Spring Fever for Hummingbirds?
Testing a Temperature Theory of Migration

 Time: 1 period + occasional time over several weeks Standards
Background: An age-old theory says that some migrating birds arrive in an area when the average temperature is a specific value. (Robins, for instance, are said to arrive with 36 degree average temperatures.) Do hummingbirds migrate northward along with a specific average temperature? Try answering this yourselves!

Preparation: To test whether hummingbirds arrive along with a specific average temperature, first find out about when these migrants generally return to your region each spring. Begin the study about a month before their average arrival date.

 Average Temperatures (last week)
Exploration

1. Click on this map to see a larger one. The lines and colored bands show places that had the same average temperatures last week. These will migrate across the continent as temperatures warm in the spring. (Look at or print a new map each week!)

* Can you find the approximate location of your hometown? What was its average temperature last week?
* How did that compare with your temperature records? If they varied, explain why you think they did.
* Name another city or state that had the same average temperatures at yours did.
* Name another city or state that had higher average temperatures.

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

2. Calculate your average weekly temperature. Think about how you could find that — or simply use Our Average Weekly Temperatures data sheet.

3. Each week, ask yourselves, "Have we seen any hummingbirds yet?" Continue to calculate your average weekly temperature and keep your eyes peeled! Finally, ask yourselves this question:
What was our average weekly temperature when hummingbirds showed up in our area?

4. Using Journey North's reported hummingbird sightings, keep track of the dates of the first 10 or so sightings in one state or province. Then calculate an "average first arrival date" for hummingbirds in that area. Then look at an average weekly temperature map; what was the average temperature on the date the hummers arrived?

Making Connections

• Describe the patterns you see on the temperature and migration maps. Do you think there is a relationship between temperature and hummingbird migration?
• Which of hummingbirds' basic needs could be affected by temperature, and how? >
• What other factors might influence the date of the hummingbirds' arrival?
• Do you see a connection between the arrival of hummingbirds and the appearance of flowers or insects? What do you think causes them to appear?
 Why Follow Certain Average Temperatures? Scientists believe that by migrating north as average temperatures reach about 35 degrees F, ruby-throated hummingbirds push the limit. At those temperatures, they are just able find insects and flowering plants that couldn't survive below freezing.

Digging Deeper
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. Make your own classroom connection or join the Journey North Classroom Exchange.