July 9, 2015 / 4:55 PM / 4 years ago

U.S. Wildlife Service baffled by exodus of birds from Florida isle

ORLANDO, Fla. (Reuters) - Tens of thousands of nesting birds vanished this spring from a Florida island refuge where they have come to breed for decades, leaving behind their unhatched eggs and mystifying wildlife officers trying to figure out why they disappeared.

The birds have been coming to Seahorse Key on Florida’s Gulf Coast for more than a century, and in recent times averaging 10,000 to 20,000 breeding pairs a year, said Vic Doig, biologist for the U.S. Fish and Wildlife Service.

The birds returned in April, said Doig, who spotted them while conducting a survey. Days later, a caretaker noticed that they were all gone.

“Nobody really saw anything. One day they were there. The next day, they weren’t,” he said.

Seahorse Key, about 60 miles southwest of Gainesville, is part of the Cedar Keys National Wildlife Refuge, established in 1929 to protect nesting birds that numbered about 200,000 at the time. The birds were under threat from hunters who sold their plumage to makers of fashionable hats for women.

White ibis, tri-colored herons, snowy egrets and roseate spoonbills are among the rare wading birds with long and attractive feathers which return to Seahorse Key every year from April through June.

The refuge is a nature lover’s paradise where tour boat operators ferry sightseers around the rookery.

“When the birds are nesting there, the island is a chaotic, loud, busy place. All of a sudden, it’s like a ghost town,” Doig said.

There was no sign of traumatic injuries or disease in the few bird carcasses left behind after the exodus, he said.

A change in the local food supply seems unlikely, and a predator, such as the great horned owl, would be hard pressed to scare off so many birds spread out over one square mile.

Although a storm with wind gusts and lightning moved in around the time the birds left, that is a common occurrence in spring.

The island might have been buzzed by an aircraft or drone, Doig said, but there is no eyewitness evidence of an aircraft scaring off the birds.

The agency is also considering whether the birds could have been spooked by a helicopter that recently began ferrying beachgoers to an island about five miles away, he said.

With the investigation hitting a dead end, wildlife officers will have to wait to see if the birds return next year, Doig said.

Editing by Frank McGurty and Mohammad Zargham

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