Monarch Butterfly Update: March 10, 2011
Please Report
Your Sightings!

Waiting for signs of a mass migration—a grand exodus that could occur any day—Estela Romero found the sanctuary at El Rosario still butterfly-filled. The monarchs can't stay in Mexico much longer, but they can't move north too quickly either. This week, explore how seasonal change affects monarchs, and the timing of their spring migration.

This Week's Update Includes:


Image of the Week
Monarch Butterflies in flight at sanctuary in Mexico.
Dr. Lincoln Brower

Ready or Not?

News: Watching and Waiting...

"Within the month of March—a relatively short time—the monarchs will vacate their winter haunt and begin the recolonization of North America," says Dr. Bill Calvert.

Estela Romero reports, "I decided to go to El Rosario Sanctuary this morning. I was astonished to see how full the sanctuary still is! It is too warm now for the monarchs to stay much longer. They must be leaving any time."

What signs did Estela notice when she visited the sanctuary yesterday? What clues do her pictures reveal?

All Eyes on Texas!
Watch the migration map for the first signs of spring migration. It's about 600 miles from the sanctuaries in Mexico to the milkweed-rich regions of Texas. Early butterflies should appear any day.

"The leading edge of the spring migration typically crosses the Rio Grande around March 15th," said Texas insect-expert Mike Quinn.

Will the first monarchs have been reported by next week at this time? South winds are predicted from Thursday through Sunday. Let's see if the south wind delivers our first northbound butterflies of spring 2011!


Monarch butterflies at winter sanctuary in Mexico.

"I was astonished to see how full the sanctuary still is!" wrote Estela Romero on Tuesday.


All Eyes on Texas!

"The leading edge of the migration typically crosses the Rio Grande around March 15th," says Texas insect-expert, Mike Quinn.

Slideshow: Spring Migration, A Race Against Time

Slideshow and Teacher Guide:
Why does spring migration begin now, and what triggers the monarchs' departure? Begin your spring migration study by exploring the time-sensitive connections between monarchs and the seasons.

Journal Page: Why Quickly, But Not Too Quickly?
Name two reasons monarchs need to leave Mexico quickly in the spring. Name two reasons they should not come north too quickly.

Maps and Invitation: Get Ready to Track the Migration!
Pre-migration map: Winter monarch butterfly sightings (January or February) Map of milkweed emergence: Spring 2011 Invitation
to Track Migration

Use this invitation letter to invite family and friends to track the spring migration. Let's find out when and where monarchs and milkweed appear this spring.

The next Monarch Migration Update will be posted on March 17, 2011.