This time of year there are a lot of young birds who have to learn to avoid many first-time hazards - some don't survive to learn. The ones that do don't tend to fly into windows again.

There are many factors and many have been mentioned. One that hasn't is that along with high numbers of young songbirds there are also high numbers of birds that prey on them. It could be their attempts to avoid being caught in an arial chase that is resulting in them speeding into your window.

It reminds me of a really unusual event in involving the European Blackbird. We were in a crowd in Cornwall. There was the sound of birds squabbling above our heads and we all looked up startled and I gained the impression of a bird flying on. But falling at our feet was the very freshly dead body of a blackbird - but without a head.

I puzzled over this and had a good look at the area on our return. I could not find the head but I did notice a telephone wire across the path at the point where the bird fell. I suspect what happened was that in either a territorial dispute or in evading a predator - the poor bird had flown (at speed) into this overhead cable, the head went off in one direction and the body fell at our feet.