I don't mind the comp as is, but to bad the heron decided to turn its head away a bit. The branch positively adds to the image. I agree with Axel that another small amount of sharpening would be good (especially the face/neck/shoulder areas).
Without a doubt, a fine capture. Focus and color are great. As is the image fine IMO, yet and you have some quality input from the forum. However, additional sharpening is likely to strengthen sharpening highlights most apparent above the blacks on the head and back.
Faint halo visible above the head & beak....most probably as a result of extra sharpening. Like the pose, angle of flight & nesting material adds nicely.
Agree with the sharpening halo on top of the head. Wish I had seen the original. Great pose and exposure. It could be a little bit higher in the frame IMO.
By the way, the sky in this pic has a slight purplish cast on my monitor. Can anyone confirm that they see the same?