Another possibility is the American Tree Sparrow which looks a lot like the Chipping Sparrow but has a breast spot. Where are you located? From the All About Birds site: "The easiest species to confuse with American Tree Sparrow is Chipping Sparrow, but their ranges don't overlap much in winter (the only time most people are likely to see American Tree Sparrows). If you are north of roughly Kansas in the winter, American Tree Sparrows are much more likely than Chipping Sparrows; south of this line Chipping Sparrows are more common. In winter, Chipping Sparrows have a less rufous (reddish-brown) cap than American Tree Sparrows. Look for a black line through the eyes of Chipping Sparrows; in American Tree Sparrows that line is rufous, the same color as its crown. Look for American Tree SparrowâÂÂs distinctly bicolored bill - dark on top, yellowish below. Chipping Sparrow's bill is often dark or pinkish. Song Sparrows are heavily streaked on the breast, whereas American Tree Sparrow has a plain breast, sometimes with a single dark spot. Field Sparrows have a pink bill and a white ring around the eye. Lark Sparrows have a much more complex head pattern including rufous on the cheeks." The tree sparrow is a winter bird in many regions where the chipping sparrow doesn't winter over. Here in southeastern MA I see tree sparrows all winter long but no chipping sparrows. This one was seen in January a few years ago in Plymouth, MA: Claire This post was edited by claire on Mon, May 6, 13 at 10:23

Hi PotatoJoe, I'm not sure where you're located, but you may want to check out tufted titmouse -- classic "peter" song. I've linked below for you. Have fun birding by ear. Cathy in SWPA Here is a link that might be useful: tufted titmouse info

Possibly a starling pair? These birds usually breed earlier and do build their nests in such places. Very aggressive birds.

Your username indicates you are in Iowa; is that where you saw this bird? It does resemble a 1st-year male Orchard Oriole.