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Robin Migration Update: March 3, 1998
Today's Report Includes:
- Today's Migration Data
- Please Report WAVES of Migrating Robins
- Notes from Journey North Observers
- Challenge Question # 4
- Watch for Migrating Earthworms
- Students Respond to Challenge Question #2
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The robins are on the move! In the 14 days since our last update, 71 robins have been reported.
- Link to Today's Migration Data
Please Report WAVES of Migrating Robins
If a wave of robins is clearly moving through your area, but you've already reported your FIRST robin, please report
this news. (Select "FIRST robin", but explain in the comments that you are reporting a wave or peak of
the migration.) Here's Why: Due to the mild weather, many robins may not have moved as far south this year as normal,
so many people have reported sightings of overwintering robins. Nevertheless, more robins will be on their way
and we want to record this migratory movement.
Notes from Journey North Observers
From the wintering grounds in the South, Jim Edson noted the stirrings last week: "We've had robins all winter,
but today they are here in large flocks," he reported from Monticello, Arkansas on February 24th. (edson@uamont.edu)
Mr. Cox's students in Lenora, Kansas reported on 02/23/98, "Nobody in our class saw a robin until this last
weekend, and then 4 of us saw them on the same weekend," (ncox@ruraltel.net)
From Michigan's upper Peninsula came this early robin sighting: "Usually it is an April Fool's joke here if
you say I saw a robin (but) we have had a real mild winter. Most of our snow is gone and the average temperature
for the month of February was 38 degrees at noon. This is why we think they have come back so early. The first
robins sighted in our class were by Bobby Han on the shores of Chicagoan Lake in Iron County. He said there were
about 6 of them together on 02/26/98." (psabotta@up.net)
Food and Fuel (and Challenge Question # 4)
Migration takes lots of energy, and robins must find food all along the
way. You can imagine how hungry they are when they finally arrive on their nesting grounds. Students at Dalton
School in New York were concerned about this:
"My second grade students want to know what robins eat. Do they only eat worms? We are in Western New York,
where the ground is covered with snow. We have not seen any robins yet, however other areas around us are reporting
sightings." (daltonschool@wycol.com)
If you're also worrying about newly arriving robins, we'd better find an answer to this question!
Challenge Question # 4
"What do robins eat when worms are not available?"
(To respond to this question, please follow
the instructions at the end of this report.)
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In areas where the ground freezes, one sign of spring is the appearance of the first earthworms of the season. This is called a "vertical migration". In his book, "North With the Spring", Edwin Way Teale describes this event. Read his description below, then keep your eyes opened for migrating worms. When you see your FIRST earthworms of the season, report them to Journey North as a "Signs of Spring".
"One morning we followed a path across a wide, dew-covered field. Ahead of us, as far as we could see, the trodden earth was speckled with the castings of innumerable earthworms. They, in their way, recorded a form of vertical migration in the spring. Earthworms, in the fall, migrate deeper into the earth, below the frostline. Sometimes they ball up to reduce moisture loss--as many as a hundred worms being bunched together--and thus spend the winter in inactivity. When spring comes and frost leaves the soil, the earthworms become migrants again, tunneling upward. They appear at the surface, leaving the first castings of the new seasons, as soon as the average temperatures of the ground reaches about 36 degrees. At the same time, the robins return from the South. This is part of the endlessly meshing gears of nature's machine--the appearance of both earthworm and robins when the thermometer rises to a give point. All over the North, the return of the humble earthworm, the completion of its vertical migration, is a symbol of the arriving spring." (North With the Spring, St. Martin's Press. 1951.)
Students Respond to Challenge Question #2
So now "Why do you think it would make sense for robins to migrate with the 36 degree isotherm?", as Challenge Question # 2 asked. In thinking this through, Tony & Linda of Griswold Middle School in Rocky Hill, CT saw the connection between earthworms and robin migration:
"We think that the robins arrive with a 36 degree isotherm because they want to get there when spring starts. This way their prey will appear and they will have plenty of food to eat. This insures their survival."
(griswold.middle.sch@snet.net)
From Dalton School, teacher Patrice Forrester reported: "This question was very difficult for my second grade class. Explaining isotherms was very challenging in itself. However, we did come to the conclusion that an isotherm of 36 degrees would allow the snow to melt and the ground to warm up, inviting the robins to search for food." (daltonschool@wycol.com)
Testing the Theory about Robin Migration and Temperature
You may find that the isotherm theory is more accurate for the PEAK of the robin migration, than for the wave of "FIRST" robin sightings which Journey North tracks. To measure the PEAK migration in your area, have your class keep records of the number of robins seen each day. You should see the number of sightings build as the migration comes to a peak. (Let us know what you discover!)
How to Respond to Challenge Question # 4
1. Address an e-mail message to: jn-challenge-robin@learner.org
2. In the Subject Line of your message write: Challenge Question # 4
3. In the body of the message, give your answer to this question:
Challenge Question # 4
"What do robins eat when worms are not available?"
The Next Robin Migration Update Will be Posted on March 10, 1998.
Copyright 1998 Journey North. All Rights Reserved.