What is a bird-building collision?
written by Grace Doss
You just heard a “Thunk!” from your window. Looking outside revealed a stunned bird on the ground! Bird-building collisions are an unfortunate event most of us have experienced, whether in a city or out of it. What happened, and what should you do now?
The main culprit is our windows; they can reflect light or otherwise appear as an open space to fly through, which confuses many birds. This effect is compounded when there is vegetation near to and reflected by a window. And the problem doesn’t go away at night! If there is light from inside the building pouring out of the window, birds appear to be attracted to it.
Certain weather conditions can combine with these window properties to worsen the problem. According to one article, increased window strike risk in spring occurs when the weather is warm and dry. In the fall, risk increases with high visibility, humidity, and air pressure, along with cool temperatures. There is also a risk when there is bad weather during overnight migration that causes birds to fly lower than usual.
But why is this a problem? Only one or two birds fly into a building a day, right?
Why does it matter, and why should we care?
It turns out, birds that collide with buildings actually have a 60% death rate. Not only that, but over 1 billion birds could collide with buildings in the U.S. in a year. That’s a lot of birds, over 1 billion “Thunks!” This is extra scary considering the previous estimate of 365 million to 988 million bird collisions a year.
Birds that migrate, including rare species, are commonly found dead from window impacts. They migrate during the spring and fall, and all of the new babies from spring cause the number of collision-related deaths in the fall to almost double. Even when a bird flies away after an impact, they are still likely to die from complications later. Most of these are birds that were otherwise healthy and could have lived much longer lives.
Is anyone doing anything?
One of the ways over 30 North American cities are helping birds is by participating in a program called Lights Out. The plan is for as many people and buildings as possible to turn their lights off between 11 pm and 6 am during migration season. Many birds migrate at night, and by keeping the lights off, they won’t get distracted. Lights Out also comes with many other benefits, such as reduced energy bills. This way, we can save birds and money!
There are also several versions of bird-safe glass that can be added during construction.
What can I, the average person, do?
You may now be wondering, “Well, that’s great and all, but what can I do about this?”
A major way people can help is by improving their windows, whether at school, work, or in their own homes. There are many methods to choose from when making an existing window bird-friendly. Cornell Labs and USFWS share some excellent ideas on how to improve your windows:
- Applying a Pattern- If patterns are applied to the outside of a window in a 2-inch by 2-inch grid, then even small birds like hummingbirds will be able to notice them. Be sure to use lighter colors so the patterns don’t blend in with the window. There are several options for this method:
- Tempera Paint- Using non-toxic tempera paint to create simple patterns or fun artwork is a cheap and effective method. You could even invite your kids or friends over to have fun with the process! Tempera paint can also be easily washed off with vinegar and water.
- Soap- Soap can also be applied in this way to create a 2in x 2in grid pattern visible to birds.
- Decals- There are many different shapes of decals available to purchase, but they still need to be applied with the correct spacing to work correctly.
- Premade Tape and External Films- These are available in a variety of colors and tints and provide an easier way to get the correct spacing.
- Netting- Netting with a small mesh can be placed outside a window so that birds can bounce off it.
- Screens- Insect screens placed on the outside of a window can be effective in reducing bird collisions.
- Paracord- Curtains made from parachute cord and hung outside windows can be bought premade or constructed yourself.
- One Way Film- A film that lets the person inside see out but prevents anyone outside from seeing in can also lower the chances of bird strikes.
In the process of working on your windows, you found a dead bird! What do you do next? If the bird is only stunned, try calling a local wildlife rehab and following the instructions they give you. Be sure to stay safe! Wild birds can carry a lot of diseases.
You may also post your sighting to a citizen science website like iNaturalist. At UTSA, if any dead birds are found around campus and are reported on iNaturalist, they automatically get included in a database. This way, we can find out which buildings have the most risk to birds.
What if the bird you found had a band on its leg? To report a banded bird, go to reportband.gov. Knowing what happened to a banded bird is very useful information!
Of course, one of the best ways to help birds is to tell others about what you have learned here. Windows can be dangerous to birds, but we have found ways to lessen that threat. All that is left is to spread this knowledge and to spur each other into action.