How This Year’s Devastating Red Tide Has Wreaked Havoc on Florida’s Birds

A handful of wobbly Red Knots have stayed in Melissa Dollard’s living room nearly every night for the past three weeks. The shorebirds are precariously underweight. Their legs tremble. Some can’t stand or hold up their heads on their own. Every hour, Dollard will clean out their mouths to make sure they don’t choke on their own spit.

On a Friday at the end of September, 16 Red Knots swaddled in dishcloths arrived at Seaside Seabird Sanctuary, the avian hospital in Indian Shores, Florida where Dollard works. Since then, beachgoers have dropped off sick birds nearly every day.

Dollard only brings home the birds in the most critical condition when the hospital closes for the day. “Just eight hours of care usually isn’t enough for them,” she says. The rest spend the night at the hospital, where they take days or weeks to fully recover.

The birds are sick from a neurotoxin produced by the rust-colored algae blooms that have flourished along Florida’s Gulf Coast this year: red tide. Always present in the waters in small numbers, the organism responsible for the blooms, the clover-shaped Karenia brevis, has boomed in the past 11-months, turning an annual nuisance into a lethal onslaught for all manner of marine life along Florida’s western coast. Scientists can't say for sure why this year’s blooms have been so cataclysmic, but the devastation is everywhere.  

Miles of dead fish have littered the beaches. Crabs and sand dollars from the seafloor have washed up beside dead manatees, dolphins, and hundreds of sea turtles. For the first time since 2007, the blooms have traveled around the tip of Florida and infiltrated the Atlantic, closing beaches along Florida’s eastern coast last week.

The red tide has left its mark on Florida’s birds, too. Sick birds have shown up at wildlife hospitals in record numbers. Some people have picked up truckloads along the shores. Meanwhile, the beaches are empty of their usual throngs of migrants. 

“It seems like a ghost town,” says Robin Bast, a veterinarian at a wildlife hospital on Sanibel Island, a three-hour drive south of Indian Shores. The pelicans and shorebirds that she usually sees along her commute are gone. “I don’t know if they’ve left the area or they’ve died,” Bast says. 

Every year, wildlife hospitals along Florida’s Gulf Coast treat red tide patients: Sanderlings, Snowy Plovers, Ruddy Turnstones, Red Knots, Black Skimmers, Brown Pelicans, Double-crested Cormorants and Laughing Gulls, to name a few. But this year has been exceptional, Bast says. “This is the worst one we’ve had in a decade.”

In the past year, the hospital where Bast works, the Clinic for the Rehabilitation of Wildlife, or CROW, has admitted more than 450 birds with red tide symptoms. “That’s just a teeny, tiny tip of the iceberg,” says Heather Barron, CROW’s medical director. Most of the sickened birds won’t end up at any hospital. Something will eat them. They’ll starve to death. Or they’ll quietly slip into the sea and drown.

The carnage is so widespread because the noxious chemical released by red tide, called brevetoxin, spreads up the food web and lingers for weeks. “It’s not just fish,” says Marianne Korosy, director of bird conservation at Audubon Florida. Brevetoxin accumulates in the tissues of worms, little coquina clams and mole crabs, and even insects, Korosy says. “All of that food is potentially contaminated.”

When brevetoxin reaches birds, it rocks their nervous systems. Symptoms vary between species and among individuals, but the results are never pretty. Poisoned pelicans won’t be able to move their wings or lift their heads. Tiny shorebirds will be too weak to stand. Cormorants act drunk. The toxin affects nerves throughout a bird’s body: It can slow their heart rate or it can halt digestion and lead to system-wide infection. “Food is just sitting there, rotting in the gut,” Barron says. “It’s a bad disease.”

About a third of the birds Barron sees will develop kidney failure from red tide poisoning. Some birds harbor parasites that exploit the birds’ weakened immune systems. Many arrive at the hospital with pneumonia after swallowing sea water. Others convulse from seizures. A few have a hard time blinking—their eyes dry out so much that ulcers can grow over their corneas. They become blind.

Although birds are being brought to hospitals in droves, not every bird is affected by red tide. “It’s not whole flocks of them sick at one time,” says Audrey Albrecht, a biologist at Sanibel-Captiva Conservation Foundation who has been monitoring shorebirds for a decade. Sanibel Island was hit particularly hard by red tide last month. On a recent morning, when a helicopter flushed about a hundred Sanderlings, just three of them were too weak to fly away, she says.

But evidence of red tide is inescapable: Albrecht finds turtles stranded on the beach nearly every day, and sees hundreds of dead crabs littering the shore. The air is heavy with the smell of rotting ocean life and the stinging toxin, swept airborne by the wind, Albrecht says. She can’t go to the beach without wearing a mask.

Fish start to die when Karenia brevis counts in the water reach over 10,000 cells per liter. In the last month, sites along the coastline have measured 200 times that—more than 2 million cells per liter. “People are reporting the water is slimy with this algae,” Barron says. “I don’t ever remember hearing that before.”

Even as the tide waxes and wanes in intensity, with the influx of foreign waters from storms like Hurricane Michael that flush out the algae, brevetoxin remains circulating in the food web. “It’s basically been non-stop since this time last year,” Barron says. Even now, experts aren’t sure what the new storm will mean for the red tide’s longevity and no one is quite sure the underlying cause of this year’s unrelenting saga. 

Records of red tide blooms go back hundreds of years, from the time of early Spanish explorers. But long-term events might be a more recent phenomenon—one that is poorly understood. “We don’t understand what leads to these year-long blooms,” says Sven Kranz, who studies phytoplankton at Florida State University.

Red tide flourishes in nutrient-rich conditions, exacerbated by runoff from farms and fertilizer-packed yards, pollution picked up by rivers, and warmer waters. Rainfall from big storms—like last year’s Hurricane Irma that overflowed dozens of rivers and creeks in central Florida—might also make the red tide worse. But for now, there’s not enough evidence to know for sure, Kranz says.

Whatever the cause, “the intensity is very concerning,” says Troy Mutchler, a marine ecologist at Kennesaw State University. “It feels not very sustainable, does it?”

Even less is known about how ride tide impacts bird populations, says Larry Niles, a biologist at Conserve Wildlife Foundation of New Jersey and an expert on migratory shorebirds. “You can count the number of birds that are going to the rehab facilities, but you can’t count the number of birds dying out on the beach, getting washed into the water, never to be seen again.”

The blooms affect Florida’s nesting birds and incoming migrants without discrimination. This summer, colonies of Black Skimmers, shorebirds with a notorious underbite who nest along Florida’s coastal islands, hovered near starvation, says Adam Dinuovo, who manages Audubon Florida’s shorebird monitoring project on the southern end of the state. Many chicks fledged, but the nesting was delayed, and their growth and development was slower, Dinuvo says. He couldn’t band many of the fledglings he caught to monitor. “They just weren’t big enough,” he says. “All indications are that those birds aren’t going to survive the winter.”

But the red tide won’t be a catastrophe for Black Skimmers. “It’s not the end of the world if you have a bad year,” Dinuovo says, “as long as you don’t string these things together over time.”

Other species are not as safe. For Red Knots, who travel from the Arctic to as far as the tip of South America, red tide is one more line on a long list problems facing the species. “It’s a serious threat,” Niles says. “The population could take another step downward.”

The algae blooms don’t only threaten Red Knots in Florida—struggling populations have also been hit hard by ride tide events in Brazil and Uruguay, Niles says. Understanding how red tide affects the birds in Florida matters far outside the state’s boundaries, he says. “These Arctic birds are an international responsibility.” 

For those with recovering Red Knots still under their care, or tottering inside their homes, the red tide rehabilitation work is especially high stakes. “It’s a lot of pressure,” says Dollard, from Seaside Seabird Sanctuary.

But with treatment, many birds sickened by red tide recover. Given fluids and food free of brevetoxin, the animals can work the substance out of their systems.

For Dollard’s charges, the prospects look promising. “They’re doing great. We are just getting some more weight on them,” she says. “They’re my little pride and joys right now.”