This is the seasn when the historic cliff swallows (Petrochelidon pyrrhonota) wing their way back toward the most famous mission in California, San Juan Capistrano. The city is frantically prepping for a fiesta on March 19 (St. Joseph Day, don’t you know) complete with a parade, cultural activities and family fun.
However, don’t expect to see the skies darken with the flapping of exhausted swallows that make the annual 7,500 mile trek from Goya, Argentina to the ocean-side city. These birds trickle in, a few here and there, and it can take weeks for them all to arrive; plus, it’s been years since the feathered-wonders have called the mission’s old church home, choosing instead to create their mud nests in other parts of the city – places like concrete underpasses or bridges near creeks. Last year, they took roost at a local country club and community college.
“They left the mission in the 1990s,” says Dr. Charles Brown, biologist from Tulsa, Oklahoma who has been studying swallows and offering mission administrators advice on how to lure the birds back to the famed site. (Dr. Brown is slated to speak at the festival this weekend.)
There are many reasons why the birds reject a nesting site: not enough food, parasites infecting the nests, lack of elbow room with mankind, to name a few.
Still, it’s possible to entice the swallows back to the mission, says Dr. Brown. “You can put up artificial nests which the birds like to take over. Saves them a lot of time and energy in making,” he explains. Finding the right structure that doesn’t harm the integrity of the mission, however, is the challenge of the day.
“The reality of the cliff swallow is that while in other parts of the country, it’s thriving, here in Southern California, it’s been in decline since the 1960s,” says the good doctor. “The most logical interpretation is the urbanization and lack of habitat.”
But even if their numbers are smaller than usual, these birds can still ruffle feathers –and cause scientists to sit up and take note.
“They are one of the most social of all the land birds in North America,” he says. “The density and size of their nesting colonies is spectacular, absolutely spectacular. I have seen 6,000 nests on one site under a highway bridge. They really present a very fascinating aspect of animal behavior.”