The American wood stork, a large wading bird nesting in coastal marshes in the Southeastern United States that scientists once thought might go extinct, is doing so well it's being taken of the endangered species list, officials say.

Thirty years after being classified as endangered amid fears it would be extinct by the year 2000, that bird has had its status upgraded a step to "threatened."

U.S. Secretary of the Interior Sally Jewell made the announcement while visiting a wildlife refuge on the Georgia coast that houses a large colony of wood storks.

"It's a day for good news about an iconic bird from the Southeast that is doing a great job of recovering," Jewell said.

However, it is not yet entirely out of danger, she warned. "There's still important work to do before we can propose to remove it from the list altogether."

Species classified as threatened effectively are given the identical legal protections as those listed as endangered.

The wood stork, American's only native stork, will remain listed as threatened until the U.S. Fish and Wildlife Service confirms a five-year average population of 10,000 nesting pairs.

In order to survive, the birds, standing almost 4 feet tall and possessing a 5-foot wingspan, need nesting sites in wetlands featuring trees with surrounding water to keep predators away from the storks' eggs.

Since populations dropped to an all-time low in the late 1970s, the storks have bounced back by extending their historic range, which covered Florida, South Carolina, Georgia and Alabama.

Restoration of wetlands in Mississippi and North Carolina allowed the birds to move into new habitats.

"One reason we're able to change their status is that the risk has been reduced because their numbers are more spread out," Billy Brooks, a Fish and Wildlife biologist who heads the recovery program for the wood stork, said. "They have improved their productivity by expanding their breeding range."

Some conservation groups say the delisting of the storks may be premature, as the birds are still struggling in the Florida Everglades, their main historic habitat, and some states the storks have expanded into do not have regulations protecting wetlands.

"We believe the Fish and Wildlife Service is really premature in any reclassification," said Brad Cornell, policy director for the Audubon Society. "There are too many gaps in the vital science on wood storks and a lack of long-term habitat protections to sustain its recovery."

Since the 1973 passage of the Endangered Species Act, conservation efforts have resulted in 27 species being taken off the list.