Why does the male always go into the other end empty box before going to the box with the nest?
So the male selects the nesting site and calls the female in to approve it. If she approves then she starts making the nest and he basically stands around acting as her security while she does.
The male spent the winter roosting in box three on the closest nights. He then selected box three to nest in and invited the female in to approve it
She initially started building the nest in box three. But after a couple of days she saw that box one was bigger inside and also had a narrower hole to prevent larger birds from attacking them.
So she threw all the nesting material out of box three and moved in to box one instead. That is where they stayed and layed the eggs.
So the male has always favoured box three. He's definitely got himself in to a routine of entering box three before moving to box one when bringing food.
It could be that either he's confused and forgot they moved.
Or it could be a tactic that a lot of birds employ which is never flying directly to the nest box but zig zagging across the garden as a decoy and only flying in to the nest when they are sure no preditors are watching so as not to reveal the location of the nest