Bald Eagle

Bald Eagle

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FINAL Bald Eagle Migration Update: May 15, 2001

Today's Report Includes:

Special Thanks to Biologist Peter Nye!
As the migration season draws to a close, we'd like to turn your attention behind the scenes. In addition to his busy job, over the past 4 months Peter Nye found extra time to share his research and knowledge with us all. Journey North would not be possible without the dedication of scientists like Peter Nye who contribute their expertise voluntarily. Thank you, Peter!

A Final Look at Bald Eagle Migration

FINAL Migration Map
as of May 15, 2001

As we close this spring, all our Bald Eagles appear to be settling back on their summer breeding grounds. But there are some interesting differences! Most eagles, like E47, E49 and E63, are moving very little. Whereas another, Eagle K58, continues to wander quite a bit--around New Brunswick, Prince Edward Island and Nova Scotia in fact!

Just as you plotted each eagle's winter home range, one could do the same with data from the summer breeding range. Is the eagle truly nesting? If so, how far do eagles wander from their nests during the breeding season? How far do they travel to find food? How does the parents' behavior change when the young birds fledge and must learn to fish on their own? These are the kinds of questions that Peter Nye can explore this summer. He often travels to a nest to confirm, or "ground truth," what the satellite data suggest. (After all, stationary readings could mean a transmitter has fallen off a bird, not that the bird is sitting patiently on a nest!)

A Final Look at Golden Eagle Migration
Golden Eagle #004 has now traveled almost 1,000 miles from New York to Labrador! Of note, he and Bald Eagle #E63 are both there, and were only 8 miles (12 km) apart as of May 11th! When we come back next fall, we'll let you know how Golden Eagle #004 spent the summer, and what Peter Nye learned from this first-time chance to track Golden Eagle migration from New York.

Comparing the Migrations of Our Nine Bald Eagles
What generalizations can you make about Bald Eagle migration, based on this spring's observations?

Go back and follow the trail and the timing of each eagle's migration. When did each eagle head north? How long did the trip take? Did the eagle take a direct "bee-line" to the nest, or did it travel an indirect route and/or move in stages? Fill in the "Comparing Spring Migrations Chart" to help you analyze the data.

Try This!
  • Describe any similarities you noticed between all of the eagles.
  • Describe any differences you noticed.
  • Describe any similarities between groups of eagles. (For example, eagles wintering in the same part of New York, eagles traveling to the same nesting region, or eagles traveling long or short distances.)
  • What questions were raised by your observations?
  • What general patterns did you observe? What generalizations can you make about Bald Eagle migration, based on this spring's observations?

Scientist Says: How Scientists Communicate Research Results
One of the most important steps in a scientist's work is sharing research results with other scientists. This is how the body of scientific knowledge is built--and how it constantly changes, as new research findings replace the old.

As a way to synthesize your learning this spring, write your own scientific paper based on the Bald Eagle research you have witnessed----just as Peter Nye is preparing to do! Or, have a scientific meeting in your classroom. Each student (or student group) can present their findings to the class and defend their results.

How Much Do Satellite Transmitters Weigh?
Discussion of Challenge Question #22

We asked, "If you wore a backpack that weighed 2% of your body weight, how heavy would your backpack be?"

Answer: The backpack for a 120 pound person would weigh only 2.4 pounds! (To calculate 2% of 120 pounds, multiply 120 by .02 and you get just 2.4 pounds. That is, .02 x 120 = 2.4 pounds.)

Try This!
Fill a backpack until it weighs 2% of your body weight to see how it feels.

This is what scientists are concerned about. They do not want their research to interfere with the life of the eagle. This is for humanitarian reasons, but also because they don't want their research to be affected. The scientists want to learn about NORMAL eagle behavior. How many ways can you imagine that the backpack might cause ABNORMAL behavior? The scientists must always have this in mind when they design their research--and when they interpret the results.

Discussion of Challenge Question #21
Why Don't Bald Eagles Have Feathers on Their Legs?

We asked, "Why do you think Bald Eagles have feather-less legs?" What adaptive advantage do naked legs have for Bald Eagles?"

Most authorities believe Bald Eagles lack feathers on their legs because feathers would cause drag in water when they're fishing. Just as Olympic swimmers wear skin tight bathing caps on their heads (and shave their legs!) to reduce the drag caused by their hair, Bald Eagles' naked legs create less drag in the water than would legs covered with feathers. This is because feathers are designed to spread out from the skin, to capture a layer of air for insulation. They would be a hindrance when the eagle was fishing, and afterwards, while the feathers were still cold and wet, sticking to the eagle's legs, they'd be rather a nuisance. In contrast, Golden Eagles do not fish for their food, and their legs do have feathers.

Journey North
Year End Evaluation
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This is the FINAL Bald Eagle Migration Update. Have a nice summer!

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