This story has been updated to include comments from the South Florida Water Management District.
Wading birds across the Everglades had a rough couple of years with annual nesting over the last two seasons below the 10-year average, according to reports compiled by the South Florida Water Management District and released Wednesday.
While rainfall played a part, the numbers suggest more work needs to be done to fix South Florida’s wild landscape and keep water where the birds need it to successfully raise chicks.
“The initial shallow conditions meant that most areas dried out too early in the nesting season,” the report said, meaning water was too low and too sparse to pond and trap enough prey fish to support hungry nesting birds and their chicks.
READ MORE: Everglades wading birds have a banner nesting season, thanks to heavy rainfall
The recent lows follow a banner year, a trend that scientists say is not unexpected. Because they forage in such specific ways, South Florida’s rich variety of wading birds, from wood storks to white herons, have long been used as a measure of Everglades health and progress on restoration. This year’s report marked the 28th year, and combined two years after the Covid shutdown slowed the tedious work which includes helicopter surveys.
"It's not just about the actual numbers of nests," said Mark Cook, a wildlife ecologist who compiles the report and heads the district's Everglades Research Group. "Ultimately what's really important is how many chicks these birds produce and whether this nesting is successful or not. And for the most part, for most species, the nesting success was quite low."
Historically, the vast majority of wading birds began the nesting season along the Gulf Coast, with its rich supply of fish and other prey. As waters receded during the dry season, the birds moved inland to the Big Cypress swamp and then tree islands further east in water conservation areas. Before canals, roads and levees carved up the landscape, more water meant that as rains eased during the dry season, water ponded naturally and gave nesting birds easy access to food.
Even natural conditions meant the birds had good and bad years. But modern flood control has left nesting areas over-drained.
One bird Cook pays particular attention to is the wood stork, because it's foraging and nesting behavior relies on historic water patterns.
"It wades along with its beak in the water with its mouth open, and the way it catches fish is it actually has to touch that fish," he said. "It's got the fastest reaction time in the vertebrate animal kingdom. It can literally snap its beak shut faster than you can blink."
That feeding pattern makes it a goldilocks among wading birds.
Water levels need to be just right. And not only along the coast where a smorgasbord of prey draw wood storks early in the season, but across the whole Everglades. As the dry season progresses, Cook said the leggy birds follow the water and find prey more densely trapped in ponding water in the Big Cypress and inland marshes.
But modern flood control has left much of the Everglades over-drained.
"So they start off well, but then they fail because they don't really have anywhere else to go," he said. "That is where we are in restoration right now.
That’s gradually changing as the $23 billion Everglades restoration project to reverse damaged from flood control moves forward. Bridging over the Tamiami Trail that allows more water to flow toward the coast gave Cook and others for the first time a better look at wood storks' more natural nesting patterns, he said.
"We've fixed some of the bottom part of the system," he said. "But there's still quite a bit of restoration to do in the northern part of the system to enable water levels to be appropriate."
While they’re reluctant to look at short-term patterns, Cook said scientists now expect to see good nesting every two to three years.
Change in make-up of wading birds
The changes over time have also meant a shift in the make-up of Florida wading birds.
While tactile feeders — like wood storks and white ibis, who use their limbs to feel for food as they hunt — dominated in the past, today there are more visual feeders — such as great egrets, who use their eyes to spot prey.
Some birds have also changed the timing of their nesting. Wood storks now nest later in the year, from January to March, rather than earlier in the dry season. Scientists say that can make chicks susceptible to prey that can more easily reach nests later in the dry season.
By far the winner in nesting so far has been the white ibis, which make up anywhere from about half to 75% of all nesting, with upwards of 16,000 nests counted nearly every year over the last five years.
Climate change has also impacted birds. Roseate spoonbills, which once flocked to Florida Bay and nested in mangrove island rookeries, have mostly disappeared from the bay as sea levels rise. But they are turning up further north on the Gulf Coast and in the central Everglades, Cook said. They're even becoming a common sight much further north in the Carolinas.
"The spoonbill population as a whole in the Everglades is doing very well. It's just not doing very well in those traditional, historical coastal colonies," he said.
Nesting for wood storks, which nearly disappeared in the 1970s, were off by about a third in 2022 but reached an average number of nests of about 2,800 the next year.
The U.S. Fish and Wildlife Service has proposed removing wood storks from the endangered species list after reclassifying the leggy birds as threatened more than a decade ago.
A earlier version of this story incorrectly said U.S. wildlife managers are considering downlisting wood storks. They are now considering delisting the birds.
