My Take (that may or may not be useful, or even correct) I think the composition and moment of capture quite extraordinary. The lighting angle was a severe detriment, and this combined with shooting at a much too slow 1/200sec (checked your EXIF), likely caused a considerable loss in image sharpness. The contrast between light and dark was too great, in what they call around here harsh lighting. If there was a case where fill-flash would have come in handy, it was here.
In the future, especially with bright sunlight, in harsh lighting conditions, a flash would have saved the day. Light more or less behind you, like you haven't heard that before, is pretty much necessary. And even if you use a tripod, movement of the bird must be accounted for by a sufficiently high shutter speed. regards~Bill One more thing, it would be more useful if you gave information about the shutter speed, aperture, ISO etc along with the image.