Steve Hillebrand - USFWS
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Whooping Crane Migration Update: April 17, 1998
Today's Update Includes:
They're On Their Way!
"The birds are almost all gone, with only 6 remaining!", exclaimed Tom
Stehn just after finishing the latest aerial crane census flight at Aransas on April
Tom has bid farewell to over one hundred and thirty whooping cranes since the
last Crane Update, and he has provided his Field Notes and the Chart below so you
can determine when the cranes departed.
A little further north, Wally Jobman has been getting more sightings on the migrating
cranes, and he reports below that they have now reached the Dakotas and Saskatchewan!
Field Notes High Above Aransas
To: Journey North
From: Tom Stehn
Aransas National Wildlife Refuge
April 16, 1998
I just finished an aerial census of the Aransas NWR and surrounding areas, and the
birds are almost all gone! Only 6 cranes were remaining, including 2 adults, 3 subadults,
and 1 young = 6 whooping cranes. With only 6 cranes left, this indicates that an
estimated 28 more cranes have migrated since my last flight on April 9.
On today's flight there was only one family group (Rattlesnake Island). The juvenile
had only a little brown on the head and back and was extremely difficult to differentiate
from the adults. All other birds were believed to be subadults.
I also did an aerial census flight on April 9 and then I could only find 34 whooping
cranes. Using the chart below, can you answer this Challenge Question?
Challenge Question # 7
"How many additional whoopers left Aransas between April 2 and April 9?"
(To respond to this question, please follow the instructions at the end of this report.)
The 34 cranes still present at Aransas on April 9 included two family groups (breeding
adult pairs with their juvenile from last summer) and 28 subadults (cranes that look
just like adults but are too young to breed, usually less than 3 years old). The
subadults aren't in a rush to migrate to Canada since they won't be building nests
or raising young. One of the last two families departed April 11. I fully expected
the other family to be gone when I climbed in the airplane on April 16 to check on
the cranes again.
Great Winds For Migrating...and Windsurfing!
One interesting departure of cranes occurred April 5 with the cranes taking full
advantage of clear skies and strong east tailwinds that day. I remember the winds
that I also used that day, since I went windsurfing in the Gulf of Mexico with a
steady 20 miles per hour of wind pushing me along. Tour Boat Captain Appell was leading
his morning whooping crane tour that day and observed 14 cranes leave between 0950
and 1030 AM. The cranes apparently waited until mid-morning for thermal currents
to develop before they left.
This satellite weather map shows that south winds blew along the Texas Coast on April
5th, after this high pressure system moved to the east.
Cranes Head Home
South winds blew along the Texas Coast on April 5th, after this
high pressure system moved to the east.
Also, here is a recap of the peak population for this winter at Aransas, which
152 + 30 = 182. With the loss of one adult crane, the flock is currently estimated
Now that almost all of the cranes have departed, hopefully the telephone will
be ringing as people call in to report seeing the whooping cranes as they speed north.
Until next time,
Whooping Crane Biologist
Aransas National Wildlife Refuge
Field Notes From The Great Plains
April 17, 1998
Wally Jobman reports from Nebraska that the migrating cranes have now reached the
Dakotas and Saskatchewan on strong south winds! The latest crane sightings are found
at the end of this report. You can see these strong winds on the weather images below.
Crossing the Great Plains with a Tailwind
Strong south wind on April 11 and 12 likely moved many of the birds into the Dakotas
Maps by: Purdue University
March 11, 1998
March 12, 1998
Wally plans to send out a further update next week!
How to Respond to Today's Challenge Question
1. Address an e-mail message to: email@example.com
2. In the Subject Line of your message write: Challenge Question # 7
3. In the body of the message, answer this question:
Using the table above, "How many additional whoopers left Aransas between April
2 and April 9?"
The Next Whooping Crane Migration Update Will be Posted on April
Copyright 1998 Journey North. All Rights Reserved.