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Monarch Migration Update: October 4, 2000

Today's Report Includes:

Highlights Along the Migration Trail

The forward edge of the monarch migration has continued to push southward. Yesterday Senora Trevino sent the latest news from Saltillo--the farthest south of any monarch sightings yet!

"Las mariposas estan pasando por Saltillo y sus alrededores, aunque son pocas aun, 3 mariposas cada 5 minutos. El sabado 30 de septiembre a las 11 de la manana me reportaron 50 mariposas por minuto en la carretera No. 57 a la altura de La Muralla, al sur de la ciudad de Monclova. Saludos desde Coahuila." Rocio Trevino, Correo Real (

Challenge Question #9
"From what Mexican state is Senora Trevino reporting? How far from the Mexican sanctuaries are the monarchs she saw? To measure, use the latitude/longitude for Saltillo (25 N, -101 W), and the latitude/longitude for Mexico's monarch sanctuaries (19N, -100W)."

For those who don't speak Spanish, this web-based translator is helpful:
"Once classes translate a note with one of the Internet translation sites, they can then use their Spanish to English dictionary to find out the meanings of words that were not translated by the site," suggests Don Davis (see more about Mr. Davis below).

Discussion of Challenge Question #7
Last week we asked about the migration report from the Mexican students in Ciudad Acuna, Coahuila. "How many monarchs per minute did the students count? How early did the monarchs arrive this year?" Thanks for the translations sent by students in Mrs. Parsons' class in Tampa, FL and Ms. Gydesen's 3rd graders in Diller, NE: "The students counted 8 monarchs per minute. The monarchs started to arrive 10 days earlier than last year's migrant monarchs," they said. Que bueno!

Migration Continues to Funnel Toward Texas

09/29/00 Fort Smith, AR (35.36 N, -94.41W)

"We have had the most fantastic sightings 9/29/00 through today, 10/02/00. On the 29th there were 200+ monarchs in our backyard. On Saturday the 30th it was wild! There were 800-1,000 monarchs everywhere--fluttering in the light breezes, feeding, resting in the trees. On Sunday there were 200-300 and today there were approximately 150-200." (

09/29/00 Soper, OK (34.02 N, -95.41 W)
"My 8th grade class saw 8 Monarchs during a 30 minute observation period. It was about 2:00p.m. and they were flying about tree-top high." Soper Public School (

09/28/00 Bedford Hills NY (41.22 N -73.69 W)
"About 50 Monarchs were sighted today in our school yard at recess. Last year we planted a Millennium Butterfly Garden in our school courtyard and interestingly, we have not seen Monarch's there in over two weeks." (

10/03/00 Austin, TX
"There now seems to be something of a lull in the migration. Early last week a strong cold front brought lots monarchs down and exciting reports. North winds and high pressure remained in place during the week, only weakening over the weekend. Monarchs moved slowly through and never seemed to bunch up as they do when south winds prevail. Reports from the north indicate that more are to come. There is not much nectar for them in Texas."
Bill Calvert, Texas Monarch Watch

More Monarchs Still Coming Down from the North
According to observers from Canada and the northern U.S. states, more migrating monarchs are still on their way. South Dakota students were concerned about the cold, "We have already had a couple of frosts," they said. Way up north in Madoc, Ontario, Ms. Conroy's students at Sacred Heart School are still seeing monarchs migrating. "The warm spell has brought more monarchs through the Madoc area this week," they said on October 3rd. "The students have reported seeing two a day in several locations- mostly in the afternoon. There are still a lot of asters blooming. The temperature this week has been in the 20C range, with a lot of sun and blue sky!"

Will These Late Monarchs Make it to Mexico?
As children in the north watch these "late monarchs" fly overhead, they're wondering if the butterflies have a chance. We asked Don Davis, Canada's veteran monarch tagger, what his data suggest. Thirty three of his own tagged butterflies have been recovered in Mexico's sanctuaries!

"The monarch is one tough butterfly!", says Mr. Davis. "The latest monarch I have tagged in Ontario that was later recovered in Mexico was September 30th. Last year, one monarch tagged on Sept. 18th was recovered in Mexico. The latest monarch I recall seeing at Presqu'ile Provincial Park near Brighton, Ontario was a single individual on a windy, cold, overcast day in early November. I do recall one monarch being found in December in Ontario during a Christmas bird count. There was some snow on the ground at the time." Don Davis, Toronto, ON ( )

Challenges of Tracking Fall Migration
These comments point out why it's so difficult to track fall monarch migration. Typically, a person observing in one place can see migrating monarchs for 4-6 weeks--or more! Our weekly migration map is intended to show the forward edge of the peak migration, but with sightings so low in the east it's especially difficult to determine the peak there this year:

09/27/00 Hebron MD (38.39N, -75.73W)
"Monarchs are scarce this year. Last year during migration the students saw an average of one per hour. This year just this one lone monarch so far." Westside Intermediate School (

09/27/00 Yonkers, NY (40.94N, -73.88W)
Last year, on September 27, 1999 we had 1,952 monarchs fly through Lenoir in 70 hours (27.8 monarchs an hour). On September 27, 2000 we had 35 monarchs in 70 hours, (1 every 2 hours). We are hoping that the numbers will increase as we get into October."
Beverly Smith, Hudson River Aududon Society (

Which Week Will the Migration Peak in the East?
Using the data from a single location, Cape May, NJ, make your prediction!

Challenge Question #10
"Based on the data collected during the past 9 years, when do you think the migration will peak this fall along the New Jersey Coast?"

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

Weekly Report from Cape May, NJ
To answer Challenge Question #10, and for those of you graphing the weekly migration count at Cape May, last week's (Week #4) average was: 37.9 monarchs per hour.

Talk About Variables! Discussion of Challenge Question #4
Challenge Question #4 asked, "As a class, list all the possible factors that you think could contribute to the low numbers of monarchs being sighted this fall."

Here are all the ideas from Ms. Dempsey's Second Grade Class in Framingham, MA, the 6th grade Science students in West Iron County, WI, Mrs. Olsen's class in Mystic, CT, and Dr. Bill Calvert:
  • The (fall) weather becoming too cold, too fast. The butterfly may not have finished its metamorphosis.
  • Maybe the amount of milkweed available to the Monarchs is decreasing caused by pollution (pesticides, smog) and destruction of the habitat where milkweed grows (new construction, flooding and fires).
  • They might have only had one baby in the summer. (Referring to variable number and timing of generations.)
  • Northeastern states are spraying to kill mosquitoes carrying West Nile virus. It is believed that the poisons are affecting the fish and crabs of Long Island sound so it is not unreasonable to assume that insects (including butterflies) are being affected as well.
  • Cool, wet summer affected health of milkweed, flowers and generation development time.
  • "I haven't a clue!" says biologist Dr. Bill Calvert. "There are just so many variables to consider."

Dr. Bill Calvert's comment reminds us how difficult the scientist's job can be! List and count all the variables mentioned by the students (above) and in Mr. Hughes's careful observations from New York (below). Describe how you could design a scientific experiment to control all the variables except one, the one you want to measure.

Here is Mr. Hughes' careful account from New York. He describes how cold, wet conditions seemed to affect milkweed vigor and health. These cool temperatures also affect the rate of monarch development at each stage of the life cycle, and in each generation.

How to Respond to Today's Monarch Challenge Questions:

IMPORTANT: Please answer ONLY ONE question in each e-mail message!

1. Address an e-mail message to:
2. In the Subject Line of each message write: Challenge Question #9 (or #10)
3. In the body of the message, answer ONE of the questions above.

The Next Monarch Migration Update Will Be Posted on October 11, 2000.

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