LIFE HISTORIES OF NORTH AMERICAN DIVING BIRDS. 107 
gone by December, leaving the bird with pure white under parts; 
the white plumes on the sides of the head sometimes begin to appear 
in December, but sometimes not until March. Early in the spring 
the horn begins to grow on the upper side and the accessory piece 
on the under side of the bill; the white plumes become quite fully 
developed, and the young bird in its first nuptial plumage becomes 
practically indistinguishable from the adult. 
The adult has a complete moult during the late summer and early 
fall, at which the horn and lower accessory piece are shed from the 
bill and the adult winter plumage is acquired. This is similar to 
the adult nuptial plumage, except that the white head plumes are 
shorter and not so fully developed. I believe that these plumes are 
seldom, if ever, wholly lacking in winter adults. The bill of the 
adult in winter is much larger than that of the young bird, and 
there is usually a soft knob indicating where the horn has been. 
Food.—From the examination of 10 specimens killed off the Cali- 
fornia coast in winter, Dr. Joseph Grinnell (1899) found that— 
The food consisted entirely of a small yellow crustacean, which filled their 
gullets. We saw none of these anywhere near the surface of the water, so 
they must have been caught by diving to a considerable depth. 
Mr. C. B. Linton (1908) states that he and Mr. Willet secured 
several specimens off the California coast in November and Decem- 
ber, and that the “ craws examined contained freshly caught sardines 
3 to 4 inches long.” The stomach contents consisted of the “meat 
and bones of small fish.” 
Professor Heath (1915) says: 
The food of the rhinoceros auklet, whether young or old, consists wholly of 
sand launces, according to the reports of the natives, and an examination of a 
few stomachs supports their claim. 
He says further, referring to their feeding habits and their long 
daily flights in search of food: 
On rare occasions they were reported by fishermen operating upward of a 
mile from shore, but in the great majority of cases they sought more open 
water at some distance from land, such as the channel between Forrester and 
Dall Island. A marked exception to this rule may be witnessed throughout the 
summer on the eastern side of Dall Island in Kaigani and Tlivak Straits. Here 
the tide sets strongly, especially in the region of the narrows of Skookum Chuck 
at the north end of Dall Island, and with an abundance of floating organisms 
serving as fish food the conditions are most favorable not only for auklets 
but for several other water birds, such as gulls, ancient and marbled murrelets, 
pigeon guillemots, and cormorants. In order to reach this locality the rhinoceros 
auklet makes a round trip journey of at least 60 miles if it flies directly over 
Dall Island. This, however, is doubtful, as flocks have been seen at nightfall 
coming down the straits on the east side of Dall, and after rounding the 
southern end their course is doubtless a bee line for home. Under such cir- 
cumstances it requires a completed journey of fully 120 miles to bring them 
