OLD CROW 179 



of scoter became more frequent after the first few days. In a week 

 the two species appeared quite segregated. 



The subsequent segregation of two species which seemed to be pro- 

 miscuously associated during early migration may be related to the 

 earlier appearance of mating behavior among surf scoters, for the pur- 

 suit behavior of males on June 5 was intense, but the mating pursuits 

 of white-winged scoters were not so intense until a week later. As 

 sexual ripeness develops, the different synchronization of its processes 

 in each species intensifies intraspecific bonds and in the Arctic must 

 practically preclude miscegenation. 



The surf scoters in summer near Old Crow were estimated to be 

 not half so numerous as white-winged scoters, but their total seemed 

 to be only about a quarter that of the migrating scoters. It may be 

 presumed, as suspected for white-winged scoters, that the eastward 

 migration of surf scoters past Old Crow about suffices to occupy the 

 Porcupine and Old Crow Valley, and that the two species of scoters 

 come by a common route from a western wintering place. 



Indians at Old Crow esteem white- winged scoters as food but dis- 

 like surf scoters, which they call Tetre la. 



Dall (Dall and Bannister, 1869) did not remark upon surf scoters 

 at Nulato, but Swarth (1936) described them as "fairly common" 

 migrants at Atlin, B. C, where they were first seen May 8, 1931, and 

 May 11-24, 1934. From this we suspect that their spring flight passes 

 through the mountains in that region from the Gulf of Alaska to the 

 upper Yukon, but that a coastal route extending further westward 

 may serve western Alaska. 



The two maritime wintering areas of surf scoters are separated by 

 the continent, although stragglers have been found in many interior 

 points. Since eastern and western winter specimens are not distin- 

 guished it may be presumed that there is no isolation to effect genetic 

 distinction. The spring arrival at Old Crow appeared to be so con- 

 sistently from the west that the mingling of the birds raised in various 

 localities evidently occurs later in summer. 



Mergus serrator serrator Linnaeus 



1 male May 22 weight 1157 g. very fat testes 19x42, 19x50 



mm. 



Red-breasted mergansers, which reach Anaktuvuk in pairs, nest 

 northward to the arctic coast of Alaska and Yukon, as far north as 

 pintails in those regions. Unlike the pintails, which approach their 

 nesting ground with flocks just disintegrating, the mergansers, highly 

 gregarious in winter, complete the separation into pairs before they 

 approach their nesting grounds. 



