After Hurricanes, Terns Find a New Home

Voices from the past help rebuild Florida tern colony

By Pat Leonard

When Roseate Terns migrated back to the Florida Keys last spring, they found their home wiped out by hurricanes. The small island called Pelican Shoal was one of only two places in Florida where the threatened species breeds. Three hundred pairs of terns had nested there before the hurricanes.

Sharyn Hood and Ricardo Zambrano prepare audio equipment for broadcasting tern vocalizations.

Florida Fish and Wildlife Conservation Commission

To help establish a new colony in a protected area, wildlife biologists turned to the Cornell Lab of Ornithology's Macaulay Library for sound recordings to be used in a technique called social attraction. Using a combination of tern-colony recordings and decoys, Florida biologists lured the birds to a safe new home in Dry Tortugas National Park.

The Dry Tortugas is a group of coral reef and sand islands 70 miles west of Key West, Florida. The terns once nested in open spaces on the islands, but through time, increasing vegetation had pushed them out.

In 2005, the hurricanes actually made areas in Dry Tortugas National Park favorable for terns again because the surf built up coral rubble and killed vegetation. Protected from human disturbance and free of mammalian predators, it seemed ideal for a new colony of terns.

To encourage terns to settle there once more, the biologists set up 38 plastic tern decoys to look like pairs interacting or individuals incubating eggs. To simulate the noise of a tern colony, they used a solar-powered portable CD player to broadcast sounds of Roseate Terns that had been recorded on Eastern Egg Rock Island in Maine and archived in the Lab's Macaulay Library.

The ruse worked. In July, biologists counted 42 Roseate Tern adults and 16 chicks among the decoys.

"We were ecstatic," says wildlife biologist Sharyn Hood of the Florida Fish and Wildlife Conservation Commission. Sometimes it can take years to establish a colony, and we had breeding birds there on the first try!" A few birds in the new colony even came from the destroyed Pelican Shoal community.

Biologists will continue the restoration this year by putting out the decoys and recordings again in April. In addition to attracting new birds, they are hoping the chicks born this year in the Dry Tortugas colony will eventually return from South American wintering grounds to start families of their own.

Several times a year, conservationists ask the Macaulay Library to supply sounds for bird restoration projects like this one. They often work with Stephen Kress, director of the National Audubon Society's Seabird Restoration Program, who pioneered the technique.

In 2003, Kress found that at least 61 agencies in 12 countries were using social attraction to help at least 39 seabird species.

"Not all of these are unqualified successes, but the range shows the potential and the great interest in this sort of restoration work," says Kress.

Most Roseate Terns are found in tropical oceans, with scattered populations elsewhere. Those along the northeast coast of the United States are listed as endangered; those off the Florida coast are considered threatened.

The Roseate Tern plunges into the ocean to catch small fish and performs spectacular aerial courtship maneuvers during the spring breeding season when its breast feathers take on the rosy hue that gives the species its name. By heeding the voices of breeding terns recorded in the past, the future may also take on a rosier hue for this fast-flying bird of the sea.

For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email: lle24@cornell.edu