This behavior is most commonly seen in robins, cardinals and even goldfinches. These birds are quite territorial and during the breeding season when they notice their reflection in a window, mirror, chrome bumper or similar shiny surface, they assume it is a rival bird and will attack the reflection in an attempt to drive it away. They may fly against the reflection, peck at it or beat it with their wings, and while these actions do not generally cause severe injuries, they can lead to exhaustion that will make the bird more vulnerable to disease, malnutrition and predators. The solution to this is to break up the reflection so the bird is not threatened by a perceived rival. There are a number of ways to do this:
- Place decals on the outside surface of the window
- Place tape, pieces of paper or plastic in an irregular pattern on the window
- Soap the outside surface of the window so that it leaves streaks (it may not be pretty, but it might be less annoying than a bird constantly pecking at your glass!)
- Place a screen outside the window – 2 or 3 inches away
- Close curtains or blinds – this makes it more difficult for the bird to see reflections particularly if they are light colored
- Hang strips of Mylar balloon, recording tape or other shiny material across the window on the outside
- Turn your windows into one-way glass! Putting a film over your window that allows people to see out, but nothing to see in will help. The window will look opaque from the birds perspective.
This behavior is at its peak during nesting season – once the young have fledged it should stop!
Here are some helpful resources: