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Monarch Migration Update: September 13, 2002

Today's Report Includes:

Highlights Along the Migration Trail

Cold Front Triggers Migration
A classic fall cold front spread across the monarch's range this week. Temperatures dropped, winds shifted from south to north, and observers everywhere noted its effect:

09/10/02 St. Peter, MN
Jim Gilbert and students tagged 50 monarchs last week at Gustavus Adolphus College. "Every day, we kept seeing the same ones hanging around the gardens. A cold front came through yesterday evening and we have a north wind today. We're not finding a single one with a tag--the old group is gone and there's a new group of about 25 there today!"

09/11/02 Two Rivers, WI
Along the Lake Michigan shoreline, 320 monarchs were counted during a 4 minute drive. Some were circling in large groups and others were heading southwest. "In many areas there were so many monarchs flying overhead it was difficult to count, particularly while driving!"

As the cold front move southward, Iowa towns reported in like a conductor announcing stops on a train line: Algona, Altoona, Cedar Rapids, Cresco, Creston, Malvern, Monona, Pella and Prairie City--each town announced their news. But along with the excitement came expressions of sadness in memory of last September 11:

09/10/02 Altoona, IA
A cold front was passing through the state, and by late afternoon, migrating monarchs were riding and floating on the wind on their southerly journey. In 45 minutes--from 5:15 p.m. to 6 p.m.--150 monarchs were counted high in the sky flying over our butterfly garden. Some could be seen with the naked eye, but this was a day when binoculars were needed to experience the magnitude of the event.

09/10/02 Cedar Rapids, IA
At 5 pm, a steady flow of monarchs is now occurring. They are flying singly, rather high and almost out of view, at a rate of 6 per minute. The weather took a marked turn today, only 69 compared to high 80's yesterday. The winds are 17 mph, NNW and it is very grey. If it was colder, I'd call it blustery.

09/10/02 Pella, IA
This evening, at about 6 pm I looked up and saw many Monarchs flying by, I counted about 60 but sure there were a lot more. We've had hot weather, but a cold front is coming through now.

09/11/02 Kalona, IA
The migration has started to pass through our playground at school. Today, at 10:00 AM, we spotted 10 Monarchs heading south like they were on a mission. This is definitely a bright spot on this solemn day.

09/11/02 Cresco, IA
Fifth and 6th graders at Crestwood Elementary released monarchs today as a part of our special Sept. 11 ceremony--true symbols of freedom and beauty!

Fall Monarch Migration: About Cold Fronts and Winds
"It's easy to see why monarchs come in on cold fronts. It's like catching a bus going your way - in this case the ride is even free!" says Dr. Calvert. For more information about monarch migration and weather see:

News Spotty from South and Northeast
From his vantage point in near the Gulf Coast, lepidopterist Gary Ross summarizes the situation to the south:

09/03/02 Baton Rouge, LA
"Monarchs are now well represented in the lower Midwest as well as the Gulf South. Also, many females are ovipositing (laying eggs)."

Meanwhile, the only news from the northeast, where the population appears to be extremely low, were scattered sightings of single monarchs:

09/07/02 Vergennes, VT
Today I saw a lone monarch. This is the fourth one I have seen this summer.

09/11/02 Walpole, NH
This is only the 2nd monarch I have seen all summer.

09/11/02 DeLancey, NY
Just looking out the window at the leaves blowing and there's the very first monarch I've seen this September.

Also Seen Migrating This Week: Dragonflies
Green Darner
Visit the Digital Dragonfly Museum
A massive dragonfly migration occurred on Monday evening as the cold front moved through Minnesota. Dragonflies filled the skies like hundreds of miniature helicopters escorting the monarchs that were traveling with them. People living 10 miles apart witnessed the event, meaning this wave of migration was at LEAST that many miles wide. "Massive swarms commonly follow the passage of cold fronts" says the North American Dragonfly Migration Project website. Where are the dragonflies going? And who eats THEM along the way? A parade crosses the sky every year at this time, with predator following prey. See:
What’s Up? Lie Down and You’ll See
Dr. Calvert watches monarchs arriving at the sanctuaries in Mexico.

With eyes on the fronts of our faces, we rarely look upward. So lie down for awhile this fall, look up at the sky, and see what you see while watching for monarchs. In this photo, monarch biologist Dr. Bill Calvert demonstrates sky-watching position. (Being a biologist is a tough job!)

  • Please tell us what other creatures are migrating where you live. (Report as "Fall Nature Notes.")

Analyzing Data From Mr. Viger’s Monarch Roost
During fall migration, some lucky people have thousands of monarchs pause in their yards at overnight roosts. Mr. Viger of Campbell, MN is one such person. He sent these pictures to share. How many tagged butterflies can you find in this roost?

"The picture of my two kids (Alex age 5 and Emily age 3) from last year has an interesting story," said Mr. Viger. "We tagged a few butterflies in the morning and I told the kids to bring their last ones to the house and I would get a picture. One of those butterflies was recovered in Mexico. It's neat to have a picture of a butterfly (I'm not sure which one) that made it to Mexico.

"It does seem like the migration is a little later this year," he continued. "So far, 38% of this year's butterflies have come after the last date they were here last year (9/6/01). Of course, the most obvious difference from last year is the lower number of butterflies. So far this year, 740 have visited compared to 10,400 last year (just 7.1%)."

Each day Mr. Viger counts the monarchs, tags them, and records information about the wind and weather. Last year monarchs were present for almost 3 weeks and he noticed an interesting pattern. You can see it too if you look carefully at his data between August 27 and September 6.

  • Link to Mr. Viger’s Monarch Roost Data
  • Make a graph to show the number of monarchs present each day between August 27 and September 6 (or print and analyze our graph above).
  • Look carefully at the wind direction he noted each day. (Write the wind direction for each date beside the data point on your graph.)
  • Then try this Challenge Question:

    Challenge Question #3:
    “Describe the pattern you see at Mr. Viger’s monarch roost between August 27 and September 6. What relationship do you see between wind and migration? Explain why you think monarchs might behave this way.”

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

Try This! Estimating the Number of Monarchs in a Roost

Courtesy of Tim Mostrom

People are dazzled by the beauty of fall "butterfly trees." How can you estimate the number roosting? Scientists often use still photos to help estimate numbers, whether counting whales or caribou, bats or butterflies. Here's a chance to practice. As a class, take a 10-second look at Picture #1 and record the number of butterflies you think you just saw.
Discussion of Challenge Question #2
Last week we read about scientists who changed monarchs' biological clocks to study how they navigate. To help understand how our behavior is effected by our sense of time, we asked you to imagine what would happen if YOUR biological clock were changed by 6 hours.

Poth Elementary students in Texas wrote, "Our third grade GT class thinks that if we arrived at school 6 hours early nothing would be going on. The school would be deserted. We would not be able to get in. If we arrived 6 hours late we would get to school at 2:00 P.M. It would almost be time to go home. We might get in trouble. We would be counted absent."

Similarly, when the monarchs' clocks were off, they behaved as their internal clocks instructed. They flew in the wrong direction because the outside environment--the location of the sun--was not where it should have been to guide them properly. (See last week's story.)

Symbolic Migration: Send Your Smiling Face!

Only 29 more butterfly-making days before the October 11th postmark deadline.

Tip: Mexican students are eager to meet you! If you can, glue your photo to your monarch and send your smiling face to Mexico to greet your new friend. In past years, we've seen wonderful butterflies with photos for faces fly by. (See example on the web.)

Please Report Your Sightings!
We can't track migration without your help. Please come to the web and share your observations.

How to Respond to Today's Challenge Question

1. Address an e-mail message to:
2. In the Subject Line write: Challenge Question #3
3. In the body of the message, answer the question above.

The Next Monarch Migration Update Will Be Posted on September 20, 2002.

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