10,000 birds trapped in Twin Towers memorial light —

Tribute in Light in 2010

Tribute in Light in 2010

Scientists have long known that artificial light can attract and disorient birds at night, causing collisions and wreaking mischief with their migratory path. Now, the annual September 11 “Tribute in Light Memorial” in Manhattan has provided a unique opportunity to study and quantify the effect.  

According to ‘The Telegraph’ an estimated 90,000 birds die each year after becoming disorientated by lights and crashing into skyscrapers in New York as they migrate south for the winter.

The multiyear study, published in the Proceedings of the National Academy of Sciences, found that birds gathered in greater densities, flew repeatedly in circles and vocalized loudly when the memorial’s powerful beams were illuminated.

However, when the lights were turned off for brief periods, the birds were quick to resume their normal flight paths and behaviors. Although the researchers were not calling for any changes to the annual event, their findings suggest a simple fix for ongoing light pollution in other places.

“Wherever we can turn lights off at night, we should be doing it,” said Andrew Farnsworth, an ornithologist with Cornell University and an author of the study, which claims to be the first to quantify bird responses to urban nighttime light.

Researchers from Cornell and the New York City Audubon Society have been monitoring the memorial, which consists of two pillars of 44 spotlights aimed directly upward to simulate the fallen Twin Towers, since it was first presented in 2002. In 2008, the team began using radar and acoustic sensors to track how many birds the light was attracting and how it affected their behavior.

In 2010, the beams attracted so many birds that the researchers convinced the memorial’s operators to turn off the lights for 20 minute intervals, which presented “a unique opportunity” to study “behavior in birds when these incredibly powerful lights were on versus when they were off,” said Dr. Farnsworth. The lights were briefly extinguished again in 2012, 2013, 2015 and 2016.

Compiling data from seven nonconsecutive years, the researchers found that bird density near the instillation was 20 times greater than surrounding areas, causing sometimes fatal collisions with structures and other birds. Alterations to the birds’ migratory paths also put them at risk of death and starvation from arriving late to their destinations.

All such behaviors ceased within minutes of the lights being turned off. The installation affected more than 1.1 million birds cumulatively in those seven years, the researchers said.

Though the study makes no specific recommendations about the 9/11 Memorial, it does recommend that cities consider “selective removal of light during nights with substantial bird migration.” Sports stadiums, car dealerships, mountaintop monuments and large buildings are among the worst offenders when it comes to nighttime light, said Dr. Farnsworth.

According to ‘The Telegraph’ two beams emanating from Manhattan, known as the Tribute of Light, had to be turned off five times to allow the migrating birds to continue on their journey last week.

The birds were on their way from Canada to the warmer climate of the Caribbean and South America. They do not always fly over New York and the last time their migratory path coincided with September 11 was in 2004.

The Tribute of Light is turned on by the Municipal Art Society every year on the anniversary of the attacks.

Monitors from New York City Audubon, a conservation organisation, observed this year’s tribute and alerted organisers to the confused birds.

An estimated 90,000 birds die each year after becoming disorientated by lights and crashing into skyscrapers in New York as they migrate south for the winter.

Owners of tower blocks are increasingly switching off or dimming their lights to reduce the risks to birds. (World PRO News & The Telegraph)

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