Bald Eagle

Bald Eagle

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Bald Eagle Migration Update: March 17, 2004

Today's Report Includes:

WOW What a Week!
It was a really exciting week for eagles! Not only did we learn of Pete and Kathy’s successful trapping of a beautiful female Bald eagle (V98), but also, the migration is on. One of the eagles has high-tailed it out of NY and is now soaring the Canadian skies. Don’t look yet - can you guess which one?

Latest Data:

Field Notes from Peter Nye
Here we are with V98 just before releasing her.

Hello again Students/Eagle Lovers!
We have some good news to start off this week. Not only are some of our eagles on the move now, but we have a new one to follow.

First, the story of our new eagle, V98.
Usually, March is not a particularly good time for our migratory eagle trapping efforts; many of the wintering birds have already begun to move around, and water is opening up making it more difficult to attract eagles to our bait, since they have more and more of their preferred habitat available. Nevertheless, last Tuesday, March 9th, Kathy Michell and I decided to try again, along the Delaware River in southeastern NY (our border with Pennsylvania). As usual, I left home at 2:30 am, drove for 3 hrs, met Kathy at our trap-site and got the bait and net all set up before dawn, which at this time of year is coming before 6 am!

…Then, a little after eight-o'clock, I spotted a large adult gliding toward our trap site from up-river, on a direct line toward the carcass. This bird came out of no where, and perched in a tree right about the carcass for about 5 minutes, watching the squabbling immatures on the carcass, until it finally decided it wanted in on the action…

In other news, as you will also see from the latest data, our golden eagle A00 has begun his northward move, about a week earlier than last year. He is already well into Canada. Unfortunately, Scott and Kathy were not successful in capturing A00's mate, but as Scott says, there is always next year!

Regards, Eagleye
Endangered Species Unit
Wildlife Diversity Group
Delmar, NY

On Wings of an Eagle
Eagle V98 with backpack satellite unit
Being at the right place at the right time certainly describes the capture of V98. This hungry Bald Eagle, lured to a fresh carcass and caught in the early dawn light was probably on migration route when she was trapped along the Delaware River on March 9. Pete writes, “I was wondering whether we caught a resident breeder or a migrant. It didn't take long to find out.” Her fueling stop was brief, and because of the transmitter she now carries we know she is now somewhere in the Adirondack Mountains.

How far did she fly? She was released March 9th at 10:15 Eastern Standard Time (EST), and her most recent signal was recorded March 12th at 17:33 EST. Can you calculate how many hours and minutes these readings are apart? During this time she traveled 192 miles (309 kilometers).

Challenge Question #13:
“V98 traveled 192 miles (309 km) between March 9 and March 12. Calculate her flight speed during this time.” (You may round the time to make this easier to calculate.)

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

Interpreting Satellite Data
What Happens When Nobody's Looking?

By now, you're probably comfortable using satellite data to track migration.

But don't get too comfortable! Let's step back for a minute. Think about the information the satellite sends us every two days, and the assumptions we might be making when we interpret the data.

Try This!
Close your eyes. Imagine being in your classroom, day and night, with your eyes closed. Every 2 days, you blink your eyes open for a few seconds. You ONLY have that time to see what is happening. The rest of the time, you see nothing but darkness. As a class, consider the conclusions you might draw, based on your limited observations.

Think about that image when you interpret satellite data. The satellite only sends a snapshot representing a moment in time. Consider what might be happening when we're not looking!

Challenge Question #14:
"How might an eagle's behavior be different than our migration map shows? That is, what might an eagle be doing during the time the satellite is NOT sending us data? Give an example."

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

What Time is it, Satellite Time?
Earth as seen from satellite
Credit: The Living Earth
Local time is meaningless to a satellite. Remember, the satellite is zooming around the earth every 101 minutes, so local times on Earth are a blur.
In Challenge Question #13 we gave you the data recorded in local time (EST). However, the satellite data time is given to scientists according to Greenwich Mean Time (GMT). GMT is an international time-keeping standard. It is based on the local time in Greenwich, England. Greenwich Mean Time is also called Universal Time (UT).

Read on for a description of GMT and challenge yourself to learn more about our use of world clocks.

Open your atlas to the time-zone map and consider these questions:

  • Locate Greenwich, England. How many time zones away from Greenwich, England are you?
  • Eagle data is given in GMT. What time is it GMT when it is 10:15 EST?
  • What time is it GTM when it is 17:33 EST?

Nesting in MA
Nesting under a live camera in MA, the eagle capturing the attention of thousands of viewers has laid her 2nd egg! Earlier this month the eagle was caught on camera sitting in her nest for every picture. We asked our expert, Pete Nye if she could be sitting on eggs already. His reply, “Absolutely! Many of our birds are down on eggs already. Realize, they sit on them for over a month, then young are in the nest for 3 more’s a long nesting season!”
Female on nest at 10:40, steps off at 10:45 AM to reveal 2 eggs! Toughing it out at 14:35 the same day.
Credit Eagles Online

Looking at these pictures, what can you say about eagle nesting behavior?

  • Visit Eagles Online often to follow this year’s nesting family.

Winter Dining: Discussing Challenge Question #11
An eagle eats 5-10% of its body weight each day. Male bald eagles weigh 8-9 lbs., and females weigh 10-14 lbs. Challenge Question #11 asked,
“How many pounds of food does an eagle need to consume each day? If you needed the same percentage of food daily, how many pounds would you need?”
Tom, Heather, Matt, Kristina and Caitlin – all 7th graders from Iselin Middle School showed us their work to solve the question:
  1. A male bald eagle weighs about 8.5lbs.
  2. Male bald eagle: weighs 8.5lbs. = 0.425lbs. at 5%
    0.85 lbs. at 10%
  3. Female bald eagle: weighs 12lbs. = 0.6lbs. at 5%
    1.2lbs. at 10%
  4. A male member of our group weighs 135lbs. To find the equivalent amount of food he eats to that of an eagle we set up a proportion:
    5% = 0.425/8.5 X x/135 = 6.75lbs of food
    10% = 0.85/8.5 X x/135 = 13.5lbs of food
  5. A female member of our group weighs 105lbs. She would eat:
    5% = 0.6/12 X x/105 = 5.25lbs. of food
    10% = 1.2/12 X x/105 = 10.5lbs. of food

5th Graders in Park Rapids, MN and Ferrisburgh, VT weighing in at 70 and 90 lbs (and consuming 10% of their bodyweight) would need to eat 7 and 9 lbs of food each day. Now that’s a lot of “quarter-pounders!”

Adaptations: The Tail - Discussion of CQ #12
“In what ways does the eagle’s tail help sustain their fishing and scavenging lifestyle?”

Jonathan has done his research! He wrote to us,

“The tail - is very important for flight and maneuvering. While the bald eagle is soaring or gliding in flight, the tail feathers are spread, in order to attain the largest surface area and increase the effect of thermals and updrafts. The tail also helps to brake the eagle when landing and assists in stabilization during a controlled dive or swoop toward prey. The strength of the feathers and the follicles holding the feathers is quite impressive, while watching the tail move back and forth and up and down during maneuvers.”

Other great adaptations included balance while flying, an aid for slowing down when landing and a signal to others that when the tail is white that the bird is mature.

Bald Eagle Adaptations: The Body
This spring we're looking closely at eagles, from head to toe. Each week, we'll pose a Challenge Question related to the next week's featured adaptation. Remember: There's always a WHY behind WHAT you see. So whenever you see an unusual behavior or body part, ask yourself WHY...

Are you ready for this week's adaptation?

Most bird bodies don't tell much about the bird's life until you look carefully at the wings, tail, and legs. For this week’s question think carefully about what is inside the eagle as well as what we see on the outside.

Challenge Question #15:
“In what ways is the eagle's body built for survival?”

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

How to Respond to Today's Challenge Questions:

IMPORTANT: Answer only ONE question in each e-mail message.

1. Address an e-mail message to:
2. In the Subject Line of your message write: Challenge Question #13 (or #14, or #15).
3. In the body of EACH message, answer ONE of the questions above.

The Next Bald Eagle Migration Update Will Be Posted on March 24, 2004.

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