Copyright registration within five years of first publication creates a legal presumption of ownership and validity. While copyright registration does not prove ownership of copyright, this legal presumption of ownership and validity constitutes a prima facie proof (on first appearance). Consequently, in cases of infringement the court will presume that the ownership of the copyright and the registration is valid and will shift the burden of proof to the defendant to disprove by showing with sufficient evidence the falsity or invalidity of the allegation.

References:
[1] Stim, R. "Intellectual Property. Patents, Trademarks, and Copyrights" West Legal Studies.
[2] Black's Law Dictionary 5th ed., (West Publishing, 1979).