Be careful what you wish for!
Last year I had my first ever House Wren in the yard. I put up a wren box with the hope it would return. It did but it decided it liked the location of the Tree Swallow boxes better and proceeded to destroy the eggs in the occupied top of the three boxes. It then went 30' away and killed two Black-capped Chickadee chicks before starting to build it's nest in the lower swallow box.
I was still willing to let it all work itself out until it started for the occupied VG Swallow box under the eaves. I explained with some force this was not going to be allowed and indicated it might find it safer to move on.
They sing pretty but..........!!