In the Swallows of San Juan Capistrano tradition, the returning bird is the cliff swallow.
Cliff swallows are small, social New World swallows that breed across much of North America and migrate to South America for winter. Their return to San Juan Capistrano, California, became a celebrated local tradition associated with the Mission San Juan Capistrano.
The birds traditionally arrived around March 19, the feast day of Saint Joseph, although modern arrival dates vary and large historic gatherings are less predictable. Cliff swallows build communal mud nests, often placing many gourd-shaped nests under bridges, eaves, and rocky overhangs.
A common mix-up is with the barn swallow, another migratory swallow with a deeply forked tail. Cliff swallows are identified by their squared or slightly notched tail, pale forehead patch, and reddish throat. The tradition is culturally famous, but not every bird returning to the area is necessarily a cliff swallow from the same colony.