Preventing Bird-Glass Collisions: One Staff Member’s Creative Approach
Help us monitor collisions and learn more about which mitigation strategies are most effective! Current FeederWatchers will be invited to participate in our Bird-Glass Collision Study starting in January. We hope you will join us and help contribute crucial data on bird collisions so we can make our neighborhoods safer for birds.
It is estimated that over 1 billion birds are killed each year due to window collisions. This devastating fact moved Dr. Mhairi McFarlane, Habitat Stewardship Manager at the Cornell Lab of Ornithology, to take matters into her own hands to make the windows of her new home safer for birds. Mhairi, who started working at the Lab last December, cares deeply about wildlife conservation, and strives to do what she can to help birds and wildlife in both her professional and personal life.
“Bird collisions happen more often than we realize,” says Mhairi. “Just think about how much time you spend away from the windows at home, whether you are away at work all day, sleeping, or running errands. When a bird strike does occur, the chance that someone will be there to witness it is quite low. Think too about how incredibly tiny and light some of our birds are – a little warbler hitting a window on the far side of a room might not be easy to hear.”
Additionally, birds that hit windows tend to fly away if they can, but few ultimately survive. Those that are too stunned or injured to fly away are also vulnerable to predators. This makes monitoring for collisions tough. “By the time we reach a collision site, it’s likely that the bird is no longer there and you’ll have no idea that a collision even occurred,” says Mhairi.
All that is to say is that even if it seems like there aren’t any bird collisions at your home, they still might be happening, which is why it is so important to do what we can to prevent collisions from happening in the first place.
Mhairi knew that as she keeps working to make her gardens more bird-friendly by adding more and more native plants, it would become increasingly important to protect birds from the dangerous windows nearby. (Check out our page on Gardening for Birds).
Earlier this year, Mhairi witnessed a Pileated Woodpecker collision at her home, and she decided to put up strings with paracord and hooks outside the window to prevent strikes. (Learn how to do this yourself here). Although this seemed to work well, Mhairi found these interfered with her view more than she liked, and wanted an alternative. Some people are hesitant to put up collision deterrents for this exact reason. However, Mhairi was able to try out another DIY method of glass-patterning.
This fall, Mhairi spent a weekend with a cherry picker, a paint pen, and a DIY template to make all her windows safe for birds. Scroll to see photos of her in action!
Mhairi hopes that one day, all exterior glass, even the smallest windows, could be treated to be safe for birds, using a variety of methods suitable to the architecture, landscaping, and local habitat. Sadly, the only way to know if a given piece of glass is dangerous for birds is to find a dead bird under it, and every bird lost in this tragic way is one bird too many.
What can you do?
There are many ways to make your neighborhood safer for birds. You can install treated windows with artistic etchings, add Feather Friendly window film, or create DIY dots for your windows, just like Mhairi! The Bird Collision Prevention Alliance website has some great resources on getting started with making your windows more safe for birds.
16 comments on “Preventing Bird-Glass Collisions: One Staff Member’s Creative Approach”
What kind of paint pen do you suggest will hold up to the TX sun? What color do you suggest?
Great question! So far I only have experience of this approach in Ontario, Canada, and New York, and it has held up well in strong sun and also winter conditions. Regardless of your conditions, you may have to do some touch up at some point but it does seem to be quite robust. I used a sharpie paint pen, metallic colour.
How is the visibility, Mhairi?
They seem to be quite visible from the outside, as intended, but from the inside, they disappear really well. You can scroll through the photos and see one looking out from inside. Now that we have snow on the ground, they show up a little bit more from the inside as the dots contrast more strongly with the plainer white background, but it is still not distracting at all. Because the dots don’t move, they also don’t interfere with wildlife photography through the glass. I so much prefer the slightly “dotty view” over the daily fear I would find evidence of a bird strike!
What a clever idea! I will be using and sharing this for sure. Thank you.
yay, thank you for helping birds!
I like the paint dots. It looks as if it would be quicker to use a template like a stencil, with a broad brush–but I suppose that wastes paint.
Yes, I made a stencil out of a “for rent” sign, you can see it in the photos. I had thought about your idea, but agree it would waste a lot of paint, and may end up involving having to try to hold more items to get the job done.
On the morning of November 18, 2025, two days after I did my third Project FeederWatch count of the 2025-26 season in Eagan, Minnesota, a Northern Cardinal and an American Robin hit two of our first-floor windows within an hour of each other. They died instantly and it was quite disturbing. The irony is that I feel they died because I had taken the screens out of the windows to have a better view for doing my FeederWatch counts. I quickly reinstalled the screens and have had no problems since.
Oh that is very sad. Good plan to put your screens back up again, that should help a lot (though I did unfortunately have a fatal bird strike on a small screened window on my garden shed, so I actually then added dots on the outside of the glass, under the screen). Thank you for participating in FeederWatch!
Great idea with the paint pen. I used to live near a meeting building with a walking path around it, and I would find dead birds that had struck the very large windows all the time. I would find red Headed Woodpeckers, American Robins, northern Mockingbirds, Chipping sparrows, Mourning Doves, all sorts of birds. It was always really sad and, as I was only about 12 at the time (I’m 15 now), I always thought it was my duty to bury them before the landscaping people got rid of them. I wish they would do something like you did to those windows, because that is one of the only spots I can find Loggerhead Shrikes in my area. I just hope most of the shrikes stick to the soccer fields instead of flying at those windows.
Thanks for sharing your tragic observations, and for caring about the birds. There are some resources on the Bird Collision Prevention Alliance website about how to work with building managers (https://www.stopbirdcollisions.org/faq/), and this resource for finding local initiatives you might be able to volunteer with, and ways to report window collisions: https://www.stopbirdcollisions.org/solutions-get-involved/#volunteer
I moved to Decatur GA just 6 weeks ago and our house is across the street from a small lake. WE have a double feeder in the front yard perhaps 15 feet from the window. Almost since we moved in we have been blessed with absolute flocks of red wing blackbirds, brownheaded cowbirds and grackles – easily 30 en toto. There are the occasional doves and songbirds as well.
The behavior of this flock is amazing. They arrive and sit in the branches of an adjacent crape myrtle, then begin to swoop to the feeders and/or the ground to retrieve seeds. Then they all swoop off together in a great rush, only to return minutes later. Twice during one of these “escapes” (I was sitting inside at my desk), a redwing hit the window, quite startling me.
I haven’t been able to find evidence of them in the bushes below the window. Does this situation warrant protection for them?
Thanks for sharing your careful observations. I would say – yes, absolutely do what you can to mark your windows to prevent bird strikes. Although birds which are able to fly off right away will do so, we are learning that many of these birds succumb to their injuries later, elsewhere. It is possible too that they may also be less able to avoid predators while they attempt to recover. I always worry too about smaller birds, including warblers and hummingbirds, which are so light they hardly make a sound when they hit the window – and also birds which may strike whenever we are not around to observe them.
Another thing you could consider is it seems from our pilot research, and others, that the highest frequency of bird-glass strikes occur in situations where feeders are between 3 and 30 feet away. You mention your feeder is 15 feet away – perhaps you could move it very close, or another 15 feet away? It seems that 3 feet or less means that birds may not be able to accelerate enough to cause themselves injury if they strike the window, and 30 feet or more away, there is a higher probability they will take a different route or perhaps have a better chance of seeing the glass.
Can the marking be done on the inside of the window (easier to reach and not subject to weather) ? Is there an ideal spacing for the dots?
Thanks for your questions. If at all possible, it is far more effective to make the markings on the outside of the glass. This breaks up the reflections and gives the birds something to focus on. Birds collide with glass because they can’t see it, and the dots make it more visible. If you have windows or glass railings which are difficult to reach, you could enquire with a window washing company, or an arborist, who may have the appropriate experience and equipment to reach from the outside. I had the same problem – I hired an arborist who brought and operated the lift. If the only option available to you is to make markings on the inside, then you can certainly try this, but it will not be nearly as effective. Above all – do stay safe!
Although the paint pen approach (and many sticker-type solutions as well) can only be applied in warmer conditions (10 C or 50 F or warmer is ideal), both last well in hot and cold conditions, including through snow, ice and rain.
Ideally, the markings should be 2 inches apart. The idea is that our smallest birds, including hummingbirds, warblers and kinglets, will see this as a gap they can’t fit themselves through. There is ongoing research on what does and doesn’t work, but this is our current understanding of what seems to be most effective for stationary markings.