite the excitement around the Robird and a few other innovations, the mood at the Halifax conference wasn’t entirely sunny. Though the progress made within the confines of airports has been impressive, the reality is that it’s impossible to turn all of the world’s airspace beneath 3,500 feet—where 93 percent of bird collisions occur—into a bird-free zone. That would be a less worrying fact if pilots had some way of knowing when a strike is imminent so they could take evasive action. But to the chagrin of Dolbeer and many others in the bird-strike community, we’re still a long way from being able to provide such intelligence to those who need it most.

Gary Cooke’s favorite snarge story—of which he has many—takes place in the skies above Nairobi, back when he was flying C-5 Galaxy transport planes for the US Air Force. It was late at night and he couldn’t see more than several feet in any direction, but he thought he heard the whump of multiple objects peppering the aircraft. It wasn’t until sunrise hours later that he spotted the gruesome remains of approximately 300 flying foxes—megabats that can weigh up to four pounds and have a wingspan of five feet—all over his fuselage.

Cooke remembers just shrugging at the mess, since that’s the standard response in his demanding line of work. “The people that I fly with, they think bird strikes, well, there’s really nothing you can do because it’s an act of God,” he says. “So we just deal with it.”

But years later, after he’d made the transition to the civilian world and become a captain for American Airlines, Cooke gradually shed his fatalistic attitude toward bird strikes. He came to believe that it’s possible for pilots to avoid birds while aloft, provided they’re given enough advanced notice that danger looms. And so as the current president of the World Birdstrike Association, he has pushed for the development of early-warning technologies that can be placed in cockpits.

One crucial piece of the early-warning puzzle is already on the market: radar systems that are specifically geared toward spotting birds. Such devices must not only be sensitive enough to detect moving objects as small as pigeons and quails, but also possess the ability to recognize the nuances of avian movement so that operators aren’t deluged with false positives. “With radar, the typical mode is that you process the signal, you do the detection, and then you do the tracking of the object,” says Tim Nohara, president of Accipiter Radar, which sells a range of bird-strike prevention tools. “But what we’ve come up with for birds is track before detect—you need to have some sense of the objects’ behavior over time before you can declare it a target.”

Yet pilots remain largely unaware that bird radar even exists. Airport biologists are the systems’ primary users right now: They compile the tracking data to help them make better strategic decisions about where and when to deploy their bird deterrents. What Cooke and many others in the bird-strike community dream of, by contrast, is a future where air traffic controllers and pilots can receive radar warnings in real time, so they can slow down or veer to the side when flocks draw close. “If you’re talking about five, 10 seconds of warning for an aircraft that’s maintaining 200 knots, that could make a huge difference,” says Flavio Mendonca, a former Brazilian air force officer and a professor at Purdue University’s School of Aviation and Transportation Technology.

The biggest reasons that bird radar has yet to be linked to cockpits is that neither pilots nor air traffic controllers are qualified to interpret the information the systems produce. “If you just give them a pure radar spot, how is that helpful?” asks Isabel Metz, a doctoral candidate at the German Aerospace Center. “They’re not ornithologists. They can’t tell you how birds move.” Chances are that, were they to be confronted by a constant stream of alerts about nearby birds, pilots would either be in a constant state of panic or simply tune out the warnings.

In the hopes of addressing this issue, Metz has been developing an algorithm capable of determining whether detected birds are likely to fly into an airplane’s path or whether they can be assumed to be heading in a nonthreatening direction. She has built the algorithm in part by analyzing reams of radar data from airports, and also by consulting with ornithologists who’ve advised her on the typical flight patterns of various avian species. Her goal is for the algorithm to someday be at the heart of a simple alert system, one that will issue warnings only when the possibility of a damaging strike is truly dire.

What radar seems unlikely to do in even the distant future, however, is help out with the problem of terrestrial mammal strikes. Though birds are involved in the vast majority of the aviation industry’s human-wildlife conflicts, planes have also been known to run into coyotes (615 times since 1990, according to the Federal Aviation Administration), striped skunks (513 times), and alligators (25 times). Since these accidents take place on the ground at relatively slow speeds, human casualties are thankfully rare. But woe to the maintenance crew that has to deal with the snarge after a Learjet meets an errant moose.

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