194 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



black and the rest of the upper parts are thickly but indistinctly 

 mottled with " fuscous black " ; the under parts are immaculate. The 

 young- bird grows rapidly and the juvenal plumage soon appears; 

 the down is retained on the tips of the feathers until the bird is 

 nearly fully grown, wearing away or dropping off gradually, until 

 the last of it finally disappears from the head, neck, flanks, and rump. 

 In this plumage the crown and the sides of the head and neck are 

 clouded or washed with different shades of " mouse gray " ; the throat 

 and under parts are pure white, and the upper parts are mainly 

 dusky or " fuscous." The feathers on the anterior gra.j portions are 

 narrowly edged with pale buff; these edgings increase in breadth, 

 extent, and intensity of color on the back, wing-coverts, and scapu- 

 lars, becoming " clay color " or " tawny olive ■' on the latter feathers. 

 The wings and tail are as described in the next plumage. The first 

 winter plumage is but a continuation of the juvenal; the buffy edg- 

 ings described above fade out or wear away during August and Sep- 

 tember, leaving the pluma^ge of the upper parts more uniform 

 " fuscous " or pale grayish brown. The primaries are dull black 

 without the conspicuous white tips of the adult wing, but the sec- 

 ondaries are white, producing the large white wing patch so charac- 

 teristic of the species. The tail is white, broadly tipped with black, 

 especially on the central rectrices ; the bill is wholly dusky. A par- 

 tial prenuptial molt takes place in the spring, at which the gray 

 hood and black collar of the nuptial plumage are partially assumed, 

 the amount of white remaining on the throat and head varying 

 greatly in different individuals. At the next complete molt, the 

 lirst postnuptial, in August and September, the adult winter plum- 

 age is assumed, and young birds become indistinguishable from 

 adults. 



Adults have a partial prenuptial molt, at which the gray hood 

 and black collar are acquired before May, and a complete postnup- 

 tial molt in August and September. The latter is very variable in 

 time and often very late ; it is often completed in August and some- 

 times does not begin until nearly the middle of September ; the black 

 collar is the last to go. The winter plumage is similar to the spring 

 dress except that the head is white, heavily clouded with dusky on 

 the occiput, and hind neck; the bill becomes black 



Food. — On their breeding grounds, the Sabine's gulls feed in the 

 small ponds and pools on the tundra, where they find small fishes, 

 aquatic worms, insects, and larvae, and small crustaceans. They 

 hover over the pools, daintily picking up their food from the surface, 

 but apparently never diving for it. Mr. Hersey says in his notes : 



These gulls spend much time, when the tide is out, feeding about the mud 

 flats, where they run about like shore birds ; so much do they resemble them 



