Pale crag martin to do so, it would cast doubts on their specific distinctness. There are several subspecies differing in plumage shade or size, although the differences are clinal, and races interbreed where their ranges meet. The pale crag martin of the nominate subspecies "P. o. obsoleta" is 12–13 cm (4.7–5.1 in) long with light brown upperparts, becoming paler on the lower back, and a short square tail that has small white patches near the tips of all but the central and outermost pairs of feathers. It has a pale grey throat, upper breast and underwing coverts, and the rest of the underparts
A Whiter Shade of Pale reached number 5 on the "Billboard" Hot 100 and sold over 1 million copies. It also peaked at number 22 on the soul charts there. The song was included on the US release of the "Procol Harum" album, in September 1967, but not on the subsequent UK version. In the Netherlands, the single entered the chart at number 1 in June 1967 and reached number 1 again in July 1972. A May 1972 re-release on Fly Records peaked at number 13 in the UK. "A Whiter Shade of Pale" has continued to receive critical acclaim. Along with Queen's "Bohemian Rhapsody",