How many? The answer is 5! Here's a video from bedtime in box 2 yesterday evening:
During the day the youngters are starting to get a bit active, here's one surveying the scenes outdoors through the entrance hole:
Meanwhile, box 3 continue to incubate - hatching should be any day now. Still nobody roosting in box 5 yet, although somebody still visits at odd hours of the day, sits for a while then exits again. Box 1 eggs are completely gone but the adults are still roosting every night so there's hope for next year.