THE SEXUAL SELECTION THEORY 143 



fication owing to the deliberate rejection of the less gaily- 

 coloured suitors. The tendency to develop colour in 

 the mouth would appear to be latent in all birds. 



It is significant that whenever bright colours appear, 

 they do so first in the males, the females and young 

 retaining the dress common, up to this time, to the species 

 at all ages. In the majority of instances, at any rate, 

 it would seem that this accession of colour appears with 

 the seasonal re-awakening of the reproductive activities : 

 it forms a " nuptial " dress, and is discarded after the 

 breeding season is over for a livery indistinguishable 

 from that of the female, this forming the so-called 

 " winter plumage." But if all the available facts are 

 taken into consideration there seems good reason to 

 believe that the nuptial plumage tends to be assumed 

 earlier and to be retained later, as this disposition to 

 develop ornament gathers force, till finally only the head 

 and neck go into " eclipse," as in the case of the Black- 

 cock, Jungle-fowl and Partridge. 



In the Pheasant we have an instance — one of hundreds 

 — where the resplendent dress is worn throughout the 

 year. The next phase in the direction of the growth 

 of colour occurs when the female, towards old age, 

 develops a more or less well marked tendency to assume 

 the hues of her lord, and this accession of colour makes 

 its appearance earlier and earlier in succeeding genera- 

 tions, till finally the adults of both sexes are coloured 

 alike, save that, as a rule, the female lacks the intensity 

 of coloration which her mate displays. The original 

 sombre dress is now only worn by the young. In due 

 course the resplendent dress is assumed also by the young, 

 as witness the numerous instances among the Kingfishers 

 and among the Parrots, where adults and young are 



