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
Pale Fire 1988), "Pale Fire" was published in 1991 in Sverdlovsk (in Sergey Ilyin's Russian translation). Some readers concentrate on the apparent story, focusing on traditional aspects of fiction such as the relationship among the characters. In 1997, Brian Boyd published a much-discussed study arguing that the ghost of John Shade influenced Kinbote's contributions. He expanded this essay into a book in which he also argues that, in order to trigger Shade's poem, Hazel Shade's ghost induced Kinbote to recount his Zemblan delusions to Shade. Some readers, starting with Mary McCarthy and including Boyd, Nabokov's annotator Alfred Appel, and D. Barton Johnson,