Love the expression. The eye's seem a tad soft, due to the small DOF with the lens/convertor combo. I would try stop down to f/6.3 or even f/8 if you have enough shutter speed to render the eyes more in focus, or just set the focus precisely on the eyes. Looking at the Camera you have used, you could easily bump up the ISO speed to allow for that smaller apeture.
Now that is in your face. :) I like the stare and open beak, and agree, regarding raising ISO to 400 or 800 to be able to stop down to f/8 or 11. As it is, I might selectively sharpen the eyes a bit more. How did you get so close to this guy?
This has some great impact Gary! Well done. I agree with Axel's suggestion about higher ISO and more DOF. Hard to think of all the variables in all the excitement of course. :) Good stuff!