American Robin Migration Update: April 1, 2003
Today's Report Includes:
- Spring Progressing Slowly but Surely: This Week's Maps and Data
- More Sightings from Northern Observation Posts!
- Worming Their Way Up the Food Chain: Challenge Question #8 and #9
- Do Robins Really Follow the 37-Degree Isotherm?
- Learning Language: Discussion of Challenge Question #5
- Timing of Calls: Discussion of Challenge Question #6
- Clues from Above: Discussion of Challenge Question #7
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What would spring migration
be without an April Fool's snowstorm or two? Fortunately, robins
expect to deal with snow during early spring. Photo at the Bridge
School by Fran Ludwig. |
Spring Progressing Slowly but Surely: This Week's Maps
and Data
Even though robins are working their way up the continent,
their progress has been slower than a lot of us wish! Stacy Tilton, a
second grade teacher at Cayuga Heights Elementary School in Ithaca, New
York, writes, "I always look for robins to reassure me that spring
is here, and winter is finally past us. It has been a long cold winter.
It seems as though March 25 is kind of late to see my first robin, and
I haven't seen another since."
Some students are probably looking at dots on the map in their area and thinking, "Wait! I haven't seen any robins yet, and I've been looking!" On March 19, sixth grader Cason, one of B.J. Kohlstedt's students at North Shore Community School in Duluth, Minnesota, spotted a robin, yet Journey North's robin expert Laura Erickson is still looking for her first one almost two weeks later! When robins first arrive in an area, they gather in the spots with the most food. In Laura's yard, waxwings finished off all the berries and apples weeks ago, and the ground is still frozen, so robins haven't turned up yet, even though other areas still have food and even some thawed ground.
Marcia Beltrami's second graders at Algonquin School in Prospect, Connecticut, reported seeing robins eating worms in their yards on March 17. Some robins are turning up in areas in the Southwest, too. Do you think those mght be robins that wintered in Texas?
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Thank goodness for berries
during wintry days of early spring! Copyright by Ann Cook |
Robins have now been reported from a third of the Northern Observation Posts. Shirley Bell writes from Pinawa, Manitoba (a Northern Observation Post), "It's bitterly cold here today -10C with a north wind of 15. The only good thing is the sky is a blue bowl from horizon to horizon. I was trudging home from my facing the wind, when I heard this silly robin singing. He was high up in the trees and though I listened for about ten minutes,there was no answering call. He must have come in from the Midwest just ahead of the snow which hit the Datokas last night."
Check your predictions and keep up to date with news from the NOPs here:
Worming Their Way Up the Food Chain
Whether they're eating berries, apples, worms, or insects, robins get their energy to stay alive from their food. But where does their food gets its energy from? To figure this out, scientists think about food chains. Let's look at some simple robin food chains. Since everyone thinks about robins eating earthworms, let's look at a simple earthworm food chain first:
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Robins get their energy from worms. Worms get their energy from dead, decaying plants (and sometimes animals) in the soil. Where did the plants get their energy from? The sun! All green plants produce carbohydrates in a process called photosynthesis, using nothing but water and carbon dioxide in the atmosphere, and the energy from the sun. So the sun's energy went from the dead plant to the worm to the robin.
Some robin food chains are even shorter:
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Robins eat berries and crabapples. This raspberry plant got its energy from the sun, and is sending it straight to the robin.
Some food chains are very long. When a robin eats a spider, there are more energy levels to the food chain.
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This rose plant got its energy from the sun. The aphid took its energy from the plant. The cricket ate the aphid, and the spider ate the cricket, and the robin ate the spider.
Of course, robins aren't always the end of a food chain--sometimes they are part of another food chain.
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Hmmmm... Something looks fishy about this one. The first part of this food chain is straightforward: The robin ate the worm who ate the decaying plant. And it's not hard to see how a sharp-shinned hawk can eat a robin. But how did a fish--a northern pike--get into the picture? While this hawk was flying over a lake, a peregrine falcon stooped on it and struck! The hawk was mortally wounded, but as it was falling into the water, someone started a motorboat that scared the falcon away. The hawk was still quivering a little, and a pike swimming nearby noticed and gulped it down. And later, a hungry bald eagle ate the pike. The peregrine falcon was an important part of this unusual food chain, but it's not shown. Why not?
Challenge Question #8:
"If a Peregrine Falcon killed the hawk that the fish ate, why isn't the Peregrine part of the food chain?"
(To respond to this question please follow the instructions below.)
Thanks to humans, a lot of food chains are very complicated. This looks like a simple food chain, but it's not:
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This Minnesota robin is eating mealworms from a bird feeder. These mealworms were ordered from a place in Ohio, where they were fed oats that the growers bought in a grocery store. The grocery store got them from a distributor that got them from a farm in Kansas. There was a lot of energy involved in planting and harvesting the oats and processing them to make oatmeal. And there was a lot of energy involved in shipping the mealworms from Ohio to Minnesota. But the energy the robin got was the same as it would have been if the mealworms had been natural food.
Even if making and transporting oatmeal and mealworms are not natural processes, the energy used still came from the sun! Let's see if you can figure out how:
Challenge Question #9:
"How does the energy farmers use for planting and harvesting come from the sun? How does the energy that runs airplanes, trucks, and trains come from the sun?"
(To respond to this question please follow the instructions below.)
Do Robins Really Follow the 37-Degree Isotherm?
Have you been trying to learn whether robins follow the 37-degree isotherm? Here's a new map to check out. Compare the maps below and answer these questions:
- What color is the part of the maps showing the average 37-degree isotherm?
- Has the 37-degree isotherm moved in the past 2 weeks?
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Average
Temperature in United States Week of March 9-March 15, 2003 compared
to March 23-March 29, 2003. (No map available of entire continent.) What color is the 37-degree isotherm? Have robin movements shown a pattern similar to the change in the 37-degree isotherm? Photo Courtesy of NOAA Climate Prediction Center. |
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Do the changes in where the 37-degree isotherm is correspond to where robins have been singing? Compare these temperature maps to the migration maps above. Do you think the migration is following the isotherm?
Learning Language: Discussion of Challenge Question #5
Last time we asked, "Real robins don't have dictionaries. How do you suppose robins learn what each of these sounds means?"
Baby robins learn their language pretty much the way we humans do--by listening and paying attention to what's happening whenever they hear their parents making sounds. Dictionaries may help us humans to learn hundreds of thousands of words and expressions, but children can talk and understand a lot long before they learn to read!
Timing of Calls: Discussion of Challenge Question #6
We asked "Which robin vocalization is most likely heard just before the sun rises? Which is heard more often at noon than any other time?"
The first part of this wasn't too hard--the answer is the "continuous song," which is nicknamed the "dawn song" because it's so often given at first light. But the second part was trickier. Robins do most of their regular singing in morning and then late afternoon/early evening. Most of the distress and warning calls can be heard at any time of day. But the time of day that hawks are most active, especially when they are flying overhead, is at mid-day, so the "High Seee" call is the one most often made around noon.
Clues from Above: Discussion of Challenge Question #7
"Working together with classmates, list at least 10 clues robins can see or hear from above that tell them about the territory down below."
Amtul and Susan, seventh graders at Iselin Middle School, listed some great clues:
- see the sun's direction
- hear other birds singing
- look for evergreen trees
- hear bulldozers
- hear the wind in a certain direction
- see or hear waterways
- see houses
- see trees with fruit
- see powerlines
- see lawns without bushes
We thought of just a couple more:
- see hawk nests in the tops of trees, or hawks soaring
- hear jays squawking or crows calling
How to Respond to Today's Challenge Questions:
IMPORTANT: Answer only ONE question in each e-mail message.
1. Address an e-mail message to: jn-challenge-robin@learner.org
2. In the Subject Line of your message write: Challenge
Question #8 (OR #9).
3. In the body of your message, give your answer to ONE of the questions
above.
The Next Robin Migration Update Will Be Posted on April
8, 2003 (data only).
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