Wry neck is one of those things that is incredibly hard to figure out. Sometimes it is obvious, such as a head injury or sometimes it is very subtle, due to a 'hidden' deficiency or disease... so many reasons! My little Derperlla had wry neck on and off for a while. She had it so bad as a chick that she was spinning circles. She did recover and lives normally-- well, as normal as she can. She's always been weird.