That question is perplexing wildlife officials, who report that thousands of nesting birds on Seahorse Key, off Florida’s Gulf Coast, have abandoned their nests. Most of them have simply vanished, seemingly into thin air.
The 150-acre crescent-shaped key, one of the few uninhabited islands in Florida and part of the Cedar Keys National Wildlife Refuge, is normally the largest bird colony on Florida’s Gulf Coast, home to thousands of great egrets, double-crested cormorants, brown pelicans, white ibises, and little blue herons.
But in May nearly all the birds disappeared, practically overnight, leaving empty nests in trees and shrubs and broken eggs on the ground.
“I’ve never seen an abandonment quite like it,” said Peter Frederick, a wildlife biologist at the University of Florida who has studied the state’s birds for nearly three decades.
“We’ve seen a lot of abandonments in the Everglades and in some seabird colonies, but there’s never been such synchronicity involving so many species at once,” Frederick said. “Nothing seems to fit together.”
Some of the birds have been accounted for. A fraction of the colony relocated to Snake Key, a few miles away, and some ospreys remain on nesting poles put up by federal wildlife officials on Seahorse Key.
“But everything else in the trees and shrubs is gone,” Frederick said. “There are zero left.”
So, Why Should You Care? The sudden abandonment of an entire colony this large—recent nesting populations have ranged from 2,000 to 15,000 birds each year—is alarming, biologists say, because many birds return each year to the same nesting sites. If the birds do not return next year, it could affect their numbers—and mean the loss of a critical island refuge.
“I’m concerned we lost a year of nesting,” said Janell Brush, an avian researcher at the Florida Fish and Wildlife Conservation Commission. “The birds that did move over [to Snake Key] reinstated nesting a lot later this season, and that may have decreased their chances of nesting success.”
So far the reason for the abandonment remains elusive.
“The jury’s still out,” said Julie Wraithmell, director of wildlife conservation for Audubon Florida, which is working with state and federal officials to solve the mystery. Mass abandonment, she said, “is always a result of some kind of tragedy. With that number of birds having invested in courting and having built nests and laid eggs, some kind of change happened.”
“Birds do not want to abandon their nests,” she added. “Making an egg is hard work.”
Sometimes abandonment results from the arrival of a predator. “A single raccoon on an island can cause nesting to fail, though it’s somewhat unusual for all the birds to leave at once in the presence of a predator,” Wraithmell said.
Researchers found a few raccoons on the island, but they doubt that was the cause.
Other possible explanations include parasitic infestation of nests, boaters coming too close to shore, or people hunting or camping on the island during nesting season, when unauthorized access is prohibited.
So far, none of those theories have panned out.
Then there is the possibility of disturbances from aircraft.
“A helicopter hovering over the island with searchlights at night would flip them out, but there’s no evidence that happened,” Frederick said. He noted that residents of Cedar Key, about five miles away, “are reporting a lot more low-altitude military flights, including jets and helicopters. But there’s lots of places where birds nest successfully near military flights.”
Frederick said local wildlife officials are “in conversations” with the U.S. military about possible flights over the island last May.
For now, scientists will have to wait and watch.
“I’m hoping the colony will revitalize next season,” Wraithmell said. “It’s possible the birds would never come back, but it’s extremely unlikely they wouldn’t return to an area where they had so much success in the past.”
“I’m hopeful,” she said. “But I’m also a conservationist. I live in hope.”