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A/CPB
Robin Migration Update: March 10, 1998
Today's Report Includes:
- Today's Migration Data
- Analyzing Weather and Robin Migration
- Challenge Question #5
- Discussion of Challenge Question # 4
- Food for Thought: What do Robins Eat?
- Challenge Question #6
- Reminder: Please Report WAVES of Migrating Robins
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Reports of migrating robins are flying into Journey North headquarters! Here are 46 new sightings to add to your map.
- Link to Today's Migration Data
Analyzing Weather and Robin Migration
Over the next few weeks, save the daily weather maps from your newspaper. (Or download WWW-based
daily weather maps.) Watch where robins are reported and see if you can discover a relationship between weather
and robin migration. Do robins seem to fly when it's cloudy or clear? What wind direction do they seem to favor?
Do cold fronts seem to slow them down? What about the storms associated with low pressure systems? Read meteorologist
Glen Schuster's weekly "Weather Forecast for
the Birds" and see if it helps predict the movement of robins. Then see if you can answer this question:
Challenge Question # 5
"What weather conditions do robins seem to favor for migration?"
(To respond to this question, please follow the instructions at the end of this report.)
Discussion of Challenge Question # 4
Last week, students were concerned about the early arrival of robins.
"What do they eat when worms aren't available?", they wondered. Here are answers from Journey North participants."I observed a flock of 20+ robins feeding in a crab apple tree near my feeding stations. We had received several inches of snow during the night & morning, and the robins were pecking at old fallen fruit," said LouAnn Krantz of Polson, MT on March 3rd. (krantzjl@ptinet.net).
Ms. Brundage's 5th grade students in Penobscot, Maine answered, "We think that the American Robin eats insects, rotten apples, berries, and other fruits when they can't get worms." (pes@penobscot.u93.k12.me.us)
Speaking from her own experience, Karen DeCrane replied, "I can answer the because I raised an abandoned baby robin last summer. My robin preferred large, juicy earthworms, but when we started getting her ready togo back into the wild, she ate almost any kind of bug, insect or worm that caught her eye. She didn't like crickets, but would eat grasshoppers, at least the soft parts of them. She didn't like ants, but she was bitten by some and that could be why. She ate corn kernels, wheat seeds, and bird seed. She probably ate berries also, although we didn't try them with her." (pjester@neosplice.com )
Food for Thought: What do Robins Eat?
In summer, when there is an abundance of all kinds of food, the adult's
diet is usually about 60% plant (mostly fruit) and 40% animal (mostly worms and insects). However, when the weather
turns cold, robins must switch to eating almost nothing but fruit. When it's very cold, a robin keeps warm by shivering,
and the sugar from berries gives it plenty of energy to shiver. When robins over-winter in northern places, they
usually stay near fruit trees, and during cold snaps in spring robins may return to them. Fruit also gives robins
energy to fuel their long migration.
Cold weather keeps fruit fairly fresh, but eventually it gets moldy just as food left too long in a refrigerator
does. And old fruit slowly ferments, which means that the some of the sugar changes to alcohol. If robins eat too
many fermented berries, they can become confused and clumsy, and sometimes crash into things or get killed by predators.
So as soon as any fresh food becomes available in spring, robins desert the old berries and concentrate on worms
and any early bugs until the trees leaf out and new fruits start to grow.
As everyone knows, robins do love worms: One baby robin raised
in an experiment actually ate 14 feet of worms in a single day! Worms have lots of protein, so are nutritious for
robins. But just as a person needs a balanced diet with many different kinds of food, robins round out their diet
with other things, too. When they're running on a lawn hunting for worms, they're also searching for other tiny
animals. They eat beetles, caterpillars, spiders, and even snails and slugs, all rich in protein, and some with
other important nutrients that robins need for growing strong bodies and new feathers.
Use binoculars to carefully study a robin on a lawn. Can you identify any of its prey besides earthworms? Make
a list of the different animals it takes.
One fun project that actually helps migrating robins, especially when spring weather turns cold or snowy, is to
set out a bowl filled with mealworms. (Mealworms are insect larvae that become black beetles as adults. You can
buy them at petshops or bird feeding stores, or order them in the mail from companies like Grubco and Rainbow Mealworms.)
How long does it take for robins to discover a bowl of mealworms? How many mealworms can a robin eat in 10 minutes? If a robin ate 100 mealworms in 10 minutes, does that mean it would eat 6000 mealworms in 10 hours? (If a kid ate one cheeseburger in 5 minutes, does that mean he or she is likely to eat 120 cheeseburgers in 10 hours? Why or why not?)
Challenge Question #6
"Assuming a typical earthworm measures 6 inches, and one robin chick can eat up to 14 feet of worms a day, how many worms might an entire nest of 4 young robins demand from their parents in a day?"
(To respond to this question, please follow the instructions at the end of this report.)
Reminder: Please Report WAVES of Migrating Robins
A few days or weeks after you report your FIRST robin, you may suddenly notice robins all over the place. This is called a WAVE. Please report this, too! Select "FIRST robin," but then explain in the comments that you are reporting a wave or peak of the migration. Here's why: Sometimes overwintering robins or a handful of intrepid early migrants appear before the main migration movements. We want to make sure we record the big migratory movement, too.
How to Respond to Today's Challenge Questions
Please 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 # 5 (or #6)
3. In the body of EACH message, give your answer to ONE of the questions above.
The Next Robin Migration Update Will be Posted on March 17, 1998.
Copyright 1998 Journey North. All Rights Reserved.