Birds such as cardinals and robins will dash repeatedly at their reflections in windows. Such actions are usually because the individual bird, usually a male, mistakenly perceives another bird in the reflection of the window. It is territorial behavior for the bird to fight off the “intruder.” This behavior, if continued over a period of weeks or even an entire season, can be annoying to people, but is usually not fatal to the bird.
On the other hand, when a bird strikes a window in free flight, it does so with such velocity that the results are significantly more serious. Sometimes the bird is merely stunned or sustains superficial injuries from which it may recover, but in over half of all recorded incidents the impact results in death. This is most common during spring and fall migration, but can happen at other times of the year.
Birds cannot readily distinguish the presence of a pane of transparent glass from an unobstructed space or passageway. Glass will reflect the most when it is darker inside than it is outside. Many people are unaware that birds are being killed at their windows because the victims are small, frequently fall behind shrubbery, and more often than not are eaten by predators.
Some birds bang into windows because they think they see another bird in their territory, some birds fly into windows because they don't see the window. Other birds fly into windows because predators are chasing them. Whatever the reason, you can make your windows safer.
Here are some steps for making your home windows safe for birds:
1. With the exception of window feeding shelves, feeders and birdbaths should be located a safe distance away from windows. If feeders are close to the window move them to within three feet so if the birds flee the feeders, they have not built up much speed.
2. Window screens are a great deterrent but are not practical for many picture windows.
3. Decals, including cutouts of raptors, and leaded glass decorations are only moderately successful.
4. Vertical exterior tape stripes not more than 10 cm apart are a good deterrent.
5. Interior vertical blinds with the slats half open will cut down on some casualties.
6. Windows can be soaped for camouflage.
7. Shade trees planted outside the window should cut down on some of the reflection.