A PROCESS OF TRANSITION 207 



merely? But then, which are the exceptional in- 

 stances, or in which direction is the change proceed- 

 ing ? Is the male becoming, or was he once, a 

 builder or a non-builder? For myself, I incline to 

 the transitional view, and inasmuch as the lapse of 

 such a habit as nest-building must be consequent 

 upon a loss of interest in it — which would mean a 

 decay of the instinct — this does not seem to me 

 consistent with the extremely attentive manner in 

 which the cock follows the hen about, and the 

 manifest interest which he takes in all she does. It 

 seems to me more likely, therefore, that he is 

 learning the art than losing it. Still, as an instinct 

 might weaken very gradually, it is impossible to 

 do more than conjecture which way the stream is 

 running, if we look only at a single species. The 

 true way would be to take all the species of the 

 genus to which the one in question belongs, and find 

 out the habits of the majority, in regard to this special 

 point. If both the male and female of the genus 

 Titrdida help, as a rule, in building the nest, then 

 this, no doubt, was the ancient state of things, and 

 vice versd. 



One might suppose — it would seem likely on a 

 prima facie view of it — that where the cock bird 

 took no part in the building of the nest, he would 

 take none, either, in incubating the eggs. This is so 

 with the blackbird — at least I have never come 

 upon the male sitting, and whenever I have watched 

 a nest where eggs were being incubated, there has 

 never been any change upon it ; the birds, that is to 

 say, have never relieved one another, but the hen, 

 having gone off, has always returned, the nest being 



