20. 



Moffat. — Colours of Birds. 



I think it may make things clearer to put a few of the 

 •incipal conchisions arrived at by advocates of this 

 explanation in the form of a catechism. 



(1) Why are ornamental colours so often worn only 



by the cock-birds ? 

 Answer. — Because only the hen-birds have that 

 aesthetic sense which gives preference to the 

 more beautifully plumaged among their 

 suitors. 



(2) Why, then, has bright plumage ever been 



developed among the hen-birds — as in the 

 hen-Robin, the hen-Kingfisher, and the hen- 

 Blue Titmouse ? 

 Answer. — By simple inheritance, when there is no 

 counteracting cause to prevent the bright 

 tints of parents of one sex from being inherited 

 by children of both sexes. 



(3) But why, then, are there so many cases in which 



the bright tints have remained a peculiar 

 inheritance of the male sex ? 

 Answer. — Because it would be positively harmful 

 to the females in many cases, and particularly 

 when they are sitting on their nests, to wear 

 such bright and conspicuous colours as those 

 they admire in their husbands. 



(4) Can you assign any reason why this need for a 



dull colour in the female should govern the 

 ' case so completely in certain species (the 

 Greenfinch and Chaffinch, for example), while 

 it has no restraining effect whatever in a 

 number of other species (as the Great and 

 Blue Titmice, the Kingfisher, and the Robin) ? 

 Answer. — Yes, for the (ireenfinch and Chaffinch, 

 and most of tlie birds whose males are more 

 brightly coloured than the females, build 

 open nests, while the Kingfisher, the Titmice, 

 and (to a certain extent) the Robin nest in 



