138 THE MIGRATION OF BIRDS. 



seebohmi)^ a species discovered by Captain Elwes 

 and myself, is only known to breed at 5500 feet 

 elevation in the Aures, and doubtless winters in 

 the oases of the desert. The Goldfinch [Fringilla 

 carduelis) is another instance. I found this bird 

 breeding in Algeria, where it is a resident, up to 

 4000 feet, and wintering on the plains. In fine, 

 wherever mountains occur, it may be laid down as 

 an almost universal rule that there is a considerable 

 amount of migration taking place between their 

 slopes and the plains. This rule, however, is by 

 no means confined to species resident in those 

 countries ; for we find in a great many Cases that 

 some individuals of a migratory species wintering 

 in southern lands and breeding in the Arctic or 

 temperate regions, ascend mountains to such 

 altitudes as render the climatal conditions similar 

 to those prevailing in the higher latitudes to which 

 the bulk of the individuals resort. This is a very 

 remarkable and interesting fact, of which the follow- 

 ing instances may be regarded as typical. The 

 Dotterel [Eudromias morinellus) breeds on the 

 tundras of the Arctic regions above the limits of 

 forest growth, but a few individuals find a similar 

 climate at high elevation in the Alps, and on the 

 mountains of Great Britain and Scandinavia. A 

 few Tree Pipits [Anthus arboreus) breed on the Alps 

 and the Pyrenees, but the great majority migrate 

 north in spring. The Redstart (Rutici/la phoenicurus) 

 winters in North Africa, passes through South 

 Europe on migration, and breeds throughout Central 



