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 and 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

The pins mark the parks where its presence is documented.