Coloration of the Mouths and Eggs of Birds. 281 



said^ ' but they are left for the other reason, too — to get rid 

 of the Ipunga (smell or flavour). Of birds that we eat in 

 the adult state we eat the nestlings too, but we like them 

 all less than we do the old birds. Very small nestlings are 

 not eaten at all except by certain people who do not seem to 

 mind the Ipunga. It is strongest in newly-hatched birds, 

 and that is the ciiief reason why we let them remain till 

 the feathers appear/ ' Is this Ipunga a taste or a smell ? ' 

 'You taste it in the mouth, but you can often smell it, too, 

 in very young nestlings/ . . . /' 



In the light of the law of complementation, the idea is 

 probable enough ; for a nestling, unable to fly away from 

 its enemies, may well require some slight additional pro- 

 tection beyond numbers and such concealment and defence 

 as the nest and its own appearance and the parent birds 

 may aff'ord. Various young butterfly larvse (also the eggsj are 

 far less readily attacked by driver ants than when they have 

 grown larger and developed emissible juices or procryptic 

 coloration. The seedling foliage in some groups of plants 

 is more disliked by herbivorous animals than the adult 

 foliage, normally out of their reach. Still, young rooks are 

 excellent eating ! So, pending special experiment, I give 

 the view, widely held amongst our natives, merely for what 

 it is worth. 



It is, in any case, not required for our purpose. Experi- 

 menting, even with adults and somewhat immature birds — 

 in two or three cases with actual nestlings — I found many 

 species that were disliked, and a fine gradation between the 

 best-liked species and the worst, as I have explained above 

 vuider "Distinctive coloration." Therefore, remembering 

 that nestlings tend to open their mouths wide to all comers, 

 and that, in youngish nestlings especially, the large wide- 

 open mouth is the most visible portion — that, in fact, there 

 is often nothing but mouths visible when all the nestlings 

 crane upwards or outwards together — I would suggest that 

 the distinctive coloration of the mouths of nestlings has, to 

 a large extent, been retained in relation to the necessity for 

 ready differentiation by enemies, or for the differentiation. 



