PARENTAL CARE AND NEST-MAKING 301 



depends on the extra-organismal tradition of the species. 

 The tradition includes the imitation of previous and con- 

 temporary nest-builders. The nest-building may thus be 

 compared to the preparations that a human mother makes 

 for the birth of a child : she has not only an instinctive but 

 an intelligent awareness that some provision of garments is 

 necessary, but it v^ill probably be admitted that this would 

 not be very effective without the guidance of social tradition. 

 As a matter of fact, external guidance is so copious that there 

 are few data to indicate how much could be done by individual 

 reflection or how much would be done instinctively without 

 deliberation at all. Man cannot get back to such detachment 

 from the social heritage ! As to birds, Wallace brought 

 forward little evidence beyond cases where birds transported 

 to a novel environment built a new kind of nest. Chaffinches 

 taken to New Zealand no longer made the typical chaffinch 

 nest ; but it is necessary to know how far the deviation was 

 due to changes in the available materials. 



(c) A third view is that the nest-building is in the main 

 instinctively determined. That is to say, the bird has a 

 hereditary pre-disposition to go through a certain routine, 

 without much or anything in the way of education or 

 experience, requiring only a succession of liberating stimuli 

 to pull a succession of triggers. On this view, the bird is an 

 instinctive artist, working as the inherited spirit and flesh 

 move it to work, following a series of inborn promptings or 

 inspirations. This is very different from intelligence ; it is 

 physiologically like a concatenation of reflex actions. This 

 does not, however, exclude the possibility that the physio- 

 logical concatenation is suffused with awareness and backed 

 by endeavour. 



{d) But even if the manner of the nest-building is in the 

 main instinctive, the expression of inborn or hereditary 

 structural pre-arrangements within the nervous system, and 

 of some measure of psychical awareness associated with these, 

 it does not follow that no importance should be attached to 

 individual intelligence or learning ; it does not follow that 

 no importance should be attached to imitation and tradition. 



