82 BULLETIN U3, UNITED STATES NATIONAL MUSEUM. 



spotted, or variegated; still other new feathers are reproductions 

 of those seen in the first year plumage. There is great individual 

 variation in the amount of "slate color " assumed during this year, 

 but probably it increases as the season advances. The wings are 

 not strikingly different from those of the first year. There are 

 more conspicuous white tips on the tertials, secondaries, and inner 

 primaries, and the coverts contain more " slate color." The under- 

 parts are largely or wholly white, increasingly so toward spring. 

 The bill is lighter near the base and has a light tip. 



The third-year plumage shows about the same stage of advance 

 toward maturity as the second year in the herring gull. The man- 

 tle is now more than half " blackish slate " ; the wing-coverts, both 

 greater and lesser, are still mottled with dusky and white, but there 

 are many adult feathers among the mottled ones; the secondaries 

 and tertials are as in the adult ; the primaries are black, tipped with 

 white, and the outer primary now has a broad subterminal white 

 space an inch and a half long. The tail is white, more or less varie- 

 gated with dusky near the tip. The underparts are pure white, and 

 so is the head, except for a few duslry streaks on the hind neck, 

 which disappear before spring. The bill still shows traces of dusky. 



At the next postnuptial molt, when a little over 3 years old, 

 some birds probably assume the adult plumage, with the pure white 

 tail, the complete dark mantle and the broad white tips of the 

 primaries, which in the first primary measures 2^ inches. But 

 probably a large majority of the birds still retain traces of imma- 

 turity in the primaries and the tail, which do not reach their full 

 perfection until a year later; and apparently the white in the 

 primaries increases a little at each succeeding molt until the maxi- 

 mum is reached. 



Both adults and young have a complete postnuptial molt in 

 August and September, and an incomplete prenuptial molt during 

 the winter and early spring. The adult winter plumage differs from 

 the nuptial only in having a few faint, narrow streaks of dusky on 

 the hind neck, which are more conspicuous in the younger birds and 

 less so in the older ones. 



Food. — The great black-backed gull is a voracious feeder, omnivor- 

 ous, and not at all fastidious. On or about its breeding grounds it 

 feeds largely on the eggs of other birds, particularly sea birds, when 

 it can find them unprotected, or upon the small young of such birds 

 as are unable to defend them. Mr, M. A. Frazar (1887) describes 

 its method of capturing young eiders as follows : 



Two or tliree gulls will hover over a brood in the water, which, of course, 

 confuses tlie mother duck and scatters the brood in all directions. Then, by 

 following the ducklings after each dive, they would soon tire them out, and 

 a skillfully directed blow at the base of the skull, which seldom missed its 



