CSI for Birds: Scientists Use Forensic Techniques to Improve Airport Safety
Carla Dove (left), Nancy Rotzel (far right) and Marcy Heacker (near right) use the Museum’s bird collection to identify birds that are involved in birdstrikes using both traditional morphological identification and molecular techniques. (Photo: James DiLoreto)
© Smithsonian Institution [Higher Resolution]
Carla Dove, a researcher at the Smithsonian National Museum of Natural History (NMNH), is used to getting feathers and globs of bloody tissue in the mail. On a Wednesday afternoon in her office at the Feather Identification Lab, she tears open a routine FedEx envelope and removes a long, dried piece of tissue and a cotton swab with bits of fluffy down stuck to it. “We get ten or twelve of these a day,” she says.
Dove's lab is one of a handful that identifies the remains of birds that have collided with aircraft—incidents formally known as “bird strikes.” These collisions present a growing problem as planes become quieter, air traffic increases, and the populations of some birds, such as Canada geese, increase. According to the National Wildlife Research Center (NWRC), 52,000 wildlife strikes were reported between 1990 and 2003, costing nearly $500 million per year in delays and damage to aircraft. Since 1988, 194 people have died in crashes attributed to bird strikes.
Frequently, the birds involved in these collisions are sucked into plane engines, making for the identification process messy and difficult. That’s where Dove and her team (which includes researchers Marcy Heacker, Nancy Rotzel, and Sarah Sonsthagen) come in. In the past few decades, the Smithsonian has played a central role in the growing effort to systematically gather data on bird strikes, this data is then used by the U.S. Air Force and the U.S. Federal Aviation Administration (FAA) to analyze bird behavior, dietary preferences and migratory patterns using the information to reduce hazards at airports.
Image courtesy of Airliners.net
In cooperation with the Air Force and the FAA, the Feather Identification Lab encourages pilots and airfield managers to collect animal remains after a strike and send them in for identification—even if it’s just a few feathers or traces of tissue. In 2006, the lab processed 3,500 cases, and the numbers are growing each year.
When Dove started at the Museum in 1989, she and her mentor, the late Roxie Laybourne, processed about 300 cases a year. Laybourne, who founded the Smithsonian forensic ornithology program in the 1960’s, pioneered many of the methods used in feather identification. After helping investigators determine that starlings were responsible for a fatal crash at Logan Airport in Boston, she began to use the Smithsonian’s collection of more than 600,000 “study skins”—preserved bird specimens used for research—to match feathers and identify species involved in strikes all over the country.
Today, Smithsonian scientists still use many of Laybourne’s tools and techniques. If a sample comes in with whole feathers that have distinctive markings, one of the Feather Identification Lab investigators heads out into the collection and tries to find a match amid the drawers of study skins. But whole feathers aren’t always available. “If we get a paper towel swipe with what we call snarge—blood, bits of tissue, and goo—we use forensic techniques,” Dove says. In these cases, if the sample contains pieces of down, called barbs, the researchers will turn to a reference set of microscope slides that Laybourne started. By comparing the microstructure of the barbs from the unknown sample with slides of known specimens, they can usually narrow in on the bird’s group. The microscope might reveal, for example, that the sample is from a duck, rather than a pigeon or a songbird, but not which species of duck. Sometimes the researchers can further narrow it down by comparing the feather fragments to study skins once they know the proper group.
The difference in microstructure between a feather from an American Kestrel and a feather from a King Penguin is very noticeable under the microscope.
Differences in size, shape, and arrangement of nodes on the feathers of various bird species can help in identification. These images from a scanning electron microscope show the difference between nodes on a Chicken feather and a Ruby-Throated Hummingbird.
The lab makes about half of its identifications using the collection, but this is becoming increasingly challenging. “In recent years, people in the field are much better at collecting the remains, and the material we are getting is much more fragmented,” Dove says. “The job is much harder now than it was 40 years ago.”
So in 2003, the NMNH decided to sharpen its identification tools. The Museum joined forces with the FAA to build a database of avian DNA to help solve cases that have insufficient feather evidence. The database, which is now part of a larger initiative called the Consortium for the Barcode of Life, was completed in 2006 and now contains the sequences of one gene, called CO1, or the "barcode" gene, for 96 percent of bird species in the U.S. and Canada. It was built using tissue samples from the Museum’s collection and specimens borrowed from other museums and universities around the country.
Sarah Sonsthagen with a few birds from the collection.
© Smithsonian Institution
Dove and her team just finished putting the database through its paces during fall migration—the busiest time of year. They’re thrilled with the results: about two thirds of the tissue samples submitted for DNA testing came back with species-level matches. While many of the results were the usual suspects—geese, gulls, and other birds common on airfields—the list included 123 species from 14 different orders.
The researchers have even been able to go back and solve some “cold cases,” including one that was two years old. “We knew it was a small perching bird—a passerine—but we didn’t know which one. It did $74,000 in damage to a B-2,” Dove recalls. “We went back in our files, pulled out the sample, and identified it as a golden crowned kinglet, which is a teeny tiny little bird. It weighs less than a quarter of an ounce.”
The precision that comes with DNA evidence is exciting to the Feather Lab team. “In the past, we probably would have said ‘perching birds’ or ‘warbler,’ but now we can say ‘painted bunting’ and ‘ruby-crowned kinglet,’ and ‘yellow-rumped warbler,’” Dove says. The forensic evidence also helps convince aircraft engineers of the results, especially when the culprit turns out to be a small bird that does not seem capable of doing thousands of dollars in damage to a jet engine.
From Feathers to Flight Paths
Identifying a culprit species is more than a fascinating biological puzzle: it has real-world consequences. “What we do here is fundamental to any other decisions made about bird strikes,” Dove says. “The first thing you have to know is what species are being hit.”
The U.S. Air Force Bird/Wildlife Aircraft Strike Hazard (BASH) Team is one group that relies on Feather Lab analyses to identify the species that do the most damage to their aircraft. Using information about the habitats of commonly struck species, their breeding behavior, and migratory patterns, the Air Force created the Bird Avoidance Model (BAM)—a dynamic map that shows birdstrike risk levels across the U.S.
“We make recommendations to our pilots not to fly in certain areas at certain times based on the concentrations of birds that are predicted to be there,” says Eugene LeBoeuf, chief of the BASH Team.
The BAM also feeds into the Avian Hazard Advisory System, which incorporates nearly real-time data from weather radars that can track large flocks of birds similar to the way they track snowstorms. Aviators can access the system online to see if a given flight path or airfield has a low, moderate, or high risk for birdstrike at a certain date and time.
Dove and her team work most frequently with the Air Force, but they are seeing an increase in non-military cases. The lab also collaborates with the National Wildlife Research Center (NWRC) Field Station in Sandusky, Ohio. Researchers there maintain the National Wildlife Strike Database for civil aviation and test various management strategies designed to prevent future collisions.
“The first line of defense is airfield vegetation,” says Robert Beason, a biologist who supervises the NWRC station’s efforts to develop tactics that discourage wildlife from congregating at airports. Researchers have found that tall fescue grass is particularly unappealing because it harbors a fungus that tastes bad to birds and gives other animals indigestion. They also test commercial products that can be sprayed onto vegetation, such as the chemical used in artificial grape flavoring, which stimulates pain receptors in birds the way hot peppers do in humans.
But simply keeping birds away from the runway may not be enough, according to Beason. “The second question is: can you make the birds see the airplane and realize it’s coming towards them?” So researchers are testing technologies such as pulsating landing lights of different wavelengths to see if birds will respond to and avoid them.
Carla Dove cleans a sample of feathers to prepare them for identification.
© Smithsonian Institution
Identifying which species are involved in strikes is critical in deciding how to manage the hazard at each airport. Techniques being used range from noisy music and propane canons, to border collies and falconers, to pyrotechnics. “Everybody wants to have a silver bullet to keep birds away from airfields, but it has to be an integrated plan. It depends on the airfield,” Dove explains.
Although no one can say exactly how effective strike reduction efforts have been overall, it is clear they’re paying off in some places. The John F. Kennedy International Airport in New York has reduced the number of gull strikes by roughly 80 percent using tactics such as grass management, eliminating standing water, and frightening birds with pyrotechnics, according to Richard Dolbeer. Dolbeer heads the Bird Strike Committee USA, a volunteer group that promotes collaboration between government agencies, the military, and private industry to prevent bird strikes.
While there may be no silver bullet, Dove is optimistic about the Smithsonian’s contribution. “There’s no doubt in my mind,” she says, “that we’re having an impact on aircraft safety.”
NMNH Division of Birds http://vertebrates.si.edu/birds/
Smithsonian Institute Migratory Bird Center http://nationalzoo.si.edu/ConservationAndScience/MigratoryBirds/
Federal Aviation Administration Wildlife Page
Bird Strike Committee USA http://www.birdstrike.org/
International Bird Strike Committee http://www.int-birdstrike.org/
Avian Hazard Advisory System http://www.usahas.com/
U.S. Bird Avoidance Model http://www.usahas.com/
Department of Defense Partners in Flight http://www.dodpif.org/
Consortium for the Barcode of Life http://www.barcodeoflife.org/
Barcode of Life Data Systems http://www.boldsystems.org
Story by NMNH IT Web Intern Christine Hoekenga.
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