216 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



more or less evenly, over all the upper parts, including the sides of 

 the head, throat, and flanks. The spots are very distinct and include 

 either the tip or the whole of the filament. The bill is light colored, 

 and the feet may be light colored, as in the preceding type, or gray- 

 ish or nearly black. 



In the dusky type the ground colors are as described above, but 

 they are largely, and sometimes almost wholly, concealed on the 

 head, throat, back, wings, rump, and flanks with black or dusky fila- 

 ments. Often the forehead and lores are solid black. The bill in 

 this type has a subterminal black tip on one or both mandibles. The 

 feet show both light and dark phases without any correlation with 

 the other colors ; in fact, my darkest specimens have the lightest, feet. 

 A larger series would probably show a great variety of intermediates 

 between these three types and perhaps other types. 



The juvenal plumage is fully acquired before the young bird is 

 fully grown. It is entirely unlike that of the Caspian tern; the 

 upper parts are mainly white with a faint creamy tinge, the feathers 

 centrally tinged with light gray and with many narrow, dusky shaft- 

 streaks; the primaries and secondaries are "slate gray" or lighter, 

 edged with white and the tail feathers are chiefly dusky, with white 

 tips and white toward base of inner web; the underparts are pure 

 white ; the feathers of the crown have narrow, blackish shaft-streaks, 

 becoming broader on the nape and auriculars, forming a dusky collar. 

 This plumage is worn until about the last of August, when the post- 

 juvehal molt begins. The wings and tail are retained and will 

 serve to distinguish the young bird, but otherwise the first winter 

 plumage is the same as the adult, the contour feathers being molted 

 during the fall. A complete prenuptial molt occurs in March, at 

 which the adult nuptial plumage is apparently assumed, but perhaps 

 young birds do not acquire such a completely black pileum as adults. 



Adults have two complete molts, the prenuptial in March or 

 earlier and the postnuptial mainly in August and September, but 

 often prolonged into October or even November, the outer primaries 

 being molted last. The prenuptial molt, which produces the clear 

 black pileum, is usually but not always soon followed by a partial 

 molt on the head, which produces the white forehead, more or less 

 variable in extent. The full black pileum seems to be the courtship 

 plumage, and the white forehead the prevailing nesting plumage. 

 Only a very small percentage of incubating birds have the pileum 

 wholly black. In the adult winter plumage the forehead is white, the 

 crown mainly so, but streaked with black, and only the occipital crest 

 is mainly black. The tail is shorter and more tinged with gray than 

 in spring. 



Food. — The food of the royal tern consists almost wholly of small 

 fish, up to 4 inches in length, which it catches by plunging down into 



