I'm hoping someone can tell me if this is normal as Ive never seen it before...........

Last night at 9.50pm the baby blue tits in the nest box on our patio wall........Left the nest  !

we have had birds each year in the box for around 15 years and every year they have left  first thing on a lovely  morning!!

As last night was wet and windy I am wondering why they would do this....

I would love to know if someone can enlighten  me ........

Margaret