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Bald Eagle Migration Update: April 30, 2002
Today's Report Includes:
- Latest News and Migration Map
- Why Blood Tests for Babies? Discussion of Challenge Question #16
- Eagles, Fish and the Food Chain
- Challenge Questions #18, #19 and #20
- Hudson River Bald Eagle Contaminants Study
- Where Would You Want to Nest? Journaling Questions
- Pesticides and Birds Campaign
- Year-End Evaluation: Please Share Your Thoughts!
Latest News and Migration Map
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?A big NE move for E50!? said Peter Nye on April 23. He repeated himself on April 25th and AGAIN on the 27th! In
the space of 6 days, E50 hopped across the map all the way to the northeast coast of Labrador. Between 4/21 and
4/27 E50 traveled 505 miles.
Print a copy of the migration map, and use the scale bar to measure the distances E50 traveled between those jumps.
Or, use the Online Distance Calculator to measure the distance by inserting the latitude and longitude from each
satellite hit:
?Is Golden Eagle A20 headed for Labrador??? Pete Nye wondered aloud on April 22nd. If so, A20 changed his mind
on the 24th, maybe due to the cold front that spread across the continent last week. Check out his zig-zagged travels
between the 22nd and 26th. He reached 50N on the 22nd, dropped back to 48N on the 24th, the jumped up to 51N by
the 26th--but to the northwest. Where is this Golden Eagle going? Stay tuned!
By the way, we mentioned that the satellite caught A20 during migration on April 15th. Exactly how far did he travel
between 1:30 and 7:06 pm that day? Here are A20's data points so you can find the total distance covered in fewer
than five hours:
1:30 pm - 3:11 pm: 53 miles
3:11 pm - 4:47 pm: 33 miles
4:47 pm - 7:06 pm: 32.5 miles
Why Blood Tests for Babies?
Discussion of Challenge Question #16
We asked, "Why do you think it's important to test the eagles' blood? What do you suppose they are testing the blood to find?"
?Infections or contagious diseases,? agreed students from St. Wendelin Highschool, Iselin Middle School and Ferrisburgh Central School.
Actually, Peter Nye is looking for environmental contaminants. ?Organochlorine contaminants such as PCBs and DDT, and metals such as lead, mercury and cadmium. The levels we find may indicate that the birds are eating contaminated prey,? says Nye.
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Eagles, Fish and the Food Chain
In order to understand how contaminants can get into eagle prey--and ultimately into eagles--we need to look at the eagle's food chain. At each level, the contaminants can build up and pass to the next level, from prey to predator.
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On average, an eagle's daily food consumption is estimated at 250-550 grams per day, or between 5-10% of its body weight. Make a diagram of the eagle's food chain, using the illustrations and facts found at the link below, then answer these Challenge Questions:
Challenge Question #18
"Do you think a small, medium or large fish would potentially contain more toxins? Explain why."
Challenge Question #19
"Why do you think loons, who eat small and medium-sized fish, have had fewer problems with environmental contaminants than have eagles, who eat large fish?"
Challenge Question #20
?If you ate 5-10% of your body weight, how many pounds of fish would you need to eat each day??
(To respond to these questions, please follow
the instructions below.)
Hudson River Bald Eagle Contaminants Study
According to one study, environmental contaminants are believed to be the single most important factor affecting the reproductive success of eagles. ("Reproductive success" is a measure of how well an animal is able to reproduce.) The higher the concentration of contaminants, the study found, the lower the number of eaglets successfully raised.
Peter Nye has studied the concentrations of the toxin known as PCBs in bald eagle prey along the Hudson River. By studying prey with known PCB concentrations, he can calculate the PCB concentration likely to accumulate in eagles that consume that prey. And, using results from other PCB studies, he can actually estimate how many young a bald eagle nest can be expected to produce. Nye's study predicted that productivity on the Hudson River would differ depending on where on river the eagle was feeding. Here's a sample of his data:
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River |
Nearest |
Predicted Productivity* |
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203 |
Glen Falls |
0.99 |
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197 |
Bakers Falls |
0.38 |
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194 |
Fort Edwards |
0.14 |
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159 |
Waterford |
0.64 |
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143 |
Albany |
0.46 |
* Bald Eagles typically lay two (2.0) eggs per year. Healthy rates of productivity
are considered to be >1.0 young per occupied breeding territory.
Where Would You Want to Nest? Journaling Questions
If you were an eagle, in which section of the Hudson River would you want to nest, based on Nye?s study of PCBs? In which section would your children be the least likely to survive?
Pesticides and Birds Campaign
Here?s a great Website if you?d like to learn more about how pesticides affect birds.
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Journey North |
How to Respond to Today's Challenge Question:
1. Address an e-mail message to: jn-challenge-eagle@learner.org
2. In the Subject Line of your message write: Challenge Question #18 (#19 or #17).
3. In the body of EACH message, give your answer to ONE of the questions above.
The Next Bald Eagle Migration Update Will Be Posted on May 7, 2002
Copyright 2002 Journey North. All Rights Reserved.
Please send all questions, comments, and suggestions to our feedback form
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