There's a new bird family moving into the blackberry trellis box - House Wrens. To make sure I had identified them correctly, I played their calls on a phone app, and sure enough, they sang back to me.
After the bluebirds moved on once their nest attempt failed (we suspect blue jays picked off the remaining living baby birds), I cleaned out the nest cup. Some bluebird enthusiasts advised leaving it in for a second round, some advised cleaning it out. Since there was still the faint odor of decay and there was no sight of mom or dad for two days, I cleaned it out and noticed there were a couple new twigs added. By the end of the day, that pair of wrens who had been calling to each other (and me) all morning had deposited new twigs into the clean box.
We have had successful nests of wrens in previous years, so hopefully our yard is better suited for them than the bluebirds. We have a high-traffic yard (birds and boys), and wrens will dutifully fuss at anyone going near their nest. I was already fussed at yesterday for trimming back overgrown asparagus growing near their box. It is going to be an exciting few weeks. We won't be able to open the box to see the eggs, because they ram the box full of twigs and place a soft nest on top of the twig "stage". I'm sure we will get to see little beaks peeping from the hole before long.