Peter,
Honestly I cant remember where I found this picture. It enchanted me as well when I saw it. There was no story with it when I found it so from what I can tell the grouse is simply being more friendly than usual for some reason. Ive heard stories about people in the woods on quads and having grouse follow them, but have never seen it. Ive been hunting them my entire life, and the damn things never do this for me. I think the gentleman in the picture is trying to feed it a twig of some kind, maybe I should try that instead of my Parker this fall!