THE LOVE DISPLAYS OF BIRDS 241 



birds find an outlet for their excessive vitality 

 and superabundant energy in the development 

 of showy plume, sweet song, and wild display. 

 Another fact about much of this song and dis- 

 play, which seems absolutely fatal to any hypo- 

 thesis of sexual selection, is that in innumerable 

 instances the male birds indulge in them at 

 times when it is perfectly obvious no female 

 choice could be exerted. We may repeat here 

 what we have already expressed in a former 

 volume as our deliberate opinion upon this 

 question. The various species that are excep- 

 tionally adorned are also remarkable for the 

 extraordinary vitality, excitability, and pugnacity 

 of the males ; and these qualities are more or 

 less frequently being invoked for the display 

 of such ornament, or in combat with rivals or 

 intruders. The meeting of a rival, the sexual 

 excitement provoked by the presence of the 

 female, or even the intrusion of some stranger 

 species into the sacred precincts of a favourite 

 haunt, is almost invariably the signal for the 

 erection of a crest or plume, the display of a 

 spangled wing or tail, the inflation of a pouch 

 or sac, or the assumption of an attitude in which 

 the special decoration of the species is displayed 

 to its utmost advantage, a declaration of defiance 



