Ain't no such thing.
Copyright exists, immediately upon creation (not publication) of a work.
It's different from trademark, in that practical applications, enforcement, registration, etc., does not invalidate the copyright.
Copyright can expire, which then becomes, effectively, "public domain."
Registering a copyright doesn't create the copyright. It simply makes it easier to go after those that disrespect it.
I'm pretty sure that the only way to truly transfer the ownership of copyright of a work, is to have agreements in place, before it is created (like "work for hire" contracts).