Wow, I can see why people invest in L series glass! You can see every individual pin-feather! In my brief photographic history, I’ve never personally had a chance to see such results from a long lens. I’ve used a cheapo 70-300 lens, which doesn’t begin to hold a candle to this!
One tip I’ve heard many times in regards to animal/people photography. Focus on the eye. If the eye is tack sharp, that goes a long way toward creating a “compelling” image. With the ability to select focus points, it shouldn’t be too hard to put one focus point over the eye, and focus on it. On the other hand, there’s a quote by world famous photographer Ansel Adams:
There is nothing worse than a sharp image of a fuzzy concept.
I like the little “catch-light” on the eye, that also helps to “make” the image. If the eye is just a black blob, how can you even tell if it’s in focus or not?
As far as cropping is concerned, I think the crop might be just a little bit tight. Try giving him a little room to breathe on the right. I’ve heard that you’re supposed to put some space in the direction that the animal is looking, so it doesn’t look like it’s looking right out of the frame.