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
Yellow-legged Gull
Larus michahellis
The yellow-legged gull is a large gull, though the size does vary, with the smallest females being scarcely larger than a common gull and the largest males being roughly the size of a great black-backed gull. They range in length from 52 to 68 cm (20 to 27 in) in total length, from 120 to 155 cm (47 to 61 in) in wingspan and from 550 to 1,600 g (1.21 to 3.53 lb) in weight. Among standard measurements, the wing chord is 40.8 to 47.2 cm (16.1 to 18.6 in), the bill is 4.6 to 6 cm (1.8 to 2.4 in) and the tarsus is 5.6 to 7.5 cm (2.2 to 3.0 in).
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play BeakBrainPhotos and recordings are credited to their authors under the licence shown. Full profiles: Glaucous-winged Gull and Yellow-legged Gull.