Every summer, chicks hatched in captivity are released at Necedah National Wildlife Refuge, where they go to crane school. The young cranes are raised by costumed biologists so that they experience as little human exposure as possible. This way, the chicks will not imprint upon humans. Imprinting is a type of rapid learning seen in many species of birds. After chicks hatch, they become socially attached to the first moving object that they see. During imprinting, a chick learns its species' identity and its habitat preference.
The young whooping cranes prepare for migration in one of two ways. Some chicks learn to follow an ultralight aircraft. They are exposed to the sound of the plane s engine at an early age so they become accustomed to it. In fact, the engine sounds are played while the eggs are still incubating! Biologists wearing whooping crane costumes fly the ultralight aircraft. The ultralights play recordings of whooping crane calls and the cranes follow behind them. At first, the young cranes can only run behind the planes, but they grow very quickly and are soon able to fly in short spurts behind the aircraft. By the time fall comes around, they are able to fly for a much longer period and are ready to fly with the ultralights on their southward migration.
Biologists are also experimenting with another way that young cranes may be able to learn their migration route - by following older, experienced birds who have made the migration before. Once they are old enough to fly in the fall, chicks are released into groups of older whooping and sandhill cranes. These birds are referred to as "direct autumn release" or DAR birds. Just like the birds that are taught to follow the ultralights, these birds are also raised by costumed biologists until they are released into the wild.
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