The Cliff Swallows (Petrochelidon pyrrhonota), famous avian ambassadors of Mission San Juan Capistrano, still return, though not in the overwhelming numbers of the past. These small birds complete an incredible 6,000-mile migration each spring from their wintering grounds in Goya, Argentina. They seek the Southern California climate to raise their young before departing in the fall. The historic Mission remains the spiritual heart of this natural cycle, but the birds’ nesting habits have shifted due to changes in the surrounding environment.
The Legend and the Tradition
The annual return of the swallows has been a celebrated tradition in San Juan Capistrano for over a century. The tradition was popularized by Father St. John O’Sullivan, the Mission’s pastor from 1910 to 1933, who offered the birds sanctuary after witnessing a local shopkeeper destroying their mud nests. This act cemented the Mission as the swallows’ safe haven.
The expected arrival date for the first scout birds is consistently marked as St. Joseph’s Day, March 19th, coinciding with a major Catholic feast day and forming the basis for the annual “Return of the Swallows” celebration. Their departure for South America is traditionally noted around St. John’s Day, October 23rd, completing the six-month nesting cycle. The phenomenon gained international fame after the 1940 release of Leon René’s song, “When the Swallows Come Back to Capistrano.”
The Current Status of the Swallows’ Return
While the migration continues, the massive nesting colonies that once clung to the Mission’s eaves are largely absent from the immediate grounds today. Cliff Swallows are colonial nesters that build their gourd-shaped mud homes in large clusters. For decades, the Mission’s historic structures provided the ideal protected vertical surfaces for thousands of nests.
The vast majority of the birds now build their nests elsewhere in the greater Capistrano Valley, relocating to nearby communities, bridges, and culverts along San Juan Creek. These alternative structures offer more stable and undisturbed nesting sites than the historic Mission walls. The swallows still arrive in the area, but the spectacle is now diffused across a wider geographic range outside the central Mission courtyard.
Why the Swallows Have Changed Their Habits
The primary cause for the shift in nesting location is the dramatic urbanization of the region over the last century, which altered the local ecology. Increased human development led to habitat loss and a significant reduction in the insect population, the swallows’ primary food source. Swallows require large quantities of flying insects to feed their young, and the development of wetlands and riverbeds has diminished this supply.
Modern construction methods also played a significant role in making the Mission less appealing for nest building. Swallows rely on rough surfaces, such as the original adobe walls, to provide a secure anchor for their heavy mud nests. The restoration of the Mission in the 1990s used smooth stucco and concrete, making it difficult for the birds to adhere their nests securely, causing them to fail. Furthermore, the loss of natural sources of wet mud, which the birds use as building material, compounded the challenges of establishing new colonies on the property.
Encouraging Future Returns
Mission San Juan Capistrano and local organizations are actively engaged in conservation strategies to encourage the Cliff Swallows to return to their historic home. A key effort involves installing artificial nests, which are pre-formed plaster or synthetic structures designed to mimic natural mud nests. These structures provide a ready-made, secure base for the birds to occupy upon arrival.
The Mission also employs acoustic attraction by playing recorded swallow vocalizations near the artificial nests to lure scout birds to the site. Swallows are highly social and are naturally drawn to the sounds of an established colony, signaling a safe and successful nesting location. Staff also maintain sources of wet mud during the nesting season, ensuring the birds have access to the necessary building material to repair artificial nests or construct their own.