Bird-window collisions can be fatal for birds, with up to 100 million birds estimated to be killed each year due to this issue. Small songbirds are the most common victims of these collisions, which often result in severe internal injuries and death. Birds collide with windows because they see the reflection of the landscape on the glass surface and do not realize that there is a hard, transparent surface between them and the apparent open space. This problem is exacerbated when birds are fleeing predators and panic, causing them to fly into windows.
During the breeding season, birds may also attack windows due to their urge to defend their territories. This behavior is typically more of a nuisance than a lethal threat, and it is caused by birds mistaking their own reflection for an intruding male.
If you come across a bird that has been dazed from a window collision, you should place it in a dark container with a lid, such as a shoebox, and leave it somewhere warm and quiet, out of reach of pets and other predators. Do not try to give it food and water, and resist handling it as much as possible. The darkness will calm the bird while it revives, which should occur within a few minutes, unless it is seriously injured. Release it outside as soon as it appears awake and alert. If the bird does not recover in a couple of hours, you should take it to a veterinarian or wildlife rehabilitator.
There are several ways to make your windows safer for birds. Start by identifying which window is the problem, as large picture windows are usually the worst culprits. Go outside near your feeders and look at your windows from a bird’s point of view. If you see branches or sky reflected in the glass when you look at your window, the birds can as well. If there is another window on the opposite wall of the house, it may give birds the illusion of a fly-through passage to the habitat outside.
To make your windows safer, you can relocate feeders and other attractants to new locations. Bird strikes usually occur at particular windows, so moving feeders farther away from them may solve the problem entirely. You can also try placing your feeders much closer to the glass. If a feeder is just a foot or two from a window, birds may still fly into it, but not with enough force to injure themselves.
Avoid apparent visual tunnels by keeping a shade drawn or a door closed, or by altering the lighting inside the house. You can also make the glass less transparent by taping paper or cardboard on the inside of the panes. Unsightly, but a good temporary measure until you can find a better solution.
Break up window reflections by sticking objects to the outside of the glass. Black plastic silhouettes of a falcon, hawk, or owl sometimes work, not because they look like predators but because they disrupt the window’s reflectivity. Semi-transparent stickers can also do the job. Sheets of plastic food wrap may work too.
Try spraying fake Christmas snow on the outside of the window, or drawing streaks across it with bar soap. Again, the goal is to break up external reflections. For a more natural look, attach dead tree branches in front of your window. They may cause the birds to slow down and avoid the window as they fly toward it. You can arrange the branches so they do not obscure your view.
Hang lightweight, shiny items in front of the window so they move in the breeze and dissuade birds from approaching. Try strips of shiny, reflective plastic, old aluminum pie plates, or unwanted compact discs. Reduce the amount of light reaching a problem window by planting shade trees close to it. This will help prevent reflections. However, it will also obstruct your view. Trees take time to grow, so consider shading your window with an awning instead. Either one may help birds by reducing the amount of sky reflected in windows.
You can also place netting over the window. It provides a physical barrier to birds flying into the glass, yet will not obstruct your view. Small-mesh netting is best—5/8″ in diameter—so if birds do fly into it, they will bounce off unharmed. You can mount the netting on a frame, such as a storm-window frame, for easy installation and removal. You could also try insect screening material.
If you are installing new windows, ask your contractor to position them slightly off vertical, facing downwards. Then the outer window surface will reflect the ground rather than the sky and trees, but will not affect your view from inside the house. However, be aware that this may void your warranty. Your contractor or architect may have other useful ideas about how to minimize habitat reflection in your windows.