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October 2, 2003

Finding the "Sweet Spot"

It's about 1228 statute miles to Chassahowitzka NWR where the new Eastern flock spends winters. By bird standards, that's not so long a migration. But when you mix ultalight aircraft and birds together, the time stretches to nearly two months of travel. That's because each is more efficient without the other.

Cranes line up in formation off the wing of the ultralight, which acts as "lead bird." The birds closest to the wing get the most benefit from the wing's air currents ("wake"), which provide lift. Each bird benefits from the lift provided by the wings of the bird in front of it.
Photos OM for WCEP

But the mix of birds and ultralights is a necessary one, at least for the chicks' first journey south. And flying with the plane CAN be of benefit to a whooper, particularly the lead bird closest to the wing. That's because the ultralight acts as lead bird, and the wing creates lift that gives the nearest crane an easier ride. That means the bird can soar more and flap less. Have you ever seen the wake created in the water behind a speedboat? You could surf on that wake. Wings create the same type of "wake," but with air instead of water. Because the ultralight is so slow and has a large wing, it creates a large wake. That's why pilots say the "sweet spot" is the position closest to the wing. Up to to six cranes can surf on the wake behind the trike's wing, and the lead bird flies only 6 to 8 inches from the wingtip!

In this audio clip (67 seconds), pilot Deke Clark talks about this question:

  • How does the trike help the cranes in flight? (Listen for answers to the questions below in Deke's audio clip.)

Pilot Deke Clark (left), with Joe Duff (top) and Dan Sprague (right) in 2001. Photo OM.

Try This! Journaling Questions

1. Deke refers to the "V" formation or chevron-shape flying formation in this audio clip. Draw a picture that illlustrates this.
2. You will hear Deke refer to soaring birds and flapping birds. What's the difference?
3. Deke will use the word vortex. Listen for a synonym for vortex. What creates the vortex?
4. To what human activity does Deke compare the flight of birds with an ultralight?
5. How do the trailing birds, which are flapping more than the lead birds, get a rest?

For more, see our in-depth lesson: How Birds Fly.

Journey North is pleased to feature this educational adventure made possible by the

Whooping Crane Eastern Partnership (WCEP).

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