An Update: the bird is still there today if anyone wants to chase it. I arrived at 7:30AM. That duck was not at the Gazebo, but I did find it as I walked the dirt path from the Gazebo Pond to the Keyhole Pond. It was with Mallards in the shallow pond (almost blocked by reeds) which one can see before turning the corner towards the Keyhole Pond. There are some gaps which allowed a nice look at the bird. It was gone from there about 20 minutes later and I did not see it at the Gazebo about 8:30AM. I suspect it is still in the vicinity. A male Western Tanager was fairly close to the Keyhole Pond.