I joined the group and discovered I was wrong. George and Gracie, who are almost indistinguishable except for size (George being smaller) have been taking turns sitting the eggs.

Couldn't tell by me.

George brought Gracie a snack at about 10:45 a.m., presumably PST, the day Gracie laid the fourth egg.

Now I can begin to put some of what I'm seeing in context. The moderator for the group is very helpful in isolating and presenting photos, and otherwise explaining what is going on.