The perfect bluetit box

Just noticed this thread which is very interesting, I also wonder Matt what it is that makes her choose a box over another, I wonder if it is just a feeling she gets that it just feels right, we will never know really. All my boxes are different and all got a good going over but no takers despite nest wriggles and showing great interest. What I found interesting this year was the female that had been checking the tree box out for months and doing wriggles in and I was 99.9% sure she had chosen it, she brought moss inside wriggled it around then went back down for more moss then was gob smacked to see her fly off else where, so after bringing moss inside and doing a nest wriggle it didnt suit her. Perhaps each female have their own preferences.
One thing I do know the leds dont bother them at all, at least dont appear to. Next year is going to be interesting for sure!