Why do they turn the 9/11 Memorial Lights off for birds?

Question

On the morning of September 11, 2001, two airplanes flew into the "Twin Towers," part of the hub of the World Trade Center in New York City, United States. The towers, which at one time had been the tallest in the world, were brought to the ground, together with some other buildings. The incident is generally referred to as 9/11, with the year omitted (at least in the United States).

The land where the buildings were is now being used for a variety of things, many of them related to the incident.

One attraction is the large 9/11 Memorial Museum. My son and daughter-in-law take my two granddaughters to it during their summer vacation. (He was on his way into the second building when the first was hit, so it's especially meaningful for him.)

Another attraction is an event that takes place each year on September 11. It's called Tribute in Light. It's a memorial to those whose lives were affected, the people who helped rebuild the area, and the resilience of New Yorkers. Many thousands of people come to see this once-yearly powerful tribute.

The lights mimic the shape and size of the Twin Towers. They shine high into the sky from dusk on the 11th through dawn on the 12th. They can be seen from a 60 mile radius around Manhattan. (Memorial Park is open for visitors from 3pm until midnight.)

Assembled on the roof of the Battery Parking Garage south of the 9/11 Memorial, the twin beams reach up to four miles into the sky and are comprised of 88 7,000-watt xenon light bulbs positioned into two 48-foot squares, echoing the shape and orientation of the Twin Towers.

On the anniversary of 9/11, the Memorial Plaza is open to the public from 3 p.m. to midnight for the viewing of Tribute in Light. The installation can also be viewed from a 60-mile radius around lower Manhattan.

Having never seen them, this year on September 11, 2019, my son and his family went specifically to see the lights in the evening. Throughout the hours, there were a few times when the lights went off for some minutes and back on. People in the crowd were saying it was at the request of the National Audubon Society, to protect birds.

I'd like to know if it's true that the National Audubon Society has enough influence to cause the hosts to periodically shut off the lights off. If so, what's the reason?

Answer 1

The basic idea of turning them off temporarily is to let the birds readjust to their surroundings.

For reasons still unknown to science, artificial light attracts birds, from fledgling seabirds to migrating songbirds (it does the same to moths). Once captivated, disoriented birds may crash into windows, or spend hours circling.

The 9/11 tribute is particularly problematic: dozens of 7,000-watt bulbs allow it to reach four miles into the sky—it’s visible from 60 miles away.

Making the 9/11 Memorial Lights Bird-Safe

Shutting the lights off temporarily appears to allow the birds to find their bearings and continue southward. And Horton said it's encouraging that the people of New York City are willing to temporarily douse the lights for the birds.

Light beams from 9/11 memorial pull in huge flocks of migrating birds

Between 2008 and 2016, the light show distracted 1.1 million birds, according to Kyle Horton at the Cornell Ornithology Lab. "The worst-case scenario is that there are birds that collide with buildings," Horton told the CBC, "or the light directly results in the mortality of birds."

...

Per a 2009 agreement between the New York Audubon Society and the National September 11 Memorial and Museum, the lights are dimmed for 20 minutes every time volunteers count more than 1,000 birds trapped in the beams.

According to radar studies conducted by the Audubon Society**, the breaks are long enough for birds to resume their migration.** Still, Horton says, the distraction is tiring for the birds.

NEW YORK'S 9/11 LIGHT TRIBUTE THREATENS 160,000 BIRDS EVERY YEAR