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Whooping Crane Migration Update: February 27, 2001


Today's Report Includes:

Welcome to the Journey North Spring Whooping Crane Migration Season!

Migration Route
Map by Claudia Fonkert
Macalester College

We begin our season each year while the world's only wild flock of endangered whooping cranes is on the wintering grounds. When their migration begins in March, we hope you'll help us track their journey north.






Thanks, Tom Stehn!
Tom Stehn
Tom Stehn, Refuge Biologist at Aransas National Wildlife Refuge in Austwell, Texas, will provide the first updates this spring as the cranes begin their journey north. Because you can't see whooping crane habitat from the refuge roads, Tom Stehn boards a plane for his weekly crane counting mission. Thanks to Tom's letters to JN in upcoming reports, we'll keep track of the cranes as they depart. Journey North is grateful to Tom for his fascinating first-hand reports!


These photos show Tom and his bird's eye view from a recent flight over crane country, as well as a map of this 54,829-acre refuge where Whooping cranes spend the winter.


Latest News from the Wintering Grounds
Aransas National Wildlife Refuge
Austwell, Texas
February 27, 2001

Dear Journey North,
"This has been a bad year for the whooping crane. Despite a record 51 nesting pairs, production was low in Canada in the summer of 2000. Although 30 chicks were present in June, only 9 completed the 2,500 milemigration and arrived at Aransas. In addition, two of the 9 have died at Aransas this winter. Total numbers in the only natural wild flock have plummeted. From last
Map of Aransas Refuge
winter's record high of 188, there are currently only an estimated 176 whooping cranes in the flock. A high number of birds died between the spring and fall, and 4 have died this winter."

Read Tom's full report to find facts that can help you answer our first challenge question. Learn what blue crabs, Texas weather, and growing human population had to do with the crane's plight this past winter. . .and find a reason for hope.

Then come back and answer:

Challenge Question #1
"Why are there FEWER whooping cranes in the population this year? How many different reasons can you find that explain why the number is so low?"


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

Introducing Dr. Bernhard Wessling
Front view of Operation Migration ultralight aircraft. Pilot Bill Lishman and
Dr. Wessling.
Meanwhile, some exciting events are taking place in the efforts to save endangered whooping cranes--officially called the Whooping Crane Recovery Program. Experts like Tom Stehn, Wally Jobman, and Brian Johns are some of the folks working hard on behalf of cranes. Together with the International Crane Foundation and Operation Migration, they are helping good things happen. The important discovery of another scientist has played a big role too. His name is Bernhard Wessling. He has discovered a valuable and surprising thing: Just as fingerprints identify individual humans as one-of-a-kind, crane voiceprints can be used to identify individual cranes!
This photo shows Dr. Wessling in front of an ultralight aircraft with pilot Bill Lishman. The photo was taken just before the first test flights for Operation Migration, during which planes equipped with Dr. Wessling's recorded crane calls led sandhill cranes on migration. It was the first time it was possible to "talk to" cranes in their own language as they followed the plane. (This important aircraft-led migration experiment was conducted in fall 2000, using 13 sandhill cranes. Experts will use what they learn to carry out a similar migration project in the near future with whooping cranes. It will be an important step in the hopes for establishing a SECOND flock of migratory whooping cranes.) For more information about Operation Migration and the exciting use of crane calls to train the cranes, see:

Dr. Wessling was recently at Aransas NWR with the whooping cranes. Today Journey North is excited to share the letter Dr. Wessling wrote to you, along with the chance to try your ear using some of his crane recordings.

Who's Calling? Crane Voiceprints

Dear Journey North Students:
As I write this on February 6, 2001, I am ready to fly back to Germany. I was just in the wintering area of the Whooping cranes at Aransas National Wildlife Refuge, where I recorded whooping crane calls for a full week. Together with some pairs recorded by Brian Johns in summer 2000 at Wood Buffalo National Park, we now "personally know" by voice 35 whooping crane pairs--or more than 70% of all breeding pairs!
The first pair I recorded back in December 1999 made it back to Aransas this winter, and I met this pair again on Heron's Flats. Known as the Mustang Lake pair, it usually stays and roosts at Mustang Lake. Thanks to my earlier recorded calls from these cranes, we just realized that this crane pair changes back and forth between Heron's Flats and Mustang Lake! After I recorded their call this time, I compared by listening to the recording from last year. My ear says it is the same pair, and I am looking forward to seeing what my computer analysis says when I get back home in Germany. Hear them here:

This is the only crane pair that can be seen from publicly accessible places at ANWR--either from the "Herons Flats Trail" or from the visitor tower overlooking Mustang Lake. All other pairs live in territories in the closed part of the Wildlife Refuge, but visitors aboard a tour boat cruising the Intracoastal Waterway can observe some pairs when the cranes are looking for food in the shallow water.
Back in Germany, I will start analyzing the many recordings I made --about 150 files. I keep track of comments where I am, from where I recorded, and the location where the calls came from. The files comprise calls from 25 to 27 crane pairs. I will try to match these with the calls recorded last winter (1999-2000). Then we will see:

    1. how many pairs are still in the same territory.
    2. how many pairs may have changed territory and / or mate.

With best regards,
Dr. Bernhard Wessling


Dr. Wessling's goal is to record the voices every year, and at different times of the year. That way scientists can better find out who is still alive and living with his former partner in his former territory. There may be pairs changing territories with other pairs, and there may be pairs splitting up, changing mates, or getting a new mate when the former mate is no longer alive. All these events happen with whoopers and other crane species. Can YOU tell cranes apart by listening to their voices? Dr. Wessling invites you to start out as he did, using just your ears. Read on!

You're the Scientist: Challenge Question #2
Three crane calls are given below. They are Eurasian (Common) Crane calls recorded by Dr. Wessling. Two of the calls are from the same pair of cranes. Begin by listening to see if you can differentiate the two cranes in each unison call. Once you realize there are two birds calling, describe how the one bird calls and what the other bird calls in between. After practice, see if you can answer:

Challenge Question #2
"Which TWO of these calls are given by the SAME pair of cranes?"


Call #1
Click to hear call

Call #2
Click to hear call

Call #3
Click to hear call


(To answer this question, please follow instructions below.)

Try This! Which is Which?
Listen to the calls of TWO crane species. Listen to compare and hear how they are different. (You will want to listen more than once! You'll hear more each time you listen.

Dr. Wessling says, "The 'tak-tak-tak' you hear in between calls is the female. Most people never get to hear whooping cranes call. If you visit the refuge, they don't call in the daytime, or it's so far away you can't distinguish male and female. Even people who have heard the call have not distinguished male and female. You can definitely hear it. Listen over and over again until you can say, 'I have differentiated two voices in the unison call. Somebody calls a little longer, starts deeper and goes higher, and in between I hear someone else.'
"Most listeners think the call of the Eurasian crane sounds clearer, more like a pure musical instrument. Whooping cranes sound less melodical and more like an old musical instrument with a rattle in it. The male and female whoopers in this call are more or less on the same tone height /frequency. They also use a relatively wide range of their frequency. But in the Eurasian crane calls, the female crane calls much higher than the male. The female's 'tak tak tak' is the same." You will see more differences on a computer-made sonogram. (See teacher Tip below.)

Teacher Tip
Students who are interested may enjoy the further challenge of visiting Craneworld, Dr. Wessling's Web site. They can click on SONOGRAPHIE (sonograms) to see crane voiceprints on the computer. For more listening challenges, they can go to BILD & TON (view and listen) and click on "Zu hören ist hier der Ruf eines Mandschuren-Kranichs am Toro Lake East in Japan." (This is German for "Red-crowned Crane at Toro Lake in Japan.") More photos from the training session for Operation Migration are found by clicking NEWS, then August 2000.

Just in Time
Why is the discovery of unique crane voiceprints such an important finding for helping the world's endangered whooping cranes? You'll find out when you read this:

Then come back to answer our challenge question!

Challenge Question #3:
"Why are crane voiceprints a good way to keep track of endangered whooping cranes? Give at least two reasons."


(To answer 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: jn-challenge-crane@learner.org
2. In the Subject Line of your message write: Challenge Question #1 (or #2 or #3).
3. In the body of EACH message, give your answer to ONE of the questions above.

The Next Crane Migration Update Will Be Posted on March 13, 2001.

Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form

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