Bluebird Establishing Territory?

It is interesting to see all of the Eastern Bluebird behavior recently. This morning, the male was pecking on some of the windows of the house and singing outside the back window. I also noticed that he was flying from the tree to the side of the house and could hear some tapping. Then he would fly to another tree, then he would go to the bird house and look inside. When looked outside, I found him sitting on the flood light above the basement door, tapping on it, maybe seeing his reflection. This behavior continued for a few hours this morning. I am still not sure whether or not they are nesting in the box, but I think they might be.