Mr. Swynuerton on Mixed Bird-parties. 353 



whicli it may be found driving systematically daily, 100 to 

 200 acres or so to a party I should guess for Chiriuda, far 

 more in the less densely-wooded country. 



Gregariousness in a species is primarily, of course, the 

 result of quite other factors than the need for co-operative 

 insect-hunting, as witness the flocks of seed-eating birds. 

 But one notices that the members of family parties of all 

 kinds of insectivorous birds play greatly into each other's 

 bills, and instances of more highly organized co-operation 

 are afforded by such birds as Creatophura carunculata (in its 

 locust drives) and Bucorax coffer. My two tame individuals, 

 of the latter species whose habits I recently described in the 

 S. A. O. U. Journal (vol. ix. 1913, p. 83), would stalk along 

 side by side at some little distance apart and attack such 

 insects as were flushed by either of them in the direction of 

 the other. And I have watched parties of as many as four 

 of the wild birds of the same species doing the same thing. 



This is co-operation pure and simple. The next step 

 is to have noticed that otiier species of birds (like grass- 

 fires) tend, in rummaging about, to put up insects, and to 

 attach yourself to them when you see them thus promis- 

 ingly engaged. The following extracts from my bird- 

 diary are typical of what I have frequently seen : — 



"April 8, 1911. — . ... In the guavas was a party of not 

 fewer than a dozen Bulbuls (^Pycnonotus layardi) moving 

 actively all over the bushes and pecking at the ripe guavas ; 

 outside, hawking backwards and forwards over and round the 

 bushes and evidently, with the Bee-eater, snapping up such 

 flying insects as were dislodged by the Bulbuls, were five 

 or six Swallows {Psalidoprocne orientalis). Only one of the 

 insects captured was large enough for me to distinguish. 

 It was either a common yellow-legged wasp [Scolius sp.) or 

 some black-winged species closely resembling it in appear- 

 ance. It flew from the Bulbuls and was at once snapped up 

 by the Bee-eater. The line of guava-bushes is divided into 

 two by a considerable gap, and it was noteworthy that the 

 Bee-eater (which was joined for a few minutes by a second) 



