http://www.pbs.org/newshour/rundown/how-does-the-ap-count-delegates-to-arrive-at-clintons-win/
HOW AP COUNTS SUPERDELEGATES
Of the 4,765 total delegates to the Democratic National Convention, 714 are superdelegates. They are all party officials, governors and members of Congress who may vote for the candidate of their choice, regardless of the outcome in their state’s primary or caucus.
The AP surveys the superdelegates throughout the primary season, over months and months, to track whom they plan to support at the July convention.
If a superdelegate tells the AP he or she plans to unequivocally support a certain candidate at the convention, that’s added to the candidate’s tally.
Those who decline to answer, who say they have yet to make a decision or express any reservations are listed as uncommitted.
The AP tally can be found here.
Nothing there indicates that it's anonymous.