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May 4, 2006
I was surprised on May 3rd when I still found 6 whooping cranes at Aransas.
Only one crane here had headed north in the past week. Although
a few whooping cranes are sometimes still found on the wintering
grounds in early May, they should start the migration very soon.
A Molt is
Coming!
The
cranes I saw are a “dingy” white color. That coloration
indicates numerous body feathers that are 2-3 years old. Those
older feathers are frayed, worn out, and in need of replacement.
The replacement of old feathers by growing new feathers is called a molt. Body feathers are replaced gradually at different times so that the birds always have a protective covering. But the long flight feathers at the ends of the wings are lost all at once, making the bird unable to fly for several weeks. During that flightless period, cranes must remain in isolated marshes and avoid predators. This flightless period occurs about once every 3 years. It usually occurs in the summer on the nesting grounds, possibly even when the adults are raising their young flightless chicks.
Discussion
of Challenge Question #11
Last week I asked why a migration pattern hasn’t evolved so that
the younger non-breeding cranes would remain at Aransas for 2-3
years until they get mates and are ready to breed. By staying at Aransas
for several years, they would avoid the dangers associated with
making at least 5 migrations trips. Why do you think all the whooping
cranes return to Canada every summer? That was your Challenge Question. You
sent your good thoughts. Now see what I think. Our ideas are here:
I'm not flying next week to give the 6 remaining whoopers every chance to migrate. We'll see what happens!
Tom Stehn
Whooping Crane Coordinator
USFWS
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