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Spring Fever
Testing a Temperature Hypothesis About Robin Migration

An age-old hypothesis about robin migration says that robins arrive in an area when the average temperature is 36°F. Is it accurate? Why not test the hypothesis yourselves?

To test whether robins seem to travel with average temperatures of 36°F, first find out when robins generally return to your region each spring. Begin the study about a month before their average arrival date.


1. Look at the map of average temperatures. The lines and colored bands show places that had the same average temperatures last week. The lines will 'migrate' across the continent as temperatures warm in the spring. (Come back to see and print the latest map each week.)

  • Find the approximate location of your hometown. What was its average temperature last week?
  • Name the states or regions that had a 36°F average temperature.
  • Names the states or regions you think were too cold for robins.

    (Definition: The lines that connect places with the same average temperatures are called isotherms.)

2. Calculate and plot your average weekly temperature. Use our Average Weekly Temperatures data sheet and follow the example shown in the sample graph.

3. Watch for Robins!
Continue to calculate your average weekly temperature and keep your eyes peeled! When your robins show up, how will you answer these questions?

Did the robins show up . . .

  • before your average weekly temperature reached 36°F?
  • when average weekly temperature reached 36°F?
  • after the average temperature was above 36°F?

Making Connections — Journaling and Discussion Questions
  • Does the isotherm hypothesis seem to hold true where you live? Why or why not?
  • Which of robins' basic needs could be affected by temperature, and how? (See below.)
  • What other factors might influence the date of the robins' arrival?
  • Do you see a connection between the arrival of robins and the appearance of earthworms? What do you think causes earthworms to appear?

Digging Deeper
  • Watch how robin habitat changes: Watch for the first earthworms and note your average weekly temperatures when worms appear. When you see the first earthworm of the season, report it to Journey North!
  • Make Predictions: Choose a faraway Journey North school and see if you can predict the arrival of the first robins and earthworms in their location. You can find the daily high and low temperatures of most cities via these links or in the newspaper. You can also exchange temperature data online with another class.
Why follow the average temperature line (isotherm) of 36°F?
Scientists believe that, by migrating north just behind the advance of this isotherm, migrating birds will find food and open water available. It also allows them to have as long a breeding season as that climate will allow.



Time: 1 period + occasional time over several weeks





Map of Average Temperatures
(Last week)

As of last week, where was the average temperature 36°F?

Data Sheet
For recording and calculating average weekly temperatures


Sample Graph
of average weekly temperatures



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