354 Mr. Swynncrton on Mixed Bird-parties. 



and the Swallows kept strictly to whichever section the 

 Bulbuls happened to be in at the moment^ crossing over 

 when they crossed. 



" Curiously enough I yesterday afternoon saw Bulbuls 

 taking the Bee-eater's role of to-day. A party of Estrilda 

 astrild was following the sunk fence, seed-hunting as is their 

 wont ; above them, keeping mostly a few feet up in the 

 higher vegetation, was a party of seven or eight P. iayardi, 

 which were keeping pace with them for the sake of the 

 insects put out by the Waxbills. A male Bishop-bird ia 

 full plumage [Pyromelana capensis a: ant home I ana) and two 

 or three of his hens were also of the party and were some- 

 times in the grass, sometimes with the Bulbuls. A little 

 lower down the slope a smaller detached party of Estrilda 

 astrild was similarly seed-hunting in the grass about the 

 foot of a young Indian ' sissoo,' and in the sissoo was a 

 solitary Bulbul watching thera." 



The closely searching birds of the large mixed parties 

 are to each other and to the Drongos and Flycatchers that 

 attend them what the Waxbills of the above observations 

 were to the Bulbuls and the Bulbuls to the Bee-eater. I have 

 even seen birds attending a party of monkeys that was moving 

 through the tree-tops in Chirinda. 



While, however, I feel that the mixed parties are primarily 

 drives, and the Di'ongo from this standpoint mainly parasitic, 

 it is, I think, likely that the great "mobbing^' power 

 afforded by numbers must be so great an advantage as to 

 probably act as a contributing factor. I think, too, that 

 the Drongo, with his boldness and readiness to attack, 

 quite likely fully " pays for his keep." 



The fact of systematic co-operative hunting on so large a 

 scale suggests the views on mutual aid amongst animals 

 that have been laid stress on by some Russian naturalists ; 

 yet is of puriicular interest as suggesting hoW keen selection 

 m.ust sometimes be and how baseless, probably, is the view 

 that the more perfect defensive adaptations of insects 

 constitute hypertely. 



