Uh-oh, a House Wren returned from migration last night. Just when we though the competition for nesting boxes couldn't get more fierce, this little bird shows up. That's OK, we have a solution. We always keep some bird houses in reserve. When House Wrens arrive, we put up some more bird houses, to keep them happy and away from the other birds. We also use some boxes that have a smaller ( 1 1/4 inch) diameter hole, unlike most of our bird houses that have a 1 1/2 inch diameter hole. House Wrens can use the smaller hole.
Keeping all the birds happy is a juggling act.