I do enjoy Wrens and their loud singing. We have built a number of Wren houses.and most are very plain but are well used. They seem to last 5-7 years before falling apart. I saw this one somewhere and just made it without plans.
It is made of Western Red Cedar and no finish. It was cut on the table saw and scrollsaw. I glue them with Gorilla glue. I have had it out for a couple of years and has been occupied.