MALES ARRIVE BEFORE FEMALES 43 



particular environment for which racial pre- 

 paration has fitted them. In the second place, 

 being already established when other males 

 appear upon the scene, and advertising their 

 presence by song, they will be less liable to 

 molestation ; thirdly, in those cases in which 

 a long journey is undertaken, they will have 

 ample time to recover from the fatigue, and, 

 if attacked by later arrivals, will thus be in a 

 better position to defend their territories ; and 

 lastly, a greater uniformity in their distribution 

 will be insured before the females begin their 

 search. 



There is, besides, another good reason for 

 thinking that the earlier males will have an 

 advantage. We will assume — and from the 

 abundant evidence supplied by the marking 

 of birds, it is quite a reasonable assumption — 

 that there is a tendency, generally speaking, 

 for individuals to return to the neighbourhood 

 of their birthplace, or to the place in which 

 they had previously reared their offspring. 

 Now the earlier arrivals will have no difficulty 

 in securing territories ; those that come later 

 may have to search more diligently, still they 

 will gain all that they require so long as any 

 available space remains. Then comes the point 

 when all suitable ground is occupied, and yet 

 there are males to be provided for. What 

 will be the position of these males ? Urged by 

 their inherited nature, they will leave the district 

 and possibly continue their search into those 

 adjoining, only, however, to add to the diffi- 



