If anyone can point me in the right direction to understanding what is wrong with our rooster, it would be greatly appreciated. -He is ~8 months old Barnevelder; was acting perfectly normal yesterday. -This morning, when I let the chickens out of the coop, he was stumbling somewhat. The other rooster started chasing and attacking him, so I finally got him away from the rest of the chickens. -He can behave normal, but then if I approach him when I get near he will start rapidly twisting/jerking his head convulsively up at an angle, flapping his wings some and looking like he is stumbling. -There are no signs of respiratory issues or distress. -His comb may be a little paler than usual; it is a little grayish towards the top, but I'm not sure if it was already like that. -He seems to be eating and drinking just as usual. -The only thing out of the ordinary in the last week is that a friend delivered some fresh horse manure a couple days ago (to use as compost/fertilizer in the garden) and the chickens have been picking through that. Does anyone have any idea what this illness could be?