For years, the "Tribute In Light" installation has served as a powerful way to mark the anniversary of 9/11, and also a major hazard to overhead birds. Less obvious, until now, is how the annual memorial is helping scientists understand the ways in which light pollution is impacting the behavior of nocturnal animals. According to one new study, it could be the key to saving some of the 90,000 birds that die each year by flying into New York City buildings.

That study, published Monday in the National Academy of Sciences, found that the memorial's 4.4 mile light beams cause birds to aggregate in high densities, decrease flight speeds, follow circular flight paths, and vocalize frequently. Between 2009 and 2016, around 1.1 million birds were influenced by the installation, with many of them becoming disoriented and collapsing in the street, or crashing into nearby buildings.

But when the Tribute In Lights was briefly turned off—as it has been several times in previous years—the birds quickly dispersed, and resumed their regular flight behavior.

The implications of that finding could open the door for bird-saving solutions that go far beyond the annual tribute, according to Dr. Susan Elbin, director of conservation and science at NYC Audubon and an author of the study.

"The direct evidence we see is a twofold issue: artificial light at night, coupled with reflective and transparent glass in buildings," Elbin told Gothamist. The way this typically works is that a migrating bird will become confused by a beam of artificial light, and wind up landing somewhere it wasn't intending. Thrown from their original path, the adrift birds often fly straight into one of the city's many reflective glass buildings. Throughout North America, more birds die this way each year than were killed in the Exxon Valdez oil spill.

"The Tribute In Light really brings attention to the fact that, even though you can't see them, there are hundreds of millions of birds flying over New York City, and there are things that humans do to impede that," Elbin added.

NYC Audubon has some solutions. Their Lights Out New York initiative, for one, has managed to get major bird-killing structures—from the Chrysler building to the Time Warner Center—to go dark from midnight until dawn during the two-month peak migration period that begins each September.

The second solution, Project Safe Flight, is aimed at collision prevention, which poses a problem throughout the city, but particularly in buildings with highly reflective glass located near a park or other greenery. Since the project began in 1997, the Audubon society has enlisted volunteers to roam the streets of New York, reporting dead or injured birds to their database (d-bird.org) for the sake of identifying areas with especially threatening structures.

As a result of this data collection, both the Morgan Mail Processing Facility in Chelsea and the Javits Center have been retrofitted with less reflective glass, along with a see-through surface known as "frit." Since those updates, bird-on-glass fatalities at the Javits Center, formerly one of the deadliest bird sites in the city, have dropped by more than 90 percent.

With over 100 species of birds currently in migration over the city, the NYC Audubon considers this an opportune moment to get involved, and to alert others about the man-made problem.

"It's not that birds are stupid or anything," Elbin said. "It's that they don't know glass is a barrier, and they haven't evolved to deal with artificial light at night."

That said, the scientist confirmed that the problem is less acute with New York resident birds, who "seem to learn their neighborhood, and tend to be a little more clued in."