Hundreds of millions of birds are thought to be dying every year as a result of colliding with skyscrapers in major US cities, according to a new study.

Scientists came to the conclusion after analysing 22 years of weather surveillance data to map trends in bird migration activity, which showed that they were being drawn to some of the most heavily lit parts of the country.

Writing in the journal Frontiers In Ecology And The Environment, they said man-made light sources such as streetlights, safety lights and buildings could all "disturb wildlife in a multitude of ways".

Image: Dallas in Texas boasts plenty of skyscrapers that can pose challenging obstacles for migrating birds

Taller structures, including skyscrapers, communication towers and power lines, were identified as particularly significant causes of "substantial mortality" among the animals, especially during the spring and fall.

Billions of birds pass through the US during these seasons as they migrate to Canada and Latin America and researchers fear that more than half a billion are dying while trying to navigate big cities.


They can be attracted towards the windows of tall buildings, making them vulnerable to a collision, while others find themselves disorientated by the sheer scope of light across any given city, causing them to flutter around for hours before falling to their deaths through exhaustion.

Chicago is ranked as the most dangerous place for birds to take flight, followed by Houston and Dallas in Texas.

The study said this was because light exposure levels in such cities are a whopping 24 times higher than the nationwide average, putting them top of the "exposure risk ranking".

Other metropolises listed in the study include Los Angeles, St Louis, Minneapolis, Kansas City, New York, San Antonio, and Washington, DC.

Image: Cities like New York generate a huge amount of light

Cecilia Nilsson, co-author of the study, said she hoped the findings would encourage further conservation efforts in each location to reduce the number of bird deaths.

"Now that we know where and when the largest numbers of migratory birds pass heavily lit areas we can use this to help spur extra conservation efforts in these cities," she told The Cornell Lab Of Ornithology website.

"For example, Houston Audubon (a conservation society) uses migration forecasts from the lab's BirdCast programme to run 'lights out' warnings on nights when large migratory movements are expected over the city."

Regarding what the average person can do to help, she added: "If you don't need lights on, turn them off. It's a large-scale issue, but acting even at the very local level to reduce lighting can make a difference.

"While we're hopeful that major reductions in light pollution at the city level are on the horizon, we're excited that even small-scale actions can make a big difference."