More than 1 billion birds in the US may die from colliding with buildings each year 鈥� a significant increase from many past estimates. Despite popular belief, skyscrapers aren鈥檛 the main culprit.
The disorienting and appealing light from buildings at night, along with confusing reflections from glass during the day, can cause birds to fly into them. Most collisions occur with low-rise buildings like homes, and the problem has worsened in recent decades with increasing light pollution.
that counted dead birds on the ground next to buildings have estimated that hundreds of millions of birds die instantly in these collisions each year in the US. But missing from those death counts were birds that survived collisions and later died during rehabilitation care. 鈥淲e know that far more birds hit glass than we find dead beneath it,鈥� says at NYC Bird Alliance, a non-profit organisation that works to protect birds in New York City.
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To get a more accurate idea of the impact buildings have on birds, Partridge and his colleagues analysed collision records from 152 species of birds hitting more than 3100 buildings around the US east coast 鈥� a major bird migration corridor 鈥� ranging from single-family homes to commercial properties. They also included data from nearby rehabilitation facilities that cared for injured birds following building strikes. Their analysis revealed that 60 per cent of birds that hit buildings later succumbed to injuries. This more than doubles some past estimates of total fatalities.
Because the injuries birds sustain by colliding with buildings are often severe, Partridge wasn鈥檛 shocked by the finding. 鈥淚t鈥檚 such a challenge to survive after hitting a window,鈥� he says. But he emphasises that rehabilitation care is giving many birds a fighting chance. 鈥淚f a bird is lucky enough to have somebody find it and bring it to rehab, those are the best conditions possible,鈥� he says.
Though the study was limited to the US, a similar pattern is playing out around the world. 鈥淭his is happening everywhere 鈥� building collisions are a global threat,鈥� says Partridge. The number of bird-building collisions is especially high during annual migration cycles, when billions of birds travel by night and are drawn in by artificial lights. North America alone hosts four major 鈥渁vian superhighways鈥�.
However, Partridge says, bird-proofing windows is relatively easy: turning off the lights at night, drawing the shades during the day or adding glass decals is often enough to save birds from a fatal crash.
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