By evening, they seem to wither a bit as their energy wanes with the setting sun:
You may already know--they are prickly pear cactus, abundant in our new environment. We encounter them on almost every hike. This particular patch is along the edge of our driveway. They were just a spikey cactus when we moved in a few weeks ago. One morning last week, I spied the yellow blossoms. When I finally remembered in the evening that I wanted to photograph them, I discovered the change that occurs as the daylight fades. Fascinating.