^°'i9if ^'"^J Gross, The Yelloiv-billed Tropic-bird. 51 



The greater part of the dry land of the islands consists of a 

 Hniestone made up of the wind-blown fragments of shells and 

 corals firmly cemented together. This rock is easily eroded, but 

 when a fresh surface is exposed to the action of the weather for 

 some time, it becomes hard and resistant. The shores of many 

 of the islands are precipitous or overhanging cliffs, which have 

 been honey-combed bj^ the incessant action of the surf or the 

 solvent effect of rains. It is among the recesses and caves of 

 these cliffs that the Tropic-birds of Bermuda nest and rear their 

 young. 



The Yellow -billed Tropic-bird, Phaethon americanus, locally 

 known as the Boatswain Bird, or the Long-tail, is the only one of 

 the two species of Tropic-birds of the West Indies which visit 

 the Bermudas. These birds are tern-like in appearance and manner 

 of flight, although belonging to the order Steganopodes. The 

 gular pouch, which is characteristic of the Steganopodes, is entirely 

 feathered and much reduced in size in the Tropic-bird, but it never- 

 theless functions as a pouch in the process of feeding. 



The plumage of the adult Tropic-bird is a satiny white with the 

 following prominent black areas: a spot in front of, and slightly 

 below, the eye, which is continued backward as a narrow band 

 through the ocular region; a large oblique band on the lesser wing 

 coverts and extending thence on to the scapulars and inner second- 

 aries; patches on the outer shafts of 5 or 6 of the primaries; and 

 stripes on the flanks. The black markings on the primaries and 

 secondaries are very conspicuous when the bird is seen in flight. 

 The iris is dark brown, the tarsus bluish, and the toes and webs 

 jet black. The bill varies from pale yellow to bright orange-red, 

 depending on the age of the bird. The tail is extended into two 

 very long central feathers, which are of variable length and color. 

 In adult birds these feathers have a marked tinge of russet brown 

 or dull salmon, but no individuals were seen in which there was a 

 distinctly reddish color, such as is frequently described. In a very 

 few there was a roseate tinge to the plumage, which was accentu- 

 ated on the feathers of the neck and breast. There is no consis- 

 tent variation in color or measurements which can be correlated 

 with sex. The measurements of eight specimens are as follows: 



