Migrating birds drawn to their death in collisions with skyscrapers at night

NEWS/COMMENT: On long migrations, in America, a study has found that birds are drawn to the lights of skyscrapers in big cities where their lives are ended in collisions with the buildings – The Times reports.

Migrating birds drawn to their death in collisions with skyscrapers at night
Illustration: MikeB

The study is published in the journal Nature Communications. Between October 5 and October 6, 1000 birds died in a single night at the site of a single building, the McCormick Place Lakeside center in Chicago. The 1000 birds that died of were made up of 33 different bird species. They were all found around the illuminated building.

The report said that: “Urban illuminated areas may act as ecological traps at macroscales that increase the mortality of birds during migration.”

I believe that the word ‘macroscales’ means at a large scale. Scientists should write in plain English.

To mitigate these traps, it’s been suggested that:

  • High-rise buildings should add dots or lines to their windows to make them easier to spot. “Retrofitting windows with decals like gridded dots or lines could help prevent collisions by revealing the barrier to birds”.
  • Brightness levels should be lowered. The colour of the lights should be softened.
    “Lowering the brightness and staffing the colour of lights can help to. Bright white or blue lights are the worst for wildlife, while warmer hues like red, orange and yellow are less attractive.

These three changes should make the buildings less attractive to migrating flocks.

Kyle Horton, an assistant professor at Colorado State University’s Department of Fish, wildlife and conservation biology said:

“Stopover locations are the fuelling stations. If you’re on a cross-country trip and there’s no fuelling stations, then you’re stranded. If they don’t have a good spot to rebuild energy supplies, migration can’t happen.”

A co-author of the study, Professor Geoff Henebry, of Michigan State University added that cities “pose multiple risks to migrating birds [but] also offer resources for the tired birds to rest and refuel”.

The task is to make cities less dangerous.

Wires can also be deadly. The report added that “Communication towers used to beam continuous red or white light to warn aircraft. Birds would circle the towers, hitting the wires that secured them. In 2016, based on conservation research, the Federal Aviation Administration started requiring communication towers to use flashing red lights, dramatically reducing bird collisions in a literal blink”

The conclusion by the study scientists is as follows:

“These findings lend support to the hypothesis that light pollution can act as an ecological trap for migratory birds, drawing migrants into suboptimal stopover habitats and potentially dangerous stopover locations with increased risk for collisions with structures and predation. If we turned off all lights tonight, there would be no birds colliding because of lights tonight. The impact is immediate and positive the birds.”

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Post Category: Birds > migration