I'm thinking some kind of a warbler - but couldn't get enough detail to be sure. Definitely saw the yellow under the feathers and below those tail feathers. Quite small - or maybe young. Cute little guy.
Great shot Milanie and I believe that @janiskay is correct. We had several around our house last winter. Looking forward to them coming back. Some of them, maybe the males, have what appears to be black mask on their face.
Yellow-rumped Warbler. You can even see a small bit of the yellow rump, along with the yellow on the sides, white undertail coverts, and broken eyering. I suspect he has just arrived for the winter or will migrate farther south. They are usually the last warblers to leave their northern breeding grounds.
