BRITISH WARBLERS 



generally some days after the first male ; but the migration of 

 the sexes overlaps, males continuing to arrive with the females. 

 There is as great a variation in the plumage of the females as 

 in that of the males, the immature birds being easily distin- 

 guished by their dull appearance and by a conspicuous absence 

 of that intensity of colouring and development of feather 

 which are such prominent beauties of a more fully mature 

 bird. 



The duration of the courtship depends, I believe, 

 solely upon the female ; for it sometimes happens that 

 on her arrival she is not in a condition to breed, and 

 in such a case she passes unnoticed amongst the unpaired 

 males, her presence having no exciting influence upon 

 them ; she is thus allowed to seek her food and pursue 

 her way unmolested. But this is by no means a usual 

 occurrence ; her presence is generally a signal for an 

 intense outburst of sexual passion. In no other way, it 

 seems to me, can we account for the variation in the duration 

 of the courtship. In one year, for instance, in which the 

 males were very late, a solitary female arrived first. The 

 first male that arrived paired immediately with this female ; 

 there was little excitement or courtship, the nest was rapidly 

 built, and the young were hatched within a month from the 

 date of his arrival. But, on the other hand, it is by no means 

 uncommon to see pairs actively engaged in their courtship 

 for many mornings in succession. 



By the term courtship I refer always to the period between 

 the time in which a female settles in the territory of a 

 given male and the time when the first egg is laid. 

 This period is always one of excitement to the male ; 

 an excitement which, varying in intensity with the ner- 

 vous organisation of the species, vanishes temporarily 

 the moment the sexual passion is relieved, but re- 

 appears, although in a lesser degree, before each act of 

 coition. 



There seems indeed to be some connection between the 



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