GOLDEN GATE ESTATES — The wood storks were flying all over Corkscrew Swamp Sanctuary, carrying sticks in their beaks for nests and even mating within sight of the sanctuary's boardwalk.
They were back, raising hopes for a successful nesting season. It wasn't to be. As quickly as they arrived, they left again, making 2012 the fifth year in the past six that North America's largest wood stork nesting colony has had no wood stork nests.
"We're kind of getting lonely without our wood storks," Corkscrew sanctuary director Ed Carlson said.
With Corkscrew a washout again this year, wood storks are nesting at other smaller colonies around Southwest Florida and the southeastern United States as federal wildlife officials weigh moving the ungainly birds from endangered to only threatened species status.
The non-nesting streak at Corkscrew doesn't indicate a problem at the sanctuary but signals that the larger Southwest Florida ecosystem has lost too many wetlands that wood storks need to trigger a successful nesting season, the sanctuary's lead wood stork researcher said.
"Here's our wake-up call," said Jason Lauritsen, assistant sanctuary director at Corkscrew. "We're in unprecedented territory here."
The U.S. Fish and Wildlife Service is waiting for data to draw the connection between wetland loss and the drop in wood stork nesting, spokesman Chuck Underwood said.
"It's a concern," Underwood said.
Aerial surveys of the region's wood stork nesting sites have found few of the telltale flecks of white in the treetops this spring.
Trackers were keeping an eye on three colonies around Immokalee and on the Caloosahatchee River, but one of the sites near Immokalee was abandoned. It had 30 nests, sanctuary natural resources manager Mike Knight said.
The two remaining colonies have about 80 nests between them and almost 100 chicks so far, some of them nearing fledging age, Knight said.
Wood stork nesting is all about water and timing. When the ungainly birds arrive in the fall, they rely on shallow wetlands to produce food they can easily catch.
As the fall wears on, and the dry season kicks in, those wetlands dry up and deeper wetlands dry down, concentrating food that the birds will need to support themselves and their young when nesting starts.
At least that's the way it's supposed to work. If not enough rain falls in the wet season to produce food or too much rain falls during the dry season and the wetlands don't dry down, the birds won't nest or will abandon nests midway through the nesting season.
A prolonged drought is amplifying the effect wetland losses are having on providing wood storks with food when they need it, Lauritsen said.
The last successful wood stork nesting season at Corkscrew was 2009, after Tropical Storm Fay caused flooding late in the 2008 hurricane season.
That year, nest watchers counted 1,120 nesting pairs of wood storks and more than 2,500 wood stork fledglings, the most productive season since 2002.
When water levels at Corkscrew reached their 50-year average last summer, Lauritsen said he gave the wood storks a 50-50 chance of a productive nesting season this year. Those odds evaporated, though, as the rains stopped and the region settled into another very dry season.
Underwood, at the Fish and Wildlife Service, said wood stork trackers have counted some 10,000 nesting pairs throughout the southeastern United States.
Scientists look at the nesting numbers throughout the wood stork's range, not at particular colonies such as Corkscrew, to determine whether they should be considered endangered or threatened.
As a threatened species, the wood stork still would be protected by federal laws but it would be a step closer to being taken off the protected species list altogether.