326 Brewster, The Red-legged Black Duck. \f^^ 



during the thirty or more years when I w'as actively engaged in 

 collecting birds I lost no opportunity of ascertaining by dissection, 

 whenever possible, the approximate ages of" my specimens. With 

 those taken in summer and autumn there w^as seldom any trouble 

 but by midwinter I found it difficult, and by early spring practically 

 impossible, to decide with certainty as to whether a bird was more 

 or less than one year old. I was accustomed to use a -strong lens 

 (but never, I wull confess, a microscope), and to give attention to 

 every detail of structure which I found available as a test of age. 

 Hence my skepticism with regard to Dr. Dwight's confident claim. 

 Nor has this, moreover, received the positive endorsement of any one 

 whom I have consulted about it. Mr. H. W. Henshaw has assured 

 me that his experience in determining the ages of birds by dissection 

 has been closely similar to my own. Dr. C. Hart Merriam writes 

 me that he does "not know any way by which the age of a duck 

 killed in winter may be positively determined." Dr. Leonhard 

 Stejneger that he is "not in a position to either deny or affirm Dr. 

 Dwight's assertion." Mr. F. A. Lucas that he is "unable to say 

 whether or not it would be possible to speak positively as to" the 

 ages of ducks taken in winter " after an examination of the bones," 

 although he has found that "in many of our small birds the back 

 of the skull does not ossify so rapidly as the rest of it and in most 

 cases one can usually tell whether a bird is a year old or more." 

 Some of these statements are accompanied by others, equally 

 qualified or non-committal, to the effect that thorough cleaning of 

 an entire skeleton, microscopic examination of some of the parts 

 of the bony structure, or minute examination of the generative 

 organs and their tissue, might reveal characters by which a bird 

 less than a year old could be identified as such. Although chiefly 

 negative in character this testimony establishes one interesting and 

 rather significant fact, viz., that some of the most eminent and 

 experienced ornithologists in this country are still in ignorance or 

 doubt about a matter to which they must have given more or less 

 attention and concerning which Dr. Dwight lays claim to definite 

 and exact knowledge that has escaped their ken. If his age tests 

 be really trustw^orthy he is to be credited with exceptional acumen 

 for discovering them; but if, on the other hand, they should prove 

 to be unreliable he will have shown himself oblivious to elements of 



