At lunchtime today I noticed a wren on our back fence. No big surprise, since we have a resident family of Carolina Wrens. But then the bird started calling and it sounded totally different from the "tea kettle tea kettle" call that Carolina Wrens make. In fact, it was the chattering call of a House Wren. I rushed outside and managed to get one quick photo before the bird moved to our neighbors' yard.
So that's species #56 for our yards: House Wren.