16 LONGIPENNES: Long-winged Swimmers 



WESTERN GULL 



(49. Larus occidentalis) 23-25 in. 



Adult: Mantle very dark (deep neutral gray) ; otherwise wholly 

 white; seen from below the wing-tips (primaries) are extensively 

 black, with mirror in outer feather; secondaries white-tipped, 

 black of primaries extending inside these white tips to body. This 

 is distinctive. Neck dusky-streaked in winter. Bill stout, with 

 heavy angle. 



Juvenile: Dusky slate, buffy-edged above, gray-tipped below. 

 Bill black. Moult and wear constantly lighten the plumage 

 until adult stage is reached in the fourth spring. 



CALIFORNIA GULL 



(53. Larus calif ornicus) 18-21 in. 



Adult: Mantle light neutral gray (between the Western and 

 Herring) ; white mirrors of wing-tips large and conspicuous. 

 Bill with irregular and generally imperfect dark band near tip, 

 touching a dull red spot on lower mandible. Sides and back of 

 head and neck dusky-streaked in winter. 



Juvenile: Similar to Herring Gull, but darker; lighter than 

 Western (note smaller size); basal two-thirds of bill white, tip 

 black. 



Four years required to reach adult stage. 



HERRING GULL 



(51. Larus argentatus) 23-26 in. 



Adult: Mantle light bluish (when seen in direct light); black 

 area of wing-tip small; back edge of open wing white; legs flesh- 

 color. Winter: Head and neck heavily gray-streaked. 



Young: Light gray above, with dusky wing-tips (compare 

 Glaucous-wing); head streaky; mantle feathers gray-edged, 

 giving scale-marking; belly dark gray, throat lighter (Western 

 has light belly, dark throat). Plumage changes parallel those of 

 California and Western species. 



THAYER GULL See Appendix. 



(51-. Larus argentatus thayeri) 22-24 in. 



