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UD professor studies city lights' effect on bird migration

 Purple to Yellow indicates increasing bird density. Black to white indicates increasing artificial light intensit
Courtesy of Jeff Buler
University of Delaware
A still frame from a graphic of birds leaving areas for migratory flight. October 10, 2017 around the KDOX Dover radar.

New research released this month says bright lights can lure migrating birds to cities at night, derailing them from their normal southbound path each fall.

The researchers, including University of Delaware professor of Wildlife Ecology Jeff Buler,  used weather radar to measure birds migrating through brightly lit urban night skies over a 7-year period.

What they found is a lot of birds are drawn to the bright lights of cities like Baltimore and Boston, even from over a 100 miles away.

"But they’re not going to land in the parking lot of a strip mall. They’re still going to seek out those habitats they prefer, but within the urban landscape," Buler said.

Many tend to stay in suburban areas on the fringes of those urban communities. Buler says those areas often offer the closest suitable habitat.

From an ecology standpoint, Buler says this trend is concerning.

"When birds are in urban areas there are a lot more potential sources of mortality to birds from human causes, like colliding with buildings or getting eaten by cats," Buler said.

There’s also concern that if they stay too long in urban areas, the habitat quality isn’t as sufficient as the natural landscapes they’re used to.

The researchers wonder how badly that will delay the birds’ journey.

They continue to study this in Maryland, illuminating a forested area and comparing birds’ behavior when the lights are on and when they’re off.

The research was published in the journal Ecology Letters

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