THE BIRDS OF ALGERIA. 5 



unequal ground of the Desert, each and all support 

 a bird population characteristic in its features, 

 almost endless in its variety. Such wide variations 

 of temperature, and such notable changes in climate 

 in summer and winter, must necessarily affect the 

 avifauna of Algeria. Migration tlierefore prevails 

 in a very remarkable manner. Not only do we 

 find much regular migration across the country 

 in spring and autumn, of species breeding to 

 the north and wintering to the south, but we find 

 also that Algeria is the winter quarters of vast 

 numbers of birds that breed in Europe, especially 

 in the British Islands. Perhaps of even greater 

 interest to the student of migration are the local 

 movements and vertical migrations of many of 

 the resident species — of birds that come up from 

 the Desert oases in spring to breed in the wooded 

 mountains of the Atlas ; and of others that visit 

 the high mountain regions in summer, where a 

 suitable temperature prevails, and retire in autumn 

 to the plains. For further particulars I would 

 refer the reader to The Migration of Birds, pp. 

 136, 137. Perhaps the most characteristic features 

 of the Algerian avifauna are its richness in desert 

 species, its singular abundance of Chats and Larks. 

 As regards the winter aspects of the Sahara region, 



