Wood storks already nesting on Caloosahatchee island are becoming active at Corkscrew Swamp

One of Florida's most iconic wading birds is showing up in greater numbers as wood storks flock to the area for nesting season. 

Storks are already nesting on an island in the Caloosahatchee River near Fort Myers while birds at Corkscrew Swamp in Naples are showing their pink legs, a sign that they're ready to mate. 

"We’re still seeing real early nesting, but at Corkscrew we’re not actually sure what’s going on because there doesn’t appear to be active nesting," said Shawn Clem, a wood stork expert at Audubon's Corkscrew Swamp Sanctuary. "But it’s still early enough in the season that if they were disrupted there’s still time to nest and be successful this year."

Historically, Corkscrew Swamp has been home to the largest nesting colony in North America. 

"It’s not the case anymore," Clem said, "and we’ve seen over the last few decades that the Corkscrew colony has continued to decline while colonies in other parts of the country are doing better. In some years those are Everglades colonies."

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Even in a land of beautiful birds, wood storks stand out. 

At nearly 4 feet tall with a wingspan of about 5 feet, wood storks are mostly white, with a charcoal-colored head, large bill and long legs. 

They typically start nesting in December or January in South Florida, with nesting taking place later in the year further to the north. 

The U.S. Fish and Wildlife Services says there were about 20,000 nesting pairs in the 1930s with only about 5,000 nesting pairs found in the 1970s. 

Today there are an estimated 8,000 nesting pairs, according to FWS records. 

More than 6,800 nests were documented in Florida in 2017, according to the Florida Fish and Wildlife Conservation Commission. 

The birds also nest in Georgia and South Carolina. 

Nesting activity is driven by water levels. 

"Prey abundance and concentration are both influenced by flooding and drying," said Craig Faulhaber, avian conservation coordinator for FWC. "During periods of extended wet conditions with deep water levels, fish reproduce, and fish numbers increase. During the dry season, prey concentrates in shallow pools, which is ideal foraging for wood storks."

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The endangered birds soar across the Sunshine State on thermals, bursts of rising warm air, and will fly 80 miles or more to find a meal. 

The trouble is that daily flight is becoming longer and longer because more of the landscape is being developed. 

Flying longer means more calories burned, and the birds simply can't sustain themselves and grow chicks without hundreds of pounds of food. 

"There are not enough areas to feed, and the wetlands that are more likely to be drained are the short hydroperiod wetlands," said Paul Gray, with Audubon Florida. "They would have been drying out in November and December and they would have had crawfish and other food, and without those the storks can’t get fat enough to start nesting."

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Both the male and female need the extra calories for courtship, nest-building, mating and hunting prey for themselves and their offspring. 

Wood storks typically lay two to five eggs, but conditions must be nearly perfect for feeding or the storks may abandon nesting. 

"They used to start nesting in December, and with all the wetland drainage that’s gone on in South Florida it’s getting later and later," Gray said. "Lately it's been February." 

Storks are an important indicators species, Gray said, because they show a correlation between the loss of smaller seasonal wetlands and water quality issues along the coast. 

Wetlands that stay dry part of year have largely been developed, and the water storage and pollution filtration services they provided are gone as well. 

More:Nesting wood storks return to Corkscrew Swamp for first time since 2014

The loss of these wetlands has hurt stork nesting. 

Gray said it's also impacting coastal algae blooms like red tide. 

"These are also wetlands that helped too much water from flowing to the coast and these wetlands help buffer against those heavy (nutrient) loads," Gray said. "So not only have we damaged the ecology but this is the stuff that flows off the landscape and feeds red tide."

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