Robin Migration Update: March 3, 1998
Today's Report Includes:
The robins are on the move! In the 14 days since our last update, 71 robins have been reported.
Please Report WAVES of Migrating Robins
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."
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." (firstname.lastname@example.org)
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: email@example.com
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:
The Next Robin Migration Update Will be Posted on March 10, 1998.
Copyright 1998 Journey North. All Rights Reserved.