BIRD-LIFE IN NORTHERN AFRICA. 103 



on the Sahara, this bird is dressed in tints precisely the 

 same in colour as the sand. So closely do the birds 

 nestle on the ground, that I have often nearly trod upon 

 them without observing their whereabouts until they 

 have risen twittering into the air. The Desert Larks are 

 clothed in similar protective tints ; so, too, are the Sand 

 Grouse, the Bustards, the Coursers, and the Chats. It is 

 also worthy of remark that most of these birds have 

 conspicuous colours in their plumage, either white on 

 the wings and tail, as in the Chats, but which is almost 

 hidden when the birds are at rest or crouching on the 

 ground ; or rich black or chestnut on the underparts, as 

 in the Sand Grouse and the Coursers, which are equally 

 as well concealed when these birds lie close to the earth, 

 which they never fail to do when alarmed by an enemy's 

 approach. There can be no doubt that constant ex- 

 posure to the burning sun has browned the plumage of 

 these birds of the Desert a circumstance which they 

 have been taught by experience to utilise to the best 

 advantage for their security. 



