California Gull
Larus californicus
Adults are similar in appearance to the herring gull, but with brown eyes, yellow legs, and a more rounded head. The body is mainly white with grey back and upper wings. The bill is yellow with a black ring and red spot near the tip. They have black primaries with white tips. Immature birds are also similar in appearance to immature herring gulls, with browner plumage than immature ring-billed gulls. Length can range from 46 to 55 cm (18 to 22 in), the wingspan 122–137 cm (48–54 in) and body mass can vary from 430 to 1,045 g (0.948 to 2.304 lb).
ID text from Wikipedia, CC BY-SA 4.0
Glaucous-winged Gull
Larus glaucescens
This gull is a large bird, being close in size and shape to the closely related Western gull (L. occidentalis). It measures 50–68 cm (20–27 in) in length and 120–150 cm (47–59 in) in wingspan, with a body mass of 730–1,690 g (1.61–3.73 lb). It weighs around 1,010 g (2.23 lb) on average. Among standard measurements, the wing chord is 39.2 to 48 cm (15.4 to 18.9 in), the bill is 4.6 to 6.4 cm (1.8 to 2.5 in) and the tarsus is 5.8 to 7.8 cm (2.3 to 3.1 in). It has a white head, neck, breast, and belly, a white tail.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
Learn this pair in BeakBrain
Photo and call practice, free in any browser.
Play BeakBrainPhotos and recordings are credited to their authors under the licence shown. Full profiles: California Gull and Glaucous-winged Gull.