The lighting was a challenge here, because it has overexposed the neck and breast, while leaving most of the bird in shadows.
You do have a nice catch light.
There is a modest amount of noise showing in the background.
Be sure to post your camera/lens info so we can better understand the creation of your image.
When working a setup with feeders, it usually looks more natural to have a small perch near the feeder that they will land on, allowing you an image with less "hand of man" impact.
Yes, your biggest issue here is light quality and angle. Using a setup is best as Randy points out, unless you do want the man-made feeder in. In that case you can move it (if you can) to a location with better light or in complete shade. As far as NR goes, you can apply that to only the background, this way you retain details on your subject.
Nuthatches sure are fun to watch, and the pose you got here shows just how entertaining they can be at something as simple as feeding.