I saw the same aggressive behavior from a Great tit a couple of years ago in my garden. I had put some solar powered garden lights around the garden so I could watch the Hedgehogs at night without disturbing them. During the day I noticed a Great tit continually fly down to one of the lights and start to peck at it. The light had a chrome surround on its side and I realised that the Great tit was attacking its own reflection.

Unfortunately both the Great tit and myself failed to see next doors cat which ran in and caught the bird just as it was launching another attack on the light.

Fred, Great Tits have been known to attack their own reflections, for example, car door mirrors.

Is your Great Tit being aggressive at all?? It doesn't sound like it from what you have said, but they can be quite aggressive and teritorial towards the breeding season and therefore the reflection to the Great Tit could be a rival to it's territory.

Not all Great Tits do this of course, but this sort of behaviour does get reported from time to time.

a great tit constantly lands on my back door handle and pecks the pvc 2 or 3 times then flies into a bush.seconds later he is back again doing it again.in fact hes doing it right now! in tyhe last week or so he has done it hundreds of times.its not hunger because there is suet and peanuts in the tree.just wondered if anyone else has seen this type of pointless behaviour.