Artificial lights in cities become a trap for birds – 12/12/2023 – Science

The long journeys of migratory birds — which already have to face adverse weather conditions, predators and the physical wear and tear of the journey — now face an additional challenge: increasing light pollution in urban centers.

A new and comprehensive study has identified that artificial lights serve as a kind of trap that attracts animals to cities.

“Cities pose multiple risks to birds,” says Geoff Henebry, a professor at Michigan State University and one of the authors of the work.

In addition to having potentially more limited natural resources, such as less food and water, urban areas also have buildings and glazed windows, which pose additional risks to the movement of animals.

Scientists analyzed more than 10 million weather radar observations, combined with information about landscape, climate and other data, to try to understand the reasons why migratory birds choose their stopping points along the way.

Among the 49 factors analyzed, light pollution was the second main predictor for the number of animals making a “pit stop” in a given location, behind only land elevation.

“Although it remains unclear why nocturnal migratory birds are attracted to artificial light, it is clear that migrants are changing their behaviors in response to this pollutant. [luz] on a large scale. Sometimes, light pollution can result in fatal collisions with aerial structures,” says the work, published in Nature Communications.

In an extreme example of this phenomenon, nearly a thousand birds died on October 4 and 5 of this year after colliding with a convention center on the shores of Lake Michigan in Chicago.

Although this particular building is a known hotspot for birds, the scale of the “carnage” was surprising. The images of lifeless animals, lined up, contributed to increasing the visibility of this phenomenon.

Experts estimate that, in the United States alone, more than 1 billion birds die annually due to collisions with buildings, windows and glass facades. There are no statistics for Brazil, but environmentalists consider the situation to be problematic in the country as well.

The article, which used data and focused only on the situation in the USA, used artificial intelligence and big data analysis tools to identify and predict regions with the greatest potential to become stopovers for large numbers of birds on their migratory journeys.

The idea is that this material can also serve to guide public policies to prevent animal deaths.

“With the loss of 28% of the migratory bird population over the past five decades and many regions becoming drier, with less forest cover and brighter at night, preserving important and ecologically functional stopover sites is increasingly important” , says the article.

Light pollution can also cause concrete risks to humans, such as disruptions in the circadian rhythm, a type of internal body clock that regulates the sleep and wake cycle. These changes can contribute to aggravating several health problems.

In the opinion of Kyle Horton, assistant professor at Colorado State University and lead author of the work, light pollution is often overlooked. “We don’t always think of light as a pollutant, but it fits all the requirements of what pollution is.”

As many birds migrate at night, scientists argue that reducing artificial lights in cities at night would be one of the main ways to reduce fatalities.

While measures of this type still seem a distant reality in many regions, researchers and environmentalists have focused efforts on means of reducing harm, such as migration monitoring platforms.

Through websites like BirdCast, it is possible to have real-time information about the movements of animals. This makes it possible, for example, to implement specific urgent measures to safeguard animals during peak days of movement in the skies.

Experts also suggest alternatives for adaptation, such as modernizing windows and other glass surfaces using special adhesives. Currently, there are specific decals that help signal to birds the existence of a barrier.

Reducing glare and softening colors also contribute to reducing the potential attraction that lights have on wildlife.