Recent trip to the zoo last week. C&C please
Nice focus. Good composition although it might be a little tight. Generally, birds don't have the prettiest faces, rather its their overall line which is pleasant to look at.
Plus, this is way over exposed. The conditions were a bit difficult considering the spotty shadows that cover part of the image. To work on a bright sunny day, you just have to have the subject all the way in or all the way out of the sun. With the lens you have and the location you should be looking for a ton of detail in the feathers, but the exposure robs the viewer of that detail.
Finally, I think you're a bit overexposed because of the wide aperture. I think you could sacrifice a bit of DoF for a more even overall exposure. If you want to separate the subject make sure you catch them against a distant background like in this image. The separation between foreground and background will more then make up the the few stops you have to dial down. Who knows, maybe the increased resolution in the background scene will help place the subject in the context of its environment instead of strictly isolating it as in the above image.