WOOD WARBLER 



their territories from intrusion as the males of many another 

 species. Conflicts occur both before and after the arrival 

 of the females, and have their origin, I believe, in the question 

 of territory ; .they take the form of a flying at and rapid 

 pursuit of one another, and are more frequent after a female 

 does arrive in a territory, possibly because the neighbouring 

 males, if still in bachelorhood, find it then difficult to resist 

 their natural inclination to approach her closely. I have 

 already called attention to the struggles between the males 

 of closely allied species regarding the question of territory, 

 and it is necessary to refer to them again in connection 

 with this species. The term, "struggle for existence," is 

 held to embrace every adverse influence that an organism 

 has to face ; it does not necessarily imply an actual trial of 

 strength between species and species, though it is always 

 supposed that such does actually occur. But to obtain 

 evidence by direct observation is no easy matter. We are 

 apt to forget that processes in Nature, even those which in 

 time lead to great results, work very gradually, and that all 

 the evidence we can ever hope to obtain of some change in 

 progress is supplied in just those details which in themselves 

 appear to be of trifling importance. Now in the conflicts 

 between the males of the same and closely allied species we 

 seem to have genuine struggles, which, without any undue 

 stretching of the imagination, may be expected to lead to 

 appreciable changes. Are they, however, really genuine ? 

 I ask this question because of statements made, not infre- 

 quently, to the effect that combats between rival males are now 

 only formal. It is somewhat difficult to understand what 

 the term "formal " is here held to denote ; does it mean that 

 they are not conflicts, or that they are conflicts to which no 

 meaning can be any longer attached ? Why should it be 

 thought that the conditions which necessitated a clashing of 

 interests in the past are not present to-day? And what 

 waste of energy if they no longer serve any purpose ! For 

 my part I believe that they are very real — the death of 



