The babies have fledged on May 14, and in the last few days, the parents have started to bring them back to the yard to introduce them to the feeder and amenities. At the same time, Gayle has started to build another nest. During the time after fledging, a Bluebird box is pretty much left unattended and thus, vulnerable to other birds claiming it. A House Wren that is nesting in the area has discovered it and explored. And two nights ago, went in and started tossing the newly started BB nest. All night I was trying to think about what I could do. Then in the morning, I watched this scene going down. First thing in the morning, the Wren came back, but this time, Mr. Business saw it and took care of business. Gayle continued to build afterwards, and the Wren has not returned. As soon as she lays her first egg, I will install a Wren guard, which is basically a visor for the box that disguises the entrance hole from view. Theoretically, only the BBs know it is there. Since the Wren was already in, I have no idea if this will work, so I have to hope for the best. But the whole family is around, including three babies (that I saw so far) who stay close by the box and will hopefully defend it.