Cliff Swallows

In Birds, Slough Life, Staff Blog by Dave Feliz

Map Courtesy of Cornell Lab of Ornithology

“When the swallows come back to Capistrano
That’s the day you promised to come back to me
When you whispered, farewell in Capistrano
Was the day the swallows flew out to the sea.”


This lovely song written by Leon Rene and first performed by the Ink Spots in 1940 illustrates how humans are affected by the rhythmic migration of wildlife. The reliability of Cliff Swallows coming back to the Mission San Juan Capistrano on the same day each year became a symbol of loyalty. You could always count on the swallows.

The reality is that the annual arrival of Cliff Swallows was a tool used by Father St. John O’Sullivan to generate interest in restoring the ruins of the Mission. Fast forward to the latter twentieth century and the creeks used by the Swallows to gather mud for their nests have been lined in concrete with little surface water available to even make mud. But what of that reliability issue?

Actually, many of our migratory birds are very much “on time” when they arrive at their breeding grounds. It is quite remarkable that our Cliff Swallows, who spend their winters in South America can find the buildings of the Elkhorn Slough Reserve on the same week every spring.

Cliff Swallows are one of seven species of swallows found in North America. The Reserve regularly hosts Cliff Swallows as well as Barn Swallows and Tree Swallows. Tree Swallows are interesting in that they are the only swallow species to stay north during the winter months. They are able to do this because their diet has expanded to include berries, in addition to the standard fare of flying insects.

Tree Swallow

Tree Swallows are infrequent residents of the 158 nest boxes maintained on the Reserve. These boxes are located in the Elkhorn oak woodlands and monitored by our fine volunteers.

The most visible of our swallow species is the Cliff Swallow. Although they are most frequently seen on buildings and bridges, they originally nested on cliff faces,hence the name. It is interesting to see these birds in their natural nesting habitat. This colony was in Los Gatos Canyon, northwest of Coalinga, California.



Our swallows take up residence on the buildings of the Elkhorn Slough Reserve every spring. Although they sure make a mess, they are most welcome and extremely popular with our visitors and staff. Ken Collins, ESF’s Land Steward, mounted a camera near one of our Cliff Swallow colonies. Please enjoy this spectacular footage shot by Ken.

About the Author

Dave Feliz

Dave Feliz is the Reserve Manager at Elkhorn Slough National Estuarine Research Reserve