Jane Chandler raises the rarest cranes in the world. For them to have a chance at surviving in the wild, the young birds must never see her face, hear her speak, or know her to be human.

If they did, these whooping cranes, named for their characteristic calls, would also come to think of themselves as human. Then they would not find a mate in the wild, or understand the true danger that people represent.

So Chandler dons a disguise whenever she comes near the chicks. Her bird suit is made up of a sheet-like drape that covers her from neck to ankles, and a full white head covering with a camouflage screen hiding her face. She wears a puppet of a crane's head on one hand, using the beak to pick up food pellets, grapes, mealworms or corn to feed the young birds.

Chandler's title is Crane Flock Manager at the U.S. Geological Survey's Patuxent Wildlife Research Center, and on a crisp morning in November, her charge was a group of 11 juveniles.

Nearly six months old, they stand about three feet high.

Their heads and wings are light brown, a hue that will fade as they become adults, giving way to sleek white plumes, black-tipped wings and a scarlet crown. These iconic North American birds poke around their outdoor enclosure, walking delicately through a pond, flapping their wings occasionally, pausing to peck corncobs and squeaking in response to the throaty sounds of adult cranes nearby.

Soon, they will be packed up and sent via private aircraft to their new home, added to a group of 23 captive-bred counterparts at the White Lake Wetland Conservation Area in Louisiana. "Historically there was a non-migratory flock in Louisiana in the 1900s," Chandler says. "So we are trying to recreate that."

Can it work?

Whooping cranes all but disappeared from the United States more than a century ago. The tallest birds in North America, reaching up to five feet, they were hunted to the brink of extinction and lost critical habitat in the 1800s when pioneers drained their freshwater marshes for farmland.

By the 1940s, the only remaining wild population was down to around two dozen birds.

Now, after five decades of efforts and millions of dollars spent annually to rebuild their numbers, there are nearly 600 - about 300 in the wild and the rest in captivity.

Conservationists say a sustainable population would have 1,000 wild birds, in at least two independent flocks.

Though she must stay invisible to the birds, Chandler forms strong bonds with them on the protected Maryland refuge, where cranes in captivity can safely reach old age.

"Some of the birds that I work with have also been here for 25 or even 40 years – our oldest bird is 42. When one of those birds dies, it is sad," she says. "It is like losing a friend."AFP