Very cool Dr. Luke I have been following and it prompted me to build one to try. We may have gotten it out a little too late for this year. My helper and I finished it and installed on March 20th. We did have 2 pair visit our pond over the weekend. They come on occasion but I was hopeful however I assume now they have already nested.
C68, don't give up hope. You may catch a late nester, or a hen that failed to get a hatch off the first go round. Plus, you may get a screech owl to use the box too. They can be seen perching in the door of the box, usually early in the morning for me.
Screech owl looking up at Mr & Mrs Duck