Following some of the comments below, please be aware that the "noise" in the sky was added during post so as to give it some texture and interest (which apparently it did). You can't really have noticeable noise at ISO 100 considering all factors.
That being Topaz Labs Clean 3 :) If done subtly it can add a smoothness without the tail artefact you see here.
I like the shot, like a where's Wallie without all the distractions. Use DeNoise and Black and White Effects and see what happens to that cloud and the crow :)