22 THE IMPOKTANCE OF BIRD LIFE 



bium, layer of bark. The spores are exceed- 

 ingly minute and may be wafted long distances 

 by the wind. Great numbers may also be trans- 

 ported from grove to grove and forest to forest 

 hidden in the feathers of birds, just as the hum- 

 ming-bird carries pollen. 



Among other minor relationships which may 

 Have a bearing on the general balance is the con- 

 tinual association of some species with large 

 four-footed beasts. For example, we have in 

 America the cowbird which has contracted a 

 habit of following a herd of cattle about a pas- 

 ture to feed upon the flies attracted by the 

 animals. The cowbird, however, seldom or never 

 alights upon the cattle themselves as does that 

 strange black cuckoo of South America, the ani, 

 and the starling-like rhinoceros-bird of Africa. 



These have an especial fondness for ticks and 

 other body parasites which abound on all beasts 

 free from the curry-comb, and they take a small 

 but valuable part in the life history of the 

 animals they attend. Unfortunately, the rhinoc- 

 eros-bird, with the coming of domestic cattle in- 

 to South Africa, has fallen into disgrace. In 

 tearing a tick from its hold on the back of its 

 host, the bird generally causes a small wound in 

 the tender hide, which soon grows infected. The 

 rhinoceros-bird of late years has also become en- 

 dowed with a taste for blood, and now inflicts 

 wounds where there are no ticks at all. 



