In decades past, late February would be when the first cliff swallows began returning to the old mission in San Juan Capistrano.
However, for the last several years, the birds haven't shown up.
The mission has tried to lure them there using food and bird calls. Nothing has worked.
Now, researchers hope a new approach might bring back these once-famous residents: fake swallow nests.
Charles Brown, a swallow expert from the University of Tulsa, says these nests might provide a visual cue to passing birds.
"These birds will use plaster nests and the hope is to create a sort of fake wall where we can attach a number of these plaster nests," he said.
These plaster nests would imitate the mud homes swallows like to build on cliffs, under bridges and occasionally on the sides of buildings.
As far back as the beginning of the 1900s, these birds would fly up from Argentina and supposedly arrive at San Juan Capistrano in droves on March 19th, St Joseph's Day.
This yearly event became a tourist attraction. The town held an annual parade to celebrate the migration and the birds even became the focus of a popular 1940s ballad, "When the Swallows Come Back to Capistrano."
The plight of the missing swallows seems to date back to retrofits done to the structure in the 1990s.
Workers shoring up the old walls of the more than 200 year old Great Stone Church knocked down many of the long-standing mud nests. Swallows often return to the same nest year after year.
With their homes gone, the birds decided to live elsewhere, says Brown.
However, he thinks this isn't the whole story.
In general, the number of cliff swallows in Southern California is on the decline. Brown thinks urbanization is to blame.
Specifically, Brown says the trees planted in parks and around homes might be messing with the birds' hunting patterns.
"They do not like areas with lots of trees because it disrupts the air currents that concentrate the insects on which they feed," he said.
Mission San Juan Capistrano brought on Brown in 2010 to help crack the case of the missing swallows.
An early attempt to encourage them back involved releasing lady bugs for the birds to feed on. That plan was a bust.
Brown suggested playing pre-recorded swallow mating calls at various times of the day.
The calls were played every year starting in 2010 but they've had little effect.
In fact, one pair of swallows did nest at the mission two years back, but they chose an area far away from the piped in birdcalls.
Now, the mission hopes the new fake nests will work where other efforts failed.
University of Tulsa's Charles Brown says he will design and construct these new swallow homes in order to have them ready for next year's migration.
He says getting the birds back to the mission isn't just about boosting tourism to the area.
While there are still swallows scattered throughout Capistrano, Brown says elsewhere in town the nests may be knocked down by home owners who think they are eyesores.
At the mission, the swallows would be welcomed and protected. That, he hopes, could help the population at large start to bounce back.
"If we could get them diverted back on to the mission I think they'll have a longer term future," he said.