LONDON, Ontario — Bird-watching becomes convenient when bird feeders lure them right up to our windows. Unfortunately for our feathered friends, birds often cannot detect a window in their path, causing them to fly straight into one — potentially killing them. You can still enjoy being up close and personal with your backyard birdies, but there are ways to help save them from possible injury. A new study reports that bird feeders should be placed within 18 inches of windows to prevent potentially fatal collisions.
“Given that birds’ flight velocity prior to impact predicts the lethality of collisions with windows, we recommend that bird attractants (feeders or baths) should be placed close to windows (within 1.5 feet or 0.5 m) to reduce the available space where birds can gain speed,” the researchers say.
Why birds fly into windows
Study co-author Brendon Samuels, a PhD candidate at Western University in Ontario, says that birds crashing into windows happens often all over the world. “But the frequency and severity of collisions seem to be underestimated by the public, especially at residential settings. One reason is that collisions happen suddenly and are difficult for people to observe directly. When birds fly away afterwards, it is unclear what ultimately happens to them,” he explains in a statement.
“Our findings highlight how common collisions can be in residential settings, especially where there are bird attractants like feeders,” he adds.
Along with their warming tunes and chirpy personalities, birds are a vital part of the ecosystem. However, these creatures are under threat. Windows reflect sky, clouds and trees. Millions of birds in the U.S. fly into windows each year, with around a third dying.
Audio and video recordings in a residential backyard now provide the first glimpse of what happens in the moments leading up to impact. An analysis of 29 collisions and nine near-misses showed flight velocity and angle of approach both predicted outcomes following a crash, authors of the study say.
Faster flights at angles of approach closer to perpendicular were most hazardous. Only a small proportion resulted in an immediate fatality and were detected by occupants. Most were followed by the bird flying away without leaving a trace. It is believed some may suffer injuries and later die far from the site.
This suggests the extent of collisions may be vastly underestimated by traditional survey methods. Surveys have focused mostly on larger structures such as office blocks. Yet residential buildings are the most numerous with windows. They represent the greatest cumulative threat.
New housing developments are being prioritized in many parts of the world. The appetite for large glass windows and railings continues to grow. Garden bird feeding has gained in popularity over the pandemic, drawing more birds into high-risk settings.
How to keep birds from potentially deadly collisions
The study shows that collisions occurred nearly as frequently with smaller windows as with large glass doors. “Given birds’ flight velocity prior to impact predicts the lethality of collisions with windows, we recommend bird feeders or baths should be placed within 1.5 feet to reduce the available space where birds can gain speed,” says Samuels.
New buildings can be designed based on practices that limit risk of bird-window collisions. Similarly, existing building windows, such as those on homes, can be retrofitted using simple materials to add visual markers to the exterior of the glass.
“An important direction for future research is to characterize how birds orient their eyes to detect and avoid collisions with windows, so collision deterrents can be designed optimally to match bird vision,” says Samuels. “This study documented birds approaching windows from variable angles. Designs and tests of collision prevention technologies should take this into account.”
The study is published in the journal PeerJ.
South West News Service writer Mark Waghorn contributed to this report.
Spanish version of this article: Su comedero podría estar enviando a nuestros amigos emplumados a la tumba