There is an invisible killer responsible for the deaths of billions of birds every year: glass. Most of us have witnessed tragic bird-window collisions in our homes or offices. But, the problem goes beyond residential windows. Just this past October in Chicago, up to 1,000 birds fatally collided with the McCormick Place Lakeside Centerthe largest convention center in North America- in one tragic incident. Why are birds getting killed in such huge numbers? And what can the architecture community (and regular consumers) do to prevent bird window collisions?

Why Do Birds Hit Glass?

Bird glass collisions are the second leading cause of bird deaths caused by human action (domesticated cats are the first). But why do birds collide with glass so frequently? The simple answer is that birds cannot see and/or become disoriented by glass. However, the common belief that birds cannot see glass whereas humans can, is not entirely accurate. In fact, If it was your first time ever seeing one, you may find that you would also run into a glass door. Even people who interact with glass every day occasionally bump into it– simply because glass is transparent. For a bird, traveling at high speeds, this mistake is often fatal. 


Besides being transparent, the reflections that glass creates are also confusing to birds. Sky, clouds, and vegetation reflected on building windows appear to birds as extensions of their habitat. So, while a highly blended and reflective building may be beautiful to us, it can be deadly to birds. 

Birds Do Not Understand Visual Cues We Use to Avoid Glass

Humans, who understand the concept of glass and have grown up around glass structures, are able to easily use visual cues to avoid it. To a human, glass is easily discernible from the outside environment due to glare, reflections, door and window frames, etc. Birds, on the other hand, cannot easily learn these visual cues. A bird may be able to learn to avoid an individual pane of glass if they have previously survived a collision against it. However, they are unable to apply this knowledge to all glass structures and are thus vulnerable to any new glass building.

Ways to Prevent Bird-Window Collisions

There are ways that architects and consumers can prevent these tragic collisions and hopefully eliminate glass as a major threat to bird populations. 

1 | Patterned/Fritted Glass

One popular and often visually appealing way to prevent bird collisions is by installing patterned or fritted glass. Fritted glass is glass printed with a ceramic frit, or dot pattern, making it easily discernible by birds. Plus, fritted glass can lessen glare, reduce cooling costs, and give buildings a distinctive look. This method can be seen in many impressive structures including in buildings by architect Frank Gehry like the IAC headquarters in New York, which “features a fritted-glass curtain wall made up of 1,437 individual panels”. Another impressive and creative structure that uses patterned glass is the Wiel Arets Architects’ Utrecht University Library in the Netherlands, which features glass printed with a fossilized papyrus pattern.  

2 | Opaque or Translucent Glass 

Opaque or translucent glass is glass tinted to appear either slightly see-through (translucent) or not see-through at all (opaque). Depending on the level of transparency, this method can greatly reduce or even eliminate the amount of bird deaths from collisions. Translucent and opaque glass can also reduce your energy bill, increase privacy, create soft and diffused natural light, and improve security for your building. Many designers use opaque and translucent glass for these very reasons. Check some of them out here

3 | Bird Window Safety Film

Window film designed specifically to reduce bird collisions can be easily adhered to existing windows and glass doors. These films are mostly invisible to humans but obvious to birds. This is typically done using narrow, horizontal striped or grid-like patterns that are more visible to birds than people. These films are  easy to find and obtain making them perfect for large projects as well as for residential window use. One example of this type of film used on a larger-scale project is the windows on the Mirage1049, an artist-made building in Switzerland. You can also buy this kind of window film from online retailers like this one and this one

4 | Window Decals

Window decals are a popular, cost effective, and accessible way to reduce bird collisions. Window decals and stickers come in many different forms and essentially work by creating a visual obstacle for the bird. This is particularly useful in shop windows where decals can create an aesthetically pleasing advertisement for what’s inside. You can purchase window decals specifically designed to reduce bird strikes, or you can simply adhere any sticker or decal that you’d like to your window. Keep in mind that you may need to place several stickers around your window in order to ensure that the birds don’t perceive any flyable space. One small sticker will not be sufficient to protect our bird friends. 

5 | UV Coated Glass

Glass coated with UV glaze or patterns is a way to prevent bird collisions without obscuring your view. This is because birds can see into the UV light spectrum while humans cannot. This method is more expensive than many other methods and thus is best used on projects where the focus is to create an unobstructed view. Additionally, while many birds are sensitive to UV light, some species are not and may still be unable to see the glass.

6 | Architectural Features

Adding architectural features that break up windows on large structures or even on your home are a great way to prevent bird collisions. You can do this with netting, grates, shutters, exterior shades, pillars, and more. One great example of architectural features that prevent bird deaths is the impressive building design of the De Young museum in San Francisco, California. The windows on the De Young museum, designed by Herzog & de Moran are either fully or partially covered by a grate-like steel frame. 

7 | Landscaping

While buildings featuring plants either indoors, on the side, or roof, are very visually appealing, they also unfortunately attract birds. Birds will view these landscaping features as part of their environment and attempt to fly through them. It is best that when using these features in your buildings, that you utilize some other kind of barrier, coating, or decal on your windows to prevent bird deaths. This also extends to green roofs, which can be beneficial to birds provided that they don’t have too many glass features nearby. 

8 | Smart Glass

Smart glass glass has the ability to switch from clear to translucent or opaque with the click of a button. It works using “tiny liquid crystals” which are randomly scattered causing the glass to appear opaque. However, once stimulated by an electrical current, these crystals align and make the glass appear see-through. This type of glass is not only high tech, it reduces your heating bills, creates softened daylight, and can prevent birds from flying into your windows. However, do keep in mind that when switched to “clear,” birds will view this window as normal glass. 

9 | Lighting

One big problem for birds is light pollution. Believe it or not, some bird species migrate at night. These birds use the earth’s gravitational pull and natural light to determine where to fly. Unfortunately, artificial light in cities caused by large illuminated buildings can cause birds to veer off course and find themselves in a difficult urban environment. Although most bird collisions occur during the day, switching off lights at night especially in large buildings can prevent birds from finding themselves in a built environment in the first place. 

Glass is an Important Architectural Feature, But We Need to Consider Birds 

Glass is an important architectural feature that brings light into our homes and beautifies our large buildings. But, its impact on bird populations is dire. A bird that has flown thousands of miles and survived harsh weather, predators, and food scarcity can die in an instant when it collides with your windows. Utilizing bird-friendly design can allow you to enjoy the sunshine while keeping our beloved wild birds safe. 

For a complete guide to preventing bird-window collisions follow this link to a handbook for bird-friendly design by the American Bird Conservancy. 


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