Monarch Butterfly Migration Update: September 10, 2004

Today’s Update Includes

• Highlights From the Migration Trail
• Cool Temperatures, Late Butterflies?
• Good Signs of Reproduction in Southern States?
• This Week’s Fall Migration Focus: Nectar
• How Many Monarchs Nectaring in the Alfalfa Field?
• Challenge Question #3
• So Busy Eating You Can Sneak Up and Grab One
• Why is Nectar Most Important in the Fall? Challenge Question #4
• Feeding a Butterfly in Dr. Fink’s Kitchen
• Mystery Animal: How Do You Know it's NOT a Hummingbird?

Click Map to Read Highlights Along the Migration Trail (Mapping Suggestions)

Sometimes, the most significant news is the lack of news. Again this week, the dramatic observations typical of fall migration have been in short supply. However, we do have these highlights:

• On the north shore of Lake Erie, migrating hawks, songbirds and hummingbirds are counted as they pass the Holiday Beach Migration Observatory near Windsor, Ontario. There, the shoreline forms a natural funnel. It forces hundreds of thousands of raptors and other migrants to concentrate as they move through. September 5th was a big day for monarch migration. "Many hundreds were flying over the hawk watchtower in early afternoon at rather low altitudes," said the report from the Observatory.

• "Monarchs are becoming more numerous in northeast Iowa," say observers in Monona, IA. "We have seen a steady number, one every 15-20 minutes, moving in a west, southwest direction through here. This is compared to almost no butterflies of any kind all summer!! Groups of 10-30 were roosting in the trees in the evening of September 7th."

• The monarchs put on a show in an Iowa prairie on Wednesday. "Today was a magical moment," wrote Robert Woodward, who saw 180 monarchs in one 45-minute span. "They were flying to and fro, swirling around my head, and landing on the blossoms of the clover to feed. It was one of those beautiful times when all seems right in our natural world."

How many more miles must this monarch fly?
Mr. Woodward sent this picture of a monarch refueling yesterday in Prairie City, Iowa during its long trip to Mexico.
Prairie City, Iowa 41.55 North, -93.25 West	See Lesson: Latitude, Longitude and Distance Traveled

Cool Temperatures, Late Butterflies?
	July	August

These maps show how much colder than normal July and August temperatures were this year in the Midwest. Monarchs grow more slowly from egg to adult in cool temperatures. Are the monarchs late to develop this year? Is that one reason there are so few? Several northern observers are still reporting monarch eggs and larvae, quite late in the season.

Over-wintering Population in Mexico

"We have had an unusually large number of monarchs in our area for this time of year," reports Anita Brisco from Texarkana, Arkansas. She and other observers across the south are finding monarch eggs on milkweed.

• Will Dr. Taylor’s prediction of good reproduction in southern states and a winter population in Mexico of 4-6 hectares be accurate?

Related Links:

• How is a Human Vacation Like Monarch Migration?
• Life is Sweet for Monarch

Surrounded by miles and miles of corn and soybean fields, the 40-acre alfalfa field shown in these photos is a magnet for hungry butterflies. On this fall day, the alfalfa was in full bloom and filled with butterflies--so many butterflies that the field was aflutter. We tried to count them and estimated one monarch every eight feet.

Challenge Question #3
"Based on the estimate of 1 monarch every 8 feet, how many monarchs do you think were nectaring in this single 40-acre alfalfa field?"

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

Listen to Dr. Brower .

"If you try to catch a butterfly between your thumb and forefinger in the summertime, you'll have a very, very hard time catching it. But they are so intently nectaring [during fall migration] that you can actually, if you're really careful, sneak up with your thumb and forefinger and just grab one. If they've had a good feed their stomachs will actually be fat. (See photo.) They feed on that [nectar], and the nectar has sugar in it. They convert that sugar into fat and that fat is the energy store that they use to fly down to Texas and then on into Mexico."

Challenge Question #4
"Why do you think feeding is more important to monarchs in the fall than in any other season? (Carefully consider the annual cycle of the monarch, in fall, winter, spring and summer.)"

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

• Feeding a Butterfly in Dr. Fink’s Kitchen

• Mystery Animal: How Do You Know it’s NOT a Hummingbird?

The Next Monarch Migration Update Will Be Posted on September 17, 2004.

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