A pair of wrens, having found the new entrance reducer entirely satisfactory, set up housekeeping in the front bird box and raised their nestlings.
Somehow, they manage to fly directly into the hole without stopping:

Outbound trips require a security check:

And away!

After those nestlings fledged, they began building a nest in one of the garden bird boxes a few hundred feet away. In short order, we’ll be awash in wrens!