LIFE HISTOEIES OP NORTH AMEBICAN DIVING BIBDS. 69 



Plumages.— Th.& downy young is plainly colored; the short thick 

 down, with which it is covered, is "light seal brown" on the back, 

 " clove brown " on the sides, head, and neck, and " light drab " on the 

 breast and belly. A specimen in the American Museum, in New 

 York, collected in northeastern Siberia on September 16, 1901, shows 

 the change from the downy stage into the first winter plumage. This 

 is similar to the corresponding plumage of the common loon, but this 

 species can be recognized by its smaller size. In the first winter 

 plumage the under parts are pure white, the throat and sides of the 

 head are largely white, more or less streaked or mottled with dusky, 

 and the upper parts are dark blackish brown ; the characteristic fea- 

 ture of this plumage is that the feathers of the back are broadly 

 margined with light gray, giving it a scaly appearance. This 

 plumage is worn during the winter and part of the following spring; 

 when the bird is nearly a year old it begins to show progress toward 

 maturity by a partial molt. Macgillivray (1852) quotes Temminck's 

 description of this stage in the European bird, as follows : 



The young, when a year old, have the head and hind neck pale gray; the 

 throat and fore part of the neck white; but on the throat and sometimes on 

 the fore part of the neck, there appear some violet-black feathers mixed vs^ith 

 wh^te feathers ; the longitudinal streaked band of the sides of the neck begins 

 to form ; the streaks of the lower part of the neck equally appear, and some 

 black feathers without spots, appear on the back, rump, and sides. 



A complete, first, postnuptial molt takes place in the latter part of 

 the summer, producing a second winter plumage which is similar to 

 and probably indistinguishable from the adult winter plumage. 

 During the winter and spring further progress toward maturity is 

 made, producing a second nuptial plumage, of which Macgillivray 

 (1852) gives Temminck's description, as follows: 



At the age of 2 years the gray of the head and nape become deeper, and 

 assume a blackish tint, but only on the forehead ; the violet black of the throat 

 and forepart of the neck appear, but are variegated with some white feathers ; 

 the longitudinal bands are formed ; the feathers of the sides and of the upper 

 part of the back, the scapulars, and wing coverts assume the white bands and 

 spots ; the upper mandible becomes blackish, but its base, as well as a portion 

 of the lower mandible, are still of a gray color. 



Perhaps some individuals may require another year to reach the 

 full maturity of plumage, but probably most birds may be consid- 

 ered adult and acquire their full plumage at an age of 2 years. 

 Certainly during the third autumn, and probably during the second, 

 the adult winter plumage is assumed. This differs from the first 

 winter plumage in being uniformly dark blackish brown above, with- 

 out any lighter margins on the feathers of the back ; the throat and 

 lower half of the head are also purer white, without any dusky mark- 

 ings. The prenuptial molt involes practically all of the contour 

 feathers and the postnuptial molt is complete. 



