Choke Canyon, Texas-- Birders with binoculars and cameras are flocking to a remote state park in search of a small yellow-chested bird that apparently crossed the U.S. border for the first time from its high-mountain habitat to the south.

At 5 inches with beige and yellow markings, the pine flycatcher doesn't look like much, but its unprecedented migration from Mexico and Guatemala is exciting birders all over the country.

"It's not a thrilling bird visually. It's thrilling because it's a first U.S. record," said Wes Biggs, who flew to Choke Canyon State Park from Orlando, Fla., to catch a glimpse.

The bird, which appears to be alone, was first spotted last month and as recently as Friday. The sightings have been confirmed by photographs and recordings of its chirping. The bird, with a solitary nature, usually stays at high elevations but made its winter home in the low Texas scrubland about 200 miles north of its usual habitat.

For the bird to be added to the official checklists of American birders, it will first have to be accepted by the Texas Bird Records Committee, then the American Birding Association. But expert birders are convinced the bird drawing the masses is a pine flycatcher.

"It's a very unexpected discovery, but this is a bird we don't much know about," said Mark Lockwood, a state parks conservation biologist and secretary of the Texas Bird Records Committee.

The committee will review the photos, written descriptions and recordings, but "there is no dispute it's a pine flycatcher," Lockwood said.

Other types of flycatchers have been seen in South Texas, but the pine flycatcher apparently traveled hundreds of miles to get to the hackberry and mesquite trees near a large reservoir.

The bird seems "very much out of whack," said John Arvin, research coordinator at the Gulf Coast Bird Observatory. "It moved over a lot of hostile-looking territory to get there. Why that happened is anybody's guess."

In the last week, word of the pine flycatcher has been spreading through birder Web sites and message boards.

Steve Matherly, from Houston, showed up in camouflage Thursday night after driving 3 1/2 hours for a glimpse early Friday.

"The dollars (spent to get here) per gram of bird is kind of amazing," he chuckled, as he looked around at dozens of other birders scanning the brush and chatting in hushed tones.

He belongs to a group that puts out e-mail alerts when a rare bird is sighted and came down as soon as he could.

"You never know. I've had my occasions where I've gotten there a day late," said Matherly, who works at a gas pipeline company. "I don't know what I'll see today, but it'll be better than a cubicle."

Dotty Robbins, from Gainesville, Fla., traveled to South Texas to see the pine flycatcher this week even though she came up empty on two previous trips to the area for rare bird sightings.

"It's a little bit of a treasure hunt," she said.

Robbins concedes the pine flycatcher is "dinky," that its distinguishing features come down to a few feathers combined with a particular call.

"He's not spectacular," she said. But "it's unique."