Surreptitious supervision

We're all at it...

Every time someone goes to the garage (an extra fridge in there serves as an overflow to the one in the kitchen), they check, with a sideways glance, on the blackbird's nest in the vine.  We therefore know that both parents are feeding the chicks but that often there is no adult in attendance (presumably they are very busy).

We are desperate not to disturb them but really keen to know how the chicks are doing.