The bluebirds seem to be following a fairly set schedule. The male arrives between 6:00 and 6:30 a.m., sitting on and in the box, catching bugs, and generally just hanging out. The female arrives with nesting material around 7:30, and they remain busy until about 9:00 when they leave for the day. Previously the male (only) would re-visit in the evening. Today the female also returned for the after-dinner check! There has been no new nest-building activity in the evenings. They just seem to drop by to check things out, then they leave for the night.
I opened the house today to check their progress, hoping to snap a picture. A gust of wind made me sorry I opened it, as the whole “nest” (if you could call it that yet, mainly just a small tangle of dried weeds) almost blew away entirely! Hence, no pictures today!