114 BULLETIN 107, UNITED STATES NATIONAL MUSEUM. 



There is apparently a complete molt in August and September and 

 probably a partial prenuptial molt during the latter part of winter. 

 Food. — Cassin's auklets feed well out at sea, where they spend 

 most of their time, singly, in pairs, or in small flocks ; some of their 

 food is obtained on or near the surface, but they must dive to con- 

 siderable depths for some of it. Mr. F. Stephens ( 1893) » found 

 that — 



The stomachs of some examined contained shrimps. For some it simply 

 dipped its head under water, for others it dove a few inches. 



Mr. Emerson noted marine insects among its food and Professor 

 Heath (1915) says: 



The food of the young, and of the adults as well, was found to consist of 

 copepods and an undetermined species of shrimp or amphipod. 



Probably a great variety of small marine animals are included in 

 its diet. 



Behavior. — The flight of Cassin's auklet is swift, steady, and 

 direct; when flying over the water it flies low, just clearing the 

 waves, and even over the land its flight is low.^ Mr. Bryant (1888) 

 writes that — 



One, attracted by a lantern carried by Mr. Emerson, flew with characteristic 

 swiftness directly at it, but missed and struck against the side of a house, 

 where it was picked up stunned. Auks have struck persons walking without 

 a light, but always below the shoulders. 



Eef erring to the clumsiness of this species, Mr. Dawson (1911) 

 writes : 



The Cassin auklet seems incapable of controlling the force of its flight, and 

 the wonder is that the birds are not every one of them dashed to pieces in a 

 single night. In this respect they remind one of nothing else so much as beetles 

 or moths, which come hurtling into the region of candlelight, crash against the 

 candlestick, and without an instant's pause begin an animated search afoot. 

 This crash-and-crawl method seems not exceptional but characteristic in the 

 auklet. It was especially noticeable in the paved area just outside our work- 

 room door. Crash ! announced the arrival of another food-laden messenger 

 from the unknown deeps. The impact of collision with the building invariably 

 stunned the bird so that it fell to the ground, but it immediately began a, 

 frantic search, and as likely as not, before you could lay hands on it, disap- 

 peared in a crack under the doorstep. 



Mr. Stephens (1893) says: 



They dive well, and can stay under water two minutes or more. They swim 

 fast for so small a bird. On being chased with a boat they often preferred 

 diving to flight, and then their speed was greater than when swimming, requir- 

 ing sharp rowing to get within shooting distance. They often changed their 

 course while under water, and several times baffled me in that way. They are 

 so small that one can not see them very far in rough water. Wounded birds 

 observed at short distances were observed to use their wings in diving, and 

 probably in all cases diving is simply a flight under water. 



