We put 6 4 month old chicks in with old flock (3 chickens, 1 year old). After 1 week they attacked one of the chicks overnight, pecked all skin off the top of her head so you can see the skull and down into the neck under the fat layer.
The chick is responsive, eating, appears to be behaving normally. We separated her back into the chick enclosure in the garage. Treated the wound with neosporin and iodine but it's a pretty nasty wound.
Does anyone have advice on how to treat the wound / handle integration? They haven't attacked any other chicks, don't fight or even acknowledge new chicks during the day.