198 The Natural History of Se I borne 



my brother in Andalusia has fully informed me. Of the 

 motions of these birds he has ocular demonstration, for many 

 weeks together, both spring and fall; during which periods 

 myriads of the swallow kind traverse the Straits from north to 

 south, and from south to north, according to the season. And 

 these vast migrations consist not only of hirundines but of 

 bee- birds, hoopoes, Oro pendohs, or golden thrushes, &c. &c., 

 and also of many of our soft-billed summer birds of pass- 

 age ; and moreover of birds which never leave us, such as 

 all the various sorts of hawks and kites. Old Belon, two 

 hundred years ago, gives a curious account of the incredible 

 armies of hawks and kites which he saw in the springtime 

 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. 1 



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

 the difficulty and hazard that birds must run in their migra- 

 tions, 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 Mediterranean ; for when 

 arrived at Gibraltar they do not 



1 It is curious to see how often and how persistently our great naturalist 

 returns to this question of migration. ED. 



