Bald Eagle

Bald Eagle

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Bald Eagle Migration Update: February 20, 2001

Today's Report Includes:

Field Notes from Biologist Peter Nye

Hi Kids,


Winter Range Map

Here are the latest satellite readings from our 6 eagles, along with an overview of our research goals this season:


"If you had my job, what would you say you've learned so far about eagle behavior?"

Until next time,

Eagle Eye Nye
New York State Dept. Environmental Conservation
Delmar, NY

You're the Scientist: Challenge Question #3
Make a "winter range map" for the 6 eagles using the data provide during the past month. (Or, simply print and analyze our map.) Your job is to define each bald eagle's home range or "winter range." How far and how often do the eagles move? What body of water might each eagle be feeding from? How are the eagles' ranges similar to one another, and how are they different? Try to write the best verbal description you can. To get started, look at your map and answer this question:

Challenge Question #3
"Based on one month's data, which eagle seems to have the largest home range?"


(To respond to this question, please follow the instructions below.)

Home on the Winter Range: Some Definitions
Here are some definitions that should help with your work today:

Home Range: The area an animal occupies in the course of its normal daily activities.

Winter Range: The area an animal occupies in the course of its normal daily activities during the winter months. (The winter range is simply a seasonal variation of the home range.)

Territory: The portion of the home range that an animal defends against intruders. (The intruders may be of the same or of a different species.)

Human Home Range
To put these eagles' movements in perspective, compare them to your own travels. What is your home range? Describe the area that you occupy in the course of your normal daily activities. Is your winter range different from your summer range? If so, think of the reasons why.

Challenge Question #4:
"How does an eagle's winter range compare to your own? How much of your home range do you consider to be your territory?"

(To respond to this question, please follow the instructions below.)

Why More Eagles in NY in the Winter?
Discussion of Challenge Question #1
On February 6th we asked, "Why do you think more bald eagles are found in New York during the winter months than at any other time of the year?"

Mr. Maanum, a 5th grade teacher in Park Rapids, MN responded: "The class felt the main reason was availability of food. With ice covering other waterways, the eagles move to where food can be found, either fish or waterfowl. Why more this time of year? The eagles will become territorial as spring moves closer. They will also disperse as other waterways open up." (smaanum@parkrapids.k12.mn.us)

Exactly! Peter Nye says that many eagles from interior Canada--where the water is frozen--move south into New York to spend the winter. The eagles aggregate in areas of New York where there is open water so they can fish and catch waterfowl. During the summer breeding season, the eagles will disperse across Canada--and we'll be tracking their trip! As you can see, Canada plays an important role in protecting the U.S. National symbol: In fact, almost half of the eagles that winter in the lower 48 States return to Canada to breed in the summer.

By the way, Mr. Maanum's lucky students are studying eagles themselves. "We travel with researchers as they check nests and band eaglets," they said. (See picture on the Web!)
How Can an Eagle Catch a Duck?!
Discussion of Challenge Question #2
We asked, if a duck can fly more than 60 mph and an eagle only 44 mph, how can an eagle catch a duck for dinner?!

"I believe the duck would have to be sick," said Emily.

Mr. Maanum shared his students' thoughts: "The class had three possibilities for catching ducks, depending on the time of year." The students think eagles might swoop down on young ducks who couldn't yet fly, on ducks that are weak or wounded, or they might spook ducks into flying and grab them on take off.

As these smart students suspected, eagles prefer the more vulnerable, "sitting ducks." Peter Nye explains: "Eagles rarely 'chase' waterfowl-- it is not typical eagle hunting behavior. It takes a lot of energy to try to 'chase down' a fast flying duck, and it usually is unsuccessful. I've seen immatures do this more than adults, which is probably due to their inexperience.

"Typically an eagle will perch near some waterfowl concentration. (The more concentrated and restricted by ice, the better.) It will take periodic 'strafing' runs over the waterfowl. I think this is in an attempt to identify the weaker individuals--just as Emily and the MN students said! The others scurry and disperse. I've seen adults do this over a period of an hour or more, over the same flock. Eventually, out one of the birds becomes exhausted from repeated dives, drowns and floats to the surface."

Naturalist Gale McCullough, of Hancock, Maine, described an amazing hunt she witnessed: "One adult eagle circled and tried to snatch the duck out of the water 36 times. Each time the duck dove." Read how the eagle finally managed to capture the duck--and deliver dinner to its young in the nest:

Eagle Talons: Get a Grip!
Compare this Alaskan biologist's hand to the size of the eagle's feet. Can you spread your fingers 8 inches across like an eagle's foot can?

Photo: USFWS
"Eagle feet aren't quite as well designed for capturing fish as Osprey feet are," explains bird expert Laura Erickson. "This is because one of an Osprey's front toes is opposable, like our thumbs, and can rotate backward. " Read this and other fascinating facts about eagle feet, toes, claws and talons:

Then see if you can answer Challenge Question #5:

Challenge Question #5
"Why do you think eagles carry their prey with their talons instead of their beaks? List as many good reasons as you can."


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-eagle@learner.org
2. In the Subject Line of your message write: Challenge Question #3 (#4, or #5)
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 March 6, 2001.

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