Monarch Butterfly Migration Update: September 12, 2003

Today’s Update Includes:

• Highlights from the Migration Trail
• Monarch Off the Map: Discussion of Challenge Question #2
• The Monarchs That Flew the Wrong Way: Two True Stories
• Free Ride to Mexico: Glide Don't Flap
• Challenge Question #4: How Expensive is Flapping Flight?
• Wind and Thermals: Two Ways Butterflies Fly Free
• Field Trip in the Sky: Flying in a Thermal
• How Fast Were We Rising? Challenge Question #5
• Migration Rate Math: Discussion of Challenge Question #3

• This Week's Migration Highlights

• Mrs. Rose of St. Joseph School found her first roost of the year in Lincoln, NE.
• A boy in Marshall, IN was climbing a tree when he discovered monarchs flying in to settle for the night.
• Dr. Chip Taylor of Monarch Watch says the leading edge of the migration just hit eastern Kansas on September 6, a little early.

US Drought Monitor

The map on the right shows drought conditions in the U.S. Find the regions with moderate, severe and extreme drought. How might drought affect the monarchs? List all the ways you can imagine.

"Central Iowa is exceedingly dry now," says Robert Woodward of Drake University. "Some wildflowers are drying out early and dying. Does the dry weather affect the monarch migration--the timing of it and the places visited?" he wonders.

• The lack of sightings reported from Wisconsin is interesting. An observer on the west shore of Lake Michigan has seen little movement, not "the normal 10-25 per minute when the migration starts."
• Further to the east in Ontario, Don Davis reported a large westerly movement of monarchs along the north shore of Lake Ontario, from at least Oshawa to Oakville on Sunday, Sept. 8. Perhaps these were among the monarchs counted the next day to the west, at Ontario’s Holiday Beach Migration Observatory near Detroit, MI. Monday was a big migration day there, with 1,380 monarchs counted compared to only 50 any previous day.
• The first big surge was reported along the East Coast on September 6 from Long Island: "There were thousands of monarchs migrating along Jones Beach. I counted 40 in one minute."

Since August, it seems an unusually high number of early monarch sightings have been reported from Texas and other southern states. Questions surround early sightings at these latitudes, so it's hard to know whether to include any on the migration map. For the record, the map on the right shows all reports received to date.

• Also read Dr. Calvert's thoughts about early sightings

The Prince of Wales visiting the monarch sanctuaries in Mexico

Dr. Bill Calvert

"The sightings in this country are mainly attributed to North American migrants that have blown over here, and a few escapees from butterfly farms," said Vince Smith, who reported the monarch. "This article sums up the general consensus of opinion of how they arrive in the UK."

• See The Monarch invasion of Great Britain, 1995

"It's conceivable that they were carried aloft and blown over 2,000 miles," believes monarch biologist Dr. Bill Calvert. "It would take more than a day, and monarchs don't normally fly at night--they get disoriented and can't fly. But if caught in high velocity, high altitude winds they can't come down."

So nobody knows for sure! Students debated the question and came up with hypotheses similar to the scientists'. Mrs. Koch's Class in Barnesville, Ohio had the winning number, including their “accidental tourist” hypothesis.

• See Mrs. Koch's Class Discusses Challenge Question #2

• The Monarchs That Flew the Wrong Way: Two True Stories

Dr. David Gibo studies monarch flight

• 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 #4:
"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.)

On sunny days, monarchs can be lifted by thermals. They spiral higher and higher in tight circles, then glide downward and southward to catch the next thermal.

• See: Up, Up and Away: Thermals and Updrafts

I've read a lot about thermals, but now I understand them. Thanks to Dr. Ian Worley, pilot and professor at the University of Vermont, I went up in the sky myself this week 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 a small plane through one?

Dr. Worley spotted a fluffy cumulous cloud and banked the plane to the left. A cumulous cloud is the tell-tale sign of a thermal. The cloud forms when the column of air rises, and then cools at higher altitudes. The moisture in the air condenses and forms the cloud.

"We're going to fly to it and see if we can get an upward rise of air, which we'll feel as a bump. And if it's a REALLY good bump we'll feel it in the seat of our pants," he said.

So off we flew toward the cloud. Here are photos, video and a transcript of the trip so you can find out what happened:

• Field Trip in the Sky: Flying in a Thermal
  

  Challenge Question #5:
  "When we hit the thermal, the plane rose at a rate of 500 feet/minute for 30 seconds. How many feet upward did the thermal carry the plane? How did the plane's speed compare to the speed of a typical elevator?"

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

• Observer #5: (1,032 monarchs/hour)
• Observer #4: (82 monarchs/hour)
• Observer #2: (32 monarchs/hour)
• Observer #1: (24 monarchs/hour)
• Observer #3: (8 monarchs/hour)

The Next Monarch Migration Update Will Be Posted on September 19, 2003.

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