By Dr. Becker
It's been estimated that up to 100 million birds die each year in the U.S. from crashing into windows. A report from Oklahoma State University in Stillwater suggested, however, that the actual number of bird-window collisions may actually be much higher.
In a review of 23 published studies, researchers estimated that between 365 million and 988 million birds are killed each year in the U.S. due to collisions with buildings (and particularly with the windows).1
Most of the bird fatalities occurred not at high-rise buildings such as skyscrapers but at low-rise buildings (56 percent) and residences (44 percent). Several species were identified as highly vulnerable to building collisions, including:
✓ Golden-winged warbler
✓ Painted bunting
✓ Canada warbler
✓ Wood thrush
✓ Kentucky warbler
✓ Worm-eating warbler
✓ White-throated sparrows
✓ Ruby-throated hummingbirds
✓ Dark-eyed juncos
Why Do Birds Collide With Glass?
Quite simply, birds hit glass because they can't see it. People can't see glass either, but if you accidentally walk into an unmarked glass door, the only thing you're likely to hurt is your pride.
Birds, however, are so small in size and fly at such high rates of speed that they're often killed on impact or experience life-threatening injuries.
Birds can learn to avoid specific pieces of glass. For instance, if the glass is clearly marked for a short period, birds in zoo exhibits will learn to avoid glass walls and windows. In the wild, birds may also learn to avoid glass areas once they know they exist.2
However, it's not thought that birds are able to use environmental clues to generalize about when a glass window or door may be present. In addition, birds trying to escape a predator or take cover quickly may be particularly likely to accidently fly into a window.
The American Bird Conservancy further pointed out why glass poses a triple threat to birds:3
1. Glass may reflect vegetation or landscape, attracting birds
2. Green habitat inside buildings with large windowed areas may lure birds to the glass
3. Birds can see through glass corners or narrow glass passages on buildings, and die trying to fly through
Top 7 Ways to Reduce Bird-Window Collisions
You've probably heard a bird bang into your home's windows at one point or another. In fact, it's estimated that a few birds die from window collisions at each U.S. home every year.4 Making simple changes can go a long way toward reducing this risk.5
Many of these options involve methods for making see-through windows more visible to birds. While ideally you would do this to all of your windows, you can also apply it only to select problem windows or during times of year when more birds are present (such as during spring and fall migration).
If you're not sure which windows to prioritize, go outside and examine your windows from a bird's point of view. Does the window reflect trees or sky? Does the window provide a clear view into your home?
Does it have another window on the opposite side of the house, giving the appearance of an open passageway? If yes, these are windows that should be bird-proofed.
1. Move Your Bird Feeders
Home windows near bird feeders are those most often struck by birds. There are two strategies you can try here. One is moving the feeder far away from your windows, so they're less likely to come in contact with the glass in their flight path.
The other option is to move the bird feeder very close to your windows. This way, the bird may not view the window route as an effective getaway path and, if he should collide with it, hopefully will not have built up enough speed to result in serious injury.
2. Add Screens
Screens on the outside of your windows will greatly reduce bird collisions. Mullions (those vertical bars that separate panes of glass on your windows) may also help.
If you don't have screens, you can put up netting on your problem windows and even tie strips of rags or yarn to it, to make the window even more visible.
3. Fake Snow, Bar Soap or Vegetable Oil
A thin coating of fake snow or vegetable oil will make your window non-reflective and less attractive to birds.
Plastic wrap also works well for this purpose, however, most people won't find these options practical for most large windows. One of the least noticeable, virtually free options is to draw streaks using a bar of soap.
4. Mylar Balloons or Reflective Streamers
String up a few of these shiny metallic-like balloons or streamers near or in front of your windows and it will likely scare birds away. A longer-lasting option is to wrap cardboard tubes in bright Mylar and hang the tubes in front of your windows. My dad used a "feather boa" to effectively prevent window strikes on a patio door.
5. CDs, Plastic Strips and Decals
Other options for making birds fly away from (instead of toward) your windows include hanging old CDs in front of them or cutting up a plastic garbage bag and hanging the strips from your window.
Decals, including owl or hawk silhouettes, may also be useful (although there's some debate that birds may grow used to them after a while, reducing their effectiveness). There are also decals designed to look like spider webs or other designs meant to reduce bird-window collisions.
6. Tree Branches
If you're looking for a more natural option, stringing up a tree branch strategically in front of a problem window may deter birds without ruining your view.
7. Vertical or Horizontal Stripes
Use tape or tempera paint (ideally in white) to add vertical stripes spaced 4 inches apart or horizontal stripes placed 2 inches apart. The stripes should be at least one-quarter-inch wide. This pattern is known to deter birds.
Six Additional Options for Making Your Windows Bird-Friendly
The American Bird Conservatory (ABC) has compiled a number of options that homeowners can use to make their windows bird-friendly. These innovative products include:6
- ABC BirdTape, translucent tape that lets light in (but does partially obscure your view). The tape lasts four years.
- Acopian BirdSavers, which are see-through curtains designed to deter birds.
- Collidescape, which is a window film that appears solid from the outside but allows you to see through it from the inside.
- Feather Friendly, adhesive dots that are applied to the outside of your windows.
- Solyx Bird-Safety Film, an external window film that comes in horizontal or vertical stripes. This may have to be installed professionally.
- Window Alert, UV-reflecting decals that are visible to birds but only minimally visible to people. It's recommended these be replaced every 12 to 18 months.
According to the ABC, these products have been shown in controlled studies to significantly reduce bird collisions. On a larger commercial scale, a number of glass products are now available to building designers interested in creating bird-friendly designs. As the importance of protecting these vulnerable species becomes increasingly apparent, perhaps one day, every new home and building will be built with glass designed to protect birds from collisions.