In the two decades since a rare flightless bird was discovered in Okinawa Prefecture, it has been pushed to the northern edge of the main island by non-indigenous predators.

Mongooses, stray cats, jungle crows and human development projects have slashed the numbers of the yanbaru kuina, or Okinawa rail, and drastically squeezed the size of its habitat.

Researchers say that unless measures are taken now, the birds could soon become extinct.

The yanbaru kuina was discovered in 1981 on the northern part of the main Okinawa island.

In 1985, the former Environment Agency estimated the yanbaru kuina population at about 1,800. Researchers at the Yamashina Institute for Ornithology said the population had plunged to around 1,220 in 2000.

Now, the number has tumbled even further.

In September, institute researchers returned to the Yanbaru forest. Led by Kiyoaki Ozaki, chief of the institute's Bird Migration Research Center, the team combed the area to determine the numbers and habitats of the midsized birds. The team found the birds in 85 plots of 1 square kilometer, down 23 percent from 116 they found in 2000.

The yanbaru kuina population had fallen at an even faster clip. Only 217 were spotted, down 31 percent from the 315 in 2000.

Ozaki estimates the total population ``probably does not exceed 1,000.''

The birds' retreating habitat is especially worrying, researchers say. In 1985, birds were found living in most parts of Ogimi and Higashi villages. Now, researchers say birds in these two villages have probably completely disappeared.

Overall, the birds' habitat had shrunk 40 percent by 2003 from 1985. Only an area in the northernmost village of Kunigamison remains habitable.

Mongooses, which were introduced to the island to control the poisonous snake population, and stray cats are believed to be the main culprits in the demise of the bird.

Despite efforts to decrease the number of predators, they are spreading. The Environment Ministry and the Okinawa prefectural government caught about 1,600 mongooses and about 230 stray cats from October 2000 to March 2004.

Experts say the yanbaru kuina are also falling prey to jungle crows. Motorists pose another danger.

But help could be on its way.

In late September, experts gathered in Tokyo to talk about the future of the rare rail.

Paul Wenninger, a researcher from the Aquatic and Wildlife Resources division of the U.S. Guam Department of Agriculture, noted the similarities between the Okinawan bird and the Guam rail, which is also endangered.

The Guam rail has been under attack since the 1940s when the brown tree snake was introduced to the U.S. territory.

With the species teetering on the brink of extinction, officials in the mid-1980s caught 21 of the birds and placed them in captivity in Guam and on the U.S. mainland. Artificial breeding went well, but plans to reintroduce the birds to the wild on Guam's neighboring Rota Island-an area free of the snakes-have yet to come to fruition. Despite an annual project cost of $16 million (about 1.8 billion yen), and the release of 684 birds, cats are now posing a danger, Wenninger says.

He says for the Okinawa rail to survive, predators must be eliminated. He also advocates artificial breeding to beef up the population. Human activity, such as road construction in or near the birds' habitat, must be kept to a minimum, he says.

Masako Izawa, an associate professor of the University of the Ryukyus specializing in wild cats, agreed that non-indigenous species should be exterminated.

``Measures for conserving the birds' environment should be taken along with artificial breeding projects, or they will have no place to return,'' she said at the September symposium.

Efforts are already under way. Village authorities in Ogimi, Higashi and Kunigami passed an ordinance in September that requires the registration of domesticated cats. They are also required to have identification microchips and must be spayed or neutered.

The Environment Ministry has begun developing artificial breeding techniques for the birds.

``We are not too late if we act now,'' said Satoshi Yamagishi, director of Yamashina Institute for Ornithology. ``We want to take every measure to save the yanbaru kuina's environment and breed them.''(IHT/Asahi: November 27,2004)