The cave swallow (Petrochelidon fulva) is a medium-sized, squarish tailed swallow belonging to the same genus as the more familiar and widespread cliff swallow of North America. The cave swallow, also native to the Americas, nests and roosts primarily in caves and sinkholes. The cave swallow measures 12 to 14 cm in length and weighs 19 g on average. The largest of the five subspecies, P. f. pallida, has an average wing length between 107.0 and 112.3 mm; the smallest subspecies, P. f. aequatorialis, has an average wing length between 93.0 and 93.5 mm. Differences between the sexes are minimal, both are similar in size and weight and are difficult to distinguish from their plumage. It has grey-blue upperparts and brown-tangerine forefront and throat.
The Cave Swallow occurs in the South-central United States, Mexico, and the West Indies including Puerto Rico, where it is a common permanent resident (Raffaele 1989a, Raffaele and others 1998) and a fairly common passage migrant in Vieques (Gemmill 2015). The Cave Swallow occurs in open country, farms, beaches, mangroves, marshes, and towns (Oberle 2018). The atlas fieldwork yielded a total of 449 records within 256 hexagons or 53 percent of the 479 total hexagons (see map). Of the 256 hexagons where this species was found, breeding met the atlas definition of confirmed in 42 percent (108) of the hexagons, probable in 4 percent (10), and possible in 39 percent (100), while the species was observed in 15 percent (38) of the hexagons but without evidence of breeding (see map). Cave Swallow distribution. The map shows the highest breeding code by hexagon and overlaying the ecological life zones in Puerto Rico. Note: percentages may not total 100 due to rounding.
The Cave Swallow breeds in colonies, by building a mud nest in a cave mouth, on a building, or under a bridge or ledge from March to July, 221Cave Swallow/Golondrina de Cuevasaccording to previously published reports (Oberle 2018, Raffaele and others 1998). Atlas results indicate that breeding activity for this species extends throughout the year and peaks in June (see chart). Results indicate that the Cave Swallow breeds in all ecological life zones, but most of the breeding activity was reported within the subtropical moist forest life zone (73 percent of the hexagons) (see table and map). Because the swallow commonly breeds under bridges, its confirmed breeding distribution appears to follow major highways on the island where bridges are common and nests are easy to find (e.g., highway from San Juan to Caguas, Cayey, and Ponce) (see map).
The overall current population trend of the Cave Swallow is increasing, and it is listed as a species of least concern by the IUCN (BirdLife International 2019). Locally, this species is not listed in any of the threatened categories of PRDNER or USFWS. In Puerto Rico, the Cave Swallow has a protected habitat in land of 13 percent or 695 km2 of the total area covered by the hexagons where evidence of breeding was found for this species (~5212 km2).