IG2 NATURAL HISTORY 



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 con- 

 sist not only of Hirundines, but of bee-birds, hoopoes, 

 Oropendolas, 1 or golden thrushes, &c., &c., and also of many 

 of our soft-billed summer birds of passage ; and, moreover, of 

 birds which never leave us, such as all the various sorts 

 of hawks and kites. Old Belon, 200 years ago, 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-men- 

 tioned, 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. 2 



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

 on the difficulty and hazard that birds must run in their 



1 Oropendola is the Spanish name for the Golden Oriole. ED. 



2 The migration of the kites and hawks no doubt depends in a 

 measure upon that of the smaller birds upon which they prey ; in the 

 same way that some of the latter are influenced by the appearance or 

 disappearance of locusts and other insects, which form their chief food. 

 In Lloyd's " Game Birds and Wild-fowl of Norway and Sweden," 

 p. 370, there is a wonderful picture by Wolf, entitled " The Bird- 

 cloud," in which, in illustration of the author's remarks, the artist has 

 depicted a vast flock of wild fowl on migration harassed by birds of 

 prey. In Andersson's " Birds of Damaraland," p. 264, a singular 

 account ;s given of the way in which the pratincoles (Glareola melon- 

 optera) attend the flying swarms of locusts in South Africa. The 

 writer says : " These birds come, I may saj r , in millions, attendant on 

 the flying swarms of locusts ; indeed, the appearance of a few of them 

 i< looked unon as a sure presage of the locust swarms being at 

 hand." ED. 



