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Image:
Klaus Nigge |
Dear
Journey North,
On
April 6, refuge staff saw 3 cranes at the refuge boat ramp, and
Tour Boat Captain
Tommy Moore had 2 on Ayres Island; these were the only cranes he
saw on his tour.
Reports indicate Nebraska was "chock full" of cranes
April 1-4. At least 15 Whooping cranes arrived
on the Platte on April 2. On the morning of
April 8th, all of the radioed birds were gone from Aransas, taking
advantage of the southerly winds. Right now the 11 radioed
birds range from N Texas to near Bismark ND. It
looks like the migration is well underway—perhaps a week
early—and the cranes may be in Canada soon depending on
snow and water conditions in the northern U.S.
A Special Pair Starts Migration
The territorial pair
at Mustang Lake in front of the refuge observation tower apparently
started the migration the
morning of April 6th. This winter, the pair consistently stayed
on their territory and were in sight daily to over 40,000 visitors
from
all over the world that came to see them. Those visitors had climbed
a 40-foot tall tower to gaze
out over the salt marsh to look for the tall white birds stalking
blue crabs and eating wolfberries. The territory of the Mustang
Lake pair is nearly a square mile in size; the pair defends
that area and protects
the
food supply it contains from all other whooping cranes. That is
the purpose of establishing and defending a winter territory: It
provides the food a pair needs to sustain themselves throughout
the winter.
Territories in Two Seasons
Whooping cranes are unusual in that they defend territories both
in the summer and in winter. Most birds only have summer territories.
What is the main difference between a summer territory and winter
territory for a Whooping crane? Think about what Whooping cranes
do every summer.
Watch
for Clues
for Departure
Most
of the whoopers should be departing by April 10. They normally
start migration flights between 9:30 and 10:30 (but could be as
late
as 11:00)
because they wait
for the thermals to build up and of course need tailwinds. Sunshine
is preferred.
If you see them between 9 and 9:30, you may start getting clues
of the impending takeoff. They will look more "antsy" than
usual, with the male showing much more alert behavior, walking
around, and even occasionally turning his head sideways and gazing
at the sky. Finally, a pair will take a final drink of water,
group up, and take off. You never
know what day
it might be. But the adult pairs should be leaving soon, while
the subadults could stay through most of April.
Tom
Stehn, Whooping Crane Coordinator
Aransas National Wildlife Refuge
Austwell, Texas
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