Male Wrens will build as many as five nests after their arrival back to our part of the world in the late spring. They are fiesty little birds with a beautiful song. The female will inspect and then choose one of the nests, leaving the other nests abandoned. So if you feel disappointed that your nest was not selected, the male did his best, and together the male and female really only need one nest in the end.
Chickadees will also nest in boxes designed for wrens. While wrens are willing to use a variety of places such as flower pots to build their nests, chickadees prefer nesting boxes. They are cavity nesters and in the wild will excavate a small round hole in a dead tree and remove wood from inside the tree to create space for the nest. For boxes we put up, you can encourage chickadees to nest there if you put sawdust or wood shavings in the bottom of the box. The chickadees prefer to have this material in the cavity, perhaps as it looks more like "home" to them.