500mm Focusing?

I am new to using the 500mm. I have attached photo that I think looks good until viewed at 100%. Can someone please tell me what I might be doing wrong. Or is it the lens. I don't think it's the lens.

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Britt I'm guessing you put your AF point right on the bird's eye? If not, that's what you need to do as getting the eye in focus is important and 500mm means super thin DOF. Focusing on the body might make the eye OOF.

Secondly, I'd suggest running tests to calibrate your lens to your camera (mk III, not 40D) I'd suggest using a tripod with cable release and IS off. Also remember that if you add a TC, you need to calibrate that separately since the camera will see it as a different lens. My 500 is around -2 on my 50D. If you're coming up with something crazy like +/-20 then alter your test method or send the lens to Canon for repair.

Finally, that looks like a decent photo, just needs more sharpening in PS.

Good luck