Since the dawn of time, people have been keeping track of natural phenomena. They looked for signs of when to plant crops, when large food animals would migrate and when trees would bear fruit.
This was some of the earliest phenology, or the study of the timing of biological phenomena in nature (not to be confused with phrenology, the discredited 18th- and 19th-century practice of studying the shape of people’s heads).
Today, people practice phenology in both casual and serious ways. Those eager for the arrival of spring, may keep an eye out for the first robin or singing cardinal. Naturalists record the first blooms of spring wildflowers and the first migrating waterfowl to land on open water.