238 BIRD BEHAVIOUR 



simply turned them over with its bill in search of 

 something better beneath, as if they had been so 

 many ends of string or bits of stick, while when I 

 had offered it a much larger green caterpillar 

 on a twig it ravenously tore it from its hold and 

 devoured it. 



This experiment, by the way, wants repeating 

 under circumstances fairer to the caterpillar, though 

 as a matter of fact I was not trying to find out if 

 the bird would miss the insect owing to its protective 

 coloration, as I have once seen a green lizard do. 

 That is to say, if the power of a bird to see through 

 a protective disguise is to be tested, the insects 

 should be in situ beforehand in a place to which 

 the bird is admitted without having been allowed 

 to see the preparations and so have its expectations 

 raised. Until it is experimentally proved that 

 birds overlook insects of protective appearance in 

 their natural environment, we are not justified in 

 saying that such appearance is of any survival 

 value as far as feathered enemies are concerned. 



In the case of birds of prey there happens to be 

 some evidence of the value of protective resemblance; 

 a tame Peregrine Falcon flown at a Houbara Bus- 

 tard (Houbara undulata) has been seen, when the 

 quarry had settled and squatted, to alight and 

 search all round on foot without success, and 

 Lloyd, an excellent observer, says in his " Wild 

 Sports in Sweden " that the Swedes when trapping 

 for Hawks use a light Fowl, Pigeon, or what not 

 for bait in ordinary weather, but a dark one if 



