Do
pilots really need to lead them south?
Adapted
from Joe Duff's Operation
Migration Field Journal: Nov. 22, 2009
Every third day that the team is unable to fly because of poor weather, they release the birds for some exercise. The birds always come back. Not until one day in 2009 h did that change. One day 16 independent crane-kids in the 20 Class of 2009 took off and kept flying. When time passed and they didnt' come back, trackers and pilots went into action. By land and air they went in seach of the birds, who had a half-hour headstart. Thanks to their leg bands with radio transmitters, ichard took off in his trike, and after a prolonged chase managed to locate the birds and lead them to fthe next site. But now many people asked: Why don’t you just let them go? They seem to know the way. Do you really need to lead them south? The answer is still yes, says Project leader Joe Duff. He explains:
First,
a Word About Crane Wings and Thermals
One look
at a Whooping crane wing and you can tell that it was intended for
soaring. Almost too big to flap efficiently,
their wings are long and thin and designed to catch every ounce of lift.
In normal conditions cranes ride on thermals (columns of rising warm
air), like hawks or eagles, barely using any energy.
The Operation Migration leaders, on the other hand, fly in the calm air
of early morning before the sun heats it enough to create thermals. As
a result, their young cranes have likely never felt the free lift
generated by warm
rising
air.
When
the young cranes were released in the late morning on Nov. 20,
2009, they circled a few times and caught their first thermal. The
warm air carried them up, and up, and the wind pushed them southeast.
They soon disappeared
from sight. It
must have felt
exhilarating
for them to feel the lift.
"They
Seemed to Know the Way." (No, They Just Got Lucky!)
The birds
that took off on Nov. 20, 2009 headed southeast because, fortuitously,
that was the direction the wind was blowing. Had the wind been blowing
to
the northeast instead, we would have likely had to crate them back
to their starting point in LaSalle County. It worked out as a lucky
advantage that helped us make some progress. With
no ingrained sense of where to go, just releasing birds into strange
surroundings
to disperse in the direction of the prevailing wind of the moment is
not a sound
or viable reintroduction method.
Why Don't You Just Let Them Go?
- With no parent, stand-in or natural, to show them a migration route to safe habitat, the population would be scattered. Each generation would winter in a different location, and it is unlikely many would make it all the way to Florida. If we had begun this reintroduction by simply releasing birds in the north and hoping they found their way south, their ability to survive as a self-sustaining population would be doubtful.
- Birds that established territories during mild winters would suffer losses during the cold ones when they returned to those same territories.
- With no other Whooping cranes in the flyway, they would likely associate with Sandhill cranes. We know that Whooping cranes can imprint on Sandhill cranes. The endangered Whooping cranes would mate with the wrong species.
The Direct Autumn Release Project (DAR) is an attempt to have inexperienced birds associate with migration veterans. This gives them the advantage of being led south by an older generation of adults that know the way. Operation Migration’s assignment is to keep building that experienced population until it becomes self-sustaining.
Journaling Question
- If someone asks you if the pilots really need to lead the birds south, what will you say?
Journey
North is pleased to feature this educational adventure made possible by
the
Whooping Crane Eastern Partnership (WCEP).
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