Great Blue Heron nests are out in the sun, top of trees, surrounded by water. This means right out in the (southern) sun. By May and June that’s hot.
Not only did these two learn the joy of flight, but they can now land in a tree, in the shade. And that apparently is a big deal to them.
The young birds kept the nest in sight, even flew back when an Egret landed there. The shade kept drawing them back. Can’t say I blame them.