Monarch Butterfly Migration Update: September 17, 2004
Today’s Update Includes
- Highlights from the Migration Trail
- Interactive Maps: Read All Reports on the "MapServer"
- This Week’s Fall Migration Focus: Flight
- Wind and Thermals: Two Ways Butterflies Fly Free
- Free Ride to Mexico: Glide Don't Flap
- Challenge Question #5
- Flapping Flight: A Look at Flight in Slow Motion
- Challenge Question #6: How Many Times Can YOU Flap?
- Video Clips and the Scientific Process
- Field Trip in the Sky: Flying in a Thermal
- Reminder: Symbolic Migration Deadline Oct 15th
Highlights From the Migration Trail
 |
| Click
Map to Read Highlights Along the Migration Trail |
We have tracked the fall migration to Mexico for eight years. For the first time, we can't determine the migration's leading edge or any peak. Reports of monarchs are coming in--100 sightings during the past week--but they are scattered all over the map. Also noteworthy are observations of eggs and larvae in northern regions, perhaps suggesting late reproduction. Comments about LOW NUMBERS, such as the following, are being reported regularly:
9/12/04 Dyart, Iowa
"We have had sporadic sightings of singleton Monarchs flying at treetop level to the south for the past 2 weeks, but Sunday, September 12th was the first time there were roosting Monarchs in our conifers. We had 35-40 Monarchs here for 5 days during a hot spell with southern winds predominating. Last year I had tagged over 500 by this date. So far I have tagged 47 this year. Yesterday a front came through and the winds shifted to the North and the Monarchs are gone this morning."
9/15/04 Campbell, Minnesota
As of September 15th, Mr. Paul Viger has had a total of only 58 monarchs at his roost site since he began counting on August 20th. This compares to 189 in 2003, 779 in 2002, and 10,400 in 2001 as of the same date.
9/13/04 Centre County, Pennsylvania
"Generally, from late July through late September, we see 6 to 10 Monarchs every day. This year, we've only seen 8 or 10 all summer!"
09/12/04 Scarborough, Ontario
"At this date a year ago I had tagged 495 Monarchs. This year my total is 19. Of those, 17 were reared indoors. Last year, only 28 of the 495 were raised indoors. This means the discrepancy is mainly due to the lack of migrating adults, not the number of eggs, larvae and pupae recovered and reared indoors."
Interactive Maps: Read All Reports on the "MapServer"
All monarch sightings that have been reported are displayed on our MapServer. You can “click” to read each observer’s comments.
 |
 |
 |
| Peak Migration Sightings | Sightings of Overnight Roosts |
Journey North Archives: Fall 1997-2003
Visit our archives and read for examples of how this year's migration is different than those in past years:
This Week's Fall Migration Focus: Flight
During the past two weeks, we have written about monarchs resting in roosts and fueling their flight with nectar from flowers. But migration is about traveling. So let's take a look at monarch flight this week...
 |
 |
 |
Wind and Thermals: Two Ways Butterflies Fly Free
On windy days, monarchs can catch a free ride. If the wind is from the north, they can glide effortlessly southward. (Which weighs more, an autumn leaf or a monarch butterfly?)
| A thermal is a column of rising air, caused by uneven heating of the earth. |
On sunny days, monarchs can rise into the sky on “thermals.” (A thermal is a column of rising air. Thermals occur in places where the sun heats the earth unevenly.) When a monarch is lifted by a thermal, it circles in tight spirals, and goes higher and higher. Then it glides downward and southward to catch the next thermal.
Free Ride to Mexico: Glide Don't Flap
 |
| Dr. David Gibo studies monarch flight |
When a monarch glides or rides with the wind, it burns no more energy than when it is sitting still. (The rate of energy burned while at rest is called the "resting metabolism.") Gliding provides a free ride. It's as easy as riding a bike downhill. In contrast, "flapping" or "powered" flight takes a lot of energy.
Dr. David Gibo is a glider pilot. (A glider is an airplane without an engine.) He is also a scientist who is interested in studying monarchs. So, Dr. Gibo has thought a lot about monarchs, gliding and energy use during flight.
According to calculations by Dr. David Gibo, who’s a glider pilot himself, a monarch burns 140 mg of fat to either:
- fly for more than 1,000 hours in soaring/gliding flight OR
- fly for 44 hours in flapping flight
How Expensive is Flapping Flight?
Challenge Question #5:
"According to the example from Dr. Gibo, how many times more energy is burned during flapping flight than during soaring/gliding flight?"
(To respond to this question, please follow the instructions below.)
Flapping Flight: A Look at Flight in Slow Motion
Here is a video clip of monarch flight in slow motion. The action is slowed down 50 times. This means the video clip lasts fifty times longer than it did in reality. In other words, we recorded this monarch flying for one half second and then stretched it out to last for 25 seconds.
 |
 |
|
| Links to Video Clip and Still Images | ||
During “powered” or “flapping” flight, monarchs flap their wings about 5 to 12 times a second, depending on how hard they’re trying to move. They flap at the slower rate when flying leisurely, such as during migration. The faster rate is needed when flying into a strong headwind, or when trying to escape from a predator, for example.
- How many times does the monarch flap in the half second video? Count the number of full strokes the butterfly takes.
- Do you think it was flying leisurely—or trying to get away from the photographer?
- When watching slow motion flight, what do you see that you’ve never noticed before? Record all the new things that you see.
Challenge Question #6
“If a monarch flaps its wings 5 to 12 times per second, how many times per minute does it flap? How many times can you flap your arms in a minute? (Try it, and let us know.)”
(To respond to this question, please follow the instructions below.)
Video Clips and the Scientific Process
Observation is the first step in the scientific process. Video clips provide an opportunity for students to make authentic scientific observations. Here are some suggestions for viewing video clips as a scientist:
Field Trip in the Sky: Flying in a Thermal
By Elizabeth Howard
 |
 |
 |
I had read about thermals, but now I understand them. Thanks to Dr. Ian Worley, pilot and professor at the University of Vermont, I went up into the sky and found out what it's like to fly in a thermal.
"I take my students on aerial field trips because we can see things from the sky that we can't see so well from the ground," said Dr. Worley. "But more excitingly, we can have a feel of the sky and learn its shape--what’s going on in the air-- because though the air is sometimes invisible we can feel it with the airplane. Today, we’re off looking for thermals, those rising columns of air that take gliders and hawks and butterflies to higher heights so they can glide to the next thermal and find their way south during migration."
We hopped aboard his plane and headed for the sky. But where would we find a thermal? And, I wondered nervously, what WOULD it feel like to fly through one in a small plane?
Reminder: Symbolic Migration Deadline Oct 15
Only 42 more butterfly-making days before the Symbolic Migration deadline. Don't be late! Butterflies received after the postmarked deadline cannot migrate.
 |
 |
 |
How to Respond to Today's Challenge Question
1. Address an e-mail message to: jn-challenge-monarch@learner.org
2. In the Subject Line of the message write: Challenge Question #5 (or #6)
3. In the body of the message, answer the question above.
The Next Monarch Migration Update Will Be Posted on September 24, 2004.
Copyright
2004 Journey North. All Rights Reserved.
Please send all questions, comments, and suggestions to jn-help@learner.org
