Not a bird but.
While standing at the foot of Twickenham Bridge, just after sunset, I had the impression that something went past my head.
This happened quite a lot.
I set the camera on auto, and pointing it at the sky in random directions kept pressing the shutter.
I only had the built in flash, no real power.
Nothing was visible all the time I took the pictures.
When I got home and looked through all the shots, I had one of this bat.
Very badly focussed, but it is clearly a bat.
I have no idea as to its size, it could have been small and close to the camera, or large and a good distance away.

I shall go back there and try again. I have not got a clue on how to set the camera, there is no way the autofocus will work under these conditions.