Blue tit babies are alive and well, Parents are awol

Hi All

I posted a story a few weeks ago of our bird box successfully being home to a nest of blue tits.

Well the update is that we still see most of the five chicks that hatched and fledged. What we haven't seen for some weeks are the parents.

It's the same story of the nest box of great tits that fledged within a week or so of the blue tits.

The nest box is now the home of the odd snail. Can anyone shed any light on the habits of blue tit or great tit parents when their young fledge? Do they often leave the area?