rAuk 



70 Gkoss, The Yellow-hilled Tropic-hird. [j^n 



Plate IX. 



Fig. 15. Young Tropic-bird. Age 20 days; length 22.9 cm.; extent 

 32.5 cm.; wing 5.5 cm.; bill 2.4 cm.; foot 5.4 cm.; weight 232 grams. 

 This view was taken from a position above the bird in order to show the 

 expanded, barred tips of the first feathers in the scapular region. The 

 sheaths of the feathers of the wings, tail, interscapular region, and breast 

 are appearing through the skin. The skin about the base of the mandibles 

 and lores is dotted with the papilla? of developing feathers. 



Fig. 16. Young Tropic-bird. Age 24 days; length 24.3 cm.; tail 1.0 cm.; 

 extent 37.6 cm.; wing 6.9 cm.; bill 2.9 cm.; foot 5.6 cm.; weight 250 

 grams. The quill feathers have pierced or are piercing nearly every part 

 of the body where such feathers occur. The quills of the primaries and 

 secondaries are so heavily charged with blood that the bird is unable to 

 support its wings continuously, but allows them to rest on the floor of the 

 nest. The tips of the secondaries ai'e expanded and these feathers now 

 range from 2 cm. to 3 cm. in length. The prinaries are not as far advanced 

 as the secondaries. The tail feathers are much slower in their growth 

 than the v/ing feathers, but at this stage the entire 12 are present. The 

 two feathers destined to become the long tail feathers of the adult are 

 already much longer than the others. These central feathers are 1 cm. 

 in length, but with the tufted downy tips they measure 2.2 cm. The 

 feathers of the breast have expanded tips, but they do not as yet show 

 through the thick mass of down. 



Plate X. 



Fig. 17. Young Tropic-bird. Age about 34 days; length 29.8 cm.; 

 tail 3.8 cm.; extent 57.8 cm ; wing 11.5 cm.; bill 3.7 cm.; foot 6.0 cm.; 

 weight 357 grams. The bird at this age, with its alternate areas of down 

 and feathers, and its queer actions, presents a very ungainly and awkward 

 appearance. The feathers in the region of the wings have undergone 

 marked development and now appear as a continuous area of barred plum- 

 age. The primaries are white excepting the outer five, which have a black 

 spot or patch in the vein near the tips of the feathers. The secondaries 

 are white excepting the innermost 3 or 4, which are barred with black. 

 The wing coverts are also barred with black. The feathers of the middle 

 of the back are appearing, but are hidden from view by the feathers of the 

 scapular region. The tips of the secondaries and coverts extend back 

 nearly to the region of the oil gland, which is well developed at this stage. 

 The shafts of the tail feathers are black, and each feather shows a black 

 spot near the tip of the vane. The pure white feathers of the breast are 

 well expanded, and replace the mat of down, which has gradually frayed 

 away giving place to this more substantial protective covering. The 

 feathers of the flanks are striped and barred with black as in the adults. 



