Many wild bird species have grown accustomed to living in urban areas, and co-exist well with humans. However, human-built structures such as homes and office buildings injure and kill millions of birds each year. Scientists estimate that one out of every two birds that strike the windows of a business or home die.
The U.S. Fish and Wildlife Service report that plate-glass windows are one of the greatest hazards to urban wild birds, and that approximately one billion birds die as a result of striking them. Anyone who has witnessed a bird striking a window may notice that sometimes the bird merely appears stunned, and is able to fly away on its own moments later. However, experts believe that many of these birds die later as a result of brain injuries or internal bleeding.
Birds come into contact with windows for several reasons. During the day, the glass will reflect nearby trees, or the bird will see potted plants placed on the windowsill inside. In these situations, the glass is invisible to the birds. At night, birds collide with windows either because the building is undetectable and within their flight path, or lights on inside the building lure birds towards them. A third type of collision occurs when territorial birds actively attack their own reflection in the glass, perceiving themselves as a rival. These types of collisions rarely result in fatalities.
There are several ways to prevent birds from colliding with the windows in your home. First, identify windows that are the most dangerous to birds. By standing outside near your feeders or common perches, you will be able to view the windows of your home the way a bird sees them. Windows that reflect trees or sky are likely the main culprits.
Exterior window treatments can help prevent collisions. Consider installing mesh netting or standard window screens on windows that are consistently hit. The netting will break up the reflection of the bird or trees and act as a cushion should a bird strike the window. Other options include external window treatments that allow people inside the home to see out, but make the window seem opaque from the outside. Awnings or other external shutters are also effective in preventing reflections.
Interior window treatments can also be effective. Partially-closed Venetian or vertical blinds can prevent strikes. Decals can be placed on the inside of the window, but these are generally not as useful as they are popular. According to the Cornell Lab of Ornithology, the commonly-used black bird decals are only effective if placed very close together, creating spaces that birds view as too small to pass through.
Other tactics can also prevent birds from striking windows in your home. Re-locate feeders and bird baths to within three feet of a window. Birds are most often killed when they take off at a distance far enough from the window to allow them to build up speed. The closer the feeder is to a window, the less likely the birds will be able to build up enough momentum to injure themselves.
