We watched them for a long time and were amazed at how patient they are. While they did play a little, hopping around after each other, they often sat absolutely frozen for minute after minute, gauging their surroundings and listening for any possible danger.
The one in front seemed to be dominant and he eventually hopped around to the other side of the dish and positioned himself for a sip.
It must have pleased him as, when he finished, he scampered about, playing with his companion for awhile before I came outside to fill the dish and they both ran through the gate and away.
I suspect they'll be back.