Eastern Bald Eagle Migration Update: March 7, 2000

Today's Update Includes:

Today's Migration Map and Satellite Data

Field Notes from Peter Nye
Two New Eagles Now Online!
"Our trapper, Blanche Town did it again! On February 29 she scored a 5.5 kg adult eagle, now numbered K72. The ice on the St. Lawrence River was receding under her bait at the time of capture! I met her the next day to handle the bird (bands, radio, blood, measure, etc.)

"Our other new satellite bird is K58, caught on February 20 on the Upper Hudson river by our eagle crew there, Craig Thompson and Brian Conway. They had been trapping this area above Albany, NY for a couple of weeks. They captured six other eagles before K58, but all were immatures that we are much less interested in tracking via the expensive satellite telemetry. Can you guess why? K58 is an adult that weighed in at a healthy 6.6 kg--near the top end of weight for eagles. Our crew used a duck as bait to attract K58 to the trap.

How Much Do Our New Eagles Weigh?

Challenge Question #6
"How much do K72 and K58 weigh in pounds? With your answer, name something else that weighs the same as each adult eagle."

The Journey North Begins!
"It looks like K58 has already started to boogie! This eagle left early! The March 3 fix puts K58 up in central ______ and two days later up in ______.

Challenge Question #7
"In which states was Eagle #K58 on March 3 and March 5?"

"Our weather here has turned quite warm. Most of our snow is gone, and the ice is disappearing fast as well. It's early March now, and many birds are on the move already. We are getting reports from many 'non-wintering' areas as the eagle population moves north.

How Can You Tell Male and Female Eagles Apart?
"In many bird species, it's easy to tell males from females because the plumage is different. Not so with eagles! We can use weight and size to tell them apart---but when we talk of bald eagle weights, we need to keep two factors in mind:

Here are the key measurements from our two new eagles, plus their weights. Can you determine the sex of each bird yourselves?

 Eagle # Bill Depth Hallux Talon Length Weight K58 37.90 mm 44.50 mm 5.5 kg K72 35.87 mm 42.72 mm 6.6 kg

Challenge Question #8
"Is eagle #K58 a male or female? How about eagle #K72? Explain why you think so."

Do Eagles Migrate at the Same Time Each Year?
As you know, this is not the first satellite-tracked trip for Eagle #43, #F81 or #F83. Peter Nye tracked all 3 birds last spring--and Eagle #43 is about to begin her 3rd trip under Nye's watchful eyes. Do you think the timing of an eagle's migration is the same every year? Do you think an eagle follows the exact same route each time it travels?

Print a copy of this Spring Departure Chart, then take a look at Nye's data for these 3 birds from previous springs and plot the departure dates for each bird:

 Spring, 1999 Migration Spring, 1998 Migration

Challenge Question #9
"What dates do you predict Eagles #F43, #F81 and #F83 will head north this spring? Summarize what you learned from past years' migrations that guided your answer."

Suggestion: Print a Spring Departure Chart for K58, K70 and K72, too. See if you can predict when they'll start their journey north.

Suggestions for Student Research With Satellite Data
How might you design a study of your own using this migration data? Make a hypothesis, then compare and contrast the data from each migration. At the conclusion of your study, write a scientific paper.

Home on the Winter Range
Discussion of Challenge Questions #4 & #5

Challenge Question #4 asked, "What is the greatest distance between two points that each eagle had visited in the past 3 weeks?" Here are the distances:
 F43: 40.48 mi (64.77 km) F81: 123.81 mi (198.1 km) F83: 46.15 mi (73.84 km) K70: 41.50 mi (66.40 km)

Congratulations to Timmy F. for measuring these distances accurately. He noticed that each eagle moved about 40 miles. Except for Eagle F81 whom he said, "Doesn't seem to care where he is going!".

Timmy also answered Challenge Question #5: "How does an eagle's winter range compare to your own? What are your reasons for moving? Why do you think an eagle moves around within its home range."

"My family has a 16 mile north/south and a 8 mile east/west range. Sometimes we take short trips up to 1000 miles. We don't move around very much. The eagles have a larger range about twice as far as ours except for F81 that has traveled 120 miles. We move because we have to do stuff like go to games, buy food, go to school, and go to scouts. An eagle moves because he has to hunt and go to his day roosting tree and visit other eagles."

"Very perceptive!!" said Nye. (We sent Timmy's answer to Eagleye Nye.)
Watch for Weekly Updates During the Migration
While the migration is underway, we'll post updates every Thuesday so you'll have the latest news.
How to Respond to Today's Challenge Questions