COLORATION 107 



Briefly, we must regard species which have a dull brown 

 coloration relieved by striations of a darker or lighter 

 shade as having retained, at least approximately, the 

 ancestral coloration. Herein male, female, and young all 

 resemble one another. But in many species the male 

 is distinguishable at a glance by his more ornate, more 

 brightly-coloured dress ; the measure, by the contrast, 

 between his plumage and that of his mate, and offspring, 

 is the measure of the distance put between himself and 

 the ancestral coloration. And this evolution of splendour 

 follows a very definite course, which can be traced with 

 tolerable certainty if a careful study be made of any 

 considerable number of species. 



The evidence so far collected seems to show conclusively 

 that the evolution of resplendent plumage begins in the 

 form of a periodical increase of brilliancy assumed by 

 the male at the breeding season, and is apparently due 

 to " hormones," or certain mysterious secretions of the 

 sexual glands. This more gaily coloured dress eventually 

 becomes the permanent characteristic of the male. Next 

 we find a similar change taking place in the female, until 

 she becomes, in many cases, almost or quite indistinguish- 

 able from her mate. 



In such cases, as for example in the common starling, 

 the young wear a distinct and soberly coloured livery, 

 answering to the earlier dress worn at first by both parents, 

 then by the female only. In other cases, as for example 

 in the golden oriole and crossbill, we find male, female 

 and young each with a distinctive dress of increasing 

 degrees of brilliancy, that of the male being brightest. 

 Here we conclude that the young wear what was com- 

 paratively recently the dress of the adult female. Finally 

 we have a host of instances where both adults and young 



