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Wood storks having good nesting year at Corkscrew Swamp Sanctuary, but threats remain

Deep in the Corkscrew Swamp Sanctuary, under the shade of ancient cypress trees, a colony of wood storks has taken up residence.

The gangly and stark-white birds wade in the shallow water, shuffling their hooked and almost prehistoric beaks from side to side, waiting for the moment a fish bumps into them before snapping shut.

It's been a good year for the storks, after a long string of bad years.

"The main driver for the success are the June rains and Hurricane Irma," said Audubon Corkscrew Swamp Sanctuary Director Jason Lauritsen referring to the unusual increase in wood storks. "They saw a landscape that was reminiscent of a bygone era." The wood storks, a threatened species under the Endangered Species Act, was drawn to the higher than normal water levels found at the sanctuary that were perfect for nesting, fishing, and raising young. "The rains masked the damage that we've done for the past 70 years," said Lauritsen. "It's the silver lining."

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More than 400 nests have been built, and chicks have started to try their wings. But biologists are worried that years like this may prove to be more of an aberration than a rule, that the sight of young storks and nests in their age-old breeding ground of Corkscrew and the western Everglades will become increasingly rare or nonexistent.

And if the storks can't live or breed in Collier County's wetlands, it remains to be seen what that means for the water quality, aquifers and other species trying to survive here, said Shawn Clem, research manager at Corkscrew Swamp Sanctuary.

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A wood stork catches a fish in the early morning at Audubon Corkscrew Swamp Sanctuary Thursday, March 22, 2018 in Naples.

"Something is wrong regionally," she said. "Environmental conditions are forcing them further east (in Florida) and north (to Georgia and South Carolina)."

Wood storks serve as something of a canary in a coal mine for Southwest Florida's swamps — an indicator of the ecosystem's integrity and health, Clem said.

"They're our Goldilocks," Clem said. "They're sensitive and they have more specific requirements for feeding and nesting. If an ecosystem is keeping them happy, it's keeping a whole suite of other species and plants happy."

The problem is with water levels. Development has sapped much of the natural wetlands surrounding the Corkscrew swamp, especially shallow wetlands. The water that does accumulate has been draining too quickly.

This season the conditions have been perfect for the storks, said Dale Gawlik, professor and director of environmental science for Florida Atlantic University.

Heavy rains in June filled up the shallow marshes early, allowing fish populations to move in and grow, Gawlik said. While the water still drained quickly, more heavy summer rains, especially Hurricane Irma, kept the swamp wet and allowed the fish to keep growing.

Wood storks have poor eyesight relative to other wading birds, Gawlik said.

They rely on touch, capturing fish that swim up to their beaks. That means the birds need long dry spells near the end of the season, to lower the water levels enough that the fish are forced into smaller pockets, making them easier for the storks to pluck up to feed their young, Gawlik said.

"They depend on both the wet period and the dry period," he said. "To the extent you can keep getting these conditions in Southwest Florida, it's just been too dry in the wet season in recent years. Because so many of those shallow wetlands have been drained, it's hard to get that fish production."

Historically, storks never nested every season, Gawlik said.

"It's always been a pulse system, depending on good and bad weather," he said. "But in the past it was easier to get good conditions. It seemed to be about every other year would be good."

In the past 10 years, though, wood storks have nested only three times. In 2009, monitors counted more than 1,000 nests. They counted fewer than 500 in 2014.

And not all seasons in which the birds have nested have been successful.

Last year wood storks also laid eggs in Corkscrew, but the water dried up so quickly that many of the nests failed, Clem said.

In the first 10 years of monitoring wood storks at Corkscrew, from 1958 to 1967, the birds produced almost 5,500 chicks on average per year. That has fallen to fewer than 300 chicks on average per year in the past decade.

The dark, dangerous swamps offer some protections for the birds. As water surrounds the nesting trees, alligators move in and surround the nests.

"Those alligators are very good at defending the nests," Clem said

Without the water, the gators slink away, leaving the eggs and chicks vulnerable to raccoons and other mammals.

To ensure more successful nesting seasons during years that don't have historic rainfalls or hurricanes, there needs to be a push to change Collier County policies, Clem said.

It's not good enough to replace a shallow wetland near Corkscrew by restoring a deeper wetland farther away.

"We need to work with developers to preserve 'like for like,' " Clem said. "We need to put a greater focus on preserving the short-hydroperiod marshes. It does nothing for wood storks or their ecology to replace shallow wetlands with big giant lakes."

The young storks now fledging show that the birds haven't abandoned Corkscrew or Southwest Florida yet, giving land managers a chance to restore water levels, she said.

"It's encouraging that they've come back to nest, but it's clear that there is a lot of work we need to do." 

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