In addition to Jim's comments I would touch up the overall brightness of the cardinal. IMO it currently doesn't 'separate' enough from the background. As to the cropping, the picture is somewhat of a "tweener" - not cropped enough to frame the head to form a portrait, but cropped too much to provide for natural framing of the bird as a whole. I guess that's the one thing that really doesn't work for me with this image - I keep looking for a nice tail.

Aside from this, would you mind sharing how far away you were from the subject? Is this a full-frame image? I am just wondering about this in regards to the quality of the Zuiko lens.

Thanks for sharing!