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The crag martins are four species of small passerine birds in the genus Ptyonoprogne of the swallow family.
The genus name is derived from the Greek ptuon meaning "a fan", referring to the shape of the opened tail.

1/ Dusky crag martin (Nhạn nâu hung, Ptyonoprogne concolor)
Procne is the name of a mythological girl who was turned into a swallow.