When my polish chick is roosting, it simply will NOT stop shaking it's head, like some kind of nervous tick! It's less frequent when it's walking around, and it doesn't seem to bother her at all. She eventually falls asleep and the twitching ceases, but this can't be normal. My silkie does it too, but I've read this is kind of just a silkie thing. No other symptoms. They act perfectly healthy.