Environment

Wood storks nest in Corkscrew Swamp for first time in five years

 
 
Wildlife biologist Mike Knight photographed this wood stork, which ride air currents to forage for food in ranges that can stretch up to 75 miles when they’re nesting and far greater so long as food is available, at the Corkscrew Swamp Sanctuary east of Naples last week.
Wildlife biologist Mike Knight photographed this wood stork, which ride air currents to forage for food in ranges that can stretch up to 75 miles when they’re nesting and far greater so long as food is available, at the Corkscrew Swamp Sanctuary east of Naples last week.
Mike Knight / Audubon Society

jstaletovich@MiamiHerald.com

The wood stork — the only stork native to North America and one that roamed Florida’s vast wetlands until it nearly became extinct in the 1980s — has come home to nest.

For the first time in five years, the toddler-sized stork that’s considered an indicator species for wetlands health has built treetop nests in the Audubon Society’s Corkscrew Swamp Sanctuary, northeast of Naples. So far, biologists have counted more than 160 nests in the 14,000-acre preserve that had once been one of its primary breeding grounds. Last year, there were none.

The news comes as the U.S. Fish and Wildlife Service wraps up a seven-year effort to reclassify the scaly-headed wading bird from “endangered” to the less urgent “threatened” status, a task that has already taken several months longer than expected.

But while the population of the stork nicknamed “the preacher” for its hunched posture and solemn coloring has increased in recent years, the number of nests in historic habitats like the Corkscrew Swamp has been low. This year, a fluctuation in weather — a year’s worth of rain in just four months — filled small pools needed to stock the 400 pounds of fish each chick consumes during a breeding season.

“They’re here because we had a lot of rain,” said sanctuary director Jason Lauritsen. “So I don’t want people to get the wrong message, that the storks are back at Corkscrew and we fixed everything. We have a lot of work to do, but this shows us we have the capacity to grow storks. We can still fix this system in a meaningful way.”

Fluctuating numbers

Between 1967 and the early 1980s, the wood stork population in South Florida dropped precipitously by as much as 75 percent as canals and changing water patterns reshaped the birds’ fishing grounds, according to Florida Atlantic University’s Avian Ecology Lab. Wood storks, the only Florida wading bird on the endangered species list, are foragers and need shallow water to perform their odd but effective fishing maneuvers. The storks fish by touch, plunging their open beaks into shallow water and sweeping them back and forth until they encounter sunfish and other small species. Then, in a fortieth of a second and with one of the fastest reflexes ever recorded in a vertebrate, they snap their beaks shut.

As the dry season progresses, the storks fly up to 75 miles a day in search of food, using their five-foot wing span to ride thermal currents and follow the flow of water receding inland. When the dry season reaches its height, and shrinking ponds concentrate fish in easy-to-hunt ponds, the storks nest.

Between 1986 and 1991, South Florida had fewer than 800 nesting pairs, according to the Fish and Wildlife Service. Then, in 1991, seven years after they were protected, their numbers suddenly doubled. They continued to grow, dropping off slightly in the mid-1990s, and have steadily risen since 1999. In 2007, after almost a quarter of a century, federal wildlife officers decided to reconsider their status. A frenetic breeding season in 2009 created numbers not seen since the 1940s, prompting property-rights attorneys opposed to wildlife restrictions that block development to demand that the agency move on its earlier finding and change the bird’s status.

“We’re certainly pleased to see the wood stork is rebounding, which is consistent with what Fish and Wildlife said a few years ago,” said Mark Miller, managing attorney for the Sacramento-based Pacific Legal Fund’s Atlantic Center, the property-rights group. “We want them to follow the law on behalf of the American taxpayers.”

Wetland barometers

In January, the South Florida Water Management District reported that the number of wood stork nests in South Florida had climbed 50 percent in 2013. But many of those nests are built outside historic habitats and often in man-made ones, like golf courses and retention ponds. That means increasing numbers don’t necessarily correspond to healthier wetlands, said University of Florida wildlife ecologist Peter Frederick.

“The Corkscrew is not connected to the Everglades — it’s a different drainage system. But it’s a microcosm of the same thing that goes on in the Everglades,” he said.

Because wood storks must consume such large amounts of fish, particularly during their 120-day breeding season, they help biologists understand whether water in wetlands is flowing as it should.

“It’s not just that you have to find a place to have fish, you have to keep finding a place that has fish over 120 days. And that’s actually the hard part,” Frederick explained.

Scientists know that the Everglades area once supported a vast population of wood storks. In his 1917 work The Bird Study Book, ornithologist Thomas Gilbert Pearson estimated that the Corkscrew Swamp alone held 100,000 wood storks before agricultural canals and coastal development began interrupting the flow of water and shrinking their habitat. But while their hunting grounds may dwindle, biologists have discovered the storks tend to be scrappy survivors.

“If the conditions are crummy here, they may simply go someplace else,” Frederick said.

Which has led conservationists to work harder at finding new habitats. The Audubon Society teamed with wildlife ecologist Tim Hall to design a wetland habitat within a Naples housing development that included an old tomato field. The 32-acre preserve was completed last year. In December, Hall spotted 30 wood storks in one area and 21 in another.

“It’s successful in the short term, but I want to get three or four years under my belt to say it’s really a success,” Hall said. “You have to have the right conditions initially. If you don’t have a site that floods every year, it won’t do any good.”

He credits Audubon and other conservationists with bringing attention to the importance of shallow wetlands.

“Everything before was trying to save the deep cypress domes and the pretty slough areas. And in the scheme of things, they kind of valued those shallow wetlands less than the deep,” he said.

Encouraging partnerships between environmentalists and developers, Lauritsen said, is one way to try to balance conservation and development in a way that can create the kind of hop-scotching habitat that wood storks need to thrive.

“We can’t just rest on our laurels and say every six or seven years we have good conditions and grow storks. We need to realize the new landscape here is these birds are going to be faced with more uncertainty, even in good years.”

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