9/11 tribute lights risk for birds:

Discovery

Darwin

Cropp

To humans, the twin blue beams shining upward from lower Manhattan each Sept 11 evoke solemn memories of the 2001 terrorist attacks. But to migrating birds, they’re a potentially fatal attraction, according to a scientific study published Monday.

During the seven-year study at National Sept 11 Memorial and Museum, researchers noticed thousands of birds were drawn to the annual light display, causing them to waste precious energy circling and calling and risking collisions with buildings or capture by predators.

In 2015, for example, the count of birds within a half-kilometer (0.3 miles) of the tribute sight went from 500 to 15,700 within a half hour of the lights coming on. And when the lights were turned off, the birds went on their way within minutes.

“Migrating is already hard enough for birds without this added danger from artificial light at night,” said Susan Elbin, of New York City Audubon, co-author with researchers from Oxford University and the Cornell Lab of Ornithology.

Their study, published in the Proceedings of the National Academy of Sciences, estimates that the light beams influenced more than a million birds — including warblers, thrushes and sparrows — over seven years of the one-night tributes.

Researchers said they could not get an accurate count of how many birds actually died since some of them fell onto scaffolding, were snatched by scavengers or disposed of by maintenance workers. (AP)