Keeping birds safe from windows during daytime

Spring bird migration is now almost over, but don’t be fooled – although in our previous installment, we focused on keeping migrating birds safe from the deadly combination of urban night lights and windows, those same windows pose just as much of a threat to our resident and breeding birds now as they did to our migrant birds just weeks ago. Collision mortality is the second-largest anthropogenic source of avian mortality (after predation by free-ranging cats) in North America, with hundreds of millions of birds dying in bird-building collisions annually. That statistic includes both nocturnally migrating birds lured into the dangerous urban environment by night lights and diurnally active resident, breeding, and wintering birds that collide with windows. If you’ve ever heard the sickening sound of a bird slamming against your window, you’ve experienced the latter phenomenon, which may be just as large in scale, if not larger, than the former. So what causes birds to fatally collide with windows in broad daylight, and what can we do about it?

The answers to both are quite simple – birds fly into our windows because they don’t see them, and in order to save them from collision, we need to make our windows visible to birds or physically prevent birds from colliding.

Let’s explore in greater detail. There are two specific situations in which a bird may collide with a window diurnally. Firstly, the bird may see the reflection of features of the surrounding environment, such as vegetation or open sky, in the window, and depending on the lighting, this reflection may look “convincing” enough to prompt the bird to attempt to fly towards it. Secondly, even in the absence of a reflection, a bird may fly into a window in an attempt to access appealing features of the interior of the building such as houseplants. In either case, the effect is the same – the bird fails to recognize the existence of a solid glass barrier, fatally colliding with it. It is important to note that even small windows can pose a great threat – almost no window, unless well-marked (more on this momentarily), is safe.

Some 44% of the nearly 1 billion estimated annual bird-building collisions occur at residences, according to an analysis from 2014. While this may seem to present a daunting challenge, it is in fact a source of great opportunity, as it means that unlike with many other pressing environmental issues, bird-window collisions are a tragedy that we, as individual residents, can easily help ameliorate. How? Intuitively, there are two solutions – either make sure the bird can see the window and steer clear of it, or physically prevent the bird from reaching the window. Both of these solutions are quite easy to implement, although the former is by far the more popular. Below, we will review a number of general approaches to implementing the solutions as well as specific well-established products that can accomplish them.

Part 1: Making Windows Visible

Research has shown that in order to make a transparent window visible for birds, markings must be present on the window, spaced at intervals of no more than 4 inches apart vertically and 2 inches apart horizontally. While this may sound like a significant obstruction to a clear view out the window, there are in fact an array of tried-and-tested methods to implement these markings in a highly unobtrusive manner, barely altering the quality of view whatsoever. Here, four of the best of these methods are presented.

Option 1: Decals

Small decals placed no more than 4 inches apart vertically and 2 inches apart horizontally are a simple and common way to make a window visible to birds. Don’t like the extent to which decals obstruct the view? There’s a simple solution – some companies, such as windowalert.com, sell transparent decals coated in ultraviolet paint, ensuring that while they remain almost imperceptible to us, they stand out in brilliant color to the avian eye.

Option 2: Hanging strips

One of the most elegant and unobtrusive ways to alert birds to the presence of a window is to hang thin vertical cords of threads from the top of the window, spaced two inches apart horizontally from one another. Birdsavers.com not only provides DIY instructions for making these strips and installing them, but also sells pre-made, custom-made strips if you’d rather have a ready-to-install product that works just as well.

Option 3: Marked tape

One of the most innovative and effective solutions to window collisions, commonly used both by large corporate buildings and by individual residents, is pasting strips of transparent tape with small dots on the window such that the dots are located 4 inches apart vertically and 2 inches apart horizontally. The result is an effective way of warning birds about the window while causing virtually no change to the quality of the view. Featherfriendly.com sells easily-installed, ready-made rolls of this tape for windows ranging from small to very large.

Option 4: One-way transparent tape.

One of the most surefire ways to guarantee both that birds are well-aware of a window’s presence and that the view from the interior is completely unobstructed is to install one-way transparent tape. Some companies, such as CollidEscape, sell tape that, when pasted on your window, is transparent from the inside but opaque on the outside – a perfect way to ward off any potential collisions.

Part 2: Physically separating bird from window

An equally effective way to prevent bird-window collisions is to place a gentle physical barrier between the outside environment and the hard window glass. Placing a mesh, net, or other soft surface in front of a window creates a “bird screen” that not only alerts birds to the presence of the window, but also provides a soft surface off which they can bounce. A simple mesh or mosquito net will do, but for those seeking a less visually obtrusive solution, birdscreen.com custom-makes easy-to-install, transparent, and gentle screens for windows of any size.

The good news is that as long as you are correctly following the basic principles – 4 inches apart vertically and 2 inches apart horizontally, or providing a soft barrier between bird and window – a robust scientific literature almost guarantees that your window will be much safer for birds – both migratory and resident. If all of us take just one of the wide array of simple steps that puts these principles into action, together, we can make our urban landscapes a safer place for birds all year long.