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Monarch Butterfly Migration Update: March 21, 2001

Today's Report Includes:

Front of the Migration Just Entering Southern Texas
Another dozen migration sightings were reported during the last week, so the leading edge of the migration seems to have arrived in southern Texas. Large numbers of monarchs should move through that region during the next two weeks. It's interesting to compare this spring's migration map to last year's. The first monarchs had already been spotted in Arkansas last spring at this time!

Also See:
Comparative Maps: Spring Monarch Migration (1997-2001)

March 21

March 22

  • Do you think the butterflies are late this spring?
  • Or, do you think there are fewer butterflies than last spring, so not as many are being sighted? (Perhaps there was a smaller population this winter in Mexico, or higher mortality during the winter, due to the unusual cold?)
  • Or, could it be that we're getting fewer REPORTS of butterflies?!

Always remember to consider how the data are being collected as part of your interpretation. (And please remember to report your sightings. We depend on you to track the migration!)

Challenge Question #14:
"Make a list of all the ways that the observers might affect the results of our migration study." (First prize goes to the class with the longest list of examples! Last year, Ms. Bailey's class in Florida thought of forty three!)

Who's Watching for Butterflies?

Here is a map showing where Journey North participants are located.

Challenge Question #15
"Describe what you notice about the distribution of Journey North observers. Why is this map always important to keep in mind when you interpret migration sightings?"

(To respond to these questions, please follow the instructions below.)

First Migration Update Sent to Sanctuary Area Schools
When the monarchs arrived in the sanctuaries last fall, the students in the region announced the news. Now your migration observations are being sent back to them! Beginning this week, Journey North is sending a weekly FAX to the town of Angangueo. Our coordinator there, German Medina, is distributing the news to 15 schools in the surrounding mountains. In each classroom there's a migration map where students can track the monarch's journey all the way to Canada. Here is the first update written in Spanish, along with an English translation:

Students and teachers at Escuela Cerro Prieto.
These students' families own critical land in the Sierra Chincua sanctuary

Students monitored the monarchs' arrival last fall and announced the news when the monarchs appeared in great numbers in mid-October.

Escuela Presidente Calles

News from the Migration Trail in Northern Mexico
Right now, the monarchs are traveling en masse through northern Mexico. Can you find these Mexican states on your map? Queretaro, Guanajuato, San Luis Potosi, Tamaulipas, Nuevo Leon, and Coahuila.

In Saltillo, Coahuila, Rocío Treviño saw her first migrant last weekend: "El sábado 17 de marzo una mariposa monarca visitó mi jardin. Era una hembra, venía un poco maltratada," she reported.

"The spring migration out of Mexico presents deliciously interesting questions, but no answers," says Dr. Bill Calvert. "On their way north, the females are probably laying eggs wherever they can find milkweed, but how much reproductive effort there is before the monarchs reach Texas--nobody knows. It would be wonderful to do transects. There are not many observations from this region, but it's not as if the monarchs are heading for the U.S. border to reproduce! I have the impression that Asclepias curassavica (Tropical milkweed) is found along the water courses; and that the wettest areas don't have as much milkweed as the mesic areas do. As for nectar, the spring flowers are way ahead of the U.S., so there's plenty of nectar. (This all varies with habitat. You have a rain shadow effect on eastern side of the ranges. Prevailing winds are from east, so it's quite wet on the east side. As you go west, you get into pretty severe Chihuahuan desert.)"

Final Field Notes from the Mexican Overwintering Region
Now back in Texas, Bill Calvert sends his final observations made last week in Mexico:

March 21, 2001


"All last week butterflies from the Rosario colony flooded the town of Angangueo. Thousands were in the air, all proceeding northward. People in Angangueo certainly notice when the monarchs descend into town en masse. When they're in town, that's a pretty good indication of remigration occurring. It's too far for the butterflies to go back to the sanctuaries--so it's virtually certain that they're ready to head north."

Final Field Notes from Eligio Garcia
"As they are migrating, it is a very pretty spectacle," remarks Eligio. "Adios amigos!"

Challenge Question Extravaganza!
Send Your Answers Now
In next week's update, we'll discuss Challenge Questions #1-#13. Review all the questions we've posed about monarch overwintering biology and send us your thoughts:

How to Respond to Today's Monarch Challenge Questions|

question in each e-mail message!

1. Address an e-mail message to:
2. In the Subject Line of your message write: Challenge Question #14 (or #15)
3. In the body of the EACH message, answer ONE of the questions above.

The Next Monarch Migration Update Will Be Posted on March 28, 2001

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