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
Buff (colour) colour "in the range of the Marschall color", meaning the colour in illustrations in a particular book. As a relatively inexpensive and readily-available paint colour, and one which went well alongside the near-universal black hull and white superstructure used on steamships at the time, White Star was far from the only shipping line to use a shade of buff as a funnel colour. The Orient Line and Norddeutscher Lloyd used an entirely buff funnel without the black top, while Canadian Pacific and the Swedish American Line employed a buff funnel with a representation of the company's house flag on them.