It doesn't have the posture or the build of a wren. From what I can tell, it looks like a Great Crested Flycatcher, but the picture was a little bit fuzzy on my computer.
edited to add:
Great Crested Flycatchers are beautiful birds. They are one of the few species that will nest in man-made nesting boxes, and are one of the few who can successfully chase off starlings who try to invade their nests. I have one here that I saw a few days ago, and I hope he finds a mate and breeds here. I don't personally believe they can eat enough bees to do damage to a healthy hive. A flock of cliff swallows, on the other hand, can be a problem because they hunt low over wildflower fields.