Clearly there is a pair of bluetits interested in Box1. Here they are doing the ritual swap-over dance.
Just in case you thought we had forgotten we had two other boxes, here are a few shots from Box1 and Box2
This is Box2. This time we have a female doing a nesting wriggle.
I suppose this means she has a male partner hanging about somewhere - or do young females start doing this sort of thing off their own bat these days?