The Eurasian crag martin is a small passerine bird in the swallow family. It is about 14 cm (5.5 in) long with ash-brown upperparts and paler underparts, and a short, square tail that has distinctive white patches on most of its feathers. It breeds in the mountains of Europe, northwestern Africa and across the Palearctic. It can be confused with the three other species in its genus, but is larger with brighter tail spots and different plumage tone. Many European birds are resident, but some northern populations and most Asian breeders are migratory, wintering in northern Africa, the Middle East or India.