[新闻背景]One of California's oldest missions wants to bring back a piece of its living history: cliff swallows. The tiny, migratory birds used flock by the hundreds to nest at Mission San Juan Capistrano, and were a major seasonal attraction for visitors.

Today, swallows are bypassing the historic site, but the mission is teaming up with scientists to lure the fabled birds back.
 
The cliff swallows' long-time roost at Mission San Juan Capistrano is celebrated every March with a parade, and 70 years ago, was immortalized through a song, "When the Swallows Come Back to Capistrano," which made Billboard’s Top Ten list.
 
The only problem is the swallows are not returning to Capistrano and haven’t for more than a decade.
 
In the 1990s, a project to restore the stone ruins of the mission's 200-year-old church dislodged several hundred nests, removing the entire colony.  
 
”It's sad but, you know we had to stabilize these ruins so they wouldn't fall over and kill man," says Mechelle Lawrence-Adams, the mission's executive director.
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The little brown birds with the white triangle on their faces still fly back to the city of San Juan Capistrano every spring after wintering in southern Argentina. You can see them in the sky, flashing their white bellies as they dive-bomb for insects mid-air.
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They just don’t go back to the mission, much to the chagrin of staff and volunteers, like Pat March, who's witnessed multiple attempts to lure the passing swallows.
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"What they would do is they would put out ladybugs to attract the swallows," she says.
 
Because the birds build their gourd-shaped nests out of mud pellets, staffers would make mud puddles for them on the mission grounds.
 
"You just dig a little ditch and put water in it and it's supposed to be the 'swallows wallows,'" March says.
 
The mission even stuck fake ceramic nests beneath the eaves of buildings. But the pre-fab homes didn't work. In fact, none of the tactics did.

So it was time to hire a professional.
 
Charles Brown, an ornithologist from the University of Tulsa, immediately saw why the mission was having difficultly getting the swallows back. Forty years of urbanization he says, has led to a 50 percent reduction in the swallow population of Southern California
 
"That is the one part of North America where the numbers have been going down,” Brown says.
 
He decided the best way to attract swallows back to the mission was to play to their sociability. 
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"The social species - they often look to see if others have settled there and have others been successful there," Brown says. "So we have to fool them into thinking that birds have been there recently."
 
Brown made a recording of cliff swallows in Nebraska and now those Midwestern chirps fill the mission’s courtyard.
 
The sounds come from a speaker system hidden behind bushes. A lot of people are counting on this approach, not just the mission employees who get the complaints about the missing swallows, but nearby businesses, too.
 
”More swallows mean more customers,” says Dominic Mayo, who works at The Capistrano Trading Post, across the street from the mission, which is packed with swallow paraphernalia. ”We have metal swallows hand-made in Haiti. We have little swallow silver charms, swallow wind chimes, swallow mugs. We have shot glasses that say ‘Just a Swallow.’”
 
But two months into the recording experiment, no swallows have come back to Capistrano.
 
Scientists have not given up; they plan to play the recording again next spring.

And Walter Piper of Chapman University - who’s serving as Charles Brown’s eyes and ears on the ground in California - made a promising discovery in early May. In a residential area a half kilometer from the mission, he spotted about 100 swallows nesting under the eaves of several houses and apartment buildings.  
 
”This is the first indication that cliff swallows were nesting nearby the mission,” Piper says. "Bit by bit, they build these huge nests. It’s cute to see them poke their heads out of there.”

According to Piper, these birds are all potential future tenants for the mission, perhaps even as soon as next year.