dvier wrote:
Yes I think that is was a possibility but in some other frames I don't see anything in the view. But I was using 200-500 lens at about 400
Understood! Let me re-emphasize that with longer lenses such as you were using (400 mm zoom range eg.) that the lens is wide open(f/stop wise...) and is presenting you with as bright an image as possible so that you can see what you need to see. This means that you are viewing
your image with the lens NOT stopped down yet and with the least amount of DOF(depth-of-field) possible for that lens (zoom) range.
Thus, anything objectionable that is to the side, or in front or behind your focal point, and at such a low DOF might not be very noticeable
by you, "pre-exposure" or "shutter-press". However, depending on how you are arranging the settings on your camera for proper exposure,
you might very well become aware of the objectionable "object" that has become slightly sharper or more contrasty due to the fact that
you lens exposed the image a few stops(possibly) smaller than when you were composing the bird and finding the focal point on the critter.
Very easy to miss these things, btw, in the heat of battle, right? Again, "if" you have the time always examine all four corners of the viewfinder before you shoot for such things as these anomalies, or better yet...if time permits, do a manual stop-down prior to shooting
(OR go to LIVE VIEW) which should give you an excellent idea of what the final DOF\overall sharpness of the image should be, including any of those
missed fuzzy area's that would not be so evident when composing your image. BTW...as everyone said this image is easily salvageable with
a little editing\cropping, etc., and I think you did an excellent job with this shot of such an elusive creature. Continued success!