The risk of airplanes colliding with birds jumps by as much as 400% during periods of migration, according to new research from the Cornell Lab of Ornithology and partners, who have been looking for patterns in bird-strike data from three New York City-area airports.

“Out of all the bird strikes recorded at Kennedy, Newark and LaGuardia airports during a six-year period, the highest number occurred during migration, especially during the fall, perhaps due to many inexperienced young birds born earlier in the year,” said Cecilia Nilsson, who led the study as a Rose Postdoctoral Fellow at the Cornell Lab, and is now at the University of Copenhagen in Denmark.

Nilsson is first author of “Bird Strikes at Commercial Airports Explained by Citizen Science and Weather Radar Data,” which published Aug. 19 in the Journal of Applied Ecology.

“Ninety percent of the strikes involved a migratory species,” Nilsson said. “Our model predicts that the risk for damaging strikes during periods with very high migration intensity increases by as much as 400% to 700%.”

Information on bird movements throughout the year can help avoid damage to aircraft and risk to passengers. Worldwide, the cost of bird collisions with planes has been estimated at $1.2 billion per year. In 2009, a US Airways plane with 155 passengers aboard made an emergency landing in the Hudson River after striking a flock of Canada geese shortly after takeoff from LaGuardia.

Study authors used weather surveillance radar from two nearby stations to learn when migration was the most intense at the airports studied. Data from the Lab’s eBird program helped define which species occurred near the airports throughout the year. A third source of information came from an invaluable dataset of detailed bird-strike records kept by the Port Authority of New York and New Jersey, which operates the three airports.

“The damage caused by a bird strike very much depends on the weight of the bird struck and the tendency of that species to move in flocks,” Nilsson said. “When large-bodied birds are moving through, the risk for damaging strikes is the highest.”

Species that most often caused damage were assigned a hazard score. Those with high hazard scores include Canada geese, great blue herons, mallards and turkey vultures – with Canada geese most likely to cause damage. The greatest number of bird strikes at the three airports involved a medium-sized songbird, the American robin.

Commercial aircraft are most vulnerable to bird strikes during takeoff and landing where birds and planes share the airspace; military aircraft are also at risk at the lower altitudes, because they fly low and fast during training exercises. At cruising altitudes aircraft are generally too high to encounter most flying birds.

“It’s important to realize that the timing and species composition of bird movements will differ for each location,” Nilsson said. “But both the eBird data and the radar data are continental datasets so the method used in our study can be applied to other airports to save time, money and possibly lives.”

Other co-authors are: Frank A. La Sorte, Adriaan Dokter, Benjamin M. Van Doren and Andrew Farnsworth of the Cornell Lab; Kyle Horton of Colorado State University; Jeffrey J. Kolodzinski of the Port Authority of New York and New Jersey; and Judy Shamoun-Baranes of the University of Amsterdam.

The research was supported by the Leon Levy Foundation, the Edward W. Rose Postdoctoral Fellowship, the European Union’s Horizon 2020 Marie Skłodowska-Curie grant agreement, the Swiss National Science Foundation, the Belgian Federal Science Policy Office, the Netherlands Organisation for Scientific Research, the Academy of Finland and the National Science Foundation.

Pat Leonard is a staff writer at the Cornell Lab of Ornithology.