Whooping Crane Migration Update: March 14, 2003
Today's Report Includes:
- Tom Stehn Reports From Aransas: Bad News and Good News
- Timing is Everything: Challenge Question #3
- When Will They Leave? Challenge Question #4
- Sara Zimorski Reports: Chicks Changing in Florida
- Crane Captures in Florida Flock: Why?
- Growing Up and Crabbing: Link to Lesson
- Population Cycles: Discussion of Challenge Question #1
- Your Population Prediction? Challenge Question #5
- Tracking Teasers: Discussion of Challenge Question #2
- Dudes! Who?s Getting an Attitude?
- Signals from the Sky
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| Wild Family at Aransas. Which is the juvenile? OM |
"Just when I thought things were looking up, a whooping crane chick turned up missing and was presumed dead on my census flight on March 6. Since chicks stay with their parents throughout their first year, finding the parents on their winter territory with no chick around almost always means the chick has died."
In better news, Tom says volunteers are hiking the marsh for an hour just as a whooping crane would, stalking blue crabs so he knows how many there are. "Last week the volunteers counted 102 crabs, quite a picnic after an hours worth of effort for a whooping crane that can eat up to 80 blue crabs a day. With the abundance of blue crabs in the marsh this winter providing the cranes with "grocery store" ponds overloaded with their favorite food, the cranes have done very well and are in excellent condition. I expect them to have a very productive nesting season if they can survive the hazards of the spring migration."
Did Tom find any proof of the dead chick? Why or why not? How can a whooping crane gobble down (or swallow whole!) a hard-shelled crab 3 inches in size? What kept Tom from finding all the cranes on his survey this week, and why isn?t it a big deal? It's all here:
Then come back send us your answers to Tom?s question for you:
Challenge Question #3:
"How do you think the cranes "know" that it is still too early to start their migration? What clues do they use to inform them? (HINT: One key to the answer is that they start the migration about the same time each spring, so think about what changes at the same rate every spring.)"
(To respond
to this question, please follow the instructions below.)
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All 17 in Florida pen! (16 birds from HY2002,
and Crane #5 from HY01) |
The same question is on the mind of Sara Zimorski. She monitors the new Eastern flock on the gulf coast of Florida, where signs of spring abound. "We are now serenaded by red-winged blackbirds and clapper rails on our nightly visits to the pen, and several native bird species have already begun to nest. Our thoughts turn toward. . .migration. One of the frequent questions I receive is, ?When will the birds leave?? This is often followed by, ?How will they know when it is time to begin migrating?? We predict that most of the class of 2002, in smaller groups, will leave in early-mid April. This is when the 2001 flock departed, and, interestingly, the time of year that the remnant wild migratory flock [That?s Tom Stehn?s flock] departs the Texas salt marshes for the Canadian breeding grounds.
Challenge Question #4:
"What date do you predict for the first departure of the new Eastern flock? Do you think all the chicks will leave at the same time?"
(To respond
to this question, please follow the instructions below.)
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Sara Zimorski rides the airboat to check
on the cranes |
Sara wrote this report to Journey North: "The birds are all doing great, all 17 of them: the 16 chicks, plus #5 from last year. They're sounding and looking less like chicks everyday. About half of the chicks have their adult voices so it's a lot louder when they all call these days. There's very little brown coloring left on their bodies. Crane #18 still has some on her neck but most of them have just small spots of brown here and there. Additionally, they're getting the red patch on their head. Just today I noticed how much red #4 has on her head now. We've noticed that #5-01 (last year's bird) has been getting more aggressive to some of the chicks over the past several weeks. He very deliberately stalks and chases them till they fly across or out of the pen. At first it seemed that he was just chasing the males off, especially #8 and #16, (maybe wanting all the females for himself!). But there are also some low-ranking females he doesn't seem to like either, especially #7 and #15. We had thought there could be problems with such a large group of birds and that was one reason we made the pen bigger this year; it's definitely turned out to be a good thing. This way the birds all have plenty of room to move around and get away if another bird is being aggressive."
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Click to enlarge and use the banding codes to identify these cranes! Can you tell which crane is the most mature one? That's yearling Crane #5, who lives with the 2002 chicks. Photo ICF |
Last week four of the chicks in the Eastern flock had to be captured. As you know from the strict protocol about raising these special cranes, handling the birds is something that?s NOT done unless absolutely necessary. Sara told us, "It's always a bit nervewracking to handle these birds, but we all have lots of experience and only do it when we have to and then keep it as short as possible. Read Sara?s log entry and you?ll see two reasons why they felt handling was necessary. How did they catch them, and which cranes were they? How did the captured cranes and the others act during this unusual event? Under what circumstances would they be captured again? It?s all here:
Growing Up and Crabbing
Sara?s report mentioned several ways the young cranes in the Eastern flock have changed in recent months. Can you see some of the changes in these photos?
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1 day old. Photos OM |
4-months old: August 2002 OM |
10-11 months old: March 2003 ICF |
And what keeps the youngsters busy? They've learned how to eat crabs, for one thing. How would you like to eat the same thing every day for 5 or 6 months every year of your life? That's what whooping cranes do on their wintering grounds, whether at Aransas NWR in Texas or Chassahowitzka NWR in Florida. Whoopers will eat almost anything, but their clear favorite is blue crabs. Above, you learned that Tom Stehn?s volunteers are even counting blue crabs at Aransas. What's so great about blue crabs? Find out here, and try a fun activity:
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Crane #7, age 6 days, looking at adult role model at Patuxent Captive Breeding Center Photo WCEP |
Last time we asked: "How does Tom explain why the population of the main flock went down from 188 birds to 180 and then 176?" Iselin Middle school seventh graders Lauren, Jordan, Cindy, Ruchi, Kaitlyn, Peter, Thomas, and Sunaina noticed that Tom Stehn mentioned that he thought the cranes' normal 10-year decline was due to a predator cycle on their breeding grounds. Some students suggested that it might have something to do with blue crabs on their wintering grounds, but cranes don't eat blue crabs on their nesting grounds in Wood Buffalo National Park in Canada because there ARE no blue crabs up there. (Cranes switch their diets twice every year, summer and winter.) Weather may be involved, but Tom's explanation said the downswing might be tied to predator cycles. We wonder how you?ll answer our next challenge question. Read on!
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Cranes reach breeding age when they are 4 or 5 years old. They normally lay two eggs, but usually only one chick survives. Look carefully at Tom Stehn's chart (below) and answer:
Challenge Question #5:
"1. What year did they produce the most babies?
2. What year will these babies first start reproducing?
3. What year would you expect these babies to first produce a significant number of young?
4. When these young start reproducing, assuming their winter food is doing well, what can we expect will happen to the population?"
(To respond
to this question, please follow the instructions below.)
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Winter Season |
Adults |
Young |
Total |
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1995-96 |
130 |
28 |
159 |
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1996-97 |
144 |
16 |
160 |
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1997-98 |
152 |
30 |
182 |
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1998-99 |
165 |
18 |
183 |
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1999-00 |
171 |
17 |
188 |
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2000-01 |
171 |
9 |
180 |
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2001-02 |
161 |
15 |
176 |
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2002-03 |
169 |
16 |
185 |
Tracking Teasers: Discussion of Challenge Question #2
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| March 2003. Click to enlarge for a good look at the leg bands. Which chick is this? PhotoICF |
Even before the chicks arrived in Florida November 30, the WCEP pilots and biologists had already decided which cranes from hatch year 2002 (HY02) would wear the PTT?s (Platform Transmitter Terminals, or satellite tracking devices). Joe Duff, pilot and Project Leader with Operation Migration said: "We hope they will be lead birds on the way back north or at least they will stay with the main flock and give us an idea where the group is." They are:
Cranes #1, #2, #8, #11, and #17.
If you think this was an easy decision, you might think again after reading Sara?s comments below. What questions do these new changes raise for you?
Dudes! Who?s Getting an Attitude?
Have the birds changed over the winter? Sara says: "Along with voices and plumage, it seems some of the individual personalities of the birds are changing as well. The chicks have been together as a large group for almost five months and have had their basic hierarchy worked out for quite a while now. However, the dominance structure of the group is not static and permanent, and we?re reminded of this by some of the recent changes we?ve observed in the bird?s behavior, especially Cranes #1 and #3."
Read Sara?s newest comments describing changes in these two cranes:
Are you wondering where the five pioneer whoopers are from HY01? Check out our chart, and don?t miss the newest question: Cranes #6 and #7, where are you? Find it here:
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| Last fall's migration to Chassahowitzka with 16 chicks. Photo OM, WCEP |
It?s anyone's guess as to when the HY02 chicks will initiate their northern journey. Thanks to the PTTs on five of them, the Argos NASA Satellite has been providing data every other day since February in anticipation of their departure. The monitoring team is ready with vehicles equipped with radio receivers. As soon as the young birds head north, Richard Urbanek and ICF interns Colleen and Lara will be on the road, tracking them as they return north--without the aid of their funny-looking ultralight "parents." After several months of crane duty, Sara Zimorski will return to ICF in Wisconsin for other duties.
The batteries in the PTTs will probably last at least 750 hours, according to project biologist Dr. Richard Urbanek. They run 8 hours on a given transmission day. The number and distribution of transmission days is programmed into the transmitter according to WCEP?s request. "It would not be unexpected if the antennae broke off before then and the units became nonfunctional," says Richard. But do you wonder what happens when the batteries run out?
Mike Putnam, ICF Crane Conservation Director, added: "The PTT is light, so it does not hinder the survival prospects for the bird. The bands and transmitters stay on the birds. The bands that support the transmitters are part of the color-banding scheme. They are used to individually identify the birds--for life. These bands are fastened securely so that we can identify the birds throughout their lives, even after the transmitters fail.
"The risk to the birds would be high if anyone were to try and catch the bird to replace the transmitter or "recharge" it. These transmitters are a small percentage (some tens of grams) on birds weighing 6000-7300+ g."
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
#3 (OR #4 OR #5).
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 28, 2003.
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