9/11 Attack Anniversary: Tributes are paid as soaring beams of light are put out on 9/11.

Two soaring beams of light are put out every year over Lower Manhattan on 9/11 or September 11, in a tribute to those killed 18 years ago in one of the deadliest terror attacks on the US soil. Researchers, however, have said that those beams of light can lure birds to veer off their normal migratory flights.

Some 160,000 birds, which are drawn to the immense light along with insects and bats, encircle these beams, seemingly unable to veer away, and are pulled off-course, putting them at risk of exhaustion or disorientation, The New York Times reported.

The anniversary of the September 11 attacks coincides with the migration period of birds across the New York City as fall approaches. But the convergence shares a stark reality of the situation which illustrates the dangers of humans and animals sharing an urban ecosystem.

The birds such as small songbirds like Canada and yellow warblers and American redstarts and nighthawks come closer to the beams to prey on insects, and peregrine falcons. When the number of trapped birds reach around 1,000, the lights are switched off for 20 minutes to let the birds disperse.

"It's very solemn," said Susan Elbin, an ornithologist and the director of conservation and science at New York City Audubon, a US-based advocacy group.

"The lights just appear in the darkness and go on forever"-- four miles up -- "and when the sun rises the next morning it just disappears," she said.

According to radar studies by Sasan Elbin and other scientists, the 20-minute breaks are enough to allow birds to resume their migration.

"It's my job to turn the lights out, and I'd rather not have lights on at all, because the artificial light interferes with birds' natural cues to navigate," the scientist added.

"Light lures them in, and glass finishes them off," she said.

The light tribute attracts bird densities up to 150 times their normal levels the researcher divulged.

In addition, another risk is that by flying in the lights, birds could use up too much of the fat they store for energy for migration, she said. "They only have enough to get where they need to go; the fatter you are, the more energy it takes to fly, so it's a fine balance," she said.

The New York City Council will today hold a committee meeting on a bill to require new or renovated buildings to use more bird-friendly glass. A similar campaign is also taking place in Chicago.