Taxonomy
The four Ptyonoprogne species are the Eurasian Crag Martin (P. rupestris) described as Hirundo rupestris by Italian naturalist Giovanni Antonio Scopoli in 1769, the Pale Crag Martin (P. obsoleta), described by Jean Cabanis in 1850, the Rock Martin (P. fuligula), described by German zoologist Martin Lichtenstein in 1842, and the Dusky Crag Martin (P. concolor) formally described in 1832 as Hirundo concolor by British soldier and ornithologist William Henry Sykes. They were moved to the new genus Ptyonoprogne by German ornithologist Heinrich Gustav Reichenbach in 1850. The genus name is derived from the Greek ptuon (φτυον), "a fan", referring to the shape of the opened tail, and Procne (Πρόκνη), a mythological girl who was turned into a swallow.
These are members of the swallow family of birds, and are placed in the Hirundininae subfamily which comprises all swallows and martins except the very distinctive river martins. DNA sequence studies suggest that there are three major groupings within the Hirundininae, broadly correlating with the type of nest built. The groups are the "core martins" including burrowing species like the Sand Martin, the "nest-adopters", which are birds like the Tree Swallow that utilise natural cavities, and the "mud nest builders". Ptyonoprogne species construct a mud nest and therefore belong to the latter group; They resemble the Hirundo species in that they make open cup nests, whereas Delichon martins build closed cups, and the Cecropis and Petrochelidon swallows, have retort-like closed nests with an entrance tunnel. The genus Ptyonoprogne is closely related to the larger swallow genus Hirundo into which it is often subsumed, but a DNA analysis showed that a coherent enlarged Hirundo genus should contain all the mud-builder genera. Although the nests of the Ptyonoprogne crag martins resembles those of typical Hirundo species like the Barn Swallow, the DNA research showed that if the Delichon house martins are considered to be a separate genus, as is normally the case, Cecropis, Petrochelidon and Ptyonoprogne should also be split off.
The small, pale northern subspecies of Crag Martin found in the mountains of North Africa and the Arabian peninsular is now usually split as the Pale Crag Martin, Ptyonoprogne obsoleta. The remaining birds are now identified as Eurasian Crag Martin.
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