The pale section at the bottom of the photo is the window sill!
This morning I noticed what looked like a bird pellet lying on the path under my aerials. At first I though it might be from an owl but examination showed it seems to be made up of seed husks and small pieces of stone.
There's that 5p again (we pensioners can't afford 10p pieces) The 5p being about 18mm across.
Research on the web brings me to the conclusion that it is from a Crow or Rook.
Writing of Rooks: One was sat on the large fat ball feeder yesterday but flew off before I could photograph the evidence. It didn't go far, just to a tree where it could watch and wait for another opportunity.
After a short wait, me still with camera in hand, it decided it was safe to return.
Unfortunately it spotted me and veered off disappearing to pastures new.
Never mind - there will be another day and I know it will be back in the not too distant future.
Nest Box Update
Everything seems to have come to a full stop for the moment. The contents have not changed for over 48 hours. This has happened before so I am not too worried yet.