These provisions required the military to consult with the U.S. Fish and Wildlife Service to determine if any of its actions would harm such species as the birds of Guam.

Caught in the tug-of-war are the tropical forests on Andersen Air Force Base. The Fish and Wildlife Service says they are essential for the conservation of the endangered Micronesian kingfisher and the Mariana crow.

The agency initially proposed designating 24,803 acres of Guam's forests as critical habitat for the birds. After Congress gave the military the exemption from critical habitat, the agency slashed its proposal to 376 acres.

It is not clear how much of the forest would be cut down for the base expansion, but the majority of the island's suitable habitat is on base land.

The Air Force says it wants to develop the land to ensure its military readiness in the region. Guam, an unincorporated territory of the U.S., is a major air and naval staging ground in the Pacific.

No blueprint of the military's plans for Andersen is publicly available. But Col. Steve Wolborsky, the vice commander of the 36th Air Expeditionary Wing, said the Air Force expected to spend $1 billion to $2 billion to develop Andersen over the next several years, according to American Forces Press Services.

Gordon Rodda, a U.S. Geological Survey biologist who was on Guam last month, said he was told to expect that most of the forest would be cut down for development. He said the message was: "Don't think buildings, think city."

Rodda and several other biologists took the unusual step of raising alarms about the effect that the military's exemption from environmental provisions would have on Guam's birds.

If Andersen Air Force Base grows as planned, the result will be "the fastest extinction I have witnessed in my life," said Susan Haig, a U.S. Geological Survey biologist who has worked on Guam bird recovery since 1987.

Some policy officials at Fish and Wildlife said they hoped the military would continue to protect endangered species.

"Expansion of Andersen is not necessarily mutually exclusive with implementing recovery for these species," said Gina Shultz, acting field supervisor of Fish and Wildlife's Pacific island office "But I'm working in a vacuum here, I have no idea where they're expanding [or] how much."

When the administration advocated exempting the military from the critical habitat provisions, it argued that the military could be trusted to protect the environment. Shultz said history suggested that the base would be a good steward of the island's natural resources.

For example, over the last few years the base voluntarily agreed to allow the introduction of 17 endangered Mariana crows and 62 Guam rails, a flightless bird that is also on the endangered species list. The rails died, but several of the crows survived and now are protected by provisions of the Endangered Species Act from which the military is not exempt, wildlife officials said.

Others have argued that because environmental protection is not the military's primary mission, the Pentagon cannot be relied on to safeguard natural resources.

The Guam birds' story "is symbolic of why environmentalists fight over regulations and sometimes are suspicious of vague sets of promises and guidelines," said John Kostyak, senior counsel for the National Wildlife Federation, an environmental group.

The wildlife agency said the future of the species would hinge on the military's commitment to them as detailed in its Integrated Natural Resources Management Plan. The document included a project, 14 years in the works, to build a snake barrier around a 60-acre area on the base for the birds' benefit.

Brown tree snakes have no natural predators on the island and their numbers have grown to thousands per square mile. Barriers are one of the few ways to manage the population and are considered essential to creating safe habitat for other species.

But last month, government biologists were told that the military was canceling the snake barrier, according to Earl Campbell, the Fish and Wildlife Services Pacific coordinator for invasive species. Some government biologists fear that canceling the snake barrier project is the first tangible sign that the military's plans will imperil efforts to protect the endangered species.

"From my perspective it looks like they reneged on that plan, which leaves no protection for any of the wildlife on Andersen," Haig said. Technical Sgt. Jeffrey Capenos, the base's spokesman, said the fears were premature. He said it was too early to say how much forest would be cut down or how rare species would be treated as the base expanded.

"We're in the planning stages of this; nothing is set in stone," Capenos said. He emphasized, however, that the expansion was being planned to "ensure that Pacific Air Forces can achieve and maintain asymmetric advantage over any potential adversary."

The Fish and Wildlife Service believes the base is critical to the future of the endangered species.

It said in its official critical habitat designation for the species that without active efforts to reduce predators and reintroduce the species on the base, "the Mariana crow and Mariana fruit bat likely would be extirpated from Guam, and no suitable area for reintroduction of the Guam Micronesian kingfisher would exist." Much of the rest of the 30-mile-long island is developed or unsuitable for habitat. Each species faces a dire future, perhaps none more so than the Micronesian kingfisher, a small bird with greenish-blue wings and back, rust-colored head and a loud, raspy call.

The kingfisher is extinct in the wild and survives only in captivity. Kingfishers were last seen — and heard — on Guam in the mid-1980s, when their numbers had dwindled to about 50. Since then, their survival has depended on zoos in the continental U.S., where the remaining birds were transported.

Currently, between 60 and 70 birds live in captivity. Four kingfishers were recently transported to an aviary on Guam. Biologists said they hoped the birds would fare — and multiply — better in their home climate and with the benefit of their traditional diet. The birds' reintroduction into the wild remains several years away.

Biologists said they feared that because Guam was off the radar screen of most environmental groups, the military would have a far easier time ignoring the needs of endangered species there than it would on most bases in the U.S.. But they emphasized that the extinction of these species would be no less tragic because it occurred in the middle of the Pacific.

"Each one of these [species] fills a special niche that can't be replaced," biologist Haig said. Losing any of them, she said, would be a "heartbreak."

But the government biologists said that their hands largely were tied because of the government's new policy on the military and endangered species.