64 Gross, The Yellow-billed Tropic-bird. [S: 



The amount of food regurgitated by No. 4 and No. 5 may seem 

 excessive, since it equals about ^ to | of the total weight of the bird, 

 yet such quantities of food in one gullet were not unusual. Since 

 the birds ordinarily are fed only during the early morning hours, 

 one should expect to find large quantities of food dehvered at this 

 single meal. The squids, which, as we have said, make up the 

 largest part of the food of the young, as they also do that of the 

 adult birds, are probably captured out at sea, for I saw very few 

 squids when making collections of marine animals about the islands. 

 Thousands of squids are eaten each day by these birds, so there 

 must be an enormous quantity of them in the vicinity of their 

 feeding grounds. 



The young birds become very fat and heavy during the last 

 10 or 15 days of their life in the nest, and in all cases under observa- 

 tion they weighed more at this stage than the heaviest of the adult 

 birds. This storing up of substance which may later serve as 

 food prepares them to withstand the strenuous ordeal required of 

 them upon leaving the nest. 



x\t the time of hatching, the young Tropic-bird is to all appear- 

 ances a ball of fluffy down with its dark colored beak and black 

 feet standing out in marked contrast to the background of white 

 (Plate VII, fig. 11). It is only the region about the beak, the under- 

 parts, and the middle of the back which are pure white, for the 

 remainder of the plumage, especially the crown, sides of the back, 

 and region of the wings has a decided tinge of dull gray. 



The eyes of the nestling remain closed for one or two days, but 

 the young birds are very active and responsive from the very be- 

 ginning. A mere touch, or even the click of the camera, is enough 

 to incite the creature to extend its neck and open its beak in eager 

 anticipation of some lucious snail or other appetizing morsel of 

 food. In taking pictures of some of these birds, it was necessary 

 to click the shutter several times before attempting the final 

 exposure, in order to avoid the gaping attitude. 



At the end of the fourth day (Plate VII, fig. 12) the birds have 

 their eyes fully opened, but they blink incessantly when brought 

 out to the open light. 



During the first ten days of life in the nest the chief changes 

 which occur are concerned with size, for no feathers appear during 



