138 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



does considerable damage on its breeding grounds by destroying the 

 eggs of other species associated with it. I have seen a party of ring- 

 billed gulls break and suck nearly every egg in a colony of double- 

 crested cormorants when the latter had been kept off their nests for 

 an hour or two ; but I doubt if they would have dared to molest them 

 if the cormorants had not been driven away by our presence. It 

 occasionally robs the nests of the avocet, but it does not seem to molest 

 the nests of the common tern, with which it is intimately associated ; 

 and I have never known of its disturbing any of the ducks which nest 

 on its breeding grounds. Probably the terns are able to defend their 

 eggs and the duck's nests are too well hidden. 



Behavior. — The flight of the ring-billed gull is not markedly dif- 

 ferent from that of the other larger gulls; it is light and graceful 

 as well as strong and long sustained. It can poise stationary in the 

 air when facing a good breeze without moving its wings except to 

 adjust them to the changing air currents, and can even sail along 

 against the wind in the same manner. It is often so poised while 

 looking for food on the water, but if the wind conditions are not 

 favorable it is obliged to hover. When food is discovered it either 

 plunges straight downward or floats down more slowly in a spiral 

 curve, and picks up its food without wetting its plumage. When 

 alighting on the water its wings are held high above it as it drops 

 lightly down with dangling feet. It swims gracefully and buoyantly, 

 sitting lightly on the surface. It rises neatly from the water. It has no 

 very distinctive field marks and closely resembles several other species, 

 but it is somewhat smaller than the California gull and very much 

 smaller than the herring gull ; it also has a lighter gray mantle and 

 less white in its black wing tips. The black ring in its bill is not 

 always in evidence and can not be seen at any distance. 



Its notes are similar to those of other closely related gulls, but 

 they are on a higher key than those of the two larger species referred 

 to above. When alarmed or when its breeding grounds are invaded 

 it utters a shrill, piercing note of protest — kree, kreeee — like the cry 

 of a hawk, but when its excitement has somewhat subsided this note 

 is softened and modified and the subdued kow, koio koto notes are 

 often heard from a flock of gulls floating overhead. It is often 

 noisy while feeding, while a cloud of hovering gulls show their ex- 

 citement by a chorus of loud squealing notes and shrill screams. 

 While pursuing its ordinary vocations it is usually silent, except for 

 an occasional soft, mellow koick. 



The ring-billed gull is a highly gregarious species, both on its 

 breeding grounds and in its winter resorts, congregating in large 

 flocks of its own species and associating with a variety of other 

 species, with all of whom it seems to live in perfect harmony. Ex- 

 cept for its cowardly, egg-robbing habits, it is a gentle and harmless 



