BIRDS OF ETHIOPIA AND KENYA COLONY 7 



ourselves with it, especially as it has been the subject of much study 

 by van Someren and others. 



1. The eastern extension of the Sudanese Arid region covers all but 

 the highlands of Eritrea and adjacent parts of northeastern Ethiopia 

 and of northern French Somaliland. Faunally, it is differentiated 

 by the presence of several palearctic forms, especially among the larks 

 [Galerida^ Alacmon^ etc.), and the rufous warbler (Agrohates galac- 

 totes). Although generally arid and consequently poor in vegetation 

 the region is not uniformly so, as more luxuriant growths of euphor- 

 bias occur along the banks of the periodic streams. (PI. 11.) Accord- 

 ing to Zedlitz,* the coastal belt of Eritrea and the Danakil lowlands 

 have their rains in winter, while the highlands get their precipitation 

 during summer. Zedlitz considers the coastal lowland belt a distinct 

 faunal zone, which may be looked upon as a subdivision of the Su- 

 danese Arid. 



2. The Somali Arid. This region takes in practically all of French, 

 British, and Italian Somililand (except the extreme northern tip 

 of French Somaliland and the highlands of British Somaliland), the 

 eastern part of the Hawash Valley (pi. 10), Gallaland and southern 

 Boran (pis. 5-8), the northern half or so of Kenya Colony, and most 

 of northeastern Uganda. On the whole, it may be characterized as a 

 dry acacia and mimosa countr}'^, with considerable barren stretches re- 

 lieved by more luxuriant growths of such plants as euphorbias along 

 the banks of the seasonal rivers. It is described by Erlanger ^ as a 

 series of terraces. As one goes successivly higher and away from the 

 sea, especially in the northern part of this region (eastern Hawash, 

 French Somaliland, etc.), one finds more and more of a truly African 

 fauna and less of a palearctic tinge. 



Roughly the Somali Arid may be divided into two subregions — 

 a Northern Somali and a Southern Somali, The former may be 

 limited in a southward direction at approximately the southern bor- 

 der of British Somaliland. The latter subregion is relatively flatter, 

 less a series of sharp, abrupt terraces than the former, but both are 

 varied ecologically, as may be seen from the vegetation map. Along 

 the coast both are covered with desert scrub and desert grass, while 

 in the interior they are largely acacia-desert grass savannahs, in- 

 terrupted by strips of thorn forest along the stream banks. The 

 annual rainfall increases from less than 10 inches on the coast to 

 nearly 20 inches in the interior. 



Some of the birds characteristic of the Northern Somali region 

 are as follows : 



Buteo rufofuscus archeri. 

 Heterotetrax humilis. 



Neotis heuglini. 



Cursorlus cursor somaliensis. 



' Journ. fiir Orn., 1910, p. 292. 



» Ber, Senck, Naturf. Ges„ 1902, pp. 15^170. 



