Fall
Migration Observation Methods
Count
Monarchs at an Overnight Roost
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Monarch butterflies only migrate during the day. At night, they come down to rest. They spend the night clustered together in "roosts." (The roosts are also called "aggregations" or "bivouacs.")
If you find monarchs at an overnight roost, estimate how many there are. Make your observations at the same time each evening. It's often impossible to count them. However, if you count the number of monarchs on a small area of a branch, and then estimate the total number.
Related Links
- Analyzing Data From a Fall Migration Roost (Contributed by Paul Viger)
- Do Monarchs Rest at the Same Roost Sites Every Fall? (by Dr. Bill Calvert)
- Field Studies You Can Do at Roost Sites (by Dr. Lincoln Brower)
