Lifc-Historics of the Booby and the Man-o'-JVar Bird. 151 



dense as in Siila leueogastra. grows from all parts of the body except the 

 inner surface of the legs, the gnlar pouch, and the throat. On the inter- 

 scapular region, however, the natal down is not given much opportunity for 

 growth, the black feathers of the second or juvenile plumage appearing in 

 the pteryla hiDiicralis and pteryla dorsalis immediately after the down of 

 these tracts has pushed through the skin, if indeed in some cases they 

 do not emerge without being preceded by down. The development of these 

 interscapular feathers is remarkable, and before there is any evidence of the 

 remiges and rectrices they cover the back like a mantle, as may be seen in 

 the photographs of young birds in the nest. 



It is surprising that in a bird famed for its power in flight, and possessed 

 of exceptional length of wing and tail, the feathers of these parts, contrary 

 to the general rule, should not take the lead in development. Comparison 

 of the young of Fregata and of Sula leueogastra, for example, in which 

 wing- feathers of the second plumage are just evident, shows that while the 

 former has the whole interscapular region black, some of the feathers being 

 3.75 inches in length, Sula shows as yet no signs of second plumage in this 

 region. 



Not only are the wing feathers in Fregata late in appearing, but the 

 secondaries precede the primaries, the former averaging 2 inches in length, 

 with the greater and median coverts showing, when the latter are just ob- 

 servable. At this time the feathers of the uropygium and tail become evi- 

 dent; the outer tail feathers appear considerably in advance of the others, 

 and give us a hint of their subsequent extreme length ; but the order of 

 growth of the feathers of the wing does not suggest that exceptional develop- 

 ment of the feathers of this member which so distinguishes Fregata. 



Specimens are lacking in which to trace the development of the plumage 

 in detail. The largest bird in the series shows, however, further departure 

 from the usual order in feather growth in the young bird, by having the 

 second plumage of the head appear wdiile the rectrices and remiges are still 

 small and the natal down still remains on the lower back, the crural and 

 femoral tracts, a large part of the ventral tracts, and at the base of the 

 secondary and primary wing-coverts. 



