Modern cities have become authentic “lighthouses”. For thousands of birds it is a problem

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Philadelphia premiered April 2021 with a curious stamp. Building Liberty Place or the towers Comcast, among other iconic skyscrapers in the city, “turned off” at the same time between midnight and six in the morning. It happened on the morning of the 1st, the 2nd, it was repeated on the 3rd and 4th… It was not due to an electrical failure, nor to an attack. What happened was in the context of “Lights Out Philly”a program that lasted until the end of May and sought turn off or dim the most powerful light bulbs of the Philadelphia skyline. Similar initiatives have been adopted in other cities, such as New York.

The goal is always the same: prevent cities from acting as “lighthouses” that disorient birds during their migratory flights and end up being turned into death traps.

Cities, dangerous “lighthouses” for birds. If lighthouses were created to guide sailors and avoid danger on the coast, cities act in exactly the opposite way with birds. Light pollution from large metropolises can disorient them at night, as they migrate from one region to another, and put them in trouble. Experts have been studying the phenomenon for some time. In 2018 a team from the University of Delaware (YOU) published a study in which he warns about how lights attract birds to urban areas and the risk that this entails.

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Like moths to streetlights. “We think that artificial light could be an attraction mechanism because we know that, on a very small scale, birds are attracted to light,” commented one of the Delaware researchers: “Just as insects are attracted to streetlights at night, birds are also attracted to places like lighthouses. Since most of the birds that migrate in the US move at night, the data is worrying.

After analyzing the distribution of birds around the brightest centers of the northeastern US, such as New York, Washington or Boston, the scientists found “an increasing density of birds as you get closer to these cities.” “The effect extends to about 200 kilometers. We estimate that these flying birds can see a city on the horizon several hundred kilometers away,” explained Professor Jeff Buler to Phys.org website.

Increasingly interested in cities. just a few weeks ago the BBC showed how some species of migratory birds are increasingly attracted to large cities. Specifically, he points out the case of Swainson’s thrushes and his “surprisingly long stopovers” in and around Montreal during his migrations to the lands of South America. Among the factors that could attract them would be the lights or the possibility of feeding and regaining strength during demanding journeys. There are birds that even molt before continuing their journey.

A danger with capital figures. The problem is not minor. Researchers have also found that hundreds of thousands of birds are killed each year in the United States alone by crashing into buildings. A 2014 study leaves the calculation between 365 and 988 million, but there are estimates that handle an even wider range. In October 2020 in downtown Philadelphia they came to collect between 1,000 and 1,500 bird carcasses on a single cloudy night. Experts estimate that only New York, the great city of skyscrapers, is charged, each year, 200,000.

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Beyond building collisions. Crashes against facades or windows are not, however, the only dangers faced by birds in cities, spaces with an intense flow of traffic and other potential threats. “One of the issues we pointed out in the study is that there could be negative consequences for birds that are attracted to urban areas. We know there is a risk of colliding with buildings, colliding with vehicles and being eaten by cats, which are a major predator”, Delaware researcher says.

Buler recalls that cats probably represent “the greatest anthropogenic source of mortality for birds” and warns of the risk that birds end up being attracted during their migrations to cities. “If they are being attracted to these heavily developed areas, it may be increasing their risk of mortality from human sources and also that the resources in those habitats are going to be depleted much faster due to competition with other birds.”

Brandon Green Xbtbuuxeovy Unsplash

Threats… and opportunities. The expert points out that the problem could be aggravated by the expansion of LED lights, which are brighter than incandescent ones. “The transition continues to increase the amount of light pollution,” Buler regrets before recalling that birds, mammals and insects have been exposed to human-generated pollution for less than two centuries.

It’s not all bad news, of course. Initiatives like “Lights Out Philly” show that there is a growing awareness and the problem would be relatively easy to alleviate. A study published in 2021 shows that McCormick Place, in Chicago, could reduce bird mortality by 59% with a gesture as simple as turning off half the lights during migration seasons. In recent years, alternative solutions have also been experimented with, such as acoustic headlamps.

Cities do not have to be a threat: The Swainson’s thrush study or on warblers in Morelia, in central Mexico, show that cities do not have to be only hostile and dangerous environments for birds. With good planning, trees and green areas could help those who decide to stop in urban areas during their migrations.

Experts warn, in any case, of the risk that urban areas end up representing “ecological traps”, spaces that attract birds but, in reality, cannot offer them all the resources they need, for example, when they reproduce.

Images Jose Vidal Velar (Unsplash) and Brandon Green (Unsplash)

Philadelphia premiered April 2021 with a curious stamp. Building Liberty Place or the towers Comcast, among other iconic skyscrapers in…

Philadelphia premiered April 2021 with a curious stamp. Building Liberty Place or the towers Comcast, among other iconic skyscrapers in…

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