86 BULLETIN 130, UNITED STATES NATIONAL MUSEUM 



of the contour plumage and producing a first-eclipse plumage, 

 which Mr. Millais (1913) describes as follows: 



The feathers of the whole head and neck are shed and replaced in a few 

 days by a plumage resembling, but somewhat darker than, that of the juve- 

 nile ; eye-stripe dull white with blackish markings ; crown, upper parts of 

 cheeks, and back of head and neck black ; rest of cheeks and throat grey-brown ; 

 mantle and scapulars blackish-brown. In a bird killed on July 6 at 

 Fitfulhead, Shetland, which has effected the above change, the wings, 

 tail, and nearly all the lower parts are still in juvenile plumage, much worn 

 and faded ; the white-and-bufi! shield on the upper chest and its sides is re- 

 placed by a new set of feathers — white with brown-black bars, and edged with 

 reddish-brown ; the long faded scapulars are still unshed and sandy-yellow 

 as well as the primaries. 



During the fall this first eclipse plumage is replaced by the second 

 winter jDlumage, which is not completed until November. This re- 

 sembles the adult plumage in a general way, but it can be easily recog- 

 nized by its imperfections. The center of the crown is mottled with 

 grayish brown ; the green areas on the head are paler and more re- 

 stricted ; the white of the back is broken by scattering dusky feathers ; 

 the lesser wing coverts are brownish and the greater wing coverts 

 are edged with dusky, both of which are pure white in adults; 

 the curving tertials are less developed and edged with dusky, 

 instead of being pure white; and the under parts, which are clear, 

 deep black in adults, are now dull, brownish black, with the anterior 

 border broken and mottled. This plumage is worn without much 

 change until the second eclipse plumage appears the next summer. 

 This is less complete than the adult eclipse plumage and can be dis- 

 tinguished from the first eclipse by the wings. The fall molt out 

 of this plumage produces the adult winter plumage, characterized 

 by the pure white back, wing coverts, and curved tertials. The 

 young bird thus becomes adult at an age of 28 or 30 months. A few 

 birds, otherwise adult, retain signs of immaturity during their third 

 winter, chiefly in the form of dusky-edged feathers in the cream- 

 colored breast. 



The adult male has one complete molt each year, reaching its 

 climax in August; the plumage of the head and neck is all molted 

 twice to produce and to replace the eclipse plumage, that of the 

 breast and back partially twice and the rest of the plumage only 

 once. The eclipse plumage is very striking and very interesting, as 

 it is beautifully^ adapted to conceal the brilliant colors of the male 

 during the time when he is quite incapable of flight and obliged to seek 

 refuge by swimming and diving on the open sea. The bright colors 

 of the head and neck are completely replaced by blacks and browns 

 in mottled effect, a complete molt of these parts beginning in July; 

 the white back is screened by a new growth of grayish white feathers, 

 broadly tipped with dusky; and the breast is completely concealed 



