BACKYARD BIRDS FAQ
w/ Katie Andersen
Birds Attacking Windows

The first call comes in late February and it usually goes something like this: "There's a cardinal and he seems to be trying to get into my house. He keeps flying at the window and pecking it over and over." The number of these calls increase in March and April, and reports include other species engaging in this behavior. So, what's going on?

This behavior coincides with the start of nesting season. Testosterone levels are rising as winter flocks begin to break up and individual birds start to establish their territories. These territories are defined and defended through the use of song, displays, and sometimes aggressive chases and attacks. Often, a bird may see its reflection in a window and mistake it for a rival bird. When sound and posturing does not drive this 'invading bird' away, the resident bird ends up attacking his reflection. Typically, the interloper would be chased off by the resident. Since this is a reflection, however, it does not go away. The continued presence of the ‘interloper' (reflection in this case) triggers repeated attacks.

Male birds are usually the ones attacking their reflections, although in species where both male and female defend the territory, like Northern Cardinals, the females may attack as well. Cardinals and robins are the most common culprits of window attacks in our area, although we've had reports of chickadees, titmice, song sparrows, and bluebirds attacking their reflections. Besides windows, birds may attack the side-view mirrors of cars and gazing balls– anything that creates a reflection!

To prevent birds from attacking their reflections, you have to break up the reflection on the outside of the window. Options include covering the outside of the window or soaping up the outside of the window so the bird no longer sees its reflection. Window screening over the outside of the window works quite well. Hanging multiple metallic streamers that flutter in front of the window works in some cases. There is low to moderate success of deterring birds by putting rubber snakes on the outside window ledge. If a bird has a favored perch they use to view their ‘enemy’, you can try making that inaccessible to them.

Window decals, which are designed to prevent window strikes by birds, do not deter birds from attacking their reflections.

Bird attacks on windows generally drop once there are young on the nest to care for. Unmated males can persist in their attacks for months at a time. Birds may also change which window they attack as the sun shifts in the sky throughout spring and summer, changing which windows have reflections.