Grey Heron downbeat

Web halos are usually the result of post processing adjustments to tone and contrast. A typical cause is use of shadow/highlight recovery applied to there entire image - it can "spill over" from the dark areas being lightened, or from the bright areas being darkened. So, if you are going to do S/H then it is best to make a careful selection (everything but the sky in this image) before using the S/H tool/sliders.

Another possible cause is from boosting contrast - that adjustment looks at boundaries between tones and makes the difference greater by making the dark side darker and the light side lighter.

Same thing with "sharpening." Sharpening is actually increasing contrast on a smaller scale.

Richard has answered you concisely and well. I would add further that this is a decent image, considering the hand held aspect of a heavy lens. Practically, I suggest "going back to the drawing board" with Richard's suggestions in mind, paying close attention to the contrast, s/h, etc., and selecting the bird for separate treatment.

If this was a RAW image originally, it would be worth doing some modest changes in ACR. If it was a jpeg out of the camera, your changes can be the same, just even more modest, and tailored to correcting for the halo and reducing contrast for the bird.

Very nice lighting and a good look at the eye here David. Richard covered some potential causes. If you limit your sharpening to just the bird and not the whole image that can go along way toward reducing halos as they are often caused by sharpening the whole image.

Richard. Thanks so much for your immediate and helpful comment in imparting more 'tricks of the trade' I appreciate your help.

Phil. Thanks for your constructive comment. It's so refreshing to get these views and insights.

Nate. Many thanks for your appreciation and encouragement.

Nice flight shot, David, with an excellent view of the eye. Looks like it's going somewhere with a purpose. I might be tempted to add a touch of canvas on the left.

Thanks Dennis for the encouraging comment. Yes, addition of a little more canvas on the left is advisable.