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 Shade of Difference A Shade of Difference A Shade of Difference () is a 1962 political novel written by Allen Drury. It is the first sequel to "Advise and Consent", for which Drury was awarded the Pulitzer Prize for Fiction in 1960, and was followed in 1966 by "Capable of Honor". The novel focuses on the politics among delegations to the United Nations and the troubles that Third World nations cause the United States as it vies for political advantages against the Soviet Union during the Cold War, as well as racial tensions within the United States surrounding the integration of public schools