Most of us know of Edgar Allen Poe’s poem, "The Raven," in which a raven is unceasingly rapping on the author’s chamber door and window. For Missourians, that rapping in the spring is more likely to be produced by a male northern cardinal. With the breeding season under way, the male birds become adamant to defend their own breeding and nesting territory. They will run off other birds of the same species from the areas that they have claimed as their personal domain. Unfortunately, they often don’t know the difference between another bird and their own reflection in a glass window or door. This can lead to an annoying, relentless tapping or bumping of birds jumping against the glass, sometimes with enough force that the window is left with blood stains.
While male cardinals seem to be the most frequent offenders, I’ve also received reports of bluebirds and crows engaging in similar antics. Sometimes they will pick on the rearview mirrors of cars, and even shiny chrome can produce that image of “another” bird. The key to stopping the behavior is to alter the surface to eliminate the reflection. Smearing liquid soap on the glass may be the easiest way to eliminate the reflection in the glass. Or you could of course tape something over the window or place something in front of it to close off access. I know that you have many other glass surfaces and the worrisome bird may just move on to the next window. I’m not claiming that you will nevermore have the problem, but the tricks above may keep you from pondering weak and weary. The breeding season won’t last more than a few weeks, and by mid-summer the birds should become less defensive.