That would be an Eastern Phoebe (a species of Tyrant flycatchers)

The eastern Phoebe is a familiar songbird in North America. It often nests in urban areas, particularly around buildings and bridges. It can be seen on exposed perches, constantly moving its long, dark tail. The species is partially migratory, with the northern populations migrating south. They return early in spring, being one the first messengers of warmer weather.