To update the previous post, the bluebird pair now officially has a second brood on the way; this time with 4 eggs.
After some more research, I found out that bluebirds only lay 1 egg per day, so maybe there will be more. I was also apparently using the wrong terminology for baby birds: they are nestlings, and at one point that I am not quite sure of, they turn into fledglings.
Recent flight patterns
The female generally has remained in the nestbox. If she does go out, she will only leave for a few minutes at a time. The male is out for longer periods gathering food for the female and himself. This is a good indication that she has started incubation.
Once all of the eggs have been laid, then the female will start incubating (so that they all hatch at the same time).
Incubation takes approximately 14 days, so stay tuned for a second brood arriving soon. That’s all for now.