For years on end, the end of April, first part of March signaled the return of little blue herons, roseate spoonbills, snowy egrets, pelicans and other birds, returning to the mangrove-covered dune near Crystal River, Florida.
The crescent-shaped key is one of the few uninhabited islands in Florida, and is part of the Cedar Keys National Wildlife Refuge. The island is normally the largest bird colony on Florida’s Gulf Coast, with thousands of birds, all chattering, squawking, and creating a din as they construct their nests, mate and lay their eggs every year.
For some unknown reason, in May, the birds left the island, leaving behind empty nests in the trees and shrubs, with broken eggs scattered on the ground.
Vic Doig, a biologist with the U.S. Fish and Wildlife Service, told the Associated Press that some of the birds had moved to Snake Key, but they are just a small percentage of the birds that were on Seahorse Key.
“It’s a dead zone now,” said Doig. “This is where the largest bird colony on the Gulf Coast of Florida used to be.”
“It’s not uncommon for birds to abandon nests,” said Peter Frederick, a University of Florida wildlife biologist who has studied Florida’s birds for nearly 30 years. “But, in this case, what’s puzzling is that all of the species did it all at once.”
Scientists have taken action. They have tested any bird carcasses found on the island for diseases, but found none. They found no new predators. They even checked out the occasional night flights over the area by surveillance planes and helicopters used to combat drug smugglers, something that has gone on for a number of years, but this was ruled out as a problem.
There is real cause for concern say biologists
The nesting colonies over the years have ranged from 2,000 up to 15,000 nesting pairs, and the abandonment of an entire colony is alarming. Scientists are worried it may have a “ripple effect.” Will the island refuge be lost? And how will the loss of a nesting colony affect other wildlife on the island. A whole ecosystem is at risk.
“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.”
“Any rookery that’s persisted for decades as one of the largest colonies is incredibly important,” Brush said. “It’s quite a large colony. There had to be some intense event that would drive all these birds away.”
This is not the first report of an abandonment of a large rookery this year. On June 27, Digital Journal reported on a rookery in Mexico’s Sea of Cortez, called Isla Rasa, a 142 acre island that comes to life every year in June, when up to 500,000 Heermann’s Gulls and Elegant Terns go there to breed.
This island was also abandoned, and scientists are blaming climate change. Could this be the reason for the Seahorse Key abandonment? With changing ocean temperatures, fish, a sea bird’s primary meal will move to cooler locations. Or could the event possibly have something to do with the BP oil spill in the Gulf of Mexico in 2010. The long term impact on marine life and birds is still being studied.
