ZIC-ZAC AND CROCODILE. 81 



a gnat." * At any rate it can no longer be doubted 

 that a link of attachment between the two crea- 

 tures does exist, and that in all probability the 

 bird is in the habit of feeding on the small flies 

 and numerous aquatic insects either adhering to 

 the crocodile itself or exposed on the slimy surface 

 of the mud during his passage from the water, and 

 admitting at the same time the truth of Roche- 

 foucault's celebrated definition of gratitude, there 

 can be no difficulty in believing that the zic-zac 

 is prompted by selfish interest to keep watch over 

 the huge saurian who supplies him with such a 

 well-furnished larder, and habitually to act as his 

 sentinel on those occasions. 



Another instance of this kind is mentioned in 

 Gordon Cuniming's " Sports of Southern Africa." 

 Here the rhinoceros enacts the part of the 

 crocodile, and is carefully tended by a swarm of 

 little birds, of the starling family, who accompany 

 him on all occasions, performing the same duties 

 for him, when asleep, that the zic-zac fulfils for 

 the crocodile ; screaming and fluttering, and 

 dashing at his eyes on the slightest approach of 

 danger : but their motives are evidently not disin- 

 terested, for when unalarmed they may be seen 

 continually feeding on the parasitic insects that 



* Sec also Bishop STANLEY'S Familiar History of Birds. 



