32 NATURAL HISTORY OF SELBORNE 



gives a curious account of the incredible armies of hawks 

 and kites which he saw in the spring-time traversing the 

 Thracian Bosphorus from Asia to Europe. Besides the 

 above-mentioned, he remarks that the procession is swelled 

 by whole troops of eagles and vultures. 



Now it is no wonder that birds residing in Africa should 

 retreat before the sun as it advances, and retire to milder 

 regions, and especially birds of prey, whose blood being 

 heated with hot animal food, are more impatient of a sultry 

 climate ; but then I cannot help wondering why kites and 

 hawks, and such hardy birds as are known to defy all the 

 severity of England, and even of Sweden and all north 

 Europe, should want to migrate from the south of Europe, 

 and be dissatisfied with the winters of Andalusia. 



It does not appear to me that much stress may be laid 

 on the difficulty and hazard that birds must run in their 

 migrations, by reason of vast oceans, cross winds, &c. ; 

 because, if we reflect, a bird may travel from England to 

 the Equator without launching out and exposing itself to 

 boundless seas, and that by crossing the water at Dover, 

 and again at Gibraltar. And I with the more confidence 

 advance this obvious remark, because my brother has 

 always found that some of his birds, and particularly the 

 swallow kind, are very sparing of their pains in crossing 

 the Mediterreanan ; for when arrived at Gibraltar they 

 do not 



" Rang'd in figure wedge their way, 



And set forth 



Their airy caravan high over seas 

 Flying, and over lands with mutual wing 

 Easing their flight :" . . . . MlLTON. 



but scout and hurry along in little detached parties of six 

 or seven in a company ; and sweeping low, just over the 

 surface of the land and water, direct their course to the 

 opposite continent at the narrowest passage they can find. 

 They usually slope across the bay to the south-west, and 

 so pass over opposite to Tangier, which, it seems, is the 

 narrowest space. 



