Sexual Selection 297 



Entirely new light upon the seasonal appearance of epigamic 

 characters is shed by the recent researches of C. W. Beebe 1 , who 

 caused the scarlet tanager (Piranga erythromelas) and the bobolink 

 {Dolichonyx oryzivorus) to retain their breeding plumage through 

 the whole year by means of fattening food, dim illumination, and 

 reduced activity. Gradual restoration to the light and the addition 

 of meal-worms to the diet invariably brought back the spring song, 

 even in the middle of winter. A sudden alteration of temperature, 

 either higher or lower, caused the birds nearly to stop feeding, and 

 one tanager lost weight rapidly and in two weeks moulted into the 

 olive-green winter plumage. After a year, and at the beginning of 

 the normal breeding season, "individual tanagers and bobolinks were 

 gradually brought under normal conditions and activities," and in 

 every case moulted from nuptial plumage to nuptial plumage. " The 

 dull colors of the winter season had been skipped." The author justly 

 claims to have established "that the sequence of plumage in these 



birds is not in any way predestined through inheritance , but 



that it may be interrupted by certain factors in the environmental 

 complex." 



1 The American Naturalist, Vol. xlii. No. 493, Jan. 1908, p. 34. 



