(Reuters) - A flock of young whooping cranes stuck in Alabama have lost interest in following an ultra-light plane leading them to a Florida winter habitat, so the rare birds' human coaches prepared on Friday to drive them to a nearby marsh.
"Whether the birds have recognized this is as far as they need to go, we just don't know," said Liz Conde, a spokeswoman for Operation Migration, a public-private U.S.-Canadian partnership aimed at re-establishing migratory flocks of whooping cranes, a species that was nearly wiped out in the 1940s.
This has been an unusual migration season already because strong storms grounded the flock three times, and the Federal Aviation Administration temporarily halted its progress.
Several birds from the 100-bird main flock have also deviated from their usual 1,300-mile (2,100-km) route to Florida. Thirty-nine of the mature whooping cranes dispersed across Indiana, perhaps fooled by the recent mild winter weather, Conde said.
The nine young cranes that wound up in Alabama have been herded into crates and driven by truck once before. They were bred and hatched at the Patuxent Wildlife Research Center in Maryland in spring, then trucked to a wildlife refuge in Wisconsin.
There, the birds were conditioned by handlers dressed in bird costumes to follow the ultra-light craft for their initial southern migration. The costumes and strict silence observed are intended to keep the cranes - North America's tallest flying bird species - from becoming familiar with humans.
Protective pens for the birds were being set up in marshland at Wheeler National Wildlife Refuge, near Decatur, Alabama, about 70 miles from where the birds are now. The birds will be moved as soon as Saturday, Conde said.
There are two flocks of whooping cranes in North America.
A wild flock of 270 birds -- identified by their "whooping" call, 5-foot (1.5-meter) height and 8-foot (2.4-meter) wingspan -- migrates between Canada's Wood Buffalo National Park and Aransas National Wildlife Refuge in coastal Texas. Many birds from that flock have stopped this winter in Kansas and Nebraska.
The human-raised eastern flock normally finds its way to Florida after being led on an inaugural flight by a costumed pilot in an ultra-light craft.
Earlier this month, the Federal Aviation Administration (FAA) grounded the migration because of concerns that the craft violated its rules, though the agency quickly granted a waiver.
Since the project was begun in 2001, the eastern flock has produced only one chick, in 2006, in its primary nesting grounds at Wisconsin's Necedah National Wildlife Refuge. Operation Migration naturalists believe infestations of two species of black flies drive the cranes, which produce only one or two eggs per season, from their nests.
The group plans to coax the birds 70 miles east to the White River Marsh Wildlife Area, which does not suffer infestations of the pesky black fly species.
(Reporting By Andrew Stern; Editing by Paul Thomasch)