254 THE VARIATION OF ANIMALS IN NATURE 



insectivorous birds in Hawaii, says : ' I should say the present- 

 day Hawaiian birds are very well educated by the parents in 

 the matter of choice of food. It was always a marvel to me 

 why the parents should tend them so long. I have doubtless 

 remarked on it often, but may here quote at random, from 

 Fauna Haw.," vol. i, p. 404, of that common species, Vestiaria 

 coccmea : " the yellow, black-spotted young follow the parents 

 sometimes till they are far advanced in their red {i.e. mature) 

 plumage, but they very early learn to obtain nectar for them- 

 selves, even at a time when the parents are still feeding them 

 on caterpillars." Again, p. 406, of Palmeria : " The young 

 follow the parents often until they have arrived at almost 

 their full plumage, and after they have acquired their full 

 song, but in the winter months these companies are disbanded. 

 In February and March they are generally paired." I think 

 similar records might be made on almost every insectivorous 

 Hawaiian bird, certainly all the common ones. I noted even 

 of the rare and extraordinary Pseudonestor, p. 432 : " they are 

 unwearying in supplying their full-fledged young with food, 

 and when the latter are soliciting this from their parents they 

 form a most comical group." ' 



It would appear that, in proportion as young birds are 

 taught rather than teach themselves, the stringency of selection 

 in favour of the formation of Mullerian groups would be 

 relaxed ; but the subject is one requiring research and is not 

 yet capable of generalisation. 



As regards (b) we are even more in the dark. It is only in 

 Europe and N. America that observations on the foods of 

 birds are so extensive that any quantitative estimate of its 

 different constituents is possible. But it is only in the tropics 

 that mimetic phenomena, especially in butterflies, are at all 

 common. Outside the Holarctic region we are quite unable 

 to answer the following fundamental questions : What pro- 

 portion of the total bird fauna actually attacks butterflies 

 (or other insects involved in mimetic associations) ? In 

 what proportions do protected and unprotected species figure 

 in the diet of the birds making such attacks ? Do young 

 birds make such attacks more frequently than old birds? 

 At what period in their life are female butterflies most attacked ? 



Until these questions can be answered from knowledge 

 based on quantitative data, we are still very much in the dark 



