BRITISH WARBLERS 



have an average chance of rearing offspring. There were, 

 moreover, no females present ; the responsibility for deserting 

 the wood rested solely with the males who had preceded them, 

 a fact which is of some importance, for the males take little 

 if any share in the actual construction of the nest. How 

 then was their decision arrived at ? The question in this 

 form savours too much perhaps of human process ; let us 

 therefore ask how the instinctive routine of activity was 

 interrupted. Now it is probable that these males were either 

 the same individuals, or the offspring of such, that nested in 

 the wood the previous season, for instead of passing directly 

 through it, as is customary with birds in search of new 

 breeding grounds, they wandered restlessly about for some 

 days before leaving, evidently expecting to find suitable 

 territories. Hitherto the environment had answered their 

 requirements, and the true course of their instinctive pro- 

 cedure therefore ran smoothly, but they were now called upon 

 to face an experience which in all probability they had never 

 met with before. I cannot, of course, prove that they had 

 never been called upon to face this particular phase of 

 experience, but bearing in mind the conditions of existence 

 of these smaller migrants and the fact that this wood had 

 only been inhabited by this species for the two previous 

 seasons, it is not, I think, unreasonable to assume that some 

 at least of these males had had no experience, so far as 

 reproduction was concerned, beyond that which was supplied 

 in those hundred odd acres. I am trying to show that for 

 one or the other, or perhaps all, of these males, the environ- 

 ment could scarcely have acquired meaning as the outcome 

 of previous experience, and that we cannot well call to our 

 aid " meaning " in explanation of their behaviour. So that 

 we are compelled to fall back upon racial preparation through 

 the natural selection of variations of germinal origin, which 

 is little enough help, for it is one thing to show how the 

 reproductive instincts of this or that species have conformed 

 to this or that environment through the elimination of the 



