140 ANNALS OF SCOTTISH NATURAL HISTORY 



In winter the whole of the head and upper neck is mouse 

 grey ; the chin, throat, and lower neck white ; the lores, region 

 round the eyes and sides of the neck mouse grey intermixed 

 in about equal proportions with white. 



The feathers on the back and wings and those forming 

 the upper tail coverts are dark blackish grey with two in- 

 distinct lighter grey spots on each feather corresponding to 

 the white spots seen in the summer feathers of the same 

 regions (Figs, i and 3). 



The tail feathers are black with white tips (Fig. 7), and 

 the wing feathers (primaries and secondaries) black. The 

 belly pearly white, a dark mouse grey band of feathers 

 forming a narrow V-shaped band across the vent. 



The young birds in their first winter plumage are 

 distinguished from the adult birds by having a broad light 

 grey margin to each feather on the back, rump, and tail 

 coverts, and an entire absence of light spots on these feathers. 



The winter plumage of the adults appears to be complete 

 but for a very short time, and the bird rapidly passes on 

 through the following stages until the full summer plumage 

 is completed. The first signs of change take place either 

 on the back or on the throat, or on both places simultaneously, 

 about December, and by the end of May the bird has 

 assumed its full summer dress, which is as follows. The 

 whole of the head, throat, and neck is deep glossy black 

 with purple and green reflections ; on each side of the neck 

 and across the throat are lateral lines of white forming 

 transverse bars. The whole of the upper part of the body 

 is rich glossy black, each feather with two large white 

 roundish spots towards the tips ; the tail and primaries 

 black, belly pearly white, and the narrow band across the 

 vent black, each feather carrying a white spot towards the 

 tip. 



The time of year at which the summer feathers first 

 make their appearance naturally varies in different individuals, 

 but, generally speaking, so far as my observations go, the first 

 new feathers begin to appear about the beginning of 

 December, and from then onwards to May there is a gradual 

 and continuous moult. At what time of the year precisely 

 the Great Northern Divers cast their primaries is at present 



