Window decals to prevent bird collisions only work if installed correctly

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Birds are in decline. Data from Cornell University suggests we've lost 3 billion birds since 1970, impacting virtually every avian species in Canada and the U.S.

There are several factors that led to this: climate change, habitat decline, and - of course - human activity. But researchers find small changes canmake a big difference.

Like keeping domesticated cats inside. According to the Cornell Lab of Orinthology, cats are responsible for 2.6 billion bird deaths each year in Canada and the U.S., and a 2013 study appearing in the journal Nature estimates cats kill upwards of 22 billion mammals of other species annually.

Window collisions are another human-led cause of avian mortality, killing about 599 million birds pa year in the U.S. alone.

There are a few ways to make windows safer - turning lights out at night, closing blinds so that birds aren't attracted to light sources, investing in specialized curtains, or using decals to let birds know a window is near.

The latter is the focus of a new study by researchers at William & Mary University, which set out to determine how effective window decals are at deterring collisions.

They found the decals - stickers in a reflective material that usually bear a decorative design - are only effective if placed on the outside of the window. When the films sit atop the internal surface, they don't make much of a difference because birds might not be able to see them.

Two brands of window film products, BirdShades and Haverkamp, were used in the study, selected because they interact with different wavelengths visible to songbirds.

A fine net was placed in front of the window to prevent collisions or harm to the birds during the experiment.

"The team found consistent evidence that when applied to the external surface of windows, the films resulted in reduced likelihood of a collision," the authors write.

"However, neither product was effective when the films were applied to the internal surface of windows. Therefore, the results of this research demonstrate the imperative that installers apply these products to exterior surfaces of windows to maximize their protective benefits and reduce the risk of daytime window collision."

The authors want to get the message out to save well-meaning homeowners time and frustration.

“Many people want to reduce bird-window collisions, as these unfortunate events kill hundreds of millions of birds each year,” lead author Dr. Swaddle [says in a statement]((https://www.eurekalert.org/news-releases/977057).

“There are lots of decals and window films that will likely make glass surfaces more visible to birds, decreasing collision risk. We were able to show that people must apply decals and films to the external surface of their windows to benefit the birds. We want people to know this as we want their time and money to be well spent."

Related: Seeing more robins in your backyard this winter? Here's why

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Other ways to help birds

• Keep bird feeders about a metre away from buildings.

• Clean bird feeders regularly and keep them filled.

• Ditch decorative plants and consider filling your garden with native foliage for birds to dine on. Experts also recommend adding a clean and maintained water source.

• In the fall, consider leaving your fallen leaves be so that ground-feeding birds have a place to forage.

• Slow down when driving on rural roads to avoid collisions.

Thumbnail image by Cheryl Santa Maria using elements from Canva Pro.