NEW YORK (GenomeWeb News) – Migratory Canada geese were the culprits in the Hudson River plane crash earlier this year, according to a team of Smithsonian Institution and US Department of Agriculture researchers who used DNA barcoding, stable isotope testing, and feather analyses to assess bird remnants pulled from the engines of the downed jet. The research appeared online today in Frontiers in Ecology and the Environment.
"Determining whether these birds were migratory or not was critical to our research and will help inform future methods of reducing birdstrikes," lead author Peter Marra, a Smithsonian Migratory Bird Center researcher, said in a statement. "Resident birds near airports may be managed by population reduction, habitat modification, harassment, or removal, but migratory populations require more elaborate techniques in order to monitor bird movements."
Thousands of birdstrikes occur each year in the US — usually during take-offs and landings — at a cost of more than a billion dollars annually. In 2007 alone, there were more than 7,400 reported birdstrikes involving civil aircrafts. The actual number is believed much higher, the authors noted, since it's estimated that just a fifth of collisions are reported.
In an effort to understand these birdstrikes more completely, the researchers used several different approaches to identify the birds involved in the birdstrike that disabled US Airways Flight 1549 and forced an emergency landing on the Hudson. The Airbus A320 hit a flock of birds shortly after taking off from La Guardia Airport on January 15th, causing both engines to lose power.
"It is important to not only know what species of birds are involved in collisions, but also understand the role that migration plays in the larger picture," co-author Carla Dove, a researcher at the Smithsonian's National Museum of Natural History Feather Identification Laboratory, said in a statement. "The more information we are able to gather in cases like this, the more we will be able to reduce the risk of birdstrikes in the future."
First, the researchers used DNA barcoding to assess DNA extracted from bird tissue samples, sequencing 650 base pair region of the mitochondrial gene cytochrome c oxidase subunit I.
Although the samples had been underwater for three to nine days, the team was able to get informative barcode data for a dozen and a half samples. The samples were a 99 to 100 percent species match with Canada goose, Branta Canadensis, sequences in the Barcode of Life Database — an identification supported by the researchers' feather analyses.
But these results did not provide insights into whether the geese were migratory or resident birds. To test this, the team used stable isotope analysis to compare hydrogen isotopes found in the crash bird feathers with isotope patterns in resident and migratory geese. Vegetation in a bird's diet influences these profiles, the authors noted, which vary by latitude.
"Because most migratory birds molt their feathers on or close to the breeding site, the feathers obtained from US Airways 1549 engines allow inferences to be made about where these birds nested in the summer of 2008," they explained.
Using isotope ratio mass spectrometry, the researchers measured hydrogen isotopes in sample feathers and compared them with resident and migratory bird feathers. The migratory specimens — originally collected in Newfoundland and Labrador, Canada — came from the Chicago Field Museum. USDA researchers provided feather samples from Canada geese living near La Guardia.
Results from these hydrogen isotope analyses indicated that the feathers resembled migratory geese from Labrador but did not match isotope profiles for resident New York City geese or migratory Newfoundland geese.
Even so, the authors speculate that the birds involved in the Hudson River crash were on a short-distance trek to find food and open water within their wintering grounds, rather than returning from a long-distance migration to their breeding areas.
"Historically, most Canada geese were long-distance migrants," they explained, "but populations have recently established a year-round residency in much of their former wintering range."
Those involved say the new research could offer hints about managing geese and other birds near airports. In addition, they noted, knowing what kinds of birds were involved in the crash and the damage they caused is "vital for engineers to improve birdstrike resistance in aircraft and engine components."
The team called for increased birdstrike reporting as well as the development of a central database for bringing together information on the frequency of strikes, species involved, time of year, and aircraft effects. Without such steps, Marra argued, "we are missing valuable information that could reveal patterns of frequency, location, and species involved — all information that is essential to reducing the frequency of birdstrikes."
Finally, the researchers noted, similar bird forensics approaches could be used to monitor and prevent other human-wildlife conflicts and to track birds involved in transmitting avian diseases such as West Nile virus and H5N1 influenza.