178 



U. S. NATIONAL MUSEUM BULLETIN 217 



have made the following measurement of length of bills with some 

 reservation as to their significance as dimensions : 







Length 







Length 





Eastern race 



{mm.) 





Western race 



(mm.) 



Mar. 7 



Woods Hole 



44 



May 8 



St, George Island 



43. 



Mar. 7 



Woods Hole 



40 



May 22 



Nushagak 



38 



Julys 



Athabaska Delta 



36 



June 1 



Old Crow 



42 



Aug. 3 



Rupert House 



36 



June 11 



Tuluak 



36 



Deo. 9 



New York 



40 



June 14 



Tuluak 



37 









June 14 

 June 14 



Old Crow 

 Old Crow 



40 

 4L 



(aver.) 





39 









June 14 



Old Crow 



41 









July 20 



AUoknagik Lake 



41 



(aver.) 



40 



The length of bill does not distinguish these eastern and western 

 specimens. 



It may be remarked that the type specimen was taken at Humphrey 

 Point, Alaska, where scoters are rare. As far as I know, scoters do 

 not nest along the arctic coast in Alaska (Bailey, 1948), in Yukon 

 (Rand, 1946), or in the Mackenzie Delta (Porsild, 1943). The type 

 specimen was taken from the northern limit of its range and not from 

 a nesting area. Distinction of an eastern and western race would 

 imply some isolating process in the habits of white- winged scoters 

 in contrast with the apparent intermingling within other species of 

 ducks at some time of year, a condition which prevents localization 

 of genetic forms. 



These scoters cannot be distinguished on their breeding grounds as a 

 western race, although I believe that they have migrated from a west- 

 ern wintering population. If this view is correct, and the two winter- 

 ing populations are genetically alike they must mingle after breeding 

 and before nesting. Since they preserve their geographical separa- 

 tion in winter and apparently during their spring migration to arctic 

 Yukon, it is to be suspected that in summer, perhaps after nesting, 

 enough scoters exchange their western or eastern wintering habits to 

 maintain a genetically mixed population. 



1 male 



Melanitta perspicillata (Linnaeus) 



June 13 weight 983 g. fat 



testes 11x24, 9x25 

 mm. 



Surf scoters were first remarked mingled in a flock of white-winged 

 scoters on May 20. Although they were usually in the minority of 

 mixed fiocks of scoters, one flock contained only one white-winged 

 scoter among nine surf scoters. Scoters were not noticed in associa- 

 tion with ducks of other species, and flocks containing only one species 



