AUDIE CORNISH, HOST:
This is the song of North America's most endangered bird.
(SOUNDBITE OF BIRD CHIRPING)
CORNISH: It's the Florida grasshopper sparrow. There are fewer than 80 left in the wild. In an effort to rescue the species, wildlife managers are, for the first time, releasing captive-raised sparrows in the wild. They're doing this despite concerns that the releases could kill off more sparrows. Amy Green of member station WMFE reports.
AMY GREEN, BYLINE: On the central Florida prairie, the early morning sun shines down on the Saw Palmetto and wiregrass and something else you wouldn't expect - an industrial-looking 60-by-20-foot aviary.
BECKY SCHNEIDER: It's made of hardwired cloth, which is basically mesh, but, you know, a kind of cage material.
GREEN: Becky Schneider of the Florida Fish and Wildlife Conservation Commission says inside are 10 Florida grasshopper sparrows; drab, brown-colored birds no larger than the palm of your hand. The sparrows are siblings and less than a year old.
SCHNEIDER: We transplanted a lot of native grass, and that's all and growing really, really well inside. There are some flowers blooming in there, too. Everything looks totally natural (laughter).
GREEN: Little do the sparrows know, they're about to take part in the next crucial step in their recovery. Schneider and a small group of researchers approach the aviary, stepping through ankle-high vegetation.
(SOUNDBITE OF FOOTSTEPS CRUNCHING)
GREEN: They open the aviary by removing the panels at either end.
(SOUNDBITE OF BANGING)
GREEN: Then the researchers hang back 300 feet to wait and watch as the birds join the world's last population of Florida grasshopper sparrows in the wild. Since May, state and federal wildlife agencies have released more than 70 captive-raised Florida grasshopper sparrows here, itself a vanishing landscape not far from Walt Disney World. The agencies are releasing the birds in small groups. They plan to set free another 30 through September. Then they'll stop until January or February, when the breeding season begins.
JUAN OTEYZA: What we're trying to do is basically giving them a head start.
GREEN: That's Juan Oteyza of the Florida Fish and Wildlife Conservation Commission.
OTEYZA: By raising them in captivity, we increase the chances that they survive until they become independent and then release them after that.
GREEN: He says so far, the released birds appear to have survived.
OTEYZA: We won't really know until next year based on how many birds return because they're so cryptic. They're usually moving on the ground. And unless they're breeding, and it's a male, we won't see them because the males are the ones that come up and perch and sing.
GREEN: The releases are proceeding despite opposition from the first researchers to breed the sparrows. Paul Reillo is the founding director of the Rare Species Conservatory Foundation. His main concern is disease. Researchers working with him have identified a pathogen that can be lethal to the sparrows. He worries about releasing potentially diseased birds into the world's last wild population.
PAUL REILLO: If this causes high rates of mortality, then the last thing we want to do is expose birds that don't have it to it because it could kill them.
GREEN: Reillo proposed a different plan, but the agencies rejected it and decided to sever ties with the organization. The wildlife managers ordered his researchers to stop breeding the sparrows and are taking them away from him.
Back on the central Florida prairie, Oteyza points an antenna toward the aviary.
OTEYZA: I'm just checking with a receiver to confirm the location of the birds that we have transmitters on.
GREEN: The researchers wait. Some train binoculars and scopes on the aviary. Schneider says each bird is identified with colored bands on its legs.
SCHNEIDER: Blue Red Red Aluminum is, right now, the oldest-known Florida grasshopper sparrow in the wild. He's at least 7 years old this year, and he's still doing his thing.
GREEN: Suddenly, two sparrows fly out. Then after about an hour, the researchers return to the structure to flush out the rest. They use walkie-talkies as they step behind the sparrows, directing them toward the openings.
SCHNEIDER: One bird on side 1A flew out on its own too quickly to see any color bands.
(SOUNDBITE OF WALKIE-TALKIE BEEPING)
SCHNEIDER: Last two just left here.
UNIDENTIFIED PERSON: Aviary all clear. Time to resecure.
(SOUNDBITE OF WALKIE-TALKIE BEEPING)
GREEN: The sparrows are free. Schneider says she's hopeful.
SCHNEIDER: You start to watch them closely. You see how intricate their plumage is. You see how beautiful their song is. You see how clever their interactions are with each other and with their neighbors.
GREEN: The Florida grasshopper sparrow would be the first confirmed bird extinction in the continental United States since the dusky seaside sparrow vanished from Florida in 1987. If the releases are successful, the population could more than double in the wild.
For NPR News, I'm Amy Green on the central Florida prairie.
(SOUNDBITE OF THE TRAGICALLY HIP'S "THE DARKEST ONE") Transcript provided by NPR, Copyright NPR.