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Whooping Crane

Whooping Crane Migration Update: March 5, 1998

Today's Update Includes:

Overview of the Season

Migration Route
Map by Claudia Fonkert
Macalester College

The whooping crane is an endangered species with a success story to tell. Their population hit an all time low in 1940 when there were only 22 cranes left in the wild. Their numbers have been steadily building, year-by-year and, as you'll read today, the comeback has broken all records this year.

Each spring the entire flock of wild whooping cranes takes the annual 2,500 mile journey from their wintering grounds in Texas to their nesting grounds in northern Canada. They usually arrive in late April or early May, just as the ice and snow are melting from the marshes.

Tom Stehn, Refuge Bilogist at Aransas National Wildlife Refuge in Austwell, Texas will provide updates this spring as the cranes begin their journey.
When the migration is underway, weekly weather reports and migration news will be shared once again this year by Wally Jobman. Wally is based at the U.S. Fish and Wildlife Service office in Grand Island, NE. Finally, from the far north, each spring Canadian biologist Brian Johns, of the Canadian Wildlife Service, shares the excitement when the cranes arrive once again on their ancient nesting grounds. We hope you enjoy traveling with the whooping cranes this spring!

Update from the Whooping Cranes' Winter Headquarters

Refuge Biologist
Tom Stehn

To: Journey North
From: Tom Stehn
Aransas National Wildlife Refuge
Austwell, Texas

Dear Journey North,
It's been a RECORD season for the whooping cranes. (Count how many times I use the word record in this letter!) During the summer, a RECORD 51 nesting pairs produced a RECORD 58 chicks, including a RECORD 16 sets of twins. Although the usual high mortality occurred on the young chicks, by mid-August between 32 and 38 juveniles reached flight age, including two sets of twins.

At Aransas, my weekly aerial counts in November and December as the flock arrived skyrocketed to 152 adults and 30 juveniles for a RECORD total of 182 whoopers. The 30 juveniles in Texas is also a RECORD, surpassing the previous high of 28. Last winter, we had 160 whooping cranes, so the flock made a huge gain of 22 birds in one year.

Especially exciting, one set of twins arrived safely. This is the first set of twins to reach Aransas since 1964. Starting in 1965, Canadian biologists visited nests in Wood Buffalo National Park and removed one egg from each two-egg nest.

Beginning in 1965, eggs were collected from wild whooping crane nests.

Since whooping cranes normally are only able to raise one chick, the population continued to grow even when the eggs were taken. In fact, researchers believe the rate of growth actually increased because biologists would ensure that each nest contained a healthy egg, sometimes swapping a good egg for a bad egg and giving the parents a second chance to hatch a chick. This egg pickup over the past 30 years has allowed biologists to start a captive breeding flock that now totals 114 whooping cranes.

Raising whooping cranes in captivity. Why the white outfits?
(See Challenge Question #2)

The captive flock is raising chicks of their own which are being transported to Florida and released to start a new non-migratory flock of whoopers. Why do you think the Florida whooping cranes wouldn't migrate up north during the summer? It is because parent cranes have to teach their "children" the migration route. The Florida whoopers were raised in captivity and thus stay in central Florida where they were released.

Back to the egg pickup and the set of twins at Aransas this year. In the summer of 1997, the Whooping Crane Recovery Team decided that the captive flock was doing well enough so that we would no longer have to take any eggs out of Wood Buffalo. So in the very first year of leaving two eggs in every nest, one set of twins made it safely to Aransas. But this shows you how difficult it is to raise twin chicks since of the 16 sets of twins found in June, only one set survived through the fall migration. Normally, whooping cranes can raise twin chicks only 14% of the time. So this made it especially exciting when I saw for the first time in my 16 years at Aransas a set of twins.

Juvenile whooping cranes are tawny colored, in contrast to the full white of the adult.

The 30th juvenile to reach Texas this winter is not at Aransas. It is apparently a juvenile that got separated from its parents during the fall migration and followed sandhill cranes to the Texas coast. It was seen January 22-24 about 100 miles north of Aransas near Brazoria, Texas. We don't know where it is now, but it WILL return to Wood Buffalo National Park in the Northwest Territories of Canada where it was hatched to find other whooping cranes.

We also know about one other wayward bird in the flock. A whooping crane was sighted in mid-February on the Platte river in Nebraska. (See last week's News Flash.) It presumably followed sandhills north to the Platte where thousands of sandhills "stage" for weeks, building up fat reserves for the migration. We don't know if the Platte whooper is one of the Aransas whooping cranes that started the migration early, or whether it possibly is a crane that wintered with sandhills someplace else. We have never had an Aransas whooping crane start the migration in February before. (Another RECORD?) A few birds sometimes leave in early March, but most of the whooping cranes won't depart until the last week in March or the first two weeks in April.

Despite the very mild winter due to El Nino, the whooping cranes know not to leave too early or they will find nothing but ice and snow when they return to their nesting grounds in Canada. How do you think they "know" this?

So despite the very warm winter, I think the timing of the whooping crane migration this spring will be similar to the way it always is. I wonder how other species are affected by mild winters. All the whooping cranes have survived the winter here so far and should be in good shape when they return to nest in Canada. I'll let you know when the birds start leaving.


Tom Stehn
Whooping Crane Biologist

Today's Challenge Questions

Challenge Question #1
"If it's not the weather that signals spring for whooping cranes, how do you think they know when to migrate?"

Challenge Question #1
"If it's not the weather that signals spring for whooping cranes, how do you think they know when to migrate?"

Challenge Question #2
"Why do you think the people who raised the cranes in captivity dressed entirely in white, with their bodies and faces covered?"(See photo on WWW.)

Challenge Question #3
"Why do you suppose biologists felt it was so important to establish additional flocks of whooping cranes? What concerns do you think they had about the single flock?" List as many as you can and send them with your answer.

(To respond to these questions, please follow the instructions at the end of this report.)

Suggestions for Analyzing Whooping Crane Population Data

Using the population data from 1940 to the present (see below), make the following 3 graphs to depict the population comeback. Graph the:
  • Number of Whooping Cranes per year.
  • Increase in the number of Whooping Cranes per year.
  • Percent increase in the number of Whooping Cranes per year.

Climbing Crane Population
Year # Cranes Year # Cranes




























* The official population count is made in DECEMBER each year.

Discussion Questions

  • Describe the different visual picture each graph gives you. Was it helpful to graph the data in these different ways?
  • Think about what each graph means. What different information does each show you?
  • Which graph do you think is the most revealing?
  • Are there times when the numbers appeared to increase significantly, but the percentage increase was not as pronounced?
  • What questions did the graphs give you about the climb in population size?
  • What reasons do you suppose are behind these changes?
  • List all the factors you can which might have caused the population to rise (or fall) as the data show.
  • During which decade did the population increase at the fastest rate?

How to Respond to Today's Challenge Questions

Please 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, answer ONE of today's questions.

The Next Whooping Crane Migration Update Will be Posted on March 19, 1998.

Copyright 1998 Journey North. All Rights Reserved.