Owls cannot turn their heads 360 degrees. It does appear that they can by just watching them, but after studying them scientists have discovered they do not actually turn their head 360 degrees.
Owls have fixed eye sockets, which means they can’t move their eyeballs. In order to see their surroundings, they instead rotate their heads up to 270 degrees in either direction. Owls do not have two pivot sockets in their neck like humans do. Since they only have one neck socket and small bones that make up the neck and spine, they are able to move their heads in such a wide range of motion to compensate for this lack.