56 



KEY TO GULLS (Cont.) 



28' Wing <420 mm; one white spot in outer primaries; Mexico to British 



Columbia. 29 



29 Legs and feet bright yellow; Gulf of California and Salton Sea. 



YELLOW-FOOTED WESTERN GULL, adult 



29' Legs and feet pink; Pacific Coast of Baja California north to 



British Columbia. WESTERN GULL, adult 



NOTE: These two forms are usually indistinguishable without the 

 leg color. 



30 Bill plain yellow-green, sometimes with dusky subterminal mottling 

 or dusky tip; outermost two primaries with large white spots near 



the tips; culmen usually <37 mm; eye dark. MEW GULL, adult 



30' Lower mandible with red and/or black at gonydeal angle; culmen 



usually >37 mm. 31 



31 Bill banded (both mandibles) with black (as in Fig. 15), no red at 

 gonydeal angle; gray of back and wings very pale; eye and legs 



yellow. RING-BILLED GULL, adult 



31' Lower mandible with red spot at angle. 32 



32 Bill almost always with both black band and red at gonys or rarely 

 with only red spot; eye dark brown; legs bluish to greenish; gray of 

 back and wings relatively dark. CALIFORNIA GULL, adult 



32' Bill without black band; legs pink. 33 



33 Upper surface of wing tips dark gray to black, under surface light 



gray; eye brownish often with dark flecks. THAYER'S GULL, adult 



33' Upper surface of wing tip black, under surface dark gray to black; 



eye yellow without flecks. HERRING GULL, adult 



34 Underparts uniform dark gray or brown; no mottling. 59 

 34' Underparts mostly white OR mottled with brown or gray. 35 



