After watching the chickens pretty closely this am, I have solved the mystery! Laverne is the egg layer! Laverne is one of our Rhode Island Reds...the larger of the two...(Shirley is the other one!). She was sitting inside the nesting pot (a large flower pot turned on its side...we're using it until we can build a proper nesting box) looking awfully suspicious then suddenly came out squawking and strutting around the coop like she was announcing something. I peeked inside the pot...and sure enough, there was an egg! Our second egg in as many days! It's a good sign for our layers!
For some reason, I expected our bossy hen, Amelia, to be the first to lay an egg. She's so round and fluffy and seemed to mature faster than the others. Perhaps she'll come on line in the next few days. So exciting! I just hope that we don't have anyone make a fuss about us having them as we're inside the city limits (got annexed in after we moved out here!). With an acre per house, they certainly shouldn't bother anyone. If any of you have had to "convince" neighbors of the benefits of backyard chickens, please pass along tips.