Steve, As such close range, I don't feel that F5.6 offered enough depth of field for you to achieve sharpness over a wide area. For a head portrait, I feel the entire head and neck should be sharp and here, the left portion of neck and head are soft. To enhance this image, you could try some selective sharpening.
Steve
Your exposure and composition are very good......as are the colors. I have to agree with Jeff.....you needed more DOF and a sharper image. When you're looking at a bird this close you really want a lot of detail.