CHAPTER VIII 



PECULIAR INTERRELATIONS 



Ostriches and Zebras. Rheas and Guanacos. Oxpecker and big Game. 

 Egrets and Elephants. Bee-eaters and Bustards. Penguins, Albatrosses and 

 Petrels. Osprey and small birds. Chaffinch and Missel-thrush. Burrowing Owl 

 and Prairie-dogs. Petrels and " Tuatera Lizard ". Puffins and Rabbits. Skuas 

 and Gulls. Frigate-birds and Gannets. Cuckoos and their dupes. The causes 

 of parasitism. 



THE subject of the last chapter leads us insensibly up to 

 the consideration of those remarkable interrelation- 

 ships which exist between different species of birds, or 

 more commonly, between different species of birds and of other 

 animals, though the part these interrelationships play in evolu- 

 tion is not very obvious. 



For example, it is not easy to see why the Ostrich in 

 Africa and the Rhea in South America should commonly 

 associate with herds of the larger ungulates of their respective 

 countries. Thus the Ostrich commonly consorts in troops 

 of from thirty to forty with herds of Zebras or the larger 

 Antelopes ; while the Common Rhea similarly associates with 

 herds of Deer, and the smaller Darwin's Rhea with herds of 

 Guanacos {Laiwi huanacos). In this association there is no 

 apparent advantage to be gained, but there are many similar 

 cases which are less enigmatical. Take, for example, the case 

 of the Oxpecker or Rhinoceros-bird {BupJiaga Africanus\ a 

 native of South Africa, and generally regarded as a species of 

 Starling. This bird is commonly found in intimate association 

 with basking herds of cattle and big game, running about all 

 over the bodies of these creatures in their search for the ticks 

 and other parasites which harbour there. Lately, however, 

 this bird has fallen into disgrace, since it has extended its 

 attentions to the horses and cattle of the colonists with any- 

 thing but happy results. It would seem that in removing ticks 



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