CHASSAHOWITZKA — On the 10th day of the 10th month of 2010, the 10th flock of endangered whooping cranes took off from their pen in Wisconsin and flapped south behind ultralight aircraft to winter in Florida.
Ten of those 11 birds made it safely to their temporary winter homes in Citrus County and the Florida Panhandle. The 11th couldn't take the arduous 1,250-mile trek and was sent home in a crate.
Any day now, an evolutionary switch will flip inside the five birds here and they will head back to Wisconsin's Necedah National Wildlife Refuge. Some of the birds at St. Marks National Wildlife Refuge in the Panhandle already have departed.
If the whoopers make it back home, it will be the 10th successful migration cycle in a multi-pronged effort to reintroduce migrating whooping cranes to the eastern United States.
As organizers mark the anniversary, they are reviewing the mixed results of the last decade. Already, some changes are being made.
This fall's migration, for instance, will not start in Necedah but from somewhere else in Wisconsin.
The birds, which mate for life, breed when they return North. But ravenous, tiny biting black flies in Necedah attack the adult cranes, driving them off their nests before the eggs can hatch.
The 106 birds in the eastern migratory flock have produced just three wild chicks in 10 years, far less than expected.
"They have done everything that we have asked them to do except, to a large part, hatching chicks,'' said Joel Trick of the Whooping Crane Eastern Partnership, adding that, overall, the program has been "highly successful.''
"This is still an experiment,'' stressed Liz Condie of Operation Migration, which runs the ultralight effort. '"We've been able to compile a lot of good scientific data over 10 years, so now it's time to apply it.''
Ben Weiss and Eva Szyszkoski have played key roles in that exercise this year. The two, clad in whooping crane suits, have been babysitting the five cranes wintering at the Chassahowitzka National Wildlife Refuge.
As much as they enjoy having the 5-foot-tall snow white birds around, they know it's time for their feathered friends to take off.
"I'm happy to go out and be with them on the water every day,'' Weiss said. "But it's what they're supposed to do. They're supposed to migrate.''
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Whooping cranes, North America's largest birds at about 5 feet tall, were on the verge of extinction in the 1940s. They now number an estimated 568, with 153 in captivity and the rest in the wild, officials say.
While the ultralight-led migration has garnered lots of headlines and awe-inspiring photos, it is just one of several projects to grow the crane population and provide a backup plan if the one wild flock of migrating whooping cranes suffers a catastrophic loss.
That flock, which flies annually between Aransas National Wildlife Refuge in Texas and the Wood Buffalo National Park in Canada, had 283 birds this winter.
In February, scientists started a nonmigratory flock by placing 10 cranes in the coastal marsh of Louisiana's Vermilion Parish, the first whooping cranes in that state since 1950.
The other nonmigratory flock was established in 1993 in Florida's Osceola, Lake and Polk counties. After introducing 289 captive-raised whooping cranes through 2004, the Florida Fish and Wildlife Conservation Commission said in 2008 it would add no more.
Only 20 of those cranes remain, officials said; the others have died off or fallen prey to predators.
More birds also will be sent to the Direct Autumn Release program, where cranes are human-raised, then released with wild whooping cranes at Necedah to learn the migration route.
Because the Eastern Partnership doesn't want more birds released at Necedah, this year the birds will be placed with sandhill cranes, which use the same migration route to Florida as the whooping cranes, Trick said.
A new program to allow captive whooping cranes to raise their own chicks and then have them released into the wild is also in the works.
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Back in Wisconsin, the search for a new nesting and launch site is focused on two spots: the White River Marsh Wildlife Area and the Horicon Marsh State Wildlife Area.
These sites offer habitats similar to what wild whooping cranes prefer, freshwater marshes with tall grass prairie. Most important, it's an environment that does not produce the swarms of gnat-like black flies.
Operation Migration, meanwhile, awaits word of where to set up its ultralight training grounds for 2011. Once the new site is approved, the partnership expects chicks to be available for the reintroduction programs.
That includes about 12 to 20 birds that should be ready to follow the ultralights to Florida later this year.
At the Chassahowitzka compound, Weiss said, watching the cranes has given him a deep appreciation of the efforts under way to save the species.
Noting that it was human activity that all but wiped out the birds in the first half of the 1900s, Weiss said humans must help bring them back from the brink of extinction.
"It's our duty,'' he said.
Barbara Behrendt can be reached at firstname.lastname@example.org or (352) 848-1434.