It's a Dark-Eyed Junco. Dark-Eyed Juncos are split into many subspecies. This one appears to be a Slate-Colored type, although the large amounts of rufous coloring makes me think otherwise. At first glance it appears to be a Oregon Junco type, but the head coloring is wrong. I'm not exactly sure if it's a slate-colored type, but it's definitely a Dark-Eyed Junco!