Female bluebirds lay four or five eggs and incubate them for about 2 weeks. The young remain in the nest for an additional 15-20 days and are cared for by both parents. Bluebirds often have two broods in a season. Sometimes, a young bluebird from the first brood will remain in the nest and assist its parents in caring for the second.
If you look closely, you can see the beak of the baby bluebird inside the box waiting patiently for dinner. I wanted to try to capture a photograph of the babies before they flew the coop, but alas, a girl's weekend getaway in Ocean City, Maryland was far more important. Upon returning from an absolute fabulous good time, the box was empty.