|A pair of adult California Gulls in breeding plumage, showing their dark eyes, red and black on the bill, and relatively dark mantle. Photographed 13 Apr 2009 at Logan, Utah.|
|An adult Ring-billed Gull in breeding plumage, showing its pale eye, black ring around the bill without red, and relatively pale mantle. Photographed 2 May 2011 at Blackfoot, Idaho.|
|Adult California Gull in breeding plumage. Even in flight, the pattern of black and red on the bill and the dark eye can be obvious. Photographed 17 Mar 2013 in Mendon, Utah.|
|Adult Ring-billed Gull in breeding plumage. Even in flight, the black ring on the bill (without red) and the pale eye can be obvious. Photographed 17 Mar 2013 in Mendon, Utah.|
The real challenge, however, is in identifying these species when they are high overhead or lit in such a way that the eye color and bill pattern are impossible to distinguish. In this case, it is helpful to pay close attention to the pattern and colors under the wing. Both species have mostly whitish wings with extensive black near the tips and white spots at the very ends of the outer flight feathers. But, California Gulls have duskier inner primaries contrasting more with the rest of the wing, and Ring-billed Gulls have paler inner primaries that are about the same color as the rest of the wing. California Gulls also tend to have more black in the wingtip than Ring-billed Gulls, but there is some overlap in this trait.
|California Gull in flight. Note again the relatively grayish inner primaries and outer secondaries, contrasting with the paler underwing coverts. Photographed 9 Feb 2008 in Logan, Utah.|