A fledgling raven (the pink in the beak is the giveaway - it actually seemed a little bigger than the parent the one time I saw them together) was hanging out at ground level several days around Yerba Buena plaza a week after all the nestlings fledged.
Its parents visited a couple times, but they and its siblings (flying about the nearby rooftops) seemed to be waiting for it to get its act together. There were 4 nestlings, so they had already lost one in fledging it seems.
They were gone over the weekend. I saw a 3 ravens fly by later in the week, but they quickly disappeared amongst the buildings. One could be sitting atop the Palace Hotel for a good while.