14S Papers from the Marine Biological Laboratory at Tortugas. 



DEVELOPMENT OF PLUiMAGE. 



At birth the young booby seems to be featherless, but closer examina- 

 tion shows that the white natal down is appearing on all the dorsal pteryla; 

 and upon the posterior margin of the wings, including the alula. The 

 abdominal pterylje show as yet no evidences of feather growth. The down 

 plumage grows rapidly and, when developed, almost entirely covers the 

 chick's body — the gular pouch, orbital and loral regions, and inner margin 

 of the humerus being the only apteriae. 



The second, juvenile,^ or nestling plumage of which the down is merely 

 the apical portion,- follows the down by continuous growth, the down being 

 a white filamentous fringe to the stronger, brownish feather of the second 

 plumage. This plumage may be first seen in the pterylcs alaris, the primaries 

 appearing first, to be quickly followed by the secondaries, tertiaries, and 

 feathers of the alula. At almost the same time the rectrices become evident : 

 soon after the uropygial feathers come. Greater, median, and less upper 

 wing-coverts and tail-coverts emerge, before feathers of the second plumage 

 appear upon the body proper, except those growing from the pteryla uropygii. 



In the next oldest specimen the juvenile plumage of the breast and ab- 

 domen approaches full development and was evidently the first to grow 

 upon the body tracts, except as noted above. On the back the juvenal 

 plumage, although well grown on the pteryla himieralis, is but just appear- 

 ing on the anterior portion of the pteryla spinalis, although posteriorly the 

 feathers are larger. The crural and femoral tracts, the outer margins of 

 the manus, a strip at the base of the secondaries, and the whole head and 

 neck are still clad in down. 



In the succeeding specimen, the second or juvenal plumage is essen- 

 tially complete, except upon the foreneck, where it is just emerging. This 

 bird is almost uniform grayish-brown above; the upper tail-coverts are 

 slightly browner; the exposed portion of the remiges and rectrices show a 

 somewhat frosted eflfect ; the primaries are decidedly blackish ; the lower 

 breast and abdomen are grayer than the dorsal plumage : the upper breast 

 (with which the throat feathers would apparently agree) is decidedly browner. 

 This is the flight plumage. \Mien it gives way to the succeeding plumage 

 does not appear to be known. 



MAN-O'-WAR BIRD. 

 Descriptions of the nesting habits of the man-o'-war bird (Fregata 

 aquila) are based chiefly on studies made in the Pacific. Bryant,^ whose de- 

 scription of the nesting habits of the booby has already been cited, gives us 

 apparently the only account of the breeding of this species as it occurs in 



'Dwight, Annals N. Y. Acad. Sci., xiii, pp. 73-360. 

 ' Jones, Lab. Bull., No. 13, Oberlin College, pp. 1-18. 

 ' Proc. Best. Soc. Nat. Hist., vn, 1859, p. 126. 



