Researchers calculate up to a billion birds may die in the US each year due to collisions with windows

AUGUST 8, 2024 **REPORT**, by Bob Yirka , Phys.org

https://phys.org/news/2024-08-billion-birds-die-year-due.html

Credit: Unsplash/CC0 Public Domain

A team of ornithologists from the Fordham University Graduate School of Arts and Sciences, the NYC Bird Alliance, Inc, and the Max Planck Institute for Geoanthropology has found evidence that far more birds are killed by window collisions than previously thought.

In their study, published in PLOS ONE, the group analyzed wildlife rehabilitation records for thousands of birds involved in window collisions.

Prior research has shown that windows are a major hazard for birds—birds cannot see windows and fly right into them. Such collisions often lead to near-instant death—others lead to a stunning effect, where the bird crashes to the ground, only to recover moments later and fly away. There are also collisions that result in injuries to the bird that it may or may not recover from.

Scientists have estimated that hundreds of millions of birds die each year in the U.S. alone due to window collisions. This new research suggests that the number is far higher.

The researchers began their study by noting that most window collision calculations are derived by adding up counts of dead birds found on the ground below windows. But such counts, they note, fail to consider the number of birds that survive the initial collision but die later due to injuries.

To estimate how many birds die from window collisions after surviving the initial impact, the team studied data from eight states regarding 3,100 avian collision cases over the years 2016 to 2021. They found that most birds that were discovered and treated still died due to injuries they sustained in the collision. More specifically, they found that the death rate was 60%—mainly due to brain injuries.

They note that it was not uncommon for a bird to wake up after a collision and fly away, seemingly unharmed. Unfortunately, many such birds can experience the same types of symptoms that happen to people in car accidents, such as brain swelling, which almost always leads to death in birds. Taking such cases into account increases the total number of bird deaths due to window collisions to approximately 1 billion a year in the U.S.

The team notes that preventing bird deaths due to window collisions is relatively easy—it only requires adhering tape or stickers to windows and to turn off lights behind them during migration season.

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