Dr. J. Kirk on the Birds of the Zambesi Begion. 313 



chelles is of old primary axial rocks, such as we now find in the 

 African mountain-ranges. Besides, we have Bourbon and Co- 

 moro, active volcanos, with others near them of the same origin. 

 These may have, and some of them undoubtedly are of, a much 

 more modern date than others, and in their fauna and flora illus- 

 trate other phenomena. The line of volcanic action is carried 

 across Africa. The peak of Kilimanjaro, 20,000 feet high, inland 

 from Zanzibar, has that origin, and on the other side the Came- 

 roons claim the same ; the intervening space is unknown, but 

 may have in it other summits equal to either. 



In Eastern Tropical Africa the year is divisible into three 

 periods — that of the rains from November until April, the cool 

 months of May, June, and July, and the hot dry season of Sep- 

 tember and October. The first showers fall in October; and, 

 light as they are, with the increasing moisture vegetation then 

 commences, and a few trees burst into bloom. Birds assume from 

 that time nuptial plumage, and begin to pair. Wild fowl come 

 in large flocks from the north with the first heavy rains. From 

 the great marshes they never entirely disappear, — a few remain 

 at all seasons ; but the mass is away in the north, coming south 

 in December to breed. 



Many birds, such as the Guineafowl, the Hornbill, &c., which 

 during the dry parched months frequent the vicinity of water, 

 are far ofi" in the forest with the commencement of the rains. 



In August, September, and October the heats become in- 

 tense; the air is extremely dry; the grass plains are burnt 

 up, and become absorbents of heat ; the forests are leafless ; 

 food and water alike are scarce. These phenomena have a 

 vast influence on organic life, limiting to narrower bounds the 

 number of species capable of enduring such conditions. Herein 

 grasses have a great advantage : dormant during the droughts, 

 with the first showers they spring up and rapidly increase, 

 choking young shrubs at one season, and leaving them exposed 

 to the fierce rays of the scorching sun at another. 



Africa is by no means destitute of sweet singing birds ; but 

 they are musical only in the seasons of the rains. The loud 

 bleating cry of the Hornbill and the cackle of the Guineafowl 

 are more characteristic of the dry season. 



VOL. VI. Y 



