WASHINGTON - To control a bizarre gathering of eagles, pigs and foxes on the California channel islands, federal wildlife officials may have to kill a protected species in order to save an endangered one.

Attracted by a plentiful supply of feral pigs rooting around the islands, a community of Golden Eagles settled in about 10 years go to prey on piglets. But they also found that the island foxes, an endangered group of subspecies, also made good meals.

The population of pigs, which reproduce year around, were little affected by the winged predators, but the foxes were decimated.

In less than a decade, wild foxes disappeared from San Miguel and Santa Rosa islands and on Santa Cruz, the population of 1,500 was reduced to just 65.

Fish and Wildlife Service experts are now capturing and removing the pigs and the eagles, but a new study suggests that if the process is not handled properly wild foxes on the islands could disappear forever.

The study, appearing in the journal Science, said that the few remaining eagles will be enough to drive the wild foxes into extinction if all of the pigs are moved first.

"You still have eagles on the islands," said Gary W. Roemer, a New Mexico State University biologist and first author of the study. "If you remove the pigs, you've only got 65 foxes running around that will make those eagles focus more intently on the foxes and drive them to extinction. The most prudent strategy is to get rid of the eagles first and then get rid of the pigs."

Federal officials have been trying. They have captured nearly all the eagles and moved them to locations on the mainland. But Roemer said there are still nesting pairs of eagles who are too smart or too wary to be captured alive. According to a population project by Roemer and his coauthors, there may be only one grisly option left: killing the protected Golden eagles to save the endangered foxes.

"Because eagle eradication is doubtful by translocation alone, other means should be pursued, including lethal removal," the researchers say in Science.

Golden eagles are protected species, but they are not threatened with extinction. The unique island fox subspecies, however, are hanging by a thread, said Roemer.

"The federal officials may have to take a little public heat (for killing the eagles) to preserve an endangered species," he said.

Killing the eagles "is an alternative that we will look into if we have to," said Bridget Fahey, a researcher for the U.S. Fish and Wildlife Service in California.

"But before we do anything drastic, we are going to know that we tried everything else," she said. It would take permits and public hearings before the eagle killing could start so Fahey said, "it is not something that will happen soon."

Fahey said that removing the pigs is the key to "breaking the chain of what is attracting Golden eagles to the islands."

Once the pigs are gone, she said, there won't be enough food for breeding pairs of eagles to stay at the channel islands. That would restore the foxes as the top predator on the islands.

Right now, Fahey said, all of the wild foxes on the channel islands are at risk because most of them don't know enough to be afraid of the eagles.

"They haven't had this type of predation in their history so they don't know that that looming shadow overhead means they are about to be preyed on," she said.

The federal officials have pen raised colonies of the foxes that can be released once the eagles are gone. There is a different subspecies of fox on each of the islands and some are now extinct. But for the surviving subspecies, Fahey said the population can be restored from the foxes raised in captivity.

Once those foxes are released, she said, officials intend to continue protecting them from the eagles.

"We're going to keep pressure on the eagles so they don't regard the islands as a friendly place," she said.