What a challenging bird to expose properly, with the large areas of white and then the black neck,head and eye. This one would require the softest possible light to have a chance of getting a good exposure for both ends of the histogram.
The image quality has suffered a bit from the large crop, high ISO, and needing all the reach you could get and having to use the lens at 300, its weakest focal length.
He is angling away slightly: if possible, catch them earlier, before they pass your position.