LIFE HISTORIES OF NORTH AMERICAiST DIVING BIRDS. 205 



more so. There are regular primary and secondary quills, as well as tail 

 feathers, but all of looser texture than afterwards. The head, throat, hind 

 neck, and the rest of the upper parts, are brownish black, the throat paler, 

 with many whitish filaments. The white lines from the bill to the eye are 

 distinct, but the secondary quills have no white at the end. The feathers at 

 the lower part of the tibia are dusky. 



Gradually these first feathers are substituted by others of a firmer texture. 

 Greenish-black quills, coverts, and tail feathers sprout forth ; the secondaries 

 terminally margined with pure white. The other parts are then invested with the 

 new feathers : The cheeks and throat now become white ; so that in this stage the 

 colouring resembles that of the adult in winter, whereas formerly it resembled 

 that of the bird in summer. The bill gradually elongates, assumes a darker 

 tint, and assumes some slight appearance of rugae; and the feet also become 

 darker. 



On the head, neck, and lower parts the feathers are again changed, and at 

 length, by the end of September, the bird has acquired its full winter plumage. 



In the first winter plumage, which is acquired as explained above, 

 young birds closely resemble the adults, so far as their plumage is 

 concerned, though the colors of the upper parts are duller and 

 paler, with more white or gray about the head and neck; but the 

 bills are very much smaller and entirely different in shape, more 

 pointed and lacking the grooves. A partial prenuptial molt occurs 

 in the spring, involving chiefly the head and neck, at which the nup- 

 tial plumage of the adult is assumed, but the bill still remains small 

 and only partially grooved. The postnuptial molt in August is com- 

 plete and young birds then assume the adult winter plumage, at an 

 age of 14 months. 



The adult winter plumage is similar to the first winter, but it is 

 darker and clearer above and the white throat is more distinctly out- 

 lined; the bill is about the same as in the spring adult, but the white 

 stripes in the grooves are less distinct. The adult has a partial pre- 

 nuptial molt in the spring, involving at least the head and neck 

 and a complete postnuptial molt. The time at which the prenuptial 

 molt takes place seems to be very variable; I have seen birds molt- 

 ing as early as December and as late as May, but probably both of 

 these extremes are unusual. The postnuptial molt seems to be ac- 

 complished in August and September. 



Food. — Audubon (1840) says: 



The food of the razor-billed auk consists of shrimps, various other marine 

 animals and small fishes, as well as roe. 



It obtains much of its food, such as small herring and surface 

 swimming Crustacea and other marine life, on or near the surface, 

 by swimming about on the ocean, often many miles from land, and 

 dipping its head under occasionally. But it must also be capable 

 of diving to great depths to obtain the various small mollusks on 

 which it feeds. 



