Bald Eagle

Bald Eagle

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Bald Eagle Migration Update: March 10, 2004

Today's Report Includes:

This Week
Temperatures last week were fluxuating in NY but the eagles are still staying put. This week may bring a new eagle or two to our list of satellite tracked birds. Stay tuned and send your luck to Pete and the team as they go out into the field for one last attempt to trap some eagles.

Here's the Latest Data and Migration Map

Field Notes from Peter Nye

Hey Students-
Looking over this week’s data, no changes to report; everyone still appears content to stay put. But, I expect things may change by next week. We had a dip back down in temperatures in the last couple days, and received about 4" of fresh snow here last night (Sunday), just to prove winter is not quite over yet.

Rocket net assembly

I wish I could give you some good news on our trapping efforts, but alas... Last week wasn't a lucky one for any of us. Scott, Kathy and I were out trapping several days, but no luck. Scott, who is after the golden eagle mate to A00 we are currently following, simply hasn't been lucky enough to have visits to his trap-site while he's all set up. The eagles have been visiting there fairly frequently, but just not when he's there! At about 17 hours per trap day, you just can't spend every day there waiting! Trooper that he is though, he is out there again this week for one last effort...keep your fingers crossed. For me, too. Although Kathy and I had a beautiful, adult bald eagle on our bait last week, our net mis-fired and we missed the bird. This happens once in a while.

Many factors have to all come together and work perfectly for a capture. Some folks think it is easy, just put out some bait and throw a net over them, but experience tells us otherwise! Kathy and I will be out for one last day tomorrow (Tuesday), and hope we can pass on some good news then. Meantime, keep monitoring these three birds and watch the NY weather!

Till next week,
Eagleye Nye
New York State Dept. Environmental Conservation
Delmar, NY

Weather Maps: Treasure Chest of Clues
Map courtesy of NOAA
Search the Web for weather information and you quickly learn there is a huge amount of information available. Like treasure chests, maps hold clues for all kinds of phenomenon. Here’s one example; a map available from NOAA and the National Weather Service.

Think about these questions as you study the clues the map reveals to us:

  • What does the title, “Departure of Normal Temperature” mean?
  • What is represented by the red color?
  • How might this information affect your predictions about when the eagles will start their migration?

Bookmark this weather map Web source:

To get the best “picture” of the weather for predicting eagle migration you will need a Canadian weather service. Try searching the Web and bookmark the best site.

Built-in Barometers
Scientists have long noticed that birds feed intensely as air pressure falls. They apparently have an inborn barometer that is extraordinarily sensitive. This is a handy adaptation for all birds, even non-migrants, because storms usually are associated with falling pressure, and birds have a hard time getting food during a storm. The sooner they can predict a storm before it hits, the more time they have to prepare.
Recognizing air pressure is also handy because birds often migrate along frontal systems, and changing air pressure is one of the first signs that a front is coming. Just as low pressure indicates storms, high pressure systems typically have clear skies. Thus, sensing if air pressure is rising or falling would enable a bird to anticipate changes in weather.

Scientists also have known for a long time that migrating birds fly at different altitudes than non-migrating birds, and maintain this altitude even on moon-less nights when they can't see the ground at all. How do they maintain a particular altitude? Many scientists suspect that this is also due to their ability to "feel" air pressure. Studies have shown that birds are extremely sensitive to small changes in air pressure, comparable to differences of only 5 to 10 meters in altitude. (Atmospheric pressure is lower at higher altitudes. If measuring with a barometer, pressure is lower by 1 cm for every 100 meters of altitude.)

How do birds judge air pressure? Scientists don't know!! They do have a couple of guesses. One is that birds may be able to detect it through their inner ear. We detect large changes in air pressure in our own inner ear when we make a fast change in altitude--that's when our ears "pop." Another guess is that the birds detect air pressure somehow though the huge air sacs that connect to their lungs and fill much of the space inside their bodies.

Try This! Watching Barometric Pressure and the Weather
1) Watch how barometric pressure changes with the weather. Record the barometric pressure over a period of at least 3-4 days. (Take a reading regularly, as often as 3-4 times during the school day. Ideally students could also be assigned to keep these records during off-school hours for these 3-4 days.) Tip: Keep your eye on the weather map! Try to time this activity when a storm is approaching.

2) After observing how pressure changes over time, study weather maps and track high & low pressure systems, and their associated wind directions and fronts. Try to do this for a week or two, to see the patterns.

3) How could you build a tool to help you measure air pressure? Discuss how a barometer might be designed--or actually build one! (A Web search will result in links to many samples and instructions.)

Eating Out: Winter Dining Challenges
As we know, in the cold winter months Eagles are found near open water so they can have fresh fish to eat. Fish are perfect winter food. Even on the coldest winter days a fish pulled from open water (32° F) is easily pulled apart with sharp and powerful beaks and is eaten. But eagles don’t live on fish alone. In winter eagles are often seen eating road-killed animals. How can an eagle eat frozen, rock-hard meat? Kathy Michell helps the eagles at the bait site by chopping the meat into chunks with her trusty axe. Without Kathy’s help, how do eagles cope in the cold winter weather?

Read on to learn about this and more:

An eagle eats 5-10% of its body weight each day. Male bald eagles weigh 8-9 lbs., and females weigh 10-14 lbs. Sharpen your pencils and your wits for these calculations:

Challenge Question #11:
“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?”

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

Eagle Head Adaptations: Discussion of CQ #10
The eagle's whole head is designed for its fishing and scavenging lifestyle. Last week you took a close look at their head and shared what you learned. Here are some of your comments:
  • Its eyes are located on the side of its head so it can see 180 degrees around itself.
  • The white feathers on its head make it look bigger to intimidate other animals.
  • The supra orbital ridges help shield its eyes from the sun as it looks for food.
  • The beak is hooked so that after it catches its prey, it can easily snip and pluck feathers or fur away from small prey, as well as, tear and bite off pieces of meat, crush twigs to build a nest and feed its young.
  • The eagle's eyes are large and they have good eyesight. They can see far away.
  • It looks as if the tongue is not long enough to go outside of the beak. This would make it hard for the eagle to bite his tongue.

Thanks to students Ruby, Lindsay, Jake, Ryan and Kris at Ferrisburgh Central School; Armand, Dominique, Slawomir, Danielle, Mike, Robert, Moaz, Chris, Jennie, Lauren, Michael H, and Gurjodh at Iselin Middle School; and Michael.

Read for more information about these adaptations.

Vision: An In-Depth Look at Eagle Eyes
Bird vision has impressed and baffled humans for centuries. Scientists consider bird eyes to be the finest in the animal kingdom. And raptors have the finest vision of all. Small wonder just about everyone knows the expressions "bird's eye view" and "eagle eyes"!
Eagle vs. Human Vision

how a distant dragonfly might look to an eagle

how the same dragonfly might look to a person

How a distant dragonfly might look to an eagle

How the same dragonfly might look to a person

Get out your journals for a closer look at the marvelous form and function of the Eagle eye. This in-depth lesson holds the details for students who want to know more!

Bald Eagle Adaptations: The Tail
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?

An eagle's body is adapted for its fishing and scavenging lifestyle.

Challenge Question #12:
“In what ways does the eagle’s tail help sustain their fishing and scavenging lifestyle?”

(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 #11 (or #12).
3. In the body of EACH message, answer ONE of the questions above.

The Next Bald Eagle Migration Update Will Be Posted on March 17, 2004.

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