Face is nice and sharpt. You must have edited this at 8 it, because I see a lot of of banding in the BG, posterized, Id say. A little smaller aperture, is you were using a tripod, may have improved depth of field and there's a little magenta cast in the whites.
A cute little guy, and you got him in a nice alert pose. Good points by Fabs. Pointing the lens more to the right would have placed the chickadee further to the left and given it some needed room in front of it. The magenta cast is an easy fix, with a number of ways to do it (RAW WB, color balance, levels, or average blur technique to name a few...)