Just a question or two...do they shake their heads once or twice as you approach or talk to them? My Buckeyes shake their heads real quick and light whenever we talk to them or walk up to them. They don't shake their heads like they are irritated, just a quick flick of the head like, as you said, they're trying to get their bangs out of their eyes. The adults do it and so do the chicks (but none of the other breeds), and they are housed separately. They are completely free of parasites. I think it's just an odd behavior some birds exhibit. If you've eliminated all other possibilities, which it sounds like you have, then you have to start looking at other possibilities. I wonder if there is a bird behavior expert out there who might have an idea? My son thinks the quick head shake is a sign of recognition. I really don't understand it yet, but I think he might be on the right track.