Introduction

The Cave Swallow is a locally common species that breeds in southeastern New Mexico, Texas, Florida, the Greater Antilles, and portions of southern Mexico, as well as along the west coast of South America. Although most populations are resident, U.S. breeders generally move south for the winter. As its name suggests, this swallow nests and roosts primarily in caves (which it often shares with bats), although breeding colonies also form in sinkholes and under bridges, culverts, or similar structures. A few small colonies are even known to nest in ancient Mayan wells and ruins, and the two South American subspecies nest on cliff faces or the sides of buildings, not unlike the Cliff Swallow (Petrochelidon pyrrhonota). The three North American subspecies of the Cave Swallow are similar in size and coloration, whereas the two South American subspecies (in Peru and Ecuador) differ considerably from their northern counterparts.

Since the mid 1980s, the Cave Swallow has undergone a dramatic range expansion in Texas and has also colonized south Florida. In each of these cases, invasion of new territory has been facilitated by the adoption of bridges and culverts for nesting, with new colonies often springing up along highways.

This species builds its nests of mud and (often) bat guano, cemented to the walls of caves and culverts, often high up and inaccessible. Data on Cave Swallows nesting in caves and sinkholes is generally lacking owing to the inaccessibility of nests in such situations. Among populations, nests vary in shape from an open cup to a semi-enclosed bowl. Females are largely responsible for incubating eggs, but both parents share equally in feeding the nestlings. Birds at the northern edge of the range have at least two, and sometimes three, clutches each season.

Although this species is potentially vulnerable to disturbance when nesting, particularly at night, its numbers are expanding in North America and key colonies appear to be stable. Pesticide contamination could be a problem for the Cave Swallow in some agricultural areas of the southwestern United States and Mexico, although farming does provides these birds with sources of water and insect foods.