Cliff Swallow

• It is the subject of the "swallows returning to San Juan Capistrano" every 19 March, one of the best-known natural history traditions in California.
• It competes for nests with the barn swallow and converts them to its own design.
• Faced with a predator it gives a warning call to the whole colony and they all pour out in a mass flock; the predator realises it has been spotted and moves off. The larger the colony, the sooner the threat is detected.

Skeleton type

Vertebrate - internal bony skeleton (bird)

Habitat & environment

Open country and savanna, above all near running water. It nests under bridges, culverts, cliffs and eaves. It winters in South America, from Paraguay and central and south-eastern Brazil to central Argentina

Size at birth

Eggs of about 20 mm, white, cream or pinkish white with brown speckles

Sexual maturity

12 months

Gestation / incubation

14-16 days, with both sexes incubating. The chicks are altricial and fledge at 21-24 days

Litter / clutch size

4-5 eggs, sometimes 3 to 6, with one brood a year and occasionally two or three. The nest, made of mud pellets and shaped like a gourd, with a tubular entrance to a spherical chamber, takes 5 to 14 days to build and is often repaired and reused

Sources consulted: IUCN Red List; Animal Diversity Web (Universidad de Michigan); Stanford Birds (Universidad de Stanford); National Wildlife Foundation; Brown y Brown (Universidad de Tulsa, investigación sobre evolución rápida); Vieillot

Best time: Spring and summer in North America; it winters in South America