Cornell tested window-safety messages on nearly 5,000 people in the US and Canada; bird lovers preferred proof, while others were more moved by emotional appeals

You’re sitting, having your morning cuppa and scrolling through social media when you hear a dull thud from your kitchen window. You look up to see a confused, sometimes unconscious songbird lying on your patio. If you live in a house or a low-rise apartment in the USA, then this is not a rare or unusual occurrence. Hundreds of millions of birds are hitting your windows each year, but most of us have absolutely no idea we are causing this issue.

According to a 2025 Cornell Lab of Ornithology study titled “Mitigating collision-caused bird mortality through message framing: Insights from residents' intentions for bird-safe windows,” published in the journal Biological Conservation, researchers asked nearly 5,000 people from the USA and Canada why they weren’t taking measures to reduce collisions. They found that different people needed different approaches to convince them to make their windows bird-friendly.

The billion bird issue


Every year between 365 million and nearly a billion birds are killed due to colliding with buildings in the USA. This figure comes from Loss et al.'s landmark 2014 study titled “Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability,” published in the journal The Condor: Ornithological Applications. The study found that window collisions are the second largest source of direct human-caused bird mortality in the US, behind only predation by free-ranging domestic cats.

What will really shock you, though, is that these collisions aren’t caused by the glittering skyscrapers in cities but actually by low-rise buildings. Most of us live in low-rise buildings or houses, and this causes the vast majority of deaths. Your neat sliding glass doors into your garden deck are causing more damage than the closest 40-storey building.

Why “just care more” doesn’t work

The researchers tested what would cause people to take action to reduce collisions, trialing different messages built around effectiveness, emotion, ethics, and social pressure. The results were unglamorous. People who considered themselves bird lovers responded best to effectiveness: seeing evidence that dots or tape spaced two inches apart on their windows would actually prevent collisions pushed them to act.

By contrast, the general public responded much better to emotional messages: seeing pictures of dead or injured birds was more likely to move them to action. Neither message type, however, worked on the other audience, and notably, neither group responded to ethical appeals or social pressure: telling people they should feel guilty, or that everyone else was already doing it, had no measurable effect. This is a damning result for a generation raised on constant cause marketing; it appears virtue signaling just doesn’t move this group to act.

How to fix your window

The great news is that you can easily stop your windows from causing issues. The American Bird Conservancy recommends covering the outside of windows with a pattern of dots, tape, or film spaced no more than 2 inches apart horizontally and 4 inches apart vertically, the “2x4 rule,” which also applies to hanging cords (such as Acopian/Zen curtains). avoid the same confusion going forward.) This spacing causes birds to perceive the glass as a solid barrier rather than open space, similar to how they’d read gaps between tree branches. Products range from DIY options like masking tape to purpose-built tapes and decals (such as Feather Friendly or ABC BirdTape), which are more weather-resistant and hold up longer than household tape or paint. Most options can be applied in a single afternoon.

What is really interesting from this research is that although the numbers are shocking, it reminds us that good intentions won’t be followed through if they aren’t personalised. Millennials and Gen Z have been bombarded with ‘save the planet’ campaigns focusing on our ethical responsibilities, but this study shows this might not be working. If the researchers from Cornell are correct, then showing people that putting 2 inches of tape will actually work is much more effective. Or showing them an honest and uncomfortable picture of what will happen if they don’t. Next time you have something hit your window, ask yourself if you actually did anything to fix the issue or just felt bad for a short while.