Here is one more image of this little rascal, hopefully helpful for an ID. Presently my best guess is the Western Kingbird, I just don't know for sure... I thought on the Western that the tail was darker, closer to black?
1/2000 sec, f/3.5, ISO 400 at 200mm with 70-200mm f/2.8 L IS II on 5D Mk III.
Any setting suggestions to lose that noise or posterization look in the background? I seem to get this on all my 5d3 images, rarely in my 7d images...