Sharpness and exposure is good. For me however the background is a problem partly since it is quite busy and partly because the sky coming through causing some in my personal opinion unpleasant mixture of bluish sky and shadows. Also I would have preferred if the bill hadn't melted in with the black on the head.
Love the pose and the bird appears sharp, but the lack of contrast due to the very busy background bothers me as well. You were already shooting at f4.5 so I don't think you could open up enough to blur out the background either.