296 DwiGHT, Plumages of the Scoters. [jiily 



The question is sometimes asked : How may the age of ducks be 

 determined? There are several ways of approximating this in 

 wild birds. Of course young birds show several skeletal characters 

 that persist for many months, but the plumage — once it is known 

 — gives us the clue that lasts the longest. It is singular that none 

 of our American authorities since Nuttall in 1834 has ever made 

 mention of the important emarginate first, or distal primary of 

 adult males of americana, nor have foreign writers on the moult of 

 nigra recognized its value. The like feather in young birds of this 

 species is of quite a different shape, a fact of importance because, 

 until a bird is a year old, the primary marks him as a young bird 

 no matter what sort of plumage he may assume. For the reason 

 that neither this nor the other primaries in ducks are moulted 

 more than once in a year this one feather is a key to the many so 

 called "immature" plumages. I have illustrated (Plate XXV) the 

 differences between the tapering feather tip in young males (Figs. 

 1-4) and the cut or emarginate tip in adults (Figs. 5-8). The 

 same condition prevails in the European species iiigra as shown by 

 Plate XXVI (Figs. 1 and 5) where, for comparison, I have also 

 placed male perspicillata (Figs. 2 and 6), deglandi (Figs. 3 and 7), 

 and fusca (Figs. 4 and 8) young and old. I have also added Plate 

 XXVII making a similar comparison between young and adult 

 females of americana (Figs. 1 and 5), deglandi (Figs. 2 and Q), fusca 

 (Figs. 3 and 7) and 'perspicillata (Figs. 4 and 8). This method, 

 which consists of holding the feather over blue-print paper, might 

 be called an avian Bertillon system with wing tips instead of fingers 

 for identification, and I feel confident that it may hold some future 

 possibilities. While a great variation is here shown by the wing 

 prints it should be noted that even where the differences between 

 the young and the adult bird overlap, there is a tendency for the 

 adults of the Scoters to have larger, wider feathers, with the excep- 

 tion of americana and nigra which alone have the singular cut 

 or emarginate primary in the adult. 



As the moults of all the Scoters of the New World, and probably 

 those of the Old are the same and the sequence of plumages identi- 

 cal, a better understanding of them may be obtained by taking 

 them up in natural sequence. The growth of new feathers always 

 begins at definite points, just as it does in other birds, and extends 



