I arrived at about 1:15 PM and saw one adult on the nest and another on top of a dead melaleuca tree very close to the nest area. I left to go to lunch after about 20 minutes.
I returned about an hour later and saw only the top of a head in the nest for quite a while. The adult in the nest then stood up, turned around and relieved itself away from the nest. It then chewed on a couple of sticks and moved its behind back and forth on the nest (I guess to get the best position) before hunkering down again.
At 2:40, I'm pretty sure I saw a changing of the incubating adults. One adult flew to the bare horizontal branch above and a little to the right of the nest. It called out as it landed on the branch. The incubating one then stood up. Then, I watched with my binocs as the one on the branch flew away a little to the south and then west. It made a circle and flew to the nest. I was not able to watch what happened with the one in the nest at the same time, but once I saw the one on the branch was on the nest, the other was gone.
Off Topic-----
My mother and I have been going to the Florida Keys Wild Bird Center on Christmas day for a few years now. We went yesterday and I saw the cutest little Yellow-crowned Night Heron. According to the sign, this bird has been returning to the Center every September since his rehabilitation there 13 years ago.