Other forms: phenologies
Phenology is the science of seasonal cycles and the way they're affected by climate and habitat. Observing the movement of migrating birds, or noting when the leaves start changing color in the fall, is all part of phenology.
You dabble in phenology yourself if you notice changes to the natural world in spring: plants with early blossoms, the first bees of the season, unfamiliar birds on your birdfeeder. Phenology is sometimes called "nature's calendar," but because it's sensitive to alterations in the climate, it's constantly changing. Global warming means that spring is earlier, winter is shorter — and phenology keeps an eye on how different plants and animals respond. The Greek root of phenology means "bring to light."