Your House Is Killing Birds, Here's What to Do

Each year in the United States, up to one billion birds die after colliding with glass. In many areas, it’s a two-pronged problem: Light pollution attracts and disorients migratory birds, most of which travel at night; in the morning, birds collide with reflective glass that hasn’t been made bird-friendly.

While many people assume this is a city problem—what with all those city lights and gleaming glass spires—a landmark 2014 study on bird collisions reached a surprising conclusion. The authors estimate that of those birds killed annually by building collisions, roughly 44% of those deaths occurred at residences, 56% at low-rises, and less than 1% at high-rises. Residences were defined as one to three stories tall, low-rises as four to 11 stories tall, and high-rise buildings as 12 stories or higher.

High-Rises Versus Low-Rises and Houses

Given the attention given to bird collisions in cities—full disclosure: I’ve personally documented over 1,300 migratory songbird collisions in New York City since the fall of 2020!—it's easy to direct our focus toward urban centers. And how bad could houses be?

Well, each individual residence or low-rise building may kill just a handful of birds each year, but there are so many of these buildings that the full toll is devastating. 

As the 2014 study authors write: “... a large proportion of all mortality occurs at structures that kill small numbers of birds on a per-building basis but collectively constitute a high percentage of all buildings.”

They go on to note that this finding suggests that “achieving a large overall reduction in mortality will require mitigation measures to be applied across a large number of structures.”

Often when I talk about my experience of rescuing and recovering window-collision victims in the city, people tell me the sad stories of a bird here or there hitting their windows at their home or low-rise apartment. This is it. This is what is killing millions of birds a year. Finding a few handfuls of birds a year at home may not seem significant, but it is.

In a way, skyscrapers are an easier fix. While overall, they kill fewer birds, each building with a bird problem has a much higher mortality rate than residences and low-rises overall. Meaning that mitigating the glass at the most lethal high-rises could have a big impact. 

But reducing mortality rates at residences remains of critical importance. Because even if every problematic high-rise were made bird-friendly, we’d still have the rest of the buildings continuing to kill birds. If we have 142 million houses in the U.S., and each one kills just five birds a year, that’s more than 700 million birds. You can see how this is a problem.

Why Do Bird-Window Collisions Matter?

A 2019 study published in Science found that since 1970, bird populations in the United States and Canada declined by 29%, or almost 3 billion birds, “signaling a widespread ecological crisis.” 

“Multiple, independent lines of evidence show a massive reduction in the abundance of birds,” said Ken Rosenberg, the study’s lead author and a senior scientist at the Cornell Lab of Ornithology and American Bird Conservancy. “We expected to see continuing declines of threatened species. But for the first time, the results also showed pervasive losses among common birds across all habitats, including backyard birds.”

Of course, this is a blow to bird lovers … and anyone who cares about nature and wildlife in general. But it goes so far beyond that. Birds provide an extraordinary array of ecosystem services, from seeding forests and scavenging waste to pest control. (Did you know that globally, birds eat 400 to 500 million metric tonnes of insects per year? Their value to agriculture runs in the billions of dollars.) Birds are vital to the mechanics of life on Earth.

The Problem With Birds and Glass

Birds don’t understand the concept of windows–and when they see habitat and sky reflected in the glass, they fly full-speed into it. In other areas, they may be able to see through the glass and try to reach what they see beyond, which could be indoor plants or another window with the outdoors beyond it. Either way, colliding with glass is often instantly deadly, thanks to head trauma and internal injuries.

If a bird does not die upon impact, it may remain stunned on the ground and become the plaything of a cat or the meal of a predator. If a bird does eventually recover from the initial impact, it may fly off to a tree. Unfortunately, up to 74% of birds will succumb later to their injuries if not treated by a wildlife rehabilitator. Of the window-collision birds I find in New York City, about 30% of the birds I find survive the initial collision—even though I get those rescues to the wildlife clinic as soon as I can, only about half of those ones survive. 

If You Have Bird Feeders or Native Plants

If you use bird feeders or have native plants that are attractive to birds, it is your responsibility not to kill the birds that you are actively attracting to your home. 

Houses with bird feeders near windows have significantly more collisions; current advice is to keep birders three feet or closer to a window (or beyond 30 feet) to reduce window collisions. But unless you treat your windows with one of the methods below, they will still be deadly. 

Make Your Windows Bird-Friendly

It might be that you have one or two windows with just the right dynamics to make them lethal to birds; maybe you have more. Regardless, there are many, many things you can do to make them safe for our feathered friends. The main idea is to break up the reflection the birds are flying into and/or alert them that glass is there and they can’t fly through it.

The American Bird Conservancy has a fantastic database of products and is a comprehensive resource for ways to prevent birds from colliding with your windows. People are attached to their big picture windows with unobstructed views; most of these will maintain the view. Here are a few options.

Grid Patterns

The glass needs a pattern on the outside with spaces no more than 2 inches between elements, for example, a grid made of dots. This can be a residential decal product or even just paint that you apply yourself. Feather Friendly makes a great DIY decal, and it’s highly effective. 

Stripes and Horizontal Patterns

A horizontal pattern will work as well, with the stripes being no farther than two inches apart. Another horizontal product is Acopian BirdSavers, which are basically cords that hang in front of your window. These can be purchased, or you can easily make them yourself (see video above). ABC BirdTape is another great option that is easy to install yourself.

Temporary Painted Patterns

Painting patterns with tempera on the outside of problematic windows is a fun approach. It's cheap and the paint can be washed away during off-season, as long as your regular birds are not colliding. You can even just recreate a dot pattern with tempera paint, just remember to keep dots no more than two inches apart.

Screens

Window screens do double duty for keeping insects out and reducing collisions by adding a visual deterrent and also providing a softer surface for a bird to bounce against.

Let Your Windows Be Dirty

Leaving your windows dirty (or making them dirty with soap) actually works really well to prevent collisions! And how nice to have an excuse to not have to clean them ... right?

For more on making your windows safe for birds, see NYC Audubon's guide to bird-friendly windows.

What Doesn't Work to Prevent Bird Collisions

Decals of birds of prey are not effective unless they are placed no more than two inches apart from each other. 

Research has shown the following collision-deterrent strategies to be mostly or entirely ineffective:

• Silhouette decals of any shape unless multiple decals are applied in a pattern two inches apart
• UV decals or liquid, which are not visible to all bird species and are least visible early in the morning, when most collisions occur
• Ribbons or string spaced too far apart
• Treatments applied to the inside of windows
• Noise deterrents
• Plastic owls
  

Dim Your Interior and Exterior Lights During Peak Seasons

Most migrating birds travel at night, and many use visual clues to navigate–including stars, the moon, and the setting/rising sun. Additionally, like moths (although scientists don’t know exactly why), birds are drawn to light. Artificial lights confuse them, often leading them to become disoriented and exhausted and use up valuable resources they need for the arduous task of migration. Dimming (or better yet, turning off) lights during peak migration can do a world of good. Spring migration peaks from the third week of April to mid-May; fall migration is longer, running from late August to mid-November. You can use the amazing tools at the Cornell Lab of Ornithology’s BirdCast to see migration forecasts for your area.

Even if you can’t turn off all of your lights, focus on dimming exterior lights. Pay attention to floodlights that face upwards and lights that illuminate broad swaths. Adding motion sensors to these lights is a great way to reduce light pollution without compromising the need for illumination when someone is present.

Check the International Dark Sky Association, which has more information on outdoor lighting basics.

Keep Cats Indoors

And while we are at it, outdoor cats are an invasive species that kill up to three billion birds a year in the U.S., more than any other cause, even windows. Indoor cats live longer, healthier lives when they are kept indoors—a fact with science to back it up. When cats are allowed to roam outside, they run a high risk of picking up pathogens and facing threats from vehicle collisions, being hunted by other predators, and maybe even ingesting poison put out for rats or other animals. For anyone who wants to share their outdoor space with cats, consider a catio or harness.

If You Find a Stunned or Injured Bird

If you find a bird that doesn't fly away when you approach, something is likely wrong. Especially if it is near a window. If it is hunched, has its eyes closed or squinting, is looking up toward the sky, has its mouth open, or is panting, it is definitely in distress and needs care. Any bird that has collided with a window needs to be seen by a licensed wildlife rehabilitator. (Again, to find a wildlife rehabber near you, use the Animal Help Now wildlife rehab finder.)

If you can pick up the bird, this is not the time for photos and a Disney princess moment—sorry to be a sourpuss! But a window-collision bird is already very stressed, and interaction with a predator, no matter how softly the human may be cooing, significantly compounds the stress. Do not pet it, do not talk to it—it needs a dark, quiet place, stat. A brown paper bag with a binder clip works perfectly, or a covered box. Do not give it food or water.

For much more on what to do if you find an injured bird, see: How Should I Care for a Stunned Bird After It Flies Into a Window?