94 PROCEEDINGS OF THE ACADEMY OF 



ON CEETAIN SPECIES OF FALCONIDJE, TETRAONID^, AND ANATID^ 



BY ALFRED NEWTON, 



PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF CAMBRIDGE, ENGLAND. 



[Communicated by Mr. Coues.] 



Magdalene College, Cambridge. 



2Sth November, 1869. 



My Dear Sir: I have just received your letter of the 9th inst. 

 I have the greatest pleasure in giving you all the information in 

 my power. 



As to the Great Northern Falcon question — I cannot count 

 more than six men in Europe who really understand it. It would 

 be invidious to name them. Two of them, Schlegel and Blasius, 

 I had the i:)lcasure of converting from their old heresies. I en- 

 deavored to bring Cassin to a right understanding (»f the matter 

 when I was in Philadelphia more than a dozen years ago, but I 

 did not succeed, and consequently his notice in the " Birds of 

 North America" (p. 13) is all wrong. I have not much to add 

 or anything to retract from some remarks of mine on this ques- 

 tion in "The Ibis" for 1862 (pp>. 44-53), in my appendix to Baring- 

 Gould's " Iceland" (pp. 404, 407), and in the " Ootheca Wolley- 

 ana" (pp. 85, 8t). 



The first thing to become fully impressed with is that these 

 large falcons have exactly the same changes of plumage as Falco 

 2')ereginus or F. anatum (supposing the}' are distinct), i. e., 

 the young in their first plumage are marked longitudinally, and 

 this plumage they keep until their second autumn, when the fully 

 adult plumage is assumed. In sajdng this, I do not mean to 

 declare that the moult is a matter of a very short time. On the 

 ontrary, I have reason to believe tliat in most examples it lasts 

 for some months ; but by the end of their second autumn they are 

 in fully adult plumage. All that has been said about these birds 

 growing whiter and whiter as they grow older is founded on mere 

 speculation and fancy. The main differences between immature 

 and adult plumage are that the browns become grays, and the 

 longitudinal markings transverse. None of the European dealers 

 understand this; and if j'ou liave skins from Paris, 3'ou will 

 find, I am sure, young white birds marked " tres adulte," and old 



[July 4, 



