SUPERNUMERARY NESTS 67 



to me to differ otherwise than one might expect the 

 final stages of any process to differ from its rough 

 and rude beginnings. The sexual impulse is, so it 

 seems to me, the governing factor in both, so that, in 

 both, it may have led up to whatever else there is. 

 In regard to the rooks, they did not, when I watched 

 them, appear to be repairing their nests. I think it 

 quite likely, however, that they do repair them after 

 a fashion, though I would put another meaning upon 

 their doing so. That, being at the nest, there should 

 often be some toying with and throwing about of 

 the sticks, one can understand, and also that this 

 should have passed into some amount of regular 

 labour : for all these things with the emotional 

 states from which they spring are interconnected 

 through association of ideas, so that one would glide 

 easily into another, and it is in this, as I believe, that 

 we have the rationale of that amount of repairing 

 which the rook does do. Personally, as said before, 

 I have seen little or nothing of it. 



When we consider that many birds are in the 

 habit of building one or more supernumerary nests 

 not with any definite purpose, as it seems to me, 

 but purely in obedience to the, as yet, unsatisfied 

 instinct which urges them to build we can, perhaps, 

 see a line along which the principle of divergence and 

 specialisation, as applied to the nest structure, may, 

 on the above hypothesis, have been led. Given two 

 uses of a nest, and more nests made than are used, 

 might not we even prophesy that one of the re- 

 dundant ones would, in time, serve one of the uses, 

 supposing these to be very distinct, and to have a 

 tendency to clash with one another ? Now courting 



