A short-tailed colonial swallow that builds gourd-shaped mud nests in dense clusters under bridges and on cliffs. Famous for the "swallows returning to San Juan Capistrano" every March 19th.

Also called: Cliff

Native status: Native; widespread

§ Quick facts

SizeBody 13–14 cm (5.1–5.5 in); wingspan 28–31 cm
Weight19–34 g
LifespanWild typically 4 years; oldest documented 11
OrderPasseriformes
FamilyHirundinidae

§ Encyclopedia

The cliff swallow or American cliff swallow is a member of the passerine bird family Hirundinidae, the swallows and martins. The generic name Petrochelidon is derived from the Ancient Greek petros meaning "stone" and khelidon (χελιδών) "swallow", and the specific name pyrrhonota comes from purrhos meaning "flame-coloured" and -notos "-backed".

Source: Wikipedia — Cliff swallow Licensed under CC BY-SA 4.0

§ Identification

Field marks. Small swallow with square (not forked) tail, rusty face, white forehead patch, pale rusty rump (visible in flight), dark blue back. Often confused with Barn Swallow but has square tail and rusty rump.

Similar species. Barn Swallow (deeply forked tail). Tree Swallow (no rust, white below). Cave Swallow (cinnamon throat).

Voice. Constant chattering "krrrr" calls near colonies.

§ Diet & behavior

Diet. Flying insects caught on the wing.

Behavior. Highly colonial — builds gourd-shaped mud nests under bridges, eaves, and natural cliffs, sometimes in colonies of thousands. Famous for the annual return of Cliff Swallows to Mission San Juan Capistrano in California around March 19 each year (the "Swallows of Capistrano"), though the colony has largely abandoned the mission since the 1990s in favor of newer freeway overpasses. Researchers have documented genetic adaptation to traffic: Cliff Swallows nesting near roads now have shorter wings, making them quicker at avoiding cars — rapid evolution in real time.

§ Range

Across North America in summer; winters in South America

§ Habitat

Bridges, overpasses, cliffs, dams — anywhere with vertical surfaces for mud nests

§ Threats

Bridge replacement during nesting season, pesticide impacts, climate-driven mismatches.

§ Conservation status

According to the IUCN Red List, the cliff swallow is currently classified as Least Concern.

§ What helps

Schedule bridge work outside April–August. Skip pesticides. Maintain wet mud sources nearby.

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§ Further reading

§ Sources cited

  • Cornell Lab — All About Birds
  • Mission San Juan Capistrano historical research
  • Brown & Brown rapid evolution research (Univ. of Tulsa)
  • IUCN Red List 2018