RECORDS OF MEETINGS OF 1907 353 



summer plumage and the white winter plumage to carry the bird from the 

 end of the nesting season to the season of snowfall in October. If the win- 

 ter plumage were to be acquired at the end of the nesting season, when molt 

 is apparently a physiological necessity, the bird would be white before the 

 coming of snow. 



All the changes in plumage, it was asserted, were accomplished by actual 

 feather loss and growth, no basis being observed for the theory of change of 

 color in the individual feather. 



The paper was illustrated with specimens and a series of slides showing 

 the White-tailed Ptarmigan and its haunts on the summits of the Canadian 

 Rockies in Alberta. 



Dr. Dwight said in brief: The birds of the genus J unco are widely dis- 

 tributed, occupying in the breeding season the whole of Canada, the higher 

 parts of the Appalachian, Rocky and Coast ranges of mountains, and the 

 pine forests of Mexico and Central America. They fall quite naturally into 

 several large groups that differ widely in plumage and are also farther divis- 

 ible into lesser groups that possess characters more or less intermediate. 

 Intergradation between the various forms seems to be complete and one 

 view is to consider them all geographical races of one species, but a view 

 more in harmony with the apparent facts, is to recognize several of the 

 groups as species and to consider the intermediates either as hybrids or as 

 races, or perhaps as both. A blackheaded junco, for instance, would seem 

 to be specifically distinct from a redheaded bird, because each possesses a 

 character not found in the other, while mere color variations, attributable 

 to climatic conditions, point to geographical races. 



Whether Mendelian principles will or will not explain the complicated 

 plumage characters of the juncos, here at least there seems to be a promising 

 field for experimental research to supplement the facts derived from field 

 study. 



The paper was illustrated by a large series of specimens brought together 

 by Dr. Dwight for his investigations, and representing collections in all 

 parts of the country. 



The Section then adjourned. 



Roy Waldo Miner, 



Secretary. 



