Great find and good-looking specimen. I would try to adjust curves and/or S/H to get more details in the blacks and desaturate a few points. Could you have moved a bit to your right to avoid the bill/leaf overlap?
Great focus on the head of this Red-breasted Sapsucker, cloning could remove the bill/leaf overlap and ditto on Axel's comments about S/H and curves..Paul
Great find and I am just picturing you on a 12 foot ladder balancing your 500mm! Nice view of the nest hole and pretty bg and setting. Wish the bird had given you a better head turn, but still a nice image.