BIRDS 121 



The Columbida? present a striking contrast to the Phasi- 

 anidse, in the general absence of sexual dimorphism. They 

 are monogamous birds of gregarious and gentle habits. The 

 male birds do not fight very fiercely, and the gestures of 

 courtship are not very elaborate. It is true that the male 

 pigeon, as seen in the domesticated state, expresses his desires 

 and his authority to the hen by loud cooings, by swelling his 

 crop, and scraping the ground with his wings. But on the 

 other hand he has but one mate, and she lays but two eggs, 

 and the male pigeon, very soon after he is mated, is incubat- 

 ing the eggs, and afterwards feeding the helpless young from 

 his own crop with quite as much assiduity as the hen. The 

 hen also coos in response to the male, and thus there is 

 little differentiation in the habits and actions of the two 

 sexes. 



There could not be a greater contrast than that between 

 the habits of the cock pigeon and the jungle cock or cock 

 pheasant, nor better evidence for the conclusion that uni- 

 sexual characters are the definite result of particular habits, 

 movements and mechanical stimulations. 



Darwin remarks that in the English Carrier and Pouter 

 pigeons the full development of the wattle and the crop 

 occurs rather late in life, and that conformably with his 

 " rule of inheritance " these characters are transmitted in 

 full perfection to the males alone. As it may appear that 

 these cases show how unisexual male characters may be 

 produced by artificial selection without such special stimula- 

 tions as those to which I attribute their origin in wild 

 species, it is worth while to examine them in some detail. 



Now I do not deny for a moment the importance of 

 selection. I take it to be a truism that whatever peculiarity 

 or modification we may consider, such peculiarity will 

 usually be increased and developed, by breeding from the 

 individuals that possess it in the highest degree, and also 



