The crag martins are four species of small passerine birds in the genus Ptyonoprogne of the swallow family. They are the Eurasian crag martin (P. rupestris), the pale crag martin (P. obsoleta), the rock martin (P. fuligula) and the dusky crag martin (P. concolor). They are closely related to each other, and have formerly sometimes been considered to be one species. They are closely related to the Hirundo barn swallows and are placed in that genus by some authorities. These are small swallows with brown upperparts, paler underparts without a breast band, and a square tail with white patches. They can be distinguished from each other on size, the colour shade of the upperparts and underparts, and minor plumage details like throat colour. They resemble the sand martin, but are darker below, and lack a breast band.
These are species of craggy mountainous habitats, although all three will also frequent human habitation. The African rock martin and the south Asian dusky crag martin are resident, but the Eurasian crag martin is a partial migrant; birds breeding in southern Europe are largely resident, but some northern breeders and most Asian birds are migratory, wintering in north Africa or India. They do not normally form large breeding colonies, but are more gregarious outside the breeding season. These martins build neat mud nests under cliff overhangs or in crevices in their mountain homes, and have readily adapted to the artificial cliffs provided by buildings and motorway bridges. Up to five eggs, white with dark blotches at the wider end, may be laid, and a second clutch is common. Ptyonoprogne martins feed mainly on insects caught in flight, and patrol cliffs near the breeding site with a slow hunting flight as they seek their prey. They may be hunted by falcons and infected with mites and fleas, but their large ranges and populations mean that none of the crag martins are considered to be threatened, and all are classed as Least Concern on the IUCN Red List.
These are exclusively Old World species. The rock martin breeds throughout Africa and through the Middle East as far as Afghanistan and Pakistan, and is replaced by the dusky crag martin further east in India and Indochina. The Eurasian crag martin breeds from Iberia and northwesternmost Africa through southern Europe, the Persian Gulf and the Himalayas to southwestern and northeastern China. Northern populations of the Eurasian crag martin are migratory, with European birds wintering in north Africa, Senegal, Ethiopia and the Nile Valley, and Asian breeders going to southern China, the Indian subcontinent and the Middle East. Some European birds stay north of the Mediterranean, and, like populations in warmer areas such as India, Turkey and Cyprus, just move to lower ground after breeding. The dusky crag martin and rock are largely resident apart from local movements after breeding, when many birds descend to lower altitudes, although some pale northern rock martins from North African and southern Arabian may winter further south alongside the local subspecies in Ethiopia, Mali and Mauritania.
The crag martins mainly breed on dry, warm and sheltered cliffs in mountainous areas with crags and gorges, and the Eurasian crag martin reaches 5,000 m (16,500 ft) in Central Asia. The use of buildings as artificial cliffs has enabled breeding expansion into lowland areas, particularly for the two tropical species, and the rock martin breeds in desert towns. In South Asia, migrant Eurasian birds sometimes join with flocks of the dusky crag martin and roost communally on ledges of cliffs or buildings in winter.