6 BULLETIN 15 3, UNITIiD STATES NATIONAL MUSEUM 



the larks, indicates that they are not mere coincidences, but must be 

 the results of similar distributional complexes. What their true 

 significance may be i^ unknown as yet. 



Bannerman ^ writes that there are some rather striking similarities 

 in the bird fauna of the Cameroon-Nigerian mountains and those 

 of Shoa, more than 1,700 miles distant. Here, however, we find no 

 genera restricted only to these two areas, and hence we may con- 

 clude that the faunal relationships may be less ancient and profound 

 than those existing between northeastern Africa and South Africa. 



If we may consider the number of forms found in northeastern 

 Africa and extending southward through eastern Africa as opposed 

 to those ranging westward to the Upper Guinean savannahs as a 

 criterion of the trend of the dispersal of the savannah and steppe 

 birds, we find that the great majority went southward and not west- 

 ward. The birds of the Upper Guinean savannahs seem to have been 

 derived as much from Mediterranean Africa as from the northeasterD 

 part of the continent. Some forms occur in both the Sudanese and 

 the eastern African grasslands, but this is probably due to subse- 

 quent dispersal after their arrival in Africa. Among forms the 

 ancestors of which went westward and not southward from north- 

 eastern Africa may be mentioned the ground hornbill {Buceros 

 ahyssinicus) , the parakeet {Psittacula hrainein)^ the roller {Coracias 

 ahyssinicus) , and the chat {Oenanthe hottae). Among the many 

 forms that spread southward and not westward were the ancestors 

 of such birds as Francolinus sephaena^ Francoliiius africanus^ Strep- 

 topelia cajncola^ Lophoceros melanoleucos, Mirafra africanoides^ An- 

 thus nickolsoni, and Turdus olivaceus. 



Our knowledge of the topographic history of northeastern Africa 

 is still too fragmentary and uncertain to enable us to attempt a 

 space-time analysis of the dispersal of the birds found there and in 

 adjacent areas, and we must therefore limit ourselves to a descriptive 

 account of the present distributional facts. We may begin by stating 

 that the faunal areas laid down by Chapin ^ have been found to hold, 

 and no reasons have been unearthed for making any serious altera- 

 tions in his map. The collections gathered by the Frick expedition 

 were made principally in two faunal areas — the Somali Arid and 

 the Abyssinian Highland. Each of these is further subdivided, as 

 will be seen later. For the sake of completeness, however, we may in- 

 clude in our discussion the eastern extension of the Sudanese Arid belt 

 (the North Somali region of Neumann, Erlanger, and others) as well. 

 Inasmuch as only a small number of specimens (and species) were 

 obtained in the East African Highland region, we need not concern 



2 The birds of Tropical West Africa, etc., vol. 1, p. xli, 1930. 

 '■" Amer. Nat., vol. 57, pp. lOG-125, 1923. 



