Bird Strikes and Windows

Windows Can Be Deadly For Birds

Ornithologists estimate that up to 100 million birds are killed each year by collisions with windows. These collisions usually involve small songbirds, such as finches, that may fall unnoticed to the ground. Sometimes the birds are merely stunned and recover in a few moments. Often, though, window hits lead to severe internal injuries and death.

Why Birds Collide With Windows

Birds cannot perceive the glass, seeing only a clear passage. In addition, birds hit windows because they see the landscape — trees, sky, clouds — reflected on the glass surface but do not realize that a hard, transparent surface lies between them and that apparent open space. Panicking birds, fleeing for cover to escape predators, are even more likely to fly into windows.

A related problem, which is more annoying than lethal, is when birds attack windows, typically in Spring or Fall, due to a bird’s urge to defend breeding territories. The male cardinal pecking at your window is fighting what he perceives as an intruding male; he doesn’t understand that it’s his own reflection. This territorial reaction can be so strong that the bird may exhaust himself, but doesn’t usually result in fatal injury. This behavior lessens as territories are worked out, the sun changes position in the sky and the glare on the windows lessens.

How to Help a Window Collision Victim

If you find a bird dazed from a window hit, 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. If the weather is extremely cold, you may need to take it inside. 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 doesn’t recover in a couple of hours, you should take it to a veterinarian or wildlife rehabilitator. Remember that, technically, it is illegal to handle a migratory bird without a permit. 

Safeguarding Your Windows For Birds

Window strikes are something you should be aware of and try to prevent, especially if you feed wild birds in your backyard. Start by identifying which window is the problem; 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. Can you see through the window into the house? If so, the birds can too. Is there another window on the opposite wall of the house? It may give birds the illusion of a fly-through passage to the habitat outside.

Ideas to Make Your Windows Safer

• Relocate feeders, birdbaths 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. Bright windows on the opposite wall from your picture window may give the illusion of a visual tunnel through which birds may try to fly. Try making one window less transparent 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 external reflections with stickers or plastic wrap 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. A statue of an owl or raptor nearby also helps to keep the birds away from the windows. Semi-transparent stickers can also do the job and some have decorative bird shapes or look like spider webs. These should be spaced about every four inches apart from each other. Sheets of plastic food wrap or wax paper may work too.
• Disrupt reflections with spray-on materials or soap. 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.
• Attach branches in front of windows. 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 don’t obscure your view.
• Attach hanging objects to deter birds, such as 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 (hung a few inches apart), old aluminum pie plates or unwanted compact discs.
• Reduce reflections with trees or awnings. Curb 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.
• Cover windows with netting. It provides a physical barrier to birds flying into the glass, yet won’t obstruct your view. The Cornell Lab of Ornithology installed crop netting—the kind used to keep birds away from fruit trees—in front of a large picture window next to the bird-feeding garden in the original building. The result? No more dead and injured birds. Small-mesh netting is best—the ones used at Cornell were 5/8″ (1.6 cm) in diameter—so if birds do fly into it they won’t get their heads or bodies entangled but 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.
• Install windows tilting downward. Ask your contractor to position newly-installed windows slightly off center vertically, facing downward. The outer window surface will then reflect the ground rather than the sky and trees, but won’t affect your view from inside the house. Be aware, though, that this may void your warranty. Your contractor or architect may have other useful ideas about how to minimize habitat reflection in your windows.
• Don’t wash your windows. The easiest and least expensive way to keep the reflective glare off windows is to leave them dirty.

Sources:

http://www.birds.cornell.edu/AllAboutBirds/notes/index_html

http://www.birds.cornell.edu/AllAboutBirds/attracting/challenges/window_collisions