This year's mystery bird

It's a Slate Coloured Junco!

Last year's mystery visitor was a Yellow Shafted Flicker. Today, I came home from the afternoon run-around to find this guy, and about 30 of his dearest friends all over the back yard. All on the ground, picking up little bits to nibble on. I'm assuming he's a finch of some sort, he's the same size and shape as a goldfinch, same beak, but a solid dark grey on top with a white belly. This picture is reasonably accurate color-wise except his beak is actually more yellow than buff.

He's got some dry leaf litter around his feet, so he looks a little more plump and ruffled than he actually is. Anyone?