BOGOTA, Colombia (AP) _ One of four American bird watchers kidnapped last week by leftist rebels in Colombia escaped his captors Thursday, the army said.

Thomas Fiore of New York City was in the custody of the Air Force, Gen. Freddy Padilla, the regional army commander, told Radionet radio.

``We're very happy,'' Padilla said. ``He's in an Air Force helicopter.''

Details of Fiore's condition or how he eluded his captors were not immediately known. The U.S. Embassy in Bogota had no comment.

Padilla did not say where Fiore would be taken.

Fiore and three other Americans were seized after stumbling upon a roadblock set up south of the capital by the Revolutionary Armed Forces of Colombia, or FARC, the nation's largest and most powerful rebel group. An Italian businessman and several Colombians also were abducted in the March 23 incident.

Comandante Romana, the local leader of the rebel group, had said the foreigners would probably have to pay a ransom. He also said negotiations could take between six months and a year.

He also warned the captives would be killed if rebels determined they were U.S. government agents.

The Americans _ Fiore, Peter Shen of New York City, Louise Augustine, a 63-year-old retired teacher from Chillicothe, Ill., and Todd Marks _ were on a bird-watching expedition on a road notorious for rebel activity. Marks's hometown was not available.

Colombia has the greatest diversity of birds in the world, with some species found nowhere else on the planet. But it also leads the world in kidnapping, and foreigners are a prized target because they often fetch the highest ransoms.

Several rebel groups have been fighting the state since the 1960s.