Hi. We have a bird box in our garden and a pair of blue tits nested there and we heard the sound of chicks approximately 2 weeks ago and the parents have been coming and going constantly. However in the last 24 hours we can no longer hear any noise from the box and keep seeing the parent birds fly up to the box, poke their heads in and then fly off. We are concerned that something has happened and now are unsure what to do. Any advice would be appreciated. Thanks
As Linda says, absolutely nothing, and it can be hard, but that is the harshness of nature.
You say you've been hearing the chicks for around 2 weeks, is it possible they may have hatched earlier than you first heard them, if so, it could be they've fledged, but that is only a long shot guess.