A copyright can also be bequeathed by will.
A copyright is a personal property right, and is subject to the same state laws and regulations that govern the ownership, inheritance, or transfer of personal property as well as legal contracts or terms business. Check your relevant state laws and/or consult an attorney.
Most often transfers of copyright are made by contract. The Copyright Office does provide any forms for transfer contracts, you have to provide your own. However, you can make a record the transfer of copyright ownership in the Copyright Office.