Anyone who has sat near a window may have experienced the startling moment when a bird smacks into it. Like the famous scene when a pelican's crash startles a dentist into an inadvertent tooth-pull in "Finding Nemo," it can seem cartoonishly silly when a gracefully soaring red-tailed hawk or empty-eyed dumpy pigeon abruptly stops and plops into a pane of glass. If the bird is lucky, it will wobble in the air for a few seconds before regaining its sense of avian dignity and flying off. Yet when the feathered navigator is less fortunate, it flops to the ground — quite often, dead.
"We also know that not all birds that hit windows die... the survivors may be injured, perhaps even breaking a wing – and it's likely that many of these individuals don't survive for long, either dying from their injuries or taken by predators."
"The U.S. has gone from approximately 10 billon to 7 billion birds in the past 50 years, which is approximately a 30% decline," explains Dr. John Swaddle, a professor and faculty director at the Institute for Integrative Conservation at William & Mary. In an email to Salon, Swaddle added that hundreds of millions of birds die every year from window collisions.
However, there is a caveat: If you put decals and other conspicuous stickers outside of your windows, the birds are more likely to see the obstruction and therefore avoid it.
The key detail, according to a recent study published in the peer-reviewed scientific journal PeerJ, is that the decals must be outside of your window. Never inside your window; always outside of your window.
"Double-glazed windows reflect and scatter a lot of light, especially when you view them from a slight angle, as a flying bird would do," Swaddle told Salon. He is the corresponding author of a recent study which tried to figure out how this basic reality of physics impacts a bird's experience as it flies near a standard window. For their experiment, researchers from William & Mary had zebra finches perform repeated and controlled flight trials near windows with film products either in the ultraviolet (shorter wavelength) range or orange (longer wavelength) range — namely, BirdShades film and Haverkamp film, respectively.
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"In our collision avoidance trials, BirdShades increased window avoidance by 47% and the Haverkamp increased avoidance by 39%," the authors concluded. (The study received funding for its tests by BirdShades Innovation GmbH, although the researchers stipulate, "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.")
The authors emphatically added, "Neither product was effective when the films were applied to the internal surface of windows. Hence, it is imperative that installers apply these products to exterior surfaces of windows to render their protective benefits and reduce the risk of daytime window collision."
"Installing window films to interior surface of double-glazed windows will rarely render any collision-reduction benefits and should be avoided in most situations."
When breaking down the problem of avoiding window collisions from a bird's point of view, Swaddle explained it is basic optics. "The glare and reflected imagery from the external surface of the glass is sufficient to obscure a film or decal (at least the ones we tested) that is stuck to the interior surface from being seen clearly," he pointed out.
Dr. Christopher Elphick, an ornithologist at the University of Connecticut who was not involved in the study, wrote to Salon that the results are "very interesting" and was encouraged that they could spread awareness about a problem that kills hundreds of millions of birds every year.
"We know that flying into windows kills lots of birds," Elphick observed. "Homeowners that are paying attention to the birds in their yards often report casualties lying below windows, although many will be hidden by vegetation or soon eaten by scavengers." Even the birds that do not immediately die may still meet a grim fate.
"We also know that not all birds that hit windows die — often they can fly away immediately, and sometimes they just sit on the ground for a while, stunned, and then fly off," Elphick explained. "Sometimes, though, the survivors may be injured, perhaps even breaking a wing – and it's likely that many of these individuals don't survive for long, either dying from their injuries or taken by predators."
"What we need is heightened awareness that people can make a positive difference. This is a conservation problem that we can all help to solve."
If you want to protect birds from easily avoidable deaths without buying window film products, there are other solutions. Swaddle wrote to Salon about "aesthetically pleasing fritted glass that could be installed in new construction and retrofits" and which are also bird-friendly. The American Bird Conservancy notes that screens can be helpful as well, not only by limiting reflectiveness but by providing birds with a cushion if they make impact. It is also possible to use everyday household objects to signal to birds that there are obstructions: Shutters, netting, duct tape, bits of string, colorful stickers, and paint can all be used to this effect.
Yet there is one point the authors of the study seemed unable to emphasize enough, and with good reason: "Installing window films to interior surface of double-glazed windows will rarely render any collision-reduction benefits and should be avoided in most situations." Indeed, if anything, scientists will need to engage in much more experimentation with window collision testing so they can learn more about which protocols and products are actually best at protecting birds going forward.
"We found much lower estimates of effectiveness when testing for collision avoidance rather than in situations where collisions are forced," the authors pointed out. "We speculate that many of the published estimates of the effectiveness of window films and decals that used forced collision paradigms render overestimates of how birds will avoid windows in more real-world settings."
If there is any good news, it is that future birds like Nigel from "Finding Nemo" do not always have to smash into windows. Their plight is complicated, but it is not inherently intractable.
"What we need is heightened awareness that people can make a positive difference," Swaddle told Salon. "This is a conservation problem that we can all help to solve."
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