10 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



plumage is practically the same as the adult in many individuals; 

 the upper parts are uniformly dark, except that the white and golden 

 collar encircles the neck; the two central tail feathers become much 

 elongated ; the under parts are mainly white, with more or less dusky 

 mottling on the neck, upper breast, and sides; and the lower abdo- 

 men and under tail-coverts become dusky, but in some individuals 

 these are veiled or mixed, more or less, with wliite. There is great 

 individual variation in the amount and extent of the dusky mottling 

 in the white areas, in the amount of v/hite in the dark under tail- 

 coverts, and in the extent of the white and golden collar at this age ; 

 but as there is not much further progress to be made toward ma- 

 turity, the third-year birds may be considered practically adult. The 

 fully adult plumage, without much mottling in either the light or 

 the dark areas and with the fully developed golden collar, increases 

 in perfection with subsequent molts; the clear dark crissum and 

 under tail-coverts are assumed when the bird is about 3 years old, 

 though vigorous birds may acquire them before that time. I have 

 never seen a specimen in which the neck, breast, and shoulders were 

 entirely free from dusky mottling. 



Birds in the dark phase of plumage, apparently, undergo the same 

 sequence of plumages to maturity, though I have not been able to 

 trace the changes so satisfactorily. In the first-year plumage they 

 are much darker than in the light phase, with the white barring much 

 more restricted. During the second year they are almost wholly 

 dark with some whitish and rufous edgings above and below. The 

 third-year and adult plumages are hardly distinguishable, both being 

 uniformly dark, but some specimens show an indication of the golden 

 collar, more or less distinctly, which are probably the older birds. 

 The molt of the contour feathers in both phases occurs in summer, 

 from June to October, and the flight feathers are molted in October, 

 beginning with the inner primaries and the central rectrices. The 

 prenuptial molts of both young birds and adults are probably in- 

 complete, but specimens of winter and early spring birds are too 

 scarce to demonstrate it. 



Food. — The predatory feeding habits of the jaegers are familiar 

 to everyone who has studied the habits of our sea birds during the 

 latter part of summer and fall. They are the notorious pirates and 

 freebooters among sea birds, the highwaymen that persecute their 

 neighbors on the fishing grounds and make them "stand and de- 

 liver." It is no uncommon sight on the New England coast to see 

 one or two of these dusky robbers darting through a flock of hover- 

 ing terns or small gulls, or giving chase to the lucky one that has 

 caught a fish, following every twist and turn in its hurrying flight 



