Swallow housing

I had a productive day out in the shop on Sunday. I made four birdhouses for swallows and put them up on fence posts around my front yard. They are for swallows, who like deep houses in the open. I put these three together. There are already two families in these, and it's only been 12 hours since they've been available.

This little one is nearby and is also already occupied.  The owners are wood swallows. They have a beautiful song, it sounds like water dripping and trickling.