|Sparrowhawk (Accipiter nisus)|
I then realised it wasn't a pigeon at all but a male Sparrowhawk.
The collision on my window had been a failed attack on one of my garden birds.
The hawk was a real beauty and luckily stayed around long enough for me to grab my camera and get a couple of record shots taken through the window.
I couldn't have wished for a better birthday present.