Hope you enjoy.  This is nestbox #8.   I whistle to get them to gape.  This helps me see their development.   Always be fast when checking on the young–the less the box is open, the less the potential predators can find them by their smell drifting out of the box via the air.  I have started a few third broods.   The season is going well thus far.   Hope yours is going well, too!