Your class can test an age-old theory about robin migration by asking, "Is it true that robins arrive when the 'isotherm' reaches 36 degrees F?"
The word "isotherm" means "same temperature". It is an imaginary line that connects places which have the same average temperatures. The isotherm migrates across the continent as temperatures warm in the springtime. We can test whether robins travel with it. The example below shows how to calculate the isotherm by averaging the daily temperatures over a period of time.
Activity
1. Find out when robins normally return to your region each
spring. Begin this lesson about one month before their
average date of their arrival.
2. Measure the daily high and low temperatures every day for seven days. (You can find this information in your local newspaper. Or, you can measure the daily high and low temperatures yourself using a "maximum/minimum" thermometer.)
3. Calculate the AVERAGE daily temperature for each of the seven days.
4. At the end of the seven days, average the 7 daily
averages. The result is the "isotherm" for that week.
Sound confusing? Here's an example for one fictitious week:
DAY Hi/Lo/Average (Degrees F)
Mon: 40/20/30
Tue: 32/20/26
Wed: 29/15/22
Thu: 26/15/21
Fri: 34/20/27
Sat: 40/20/30
Sun: 42/28/35
30 + 26 + 22 + 21 + 27 + 30 + 35 divided by 7 = 27 degrees F.
Isotherm for the week: 27 degrees F. (No robins yet!)
5. Have students watch for the first earthworms and note the isotherm when worms appear.
6. Contact a faraway school and see if your students can predict the arrival of the first robins and earthworms there. You can find the daily high and low temperatures of most cities on the Internet or in the newspaper. You could also exchange temperature data on-line with another class. To connect with another classroom, send an e-mail messsage to: jn-talk@learner.org
7. Remember to report the first robin you see this spring to: jn-report@learner.org
Questions for Class Discussion
1. Does this theory seem to hold true where you live? Why or why not?
2. What other factors might influence the date of the robins' arrival?
2. Why do you think robins might move north at this temperature?
3. Do you see a correlation between the arrival of robins and the appearance of earthworms?
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