Yesterday I finally saw the baby Bluebirds in their birdhouse.
They stayed inside the birdhouse, and had not fledged yet, although it could be a matter of days now. There were probably two or more baby birds. Their parents were busy as usual.
Keeping guard is essential for the survival of the Bluebirds. Last week, while both parents were away, a House Wren inspected the birdhouse thoroughly, and even went inside for a few seconds. It exited without dragging out any baby, but that was scary. House Wren can kill Bluebirds, adults as well as babies.
I have also seen a Black Crow and a Blue Jay landing on the roof of the birdhouse and bending their necks to look inside through that round hole. I had to shout and shoo them away forcefully. Later in the evening, the male Bluebird dive bombed a Blue Jay that came too close the nest.