98 Mr. C. F. M. Swynnerton on 



instantaneously to pick out from amongst masses of ashantl 

 unacceptable objects racing upwards in the smoke and wind of 

 a grass-fire just such insects as are acceptable to them; the 

 methods by which insectivorous birds circumvent winged and 

 wary prey — the furtive approach, culminating in a sudden 

 quiet nip, of a Telephoiius or a Dri/oscojnis guttatus, the 

 short, sharp attack on an insect flying past of the average 

 small bird, the longer-range attacks and bolder pursuits of 

 a Drongo or Paradise Flycatcher, the yet bolder and more 

 graceful work of Bee-eaters, Swallows, and Kites, the 

 headlong drop after an insect that falls, and the ensuing 

 search should it reach the ground, the flying wing-fragments, 

 the marvellous twistings and doublings, the empty bill- 

 snappings that characterize the headlong fall should the 

 insect be a butterfly, the mid-air struggle to hold a Cliaraxes 

 imperfectly caught, and the rush to the spot of the bird's 

 companions on his losing his exclusive right to the insect 

 through its escape from his bill. None of these things are 

 readily illustrated by birds in captivity, but all should be 

 mentioned in any discussion of the relations of birds to their 

 prey. The one thing that idcis illustrated above was the 

 normal response of a butterfly to attack. Eurytela hiarhas 

 in experiment 511 "took cover ^^ and stayed there, using 

 the projecting rim of a saucer as in nature it would have 

 used a leaf. 



We have now, so to speak, discussed how our hypothetical 

 Puff-back Shrike slew his wasps, reduced his beetle, and 

 captured his very wary butterfly. We have yet to consider 

 why, out of vastly more abundant species that were present 

 at the time, he should have chosen to eat these three. We 

 have to discuss, in other words, his digestive limitations and 

 how he came to realize them. 



The existence of nauseating qualities in certain prey was 

 well attested by certain incidents in the experiments on the 

 Wood-Hoopoes. A, the wisest of them, was over-persuaded 

 by myself and ate a Danaida and an Acr<xa acara. C fol- 

 lowed suit with a Danaida. B ate only the abdomen of a 

 Danaida. Even B became fairly miserable. The other two 



