Bird of the Month: Cliff Swallow

By Hugh Jennings

Scientific Name: Petrochelidon pyrrhonota

Length 5.5-6 in

AOU Band code CLSW

The Cliff Swallow (CLSW) is 5-1/2 to 6" in length. The genus name is from Greek petros, stone, or petra, rock, in allusion to places where nests are often built, and chelidon, swallow. Species name is from Latin, red-backed, an allusion to the rump. A squarish tail and "buffy rump" distinguish this swallow from others in our area. Most have a dark chestnut and blackish throat with a pale forehead.

Its range has expanded greatly in the last two decades. Originally it built jug-shaped mud nests on the sides of cliffs. But, now the sides of barns and bridge supports provide sheltered sites that are more widespread than natural sites. The CLSWs have invaded many areas where they have never nested before. In the west, there are colonies in almost all culverts and highway bridges. They are found in open to semi-open land, farms, cliffs, river bluffs and lakes.

It forages in close-knit flocks and eats mainly insects. It feeds mostly on the wing and may feed low over water or very high over other terrain. In bad weather, it may feed on the ground.
The species typically nests in colonies, sometimes with hundreds of nests crowded close together. The nests are usually on vertical surfaces with some overhead shelter and made of dried mud. Both sexes help build the nest which is lined on the inside with grass and feathers. There are usually 4-5 eggs, sometimes 3-6. The eggs are white to pale pinkish, spotted with brown.

Incubation by both parents is 14-16 days. Both parents feed the nestlings which leave the nest about 21-23 days after hatching.

The CLSW is a long-distance migrant, wintering in southern South America. It migrates in flocks during the day. This is the famous swallow that returns to the mission at San Juan Capistrano, California every spring. Traditionally, the return is celebrated on March 19th, although the birds actually return to the general area starting in late February.