I'm not expert in photoshop, but my eye tells me it is. Eagles are very large, but I agree that the pixel halo is definitely off (esp if this guy is using any decent nikon it should be a decent photo clarity, and knowing how to use the basics)and the shadow cast by that particular grave looks a shade lighter than the other shadows and a very crisp outline/ edge on it.
Just go on sites like deviantart to see wonderfully made photoshops, and your magazines.

Perhaps the eagle had flow or swooped by, and it made a great idea for it to have landed. It isn't out of the question that this might have actually happened, and the guy just tried to recreate what he had saw before.