The bird box has been recently used as an overnight roost for a blue tit. On a couple of occasions we've had two in there. Today was a little different since tit 1 didn't appreciate tit 2 in the same space, as can be seen in the following clip:
It's interesting that in addition to feet and beaks being used as offensive weapons, there are a couple of hooks using a wing...
The posturing at the beginning is also interesting: