Expert: Roger Lederer - 3/14/2007

Question
We have a chaffinch that keeps tapping on the outside of our windows, all day and every day, apart from winter months. He also flys up to the top of the window to tap. He is not fussy about which window, as he appears to do it on all the windows at some stage, but can tell his favourite by the marks he leaves on the glass with his beak pecking, and it is a different favourite window to last years. Is this usual? and what is the reason he is doing it?

Answer
Chaffinches and many other birds are territorial and when they establish territories in the
spring they become aggressive and chase off intruders. Unfortunately, they don't distinguish between their own reflection in a window (or car mirror) and try to chase that off. The solution to the problem is to eliminate the reflection. Misting the outside of the window with a very weak detergent or soda solution will eliminate the reflection but will also impair visibility for you. Awnings, eave extensions, and window screens will eliminate all reflection and stop the collision problem. Hanging ornaments may also help. But they will stop when nesting begins. Roger Lederer at Ornithology.com