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"Flight Risk" -- The Discovery Files

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Birds that produce faint chirps, called flight calls, during nighttime migration collide with illuminated buildings much more often than closely related species that don't produce such calls, according to a new analysis of a 40-year record of thousands of building collisions in the Midwest. The study cited a 75-percent reduction in fatal collisions at a particularly crash-prone structure in Chicago by changing the light regime. This finding suggests that, during migratory periods, reducing the amount of artificial light could vastly cut down the number of bird fatalities.

Credit: NSF/Karson Productions

Audio Transcript:

Super colliders.

I'm Bob Karson with the Discovery Files, from the National Science Foundation.

(Sound effect: bird sounds) Migratory songbirds like thrushes, sparrows and warblers have a history of fatally crashing into buildings during their nocturnal flights. (Sound effect: cartoon BONK!) Researchers believe it may have to do with "tweeting" while flying.

The team analyzed existing data from over 70,000 nighttime songbird collisions in Chicago and Cleveland, dating as far back as 1978.

Their study provides evidence of two particular factors present in high-collision species: First, the use of "flight calls" -- faint chirps the birds give out that help migrating groups orient and navigate. Second, artificial light from illuminated buildings. The team's analysis shows that light may disorient the birds, causing them to send out flight calls that inadvertently lure other birds to their deaths. Meanwhile, species that do not use flight calls were found to collide less frequently, and nighttime light levels didn't much affect their collision counts.

The study suggests that during migratory periods, reducing the amount of artificial light could vastly cut down on the number of bird fatalities. The team cites a 75-percent reduction in fatal collisions at the particularly crash-prone Chicago Convention Center through the simple act of changing the light regime.

Turning down the lights for safer migratory flights.

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