Blue tits nest

Hi All,,

I need some advice please...... I have Blue tits nesting in the bird box in the garden the last few months.

Baby's have been chirping away and mum and dad have been busy feeding them, until mum (I think) disappeared and it seemed it was only one the last few days.

Until today no sign of either, baby's are still chirping away but still no adults I haven't even seen them about today.

Is there anything I should do or leave well alone?

I've done nothing but than look for advice but nothing to help.

Any help would be gratefully received .

This is the first year of having a nesting box so all very new.

Thank you