Agreed, but all credit goes to the unidentified photographer that directs us to see guineafowlbirds.com for more, like this one:
This photo demonstrates somethin' I'd noticed with my own, and the chickens as well ... if they're lookin' at something while you're holding them, you can more 'em around and see their heads won't, at least 'til their necks have reached their limits. I think that they can maintain constant adjustment while moving, so as to spot even the slightest changes in what they're lookin' at. In this picture? Notice the blurring of the wings, showing the limitations of the camera used, but also that there's slight blurring in the feathers covering the neck, which is clearly compensating (for some reason) for the movement.