Wading birds in South Florida had a dismal nesting year in 2019, but scientists say there’s a silver lining: the birds that did nest were doing it in the right places.
In the 2019 nesting report compiled by the South Florida Water Management District, Audubon Florida and Florida Atlantic University, nesting numbers amounted to just 72 percent of the 10-year average, said district avian ecologist Mark Cook. That follows a record-breaking season that produced super colonies and numbers not seen since the 1930s.
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Cook blamed poor nesting on heavy rain that flooded foraging grounds during the start of the dry season as chicks were hatching.
“Basically, these birds lost their restaurants in the Everglades. Their meal, their food, is just dispersed all over the Everglades again and they just are unable to get enough food to feed their chicks,” he said.
But while that drove down numbers overall, historic nesting grounds in Everglades National Park and an area of southwest Florida called the Fertile Crescent hit their highest numbers since 1986.
Cook suspects spillover from the 2018 nesting boom helped, but said the numbers are a good indication that efforts to send more water into parched marshes is working.
“We're still seeing relatively large numbers of birds nesting down there, regardless of whether we're having these big rainfall events,” he said. “So something's changed down there. These coastal regions are getting some increased freshwater flows. It’s certainly created better foraging conditions.”
The annual wading bird report, which marked its 25th anniversary this year, serves two purposes. It provides a yearly look at how beloved wading birds like roseate spoonbills and wood storks are faring. It also provides a measure of Everglades restoration.
“Wading birds are almost an ideal canary in the coal mine, so to speak,” Cook said, because they respond so quickly to changing water conditions.
Wading birds once numbered in the tens of thousands in the lower Everglades and southwest coast. Numbers that high made them an essential part of the ecosystem, balancing prey fish and providing guano to fertilize mangroves and tree islands.
“There are these big knock-on effects when you lose large numbers of animals like that,” Cook said.
When flood control — starting in the 1920s — began drying up the southern Everglades, the birds moved north into water conservation areas. Restoration is aimed at bringing them back, along with the historic habitat that made Florida Bay, the Ten Thousand Islands and other coastal areas rich fishing grounds and more resilient to hurricane strikes.
While yearly declines are worth noting, Cook said running trends are more important, with big nesting years occurring every two to three years.
"Even when we've restored the system and we're getting the water right again, we'll have good years and bad years because historically that's what happened," he said. "Right now, we're not quite reaching that frequency of good nesting."
Climate change and invasive species are also complicating efforts to revive nesting.
Pythons that have wiped out populations of small mammals are increasingly targeting wading birds and gathering around nesting islands. And rising sea levels are changing habitat and have likely driven roseate spoonbills away from Florida Bay, where numbers began declining a decade ago.
“So there are uncertainties,” he said. “This needs to be adaptive. We can't just have a fixed course for our restoration. We're still learning things.”
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