Overview
Phenology is the study of the seasonal timing of life cycle events. You are studying phenology when you record the date a certain plant grows, a tree's leaves emerge, an insect hatches, or a migratory bird appears on its nesting grounds. Factors such as daylength, temperature, and rainfall influence the dates on which events occur each year.
The Global Climate
Citizen scientists plant tulip test gardens in places with different climates. Explore climate variables to predict how different conditions will affect where and when tulips emerge and bloom.
Monarchs are changing dramatically in the fall, in physiology and in behavior. They are:
1. Becoming Migratory
Watch for signs of migratory monarchs:
- flying in directional flight
- clustering in overnight roosts
- nectaring intensely
2. Responding to Daylength
Declining day length is a central cue that triggers the monarch's migratory state. In the northern breeding range photoperiod is falling by 20 minutes by mid-August. This sends a signal that it's time to migrate.