I like the simplicity of this image Rob. The BG is beautiful and the perch is just the right size. I like the pose and head angle of the blackbird. There are a few things you could try in processing to improve the image. Overall it's soft on my monitor- in particular it needs to be sharp around the face, eye and bill as your eye is drawn to this part of the image. Some sharpening might bring this up. I don't see any part of the image that is tack sharp and wonder of you made a big crop. The other thing I think you could try is boosting the contrast a little and removing what looks to me like a faint greenish cast. Finally, regarding the crop, if you did make a big one for this image you could think about loosing this up and give the bird a bit more room. This will help IQ.
Rob, the square crop does not work in this composition. Do you have room on the bottom? If so, I would try 8x10 in portrait mode.
There is more room on this shot to be improved in PP. Try the contrast, sharpening etc.