HILO » Detecting three of Hawaii island’s rarest endangered forest birds at lower elevations of Hakalau Forest National Wildlife Refuge for the first time in 30 years is giving scientists some hope about recovery efforts.

Government scientists heard songs of the Hawaii creeper and akepa at the 4,200-foot elevation, within a mile of where they were last seen in 1977. They also heard and saw at least one endangered akiapolaau at an elevation 1,000 feet lower than previous sightings in the 1970s, the U.S. Fish and Wildlife Service and U.S. Geological Survey said Monday.

One-third of the nation’s endangered birds are in Hawaii. More bird species are vulnerable to extinction in the islands than anywhere else in the country.

Hawaii’s native birds are threatened by the destruction of their habitats by invasive plant species and feral animals such as pigs, goats and sheep. Diseases, especially those borne by mosquitoes, are another killer.

The 38,000-acre refuge on the slopes of Mauna Kea and Mauna Loa is home to 14 native bird species. The area includes more than 30,000 acres of native forest and grassland on Mauna Kea’s windward slope and over 5,000 acres of forest on Mauna Loa’s leeward slope.

"The observation of three endangered species possibly expanding their range in a wildlife refuge gives us hope that with some care, the road to extinction need not be a one-way street," said USGS Director Marcia McNutt.

The findings were part of a project on the potential impact of climate change on avian disease. All three species are believed to be highly susceptible to mosquito-transmitted diseases, limiting their distribution to cooler, higher elevations of the refuge, the federal agencies said.

"With global climate change, there is concern that transmission of these avian diseases could increase at higher elevations, affecting endangered and other native forest birds," said USGS biologist Jackie Gaudioso.

The three species were not detected the last time USGS biologists visited the remote location, said Steve Kendall, a biologist with the fish and wildlife service.

Due to habitat management and restoration, the Hakalau refuge is one of the few places on Hawaii island where populations of native forest birds are increasing or are at least stable.