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Photo
Howard Murph |
Dear
Journey North,
A
cold front brought northwest winds to the area on March 28
that would have halted all bird migration. It took a full day
on the 29th for the winds to swing around from the opposite direction
and strengthen. As soon as the
winds calmed down and shifted direction on that morning, the cranes
you know as "Al
and Diane," the resident pair on the Lamar Unit of the Aransas
NWR and also known as the "Johnson" cranes, apparently
started their migration. This is in
keeping with their normal pattern of starting the migration around
April 1st!
On
March 30 the conditions were perfect for migration: clear skies
with sunshine providing thermal
currents, and
strong southeast winds (tail winds) at 15-20
mph. At least three cranes took full
advantage and headed north at 10:45 a.m. when refuge volunteers
saw them in flight over Jones Lake on the Aransas National
Wildlife Refuge. The three cranes were low, but quickly
gained altitude as they spiraled up. We think they might have
been the "Boat Ramp" family group. The Boat Ramp
female was color-banded as a juvenile in 1987, so we know she
is nearly
23 years old.
Other
Cranes Getting Ready
The remaining cranes have been busy, doing their daily chores of catching
crabs and patrolling their territories to keep all other cranes out and thus
protecting their food supply. Many will be leaving any day now. It will be
6 or 7 months before they return to Aransas. They will migrate 2,400 miles,
a trip that takes 3 to 4 weeks. They will travel anywhere from 200 to 400 miles
per day. When conditions are favorable
(providing thermal currents and tail winds), the cranes will fly about 7 hours
per day. If the winds are in their faces, they will stay put. They will look
for food to eat near wherever they have found a small pond or wetland to roost
in for the night where they are safe from predators. They have to do the what
YOU do when you travel: cover a lot of miles, and then look for food and a
safe place to sleep.
We're
now approaching the peak departure time at Aransas. I expect
many whooping cranes to depart in the next two weeks, and nearly
all will wait for excellent conditions like we've had the past
couple of days. Here we go!
Tom Stehn
Aransas National Wildlife Refuge
Austwell, Texas
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