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Monarch Butterfly Migration Update: October 17, 2003

Today’s Update Includes:

Highlights From the Migration Trail

Click Map to Read Highlights Along the Migration Trail

The migration continued in full force across Texas during the last week. Like a postponed parade, its progress southward had been held up by the rainy weekend. But when the weather cleared, “We began seeing monarchs dropping down out of the clouds,” said one awestruck observer. The migration also poured across the border into Mexico in the wake of the cold front. U.S. weather maps may stop at the border, but weather systems and monarchs move across without notice--and bring the same excitement to the people waiting there:

"¡Por fin llegaron!," wrote Rocio Trevino. "Después de varios días de llamadas y correos electrónicos preguntando por qué no llegaban las mariposas, al fin las tenemos con nosotros, volando a diferentes alturas, tranquilas como sin prisa por llegar a su destino, disfrutando de los campos floridos que nos han dejado las lluvias de los últimos días."

Here are other highlights of the week:

Mrs. McCoy's first grade class at Willie Brown Elementary in Mansfield, TX saw the most monarchs they had ever seenor even imagined:

"As we walked out of the gym at 11:10 on Friday, we looked up to see a dark gray cloud. No, it wasn't a rain cloud; we were watching thousands of monarchs flying south. The class observed for thirty minutes as the mass of monarchs grew smaller and smaller. We found that, if we were very quiet, some of the butterflies would float down close enough for us to be able to see through their wings. What a sight!"

"They are here! Finally!" called out Carol Cullar from Eagle Pass, TX. "I had to leave the house at 5 and didn't see a single monarch all afternoon, but I took the flashlight out just now and found one tree with several branches covered. NOW THEY'RE HERE!!!!!!!!"

Monarchs Resting on Mesquite in Texas
October, 2002

Photos courtesy of Carol Cullar

"After two days of near constant drizzling rain, I did not expect to see so many butterflies in our trees. But, this afternoon the rain stopped and I see they have come to roost in huge numbers. Two days ago, I estimated their numbers to be a few hundred; today I am seeing several thousand. I wish I knew a better way of determining their numbers. Anyone know a method?"

Estimating the Number of Monarchs in a Roost
Scientists often use still photos to help estimate numbers, whether counting whales or caribou, bats or butterflies. Here's a chance to practice so you're ready if you happen upon a major monarch roost some day:

Two Migration Pathways in Texas

Courtesy of Texas Monarch Watch

Meanwhile, on the Texas Gulf Coast, Harlen Aschen reported: "The fall migration of monarchs has started along the Texas midcoast. Between 5:45 and 6:15 we were counting almost one a minute dropping out of the sky near the north end of the Lavaca Bay Causeway."

The migration actually moves through Texas on two different flyways, and at two different times, or pulses. The first pulse travels down the Central Flyway and the second pulse moves along what's known as the Gulf Coast Flyway. The monarchs that use the Central Flyway probably come from the mid-western prairie states. The coastal monarchs most likely come from east of the Mississippi River. Typically, the second pulse reaches Texas later because the monarchs have come from farther away. Look at a map of North America and compare it to this map of migration pathways in Texas, made with Texas Monarch Watch data.

Watching and Waiting at the Mexican Sanctuaries
Once again, no monarchs were seen last week by students who are waiting beside the sanctuaries in Mexico:

The Importance of Negative Data: Challenge Question #11
For 4 weeks in a row, these students have been watching for the migration to arrive. Day after day, they report having seen "zero" monarchs. Watching for something, and recording what you DON’T see, is called collecting "negative data."

Challenge Question #11:
"What wouldn’t we know about the arrival of the migration in Mexico without having collected 'negative' data? When the monarchs finally do arrive, explain why the zeros will be so helpful."

(To respond to this question, please follow the instructions below.)

Can a Late-Season Monarch Make it to Mexico?

Tagged by Mrs. Kloewer's Class in York, Nebraska

Despite the fact that it's mid-October, monarchs are still migrating down from the north. They were even reported last week in places like Ontario, Minnesota, Michigan, Vermont and New York.

When fall weather suddenly turns cold, many students write to say they’re worried about the butterflies they're raising in their classrooms. Is it possible for a late-season monarch to make it to Mexico? You can answer this question yourself by analyzing tagging data. Tag recoveries are posted on the Monarch Watch site. (A "recovery" means the tagged butterfly was captured again later.) Look through the records and find recoveries of monarchs that were tagged in your state or province. What is the latest date a tagged monarch has made it to Mexico?

Animal Adaptations: Migration as a Survival Strategy
An "adaptation" is a physical or behavioral feature that evolved in response to an organism's environment, due to pressures for survival. How a species looks (its anatomy and morphology), as well as how it behaves (how it moves, obtains food, reproduces, responds to danger, etc.) are all adaptations for survival.

Monarchs and Milkweed: Comparing Strategies
Monarchs and milkweed occupy the same habitat during the breeding season. But when freezing temperatures approach, they show very different adaptations for survival. Monarch butterflies carry their seed stock all the way to Mexico; Milkweed seeds stay home. When the two meet again next spring, imagine how different their lives will have been!

Try This!

  • Describe the life cycles of monarchs and milkweed. Draw a picture of each during each season.
  • How are milkweed and monarch survival strategies similar in the fall? How are they different?
Milkweed seeds blowing in the wind

Monarch butterflies flying to Mexico
Photo: Lincoln Brower, Sweet Briar College

Three Cheers for the Ones That Spend the Winter!
As incredible as monarch migration is, other butterflies and moths are incredible in the fact that they do NOT migrate! This winter, when you're freeeeeeeezing cold, think about the moths and butterflies that stick around for the winter. How do they do it? Learn about these three species and let us know:

How Do These Survive the Cold?

NectarFeedingFink01  NectarFeedingFink04  NectarFeedingFink06 
1. Viceroy  2. Black Swallowtail   3. Sphinx Moth

Challenge Question #12
"In what stage of their life cycle do these butterflies and moths over-winter?"

(To respond to this question, please follow the instructions below.)

How to Respond to Today's Challenge Question
1. Address an e-mail message to:
2. In the Subject Line of the message write: Challenge Question #11 (or #12)
3. In the body of the message, answer the question above.

The Next Monarch Migration Update Will Be Posted on October 24, 2003.

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