184 BULLETIN 121, UNITED STATES NATIONAL MUSEUM. 



Young. — From Doctor Gross's (1912) extensive notes on the de- 

 velopment of the young bird, I shall make only a few quotations ; 

 he found that "the length of time spent by the young tropic-bird 

 in the nest extends over a period of 63 days, or about two months. 

 The time required for incubation, previously noted, is about 4 weeks, 

 making the complete period about 3 months. The adult birds remain 

 in the islands about 7 months, which affords them ample time to 

 rear two broods, but not more, during any one summer in Bermuda." 

 Of the food and care of the young, he says : 



The food of the young during the first 10 or 1.5 days consists of snails and 

 soft marine animals. In some cases it seemed to be merely the regurgitated 

 juices and semi-digested food from the gullet of the parent bird. AVhen the 

 birds are between 15 and 30 days old, more than 90 per cent of the food 

 consisted of squids, the remainder being made up of small minnows and some 

 unidentifiable material. During the latter half of the young bird's life fish 

 constitutes a large part of the food, although many squids, some of consid- 

 erable size, were present in nearly every specimen examined. The food is 

 transferred from a pouch-like gullet of the adult to that of the young by process 

 of regurgitation. This transfer of food is accompanied by a series of gulps, 

 strains, and wrigglings of the head and neck on the part of both birds. 



The adult birds remain very closely with the young during the first ten 

 days. The little fellow is usually tucked in under the feathers of the adult 

 and frequently sleeps with its head projecting through the feathers, just as a 

 little chicken does when it is brooded by the old hen. When the little creature 

 became restless the old bird uttered a series of low guttural sounds, which, 

 I assume, were intended as disapproval. 



The young birds are unable to fly well when they leave the nest although 

 the wings have been exercised very frequently for some weeks. Those which 

 I observed leaped into the water from the edge of the nest and then made their 

 way out to sea by paddling. The young birds flopped their wings vigorously, 

 as if attempting to fly, but were never able to rise from the water during the 

 time I observed them. Such an event created considerable excitement among 

 the adult tropic-birds, which assembled to witness the affair. The young bird 

 while thus floating on the water may be fed by the adults, but more probably 

 depends on its stored fat until it gains enough strength to fly and fish for itself. 



Plumages. — Doctor Gross (1912) describes the downy young, as 

 follows: "At the time of hatching, the 3'oung tropic-bird is to all 

 appearances a ball of fluffy down with its dark colored beak and 

 black feet standing out in marked contrast to the background of 

 white. It is only the region about the beak, the underparts, and the 

 middle of the back which are pure white, for the remainder of the 

 plumage, especially the crown, sides of the back and regions of the 

 wings, has a decided tinge of dull gray." Not much change takes 

 place, except an increase in size, until the 16th day, when the first 

 feathers appear in the scapuhar region ; " by the end of the 35th day 

 the wing feathers, including the coverts, are well expanded and 

 now form, with the scapulars, a continuous band " and " by the 40th 

 day the young is completely feathered, but dowm still shows about 



