^"''igi?^'"] Brewster, The Red-legged Black Duck. 327 



uncertainty which should not have been overlooked or ignored. 

 Thus he would seem to have placed himself in a position which 

 makes it desirable if not imperative for him to describe fully and 

 clearly the precise methods of dissection which he is accustomed to 

 follow and the resulting proofs of age and immaturity on which he 

 so implicitly relies. When he has done this it will be easier to 

 judge whether his interpretation of the color variations in Black 

 Ducks is or is not literally correct. 



It is considered legitimate, I believe, to turn the guns of an 

 opponent against his own fortifications provided one can make 

 such use of them. If, then, I may be permitted to restrict Dr. 

 Dwight's account of the progressive color changes in the bill, legs 

 and feet of Black Ducks to the form ruhripes it will be of direct 

 ser\'ice to me. For if, as I am quite ready to believe — having no 

 grounds for maintaining the contrary — the legs and feet of young 

 ruhripes are not much more strongly reddish in autumn and early 

 winter than are those of young tristis, and if the former bird does not 

 acquire the full coloring of these parts until he is nearly or quite 

 one year old, it is easy to account for the undeniable large percentage 

 of autumnal and winter specimens which seem to be intergrades 

 betw^een these races by assuming that very many of them are im- 

 mature representatives of ruhripes. This, of course, is in the nature 

 of a tentative and possibly untenable proposition. Not so, how- 

 ever, with the moral which I propose to draw from another of Dr. 

 Dwight's statements already quoted and expressed in the following 

 words: "Once the adult colors of the soft parts are attained they 

 are never lost." This assurance, coming from one who speaks 

 with such confidence and authority, is peculiarly welcome. For it 

 encourages me to believe that a doubt, which I have hitherto enter- 

 tained, may be unfounded and a claim, on which I have hesitated 

 to insist, justified. The doubt has been as to whether fully mature 

 Black Ducks, showing bright coral red legs and feet in late autumn, 

 winter and early spring, may not afterwards have these parts dull 

 colored in late summer and early autumn — the seasons of "eclipse" 

 ])lumage with so many of the Anatinje. The claim — directly 

 affected, it will be perceived, by the doubt — is that if no such 

 retrogressive change ever takes place the apparently undisputed 

 fact that Black Ducks with conspicuously red legs are wholly absent 



