It looks as though the eggs in Box3 are starting to hatch.
As far as I can tell, there are two chicks here.
John seems to have realised there is a chick to feed pretty quickly. I wonder how the male finds out when this has happened?
Anyway, here he is with something in his beak . . .
. . . which he passes to Chris.
Chris with what looks like a little green caterpillar, which she proceeds to feed to the chicks.
At the end of the day it looks as though there are three unhatched eggs. I expect that if they are going to hatch, they will do so overnight tonight.