22 FROM THE NIGER TO THE NILE 



bush, his path may often cross a stream, the waters of which 

 are cooled by roofings of well-grown trees that afford delightful 

 shade. Such a stream as this becomes the highway for many 

 birds, which travel up and down in small parties, enlivening 

 the cool depths with their voices, and all busy feeding, 

 intent upon keeping their bodies and souls together. In 

 the desert countries to the north, the birds follow the course 

 of wells, and so we find that over the vast area there is a 

 continual migration going on according to the rainfall. 



When one considers the even distribution of the fauna 

 of the country lying between the Niger and the Nile, one 

 sees that there can be nothing to hinder a wide distribution 

 throughout. Take, for example, the route followed by the 

 Sudan fauna. Birds occurring in Senegal and around Lake 

 Chad are again found to the east of Darfur, thereby demon- 

 strating that there can be no serious obstacles like mountains 

 in the unknown provinces of Wadai and Darfur to stop 

 an extended distribution. On the other hand, one finds that 

 the Sudan and Senegambian faunse are separated in their 

 courses eastward by the mountainous hills like the Murchison 

 range in Central Nigeria, which runs to a height of some 5000 

 ft. Throughout the route which we have already mentioned 

 as that taken by the Senegambian birds, one finds in the 

 bush-covered plains small isolated groups of ironstone hills 

 which are inhabited by peculiar species not found on the 

 plains and which form links for the distribution of these 

 birds across Africa. As an example, I will give that of a 

 rock nightjar {Caprimulgus sharpei) which I discovereil on 

 some rocky hills 500 ft. in height on the borders of the forest 

 region in the Gold Coast Hinterland. Even so far away as 



