SENSES, INSTINCTS, AND INTELLIGENCE 341 



§ 6. Intelligent Behaviour 



When the Greek eagle lifts the Greek tortoise in its 

 talons and lets it fall from a height so that the carapace is 

 broken and the flesh exposed, it is making inteUigent use 

 of an expedient. Whether it discovered the expedient by 

 experimenting, as is possible, or by chance, as is more likely, 

 it uses it intelligently, appreciating the situation. To put 

 it all down to the blind imitation of some original genius 

 who discovered the device seems a violent scepticism. 

 The same expedient is illustrated by herring gulls, which 

 lift sea-urchins and clams in their bills and let them fall on 

 the rocks so that the shells are broken. Rooks, which 

 are notoriously clever birds, do the same with fresh- water 

 mussels. There are records of a bird of prey letting food 

 drop upon its beleaguered nestlings and of another which 

 makes a habit of letting a stone fall into the midst of a clutch 

 of ostrich's eggs with consequences highly satisfactory to 

 itself. 



There is much evidence that many a bird could be more 

 intelligent if it liked to try. But given an endowment of 

 instinctive aptitudes and a youthful schooling during which 

 it learns with prodigious rapidity, why should a bird trouble 

 its head with perceptual inference ? To enjoy is better 

 than to experiment, and singing a finer art than playing 

 with syllogisms. But every now and then we hear a diflFerent 

 note, a throb of a restless brain, the note of inquisitiveness 

 and adventure. It implies (i) a fine brain to start with, 

 like that of crow or parrot ; (2) a certain measure of success, 

 enabling the animal to look round with some confidence ; 

 and (3) the inducement of some probable or certain reward. 

 Speaking of the weaver-bird {Ploceus hay a) Mr. C. H. 

 Donald has written (1920) : " His extraordinary intelli- 

 gence and his natural love for inspecting everything he sees 

 and picking it up in his beak has been taken advantage of 

 to teach him tricks. He is a very apt pupil, and if carefully 

 and kindly taught will within a week select a particular 



