This morning, one of the pair in box 3, presumably the male, came in with more feathers for the nest:
We were expecting the normal morning changeover, but the partner on the nest won't budge so he climbs right over her and starts putting the feathers at the back. She lends a bit of help at this stage, but still won't budge:
in the end he gives up, leaving her on the nest. You can just get a glimpse of the two eggs in this video:
Finally, he leaves the box again. The bird on the nest appears to be straining a bit. Is it about to lay another egg and is this why it didn't want to move off the nest?
Hopefully more news later.