Probably a house wren. If it has a white stripe over its' eye, it is a Carolina wren.
House wrens have a wonderful, loud song. I am always amazed so much sound can come out of such a little thing. However, they are extremely mean birds. They will destroy nests, eggs, and nestlings of other birds, including chickadees, bluebirds, and other wrens. We have a pair that return every year to a birdhouse in our yard. It was not too much of an issue until this year when a pair of chickadees nested in a nearby birdhouse. The wrens were relentless in pulling apart the nest and deviling the parents while they were brooding. The wrens even went after the fledglings. We will be taking the birdhouse down so the wrens don't come back next year.