^^\^^-^] Gross, The Yellow-billed Tropic-bird. 65 



this stage of the nesthng. The beak becomes Hghter in color, but 

 the skin in front of the eyes (lores) and at the base of the upper 

 mandible (front) remains jet black. The tarsus is bluish, but the 

 toes and webs are black, as in adult birds. The down on the breast 

 is much shorter and denser than elsewhere, thus forming a firm 

 mat, which protects the tender body from the sharp stones or 

 rough surface of the rock on which the bird is usually obliged to 

 rest. A characteristic pose of the bird at this age is one with its 

 body and head outstretched on the bottom of the nest (Plate VIII, 

 fig. 14). This position was frequently assumed whether the bird 

 was awake or asleep. The young showed no evidence of fear during 

 the first two weeks, for when I approached the nest, they did not 

 seem to be afraid of me. Often when I placed my hand near them 

 they would pick at my fingers as if testing some new and strange 

 kind of food. The young birds which I visited daily never devel- 

 oped an instinct of fear; but, on the contrary, as they grew older 

 they seemed to be pleased to have me make a call during the long 

 hours when they were left alone. 



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. 



At the end of the 16th day were seen the first feathers. They 

 made their appearance on the scapular region of the spinal tract 

 (Plate VIII, fig. 14). By separating the down, the tips of the bluish 

 colored sheaths of the feathers may be seen projecting through the 

 dark skin. The feathers grow rapidly, soon lose their sheaths, 

 and by the 20th day are well expanded, producing a conspicuous 

 patch of black-and-white barred feathers (Plate IX, fig. 15). By 

 this time the sheaths of the feathers of the breast, the primaries, 

 secondaries, and tail feathers appear, but they do not show 

 through the coat of down until several days later. During the 

 first twenty days the bill assumes more and more the shape and 

 proportions of that of the adult. Its dark bluish color changes 

 to a white or flesh color, but the tip of the mandibles retains a 



