Barn Owls waste no time

Just been out to check a box near Hose (yes, starting to stray outside South Notts now, but then I'm no longer a Notts resident!). It's one of the boxes organised by the recently formed Vale Barn Owl Conservation Group. It was only put up in May (after the start of the breeding season) and a pair have already raised 3 chicks in it. Is this some sort of record I wonder? As can be seen from the pic below, the chicks (yes this is a chick) were close to fledging.
Pete