The Florida Keys are quickly going to the birds : Presence of rare species has led to islands’ reputation as the latest hot spot for Audubon members.

For weeks now, strangers with binoculars have been showing up at the corner of Whalton and Johnson streets to peer into the bushes.

“At first,” said retired Navy Capt. Aldis J. Browne Jr., who lives on the corner, “I didn’t know what was going on. Except that it probably had to do with birds.”

Indeed.

Drawing a crowd to Browne’s quiet neighborhood were reports that, for the fourth consecutive spring, a lone Bahamas mockingbird had shown up here, singing lustily in apparent advertisement for a mate. Sadly for this bachelor, he may be the only Bahamas mockingbird on the continent.

Browne, 82, is not much interested in bird-watching--he recently earned a black belt in karate and is busy with that. But the other day, he said, he did meet “18 very nice people from San Francisco, all looking at this bird in my orchid tree.”

The reappearance of this accidental tourist from the Caribbean is a brightly colored bit of good news for the local tourist industry--as well as a bonus for the thousands of serious bird-watchers who come here each year.

Not only do birders flock to the Florida Keys for the spring migration of warblers heading north to nesting sites, but they also come to see rare and unusual species--the white-crowned pigeon and mangrove cuckoo, for example--found here year-round.

“I’ve picked up 26 new species already,” said Julie Myers, a restaurant designer from Chicago who with a friend had planned her vacation around birding in the Keys. “And we haven’t even been to the Dry Tortugas yet.”

This resort town, the southernmost spot in the continental United States and the end of the road along the Eastern Seaboard, has long been a mecca for tourists.

In the summer, Key West holds its annual Hemingway Days festival, and among the throng of literary revelers are dozens of people who look just like Papa. In October, Fantasy Fest turns the streets into a carnival.

But this is the time of year, between the winter and summer seasons, when Key West is host to a more sober breed of tourists, more interested in listening to the song of the black-whiskered vireo at dawn than in singing Jimmy Buffett tunes over the sunset drink specials at Mallory Square.

Bird-watchers make up only a small part of the estimated 4 million people who visit the Florida Keys each year. Still, thanks to the Bahamas mockingbird--whose presence has been noted on national birding hot lines--and other rare species, the Keys’ reputation as a birding hot spot is growing, said Wayne Hoffman, a research scientist with the National Audubon Society’s field office in the Upper Keys.

“We get a dozen people a day in here picking up maps and checklists,” he said. “We’ve also got in Key West right now a short-eared owl that’s come up here from Cuba. That’s rare, and it’s been getting some attention too.”

One of the requisite stops for visiting birders is Audubon House, a restored early 19th-Century home and museum operated by the Florida Keys Audubon Society to commemorate the famed painter’s visit to Key West in 1832. John James Audubon did not live here; he visited just long enough to add 18 species to his own life list.

Most serious birders also make a day trip to the Dry Tortugas. Lying 70 miles west of Key West in the Gulf of Mexico, the Dry Tortugas are seven coral reefs that serve as a major rest stop for migratory birds--as well as the nesting ground of the sooty and noddy tern.

The islands, site of the 19th-Century Ft. Jefferson and overseen by the National Park Service, are accessible only by seaplane or boat and have no overnight accommodations.

But at this time of year, they are alive with birds. “Seabirds like the brown booby, the masked booby, dozens of warblers, hummingbirds, thrushes, tanagers, buntings, orioles, swallows--anything might show up,” Hoffman said. “I was there one day at the peak of the season, about May 1, and saw 95 species. I was pretty excited.”

Most birders would call spotting 95 species in a day a once-in-a-lifetime bonanza. But Fran Ford, a Key West merchant and past president of the local Audubon Society, said she can almost guarantee a higher one-day count this May 1 during the annual fund-raising Birdathon.

“We start in the Dry Tortugas at dawn, spend an hour there, then fly back to Key West for breakfast in the park, and then work our way up the Keys,” she said. “By nightfall, when we hear the screech owl in Key Largo, we could have 130 different species.

“Now where else can you do that?”