OK, since it's been a while I thought I would add another post and photo. I watched this Tree Swallow fly in and out of the holes on this tree for about 15 minutes. It would have food in it's mouth when it went in and none when it came back out. It's hard to be 100% positive because I couldn't hear or see young, but I would bet this was a Tree Swallow on the nest. Either way, it was pretty cool to watch.