The tiny Cape Sable seaside sparrow, a bird perilously perched on the edge of extinction, is getting closer to vanishing.
Helicopter surveys this year, over grassy prairies where the bird lives in Everglades National Park, detected the lowest number in five years. The surveys found none in what had once been the birds’ largest population west of Shark River Slough, an isolated group considered to be their best bet at survival.
A ground search later turned up a male and female bird in a nest. But the nest failed, said Larry Williams, Florida’s state supervisor for the U.S. Fish and Wildlife Service.
While Everglades restoration is expected to increase the sparrow’s prairie habitat elsewhere, the safer, remote area on the park’s western border has mostly switched to inhospitable sawgrass, where the birds won’t nest. Repairing it will take a decade or more, Williams said.
“That used to be a major population. So the question in front of us now is, 'is it viable to get that area back to a major population?'” he said. “And we don't know.”
This year’s surveys turned up 2,448 birds in total, an estimate based on a survey technique that counts male birds based on their calls and approximates the number of nearby females. That’s down from more than 6,600 in the 1980s. The western population numbered more than 2,600 in the 1980s and 1990s. Last year’s surveys were cancelled because of the COVID-19 pandemic.
Such a decline on protected federal land should be cause for alarm, said Stuart Pimm, a Duke University conservation biologist who has studied the sparrows since the '90s.
“You would hope that we would be able to protect [it] adequately simply because it lives on protected land. And the sad fact is that the last 25 years of water management by the South Florida Water Management District and the Army Corps of Engineers has wiped out half of the range of this endangered species,” said Pimm, who keeps a carved sparrow on his desk.
The History Of The Sparrows Population
The golfball-sized birds were first discovered on Cape Sable, the southwest tip of the Florida mainland, in 1918. The birds inhabit marl prairie, the grassy uplands where they can build nests in clumps of grass among wildflowers and orchids.
“When it’s dry, there’s an incredible variety of flowers,” Pimm said. “It looks like your sort of vision of a western prairie, with a lot of different kinds of flowers. It's a beautiful place to be.”
The Labor Day of Hurricane in 1935, and the heavy flooding it produced, is suspected of launching a shift in the cape’s vegetation that drove the birds inland. They were first found in the park in the 1950s and by the 1980s they had turned up west of Shark River Slough, and east of the slough, and along the park’s eastern border near Homestead. They can now be found in six locations.
Over the years, Williams said the sparrows became a key indicator for Everglades health and the variety of plants that the ecosystem needs to flourish.
“If it was all under three feet of water, it would all look the same,” Williams said.
Then Hurricane Andrew made landfall in Cutler Bay and flooded the area. Water managers also began draining the vast water conservation area to the north into the western Everglades.
“That does two things,” Williams said. “You have a nest there that's being tended and it gets a ton of water dumped on it. That nest is going to fail. It also causes the plant community to shift so that the plant community is no longer the muhly grass that the birds prefer.”
By 1993, the western population that had once outnumbered groups to the east had dropped to below about 500 birds.
The bird also took center stage in the debate over where and when to move water needed to the south. Over the years, the Corps has tried to referee the dispute by closing western flood gates along the Tamiami Trail during nesting season. But the gates can be open out of nesting season or to deal with flooding.
Last year, when the Corps approved a new operating plan for moving water east and south, Williams said that eased the pressure dramatically.
“The combined operating plan has been sort of the holy grail that all the restoration partners were after for years and decades,” he said. “We're only a year into it, but so far it looks like it's working pretty well.”
As more restoration projects are completed, and more water is moved into the park’s two main sloughs, Williams said modeling shows the amount of prairie increasing, which could help the birds.
Clues From Saving Another Sparrow Species
He added that lessons learned from reviving the grasshopper sparrow, that expanded the list of threats beyond habitat to parasites and predators, could help the Cape Sable sparrow.
“What we learned is all of those factors were working together and driving down the Florida grasshopper sparrow population,” he said. “We're trying to see is there maybe a similar pattern with Cape Sable sparrows? Because it looks like we have places where there's good habitat, but it's not occupied.”
But Pimm worries that may be too late for restoring the western population and ensuring enough groups survive to save the species.
“It's a matter of having your eggs in more than one basket,” Pimm said. “And that population west of the slough was a very important basket.”
It also misses the point of protecting the habitat, he said — a practice critics often deride as single species management.
“It's never been about single species management. It's always been a matter of of restoring the Everglades vegetation to its natural state,” said Pimm. “That's why the Endangered Species Act is so prescient. It anticipates that it's always going to be this connection between an ecosystem and the species. It's not about the spotted owl. It's about the spotted owl and the old growth forest. It's not about the Cape Sable Sparrow. It's about the Cape Sable Sparrow and the Everglades ecosystem. If you get the water right, the sparrow will come back.”
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