By the 1940s, the wild whooping crane population in North America had dropped to about 15. Thanks to the work of dedicated conservationists since then, it has risen to about 500. It's a tough job and the project has demanded innovative thinking, including leading whooping cranes on migratory journeys with whilte ultralight aircraft:
A Canadian ultralight aircraft enthusiast named Bill Lishman — who would later become Duff’s co-founder — theorized that certain waterfowl could be trained to follow such a plane to a different migratory destination. In 1993, Lishman successfully led a group sixteen of Canada geese from Ontario to Virginia. Thirteen of the sixteen returned to Ontario the next year — without needing a human guide.
Lishman’s innovation centered on the fact that waterfowl, soon after their birth, imprint upon the first creature they see. Typically, this is their birth mother, but in a controlled environment, it could be basically any animal — including a person, if conditions are right. Duff, in an interview with NPR’s Talk of the Nation, explained: “Whooping cranes are hatched in the nest, in a marsh on the ground, basically, and they leave the nest almost immediately and follow their parents out to forage for food. And if they don’t follow their parents, they’re lost. So that natural instinct to imprint is there, and we just substitute parent for pilot and make sure they imprint on us.”
The pilots wear white costumes while leading the cranes because they don't want the cranes to think that humans will take care of them.