RHINOCEROS AUKLET 107 



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 molt 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. Willett 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 and 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 

 to the feeding grounds and back again, Whatever their route, it is certain 



