After work today, I caught a glimpse of blue: a Western Bluebird, first time in my yard! Not just one, but a pair, and they investigated the wooden nest box that has been up for 1.5 years. The resident House Wren, which has ignored the bluebird box all that time, immediately came over and tried to get inside. When things settled down, we put up the wren nest box that we bought 1.5 years ago but never installed. I added a few sticks, and two minutes later the wren was back, checked it out, then went over and entered the larger bluebird box! Oh well. We'll see how this works out over time. I am really excited about this new addition to the yard.