Chap. XV.] SUMMER PLUMAGE. 173 



But this view cannot be extended to the many waders, 

 in which the summer and winter plumages differ very 

 little in color. With defenceless species, in which either 

 both sexes or the males alone become, extremely conspicu- 

 ous during the breeding-season — or when the males ac- 

 quire at this season such long wing or tail feathers as to 

 impede their flight, as with Cosmetornis and Vidua — it 

 certainly at first appears highly probable that the second 

 moult has been gained for the special purpose of throwing 

 off these ornaments. We must, however, remember that 

 many birds, such as Birds of Paradise, the Argus pheasant, 

 and peacock, do not cast their plumes during the winter; 

 and it can hardly be maintained that there is something 

 in the constitution of these birds, at least of the Gallina- 

 ceae, rendering a double moult impossible, for the ptarmi- 

 gan moults thrice in the year. 31 Hence it must be con- 

 sidered as doubtful whether the many species which moult 

 their ornamental plumes, or lose their bright colors, during 

 the winter, have acquired this habit on account of the in- 

 convenience or danger which they would otherwise havf* 

 suffered, 



I conclude, therefore, that the habit of moulting twice 

 in the year was in most or all cases first acquired for some 

 distinct purpose, perhaps for gaining a warmer winter cov- 

 ering; and that variations in the plumage occurring 

 during the summer were accumulated through sexual se- 

 lection, and transmitted to the offspring at the same season 

 of the year ; such variations being inherited either by both 

 sexes or by the males alone, according to the form of in- 

 heritance which prevailed. This appears more probable 

 than that these species in all cases originally tended to 

 retain their ornamental plumage during the winter, but 

 were saved from this through natural selection, owing to 

 the inconvenience or danger thus caused. 



31 See Gould's • Birds of Great Britain.' 



