MIAMI — The fate of a generation of endangered migratory whooping cranes now rides on the fragile wings of a 10-month-old chick known as No. 15.
He is the sole survivor of the class of 2006, 18 captive-reared crane hatchlings that were guided by four costumed ultralight aircraft from Wisconsin to Florida wintering grounds in December.
Conservationists with Operation Migration had feared that all of the hatchlings died in the Friday storm that killed at least 20 people in central Florida and put hundreds out of their homes.
But No. 15, a male chick, managed to break loose from a top-netted pen when tornadoes struck.
A radio transmitter on the crane's leg sent out signals over the weekend, said Joan Garland of the International Crane Foundation in Baraboo, Wis.
Just before nightfall Sunday, an aerial search team of foundation volunteers spotted No. 15 with two sandhill cranes in the Chassahowitzka National Wildlife Refuge on the Gulf Coast, about 70 miles north of Tampa.
"What a bright spot he is in this sad time," said Joe Duff, a founder of Operation Migration and one of the ultralight pilots who guide each year's young cranes from their summer home at the Necedah National Wildlife Refuge in central Wisconsin. "We've lost a whole generation."
The loss is devastating to Operation Migration's work, as part of the Whooping Crane Eastern Partnership, to restore the migratory population in North America. It's also devastating to those dedicated to preserving the species, which numbered only 15 in 1940.
Scientists and wildlife conservationists try to stay aloof from their wards. They refrain from naming the birds, to reinforce the idea that they are not pets but wild creatures, said Duff.
"Still, you get attached," he said of those, like himself, who intervene so gently that they wear white birdlike costumes when working near the cranes. Even the ultralights the birds are trained to follow on their maiden winter migration are designed to look like whooping cranes in flight.
No. 15 and his classmates were a story of success against all odds. A snowstorm a year ago disrupted breeding at Maryland's Patuxent Wildlife Research Center for a month. Despite the late hatching and return of the fledglings to Wisconsin, Operation Migration managed to get a flock of 18 trained in time to trail the ultralights on the trip south, starting in October.
Inclement weather along the migration route slowed the birds' journey to Chassahowitzka from the usual 50 days to 78. No. 15 dropped out on the last leg of the journey but was spotted two days later and reunited with the flock.
Then Friday's tornadoes wiped out a year of work to bolster the species, which numbers fewer than 500 across North America and now only 64 in the Wisconsin-Florida flock.
"These chicks were like our children; the start of a new generation of life for the species," Operation Migration said in a note of bereavement on its website, www.operationmigration.org.
The Craniacs, as they call themselves, have created a fund in memory of the 17 killed and to celebrate No. 15's survival.
"Remembering the Class of 2006 Fund will go a long way to help us recover from a costly setback that amounts to a year of time and effort and approximately $500,000," the website says.
Wildlife biologists aren't sure exactly how the birds were killed. They suspect a lightning strike during the ferocious pre-dawn storm. The birds also might have drowned in their enclosure if they were trapped by the net during a storm surge brought on by 165-mph winds, Duff speculated.
The crane carcasses have been sent to the University of Florida in Gainesville for necropsies to be carried out with a grant from the Disney Wildlife Conservation Fund, said Jim Kraus, the Chassahowitzka refuge manager.
Kraus said that the conservationists might rethink the practice of covering the newly arrived cranes' territory with netting to keep older cranes from harassing the newcomers, which are fed in pellet form until they learn to forage for themselves. The youngsters are kept under the netting until they are strong enough to be released into a larger, uncovered 5-acre pen, said Garland, of the crane foundation.
The 17 that died were within a few weeks of graduating from the covered pen, which is only about 150 feet wide, she said.
Until Friday's disaster, the project had been a "wonderful success," said Rachel Levin, a spokeswoman for the U.S. Fish and Wildlife Service and for the Whooping Crane Eastern Partnership. The eastern flock has been developed since 2001 to augment the continent's only other migratory flock, about 250 whooping cranes that breed at the Wood Buffalo National Park of Canada in Alberta, and winter at the Aransas National Wildlife Refuge on the Texas Gulf Coast.
"As was unfortunately demonstrated by the storms Friday, it only takes one catastrophic weather event or disease outbreak to kill a large number of birds at one time," said Levin.
While No. 15 has been pushed prematurely out of his coddled childhood, he is expected to mingle with other whooping cranes not yet of mating age in what the project supporters call "bachelor cohorts."
Being the only survivor of his generation shouldn't affect No. 15's breeding potential, the crane advocates said. Generally monogamous, whooping cranes don't mate until they are about 5 years old and often pair off with a bird from a different generation.
Wildlife biologists are hoping No. 15 will remain with the older whooping cranes at the refuge, learning to forage and roost until it is time to fly north.
"He's been led on migration once, so he has an idea where he's going," Duff said. "I expect we will see him in Wisconsin in the spring."