Monarch Migration Update: Sept. 9, 2010
Please Report
Your Sightings!

Excitement filled the air this week. Cool temperatures arrived and people saw waves of monarchs leaving for Mexico. "Monarchs are flying in from the east, over our garage, and heading out of sight toward the west," exclaimed one woman in Michigan. "We counted 150 in 45 minutes!" How many monarchs can you count in an hour? Find out how to compare the pace of migration in different places by using standard units of measurement.

This Week's Update Includes:

Image of the Week
How many monarchs
per hour?

News: Look at them go toward Mexico!

Look at the migration map and you can plainly see, the monarchs are moving toward their winter home in Mexico:

  • After Friday's cold front hit the Midwest, the migration swept into Iowa like a wave. Reports of roosting monarchs suddenly appeared all across the state.
  • The Great Lakes' shorelines in Wisconsin, Michigan and Ontario were a "migration highway," according to observers there.
  • Riverside Public School wrote from Ontario, "We had 200 to 300 Monarchs in the large trees at the back of our schoolyard at afternoon dismissal. Our school is only 1 block away from Lake Ontario so it was a good place to rest before heading onward."
  • Look at the state of Wisconsin on the roost map and notice where the roosts are clustered. We've never had so many reports from that region. Check the dates the butterflies arrived. Did the strong west winds shown on this map blow the butterflies to Lake Michigan's shore?

As the monarchs picked up their pace, people were delighted by the show. Observers reported "thousands of monarchs," "a constant stream," "hundreds per hour," and "a sore neck from watching more than I've seen in a decade!" Monarchs were counted from the driver's seat of a school bus and from the longest porch in the world, at the Grand Hotel on Lake Michigan.

How to Count Migrating Monarchs
Students at Mount Abraham Union Middle School are monitoring the migration in Bristol, Vermont. "I saw 2 monarchs in 25 minutes," reported one of the 7th graders on Tuesday.

Notice how the following observers also measured the pace of migration by counting monarchs per minute:

  • There were 31 monarchs in 40 minutes in Rochester, Minnesota on Sunday.
  • There were 47 monarchs in 5 minutes in Shawano, Wisconsin on Tuesday.
  • There were 150 monarchs in 45 minutes in St. Ignace, Michigan on Tuesday.

Who saw a stronger migration? Use this week's journal page to convert monarch observations to standard units and you'll see!

Monarch butterflies during fall migration roosting in Ohio

Eye Candy
A photo gallery full of roosting monarchs is a feast for the eyes.
Image: E. McCormick
Report monarchs per hour!
When you report your own migration sightings, please include standard units of measurement. Tell us how many monarchs you see per hour (or per minute).


The Migration: Maps and Journal Page 
Map of All Monarch Butterfly Sightings: Fall 2010 Map of Monarch Butterfly Roosts: Fall 2010 Migration

ALL Monarch


Fall Roosts


For Your Journal
This Week's
Migration Questions

Seeing Monarchs? Please let us know!

Lesson: Fun With Migration Rate Activities

The four activities below help you practice with the standard units we use for migration data. See these Teaching Suggestions to introduce students to the concept of migration rates.

Monarchs per Hour

Online Practice Activity

Migration Rate Math

Practice Activity

My Migration Rates

Data Sheet

This Fall's Record Flights

Data Sheet


The Next Monarch Migration Update Will Be Posted on September 16, 2010.