The record rain that pounded South Florida and left the state a sodden mess last spring had a silver lining: an explosion of wading birds.
Threatened wood storks, which nearly disappeared in the early 1980s, doubled their 10-year nesting average. Little blue herons and snowy egrets were up 62 and 54 percent, respectively. Even roseate spoonbills fell just slightly below a dismal average, which is better than plunging even lower.
But while the numbers were up, nesting patterns revealed that a troubling pattern continues. The birds appear to be giving up on the southern Everglades, once the bread basket for the state’s wading birds.
Spoonbills, which naturalist John James Audubon said were so numerous in Florida Bay when he visited in the 1830s that “the air was darkened by whistling wings,” had one of their worst nesting seasons in the bay on record. If the trend continues, researchers and conservationists worry they’ll follow the lead of wood storks, the gangly white and black-winged birds that once nested by the thousands in the Corkscrew Swamp. In the 1960s, the swamp was home to 7,000 nests each breeding season. Last year, just 250 nests were counted, with most of the Florida’s storks now nesting farther north.
“Some of these things are heading in the right direction and others aren’t, so it’s a mixed bag. But that’s all in the context of we haven’t really started full restoration in the Everglades yet,” said South Florida Water Managment District scientist Mark Cook, the lead author on the agency’s annual wading bird report released Thursday.
“We have to be careful what these numbers mean. And that’s important in a good year and a bad year,” he added.
The report is meant as an assessment of Everglades restoration, with birds January through May nesting season as a measuring stick. If restoration works, it should bring the birds home.
“In a fully restored River of Grass, wading birds in these areas should be nesting by the thousands,” Audubon Florida’s Everglades Policy Director Celeste de Palma said in a statement. Speeding it up, she said, could also be the difference between surviving or succumbing to another looming threat: climate change.
With so little restoration work complete, the birds remain at the whim of weather. The record rain that fell in the winter of 2016 left many areas too deep, with high water levels throughout the Everglades, the Fakahatchee, Big Cypress and farther north producing the lowest nesting season in a decade.
But the high water also produced an abundance of fish. Scientists predicted the 2017 nesting season from January through May would likely be far better given the abundance of fish. But what was surprising was just how widespread it was. Cook said that supports the notion that variability in conditions, even in the extreme, can ultimately be a good thing, leading to periodic super colonies.
“It doesn’t matter if we have good and bad years, but we need super events,” he said.
With this past rainy season recorded as the wettest in 86 years, Cook is optimistic the birds will have a repeat performance this year.
But the nesting also proved that not all birds respond the same. Cook said scientists were long puzzled by white ibises, which unlike other birds do better following droughts.
“That really got people scratching their heads,” he said.
In recent years, scientists conducted a series of studies and found their primary sources of food are crayfish. Crayfish in turn eat almost anything: rotting vegetation, fresh leaves and scraps typically found in the Everglades’ low-nutrient environment. In wet years, crayfish tend to be less plentiful because after baby crayfish emerge from their burrows, they get gobbled up by fish, Cook said. But in drier years with fewer fish, the crayfish grow and flourish.
“So the thing I tell my [water] managers is you can’t imagine straight lines all the time,” Cook said. “Wet conditions need to be wet, but you need to incorporate natural variability.”
Another puzzling find remains unanswered. The number of smaller herons, including tricolored herons and snowy egrets, didn’t do as well. Cook said wet conditions should have driven their numbers up along with other birds. Some scientists suspect the answer may lie in the increase in black-crowned night herons. In addition to fish, the night-feeding herons gobble up baby chicks so they could be preying on the smaller birds.
“So it’s possible these guys are somehow preventing egrets from nesting,” he said. It’s also possible they are nesting in smaller colonies and being under-counted in aerial surveys because they are smaller and better camouflaged than other birds surveyed.
As global warming drives up sea levels, scientists are also finding they need to tweak Everglades restoration. And it turns out the birds, especially spoonbills, are helping to explain how.
Since the 1990s, spoonbill nesting in Florida Bay has spiraled downward. In recent years, the birds appear to be repeating the northward exodus of wood storks. Up until the ’90s, spoonbills regularly nested in Florida Bay, Tampa Bay and Indian River Lagoon, with their northern boundary around Merritt Island and Cape Canaveral and Tampa Bay. Twenty different nesting colonies now live north of that boundary.
But what’s driving them away is different and closely tied to rising sea levels and rising temperatures, said Audubon Florida’s state research director, Jerry Lorenz. In the next two decades, he suspects they will stop nesting altogether in Florida Bay.
“Their legs are only so long and so’s their bill, so at some point the water is going to get too deep and that’s just the way it’s going to be,” he said.
But if Everglades restoration puts more fresh water in the Everglades, Lorenz said inland habitats where they now nest — like Paurotis Pond, just off the main road into Everglades National Park, and Madeira Bay — could become critical measures of success.
“If we don’t do Everglades restoration, the habitats where they’re foraging will become marine and then we lose everything,” he said.
One of the biggest challenges, he said, is being able to identify problems caused by sea rise and warming temperatures, and the decades of flood control that altered the natural water patterns.
“That’s not to say as scientists we can’t do that,” Lorenz said. “But it used to be clear-cut and now it’s kind of clouded and we have to figure out a way to tease apart the various stressors causing problems. It’s complicated, but it’s not undo-able.”
The birds’ successful responses last year also serve as a lesson for restoration efforts, Cook said: “It’s a good sign the Everglades is fixable.”
Follow Jenny Staletovich on Twitter @jenstaletovich