Mystery Bird Phoebe!

The East is full of mystery ... East Tennessee, that is. First the tree, and now a bird. Two birds - a pair, probably. They're smallish - a little bigger than a sparrow. My father says they - or one of them - repeatedly tried to fly through the window back when his Easter cactus was blooming. Now they just flit around and perch on rails and branches. They aren't in the bird book... Any ideas?

update: Deborah says Eastern Phoebe - and I'm pretty sure I heard one this morning. And yes, looking in the bird guide, that's what it looks like. Except the guide has the phoebe in with the green birds. I would never (did never) think of looking under green for this one!

Thanks, Deborah!